REVIEW ARTICLENew vaccines for neglected parasitic diseasesand dengue

COREEN M BEAUMIER PORTIA M GILLESPIE PETER J HOTEZ and MARIA ELENA BOTTAZZI

HOUSTON TEX

From the SabinVaccine Institute an

for Vaccine Development Nation

Baylor College of Medicine Houst

Conflicts of interest The authors a

the hookworm and schistosomiasis

as well as potential vaccines again

and onchocerciasis All authors hav

closure of potential conflicts of inte

Coreen Beaumier and Portia Gill

manuscript

Neglected tropical diseases (NTDs) are a significant source of morbidity and socio-economic burden among the worldrsquos poor Virtually all of the 24 billion peoplewho live on less than $2 per d more than a third of the worldrsquos population are atrisk for these debilitating NTDs Although chemotherapeutic measures exist formany of these pathogens they are not sustainable countermeasures on their ownbecause of rates of reinfection risk of drug resistance and inconsistentmaintenanceof drug treatment programs Preventative and therapeutic NTD vaccines are neededas long-term solutions Because there is no market in the for-profit sector of vaccinedevelopment for these pathogens much of the effort to develop vaccines is drivenby nonprofit entities mostly through product development partnerships This reviewdescribes the progress of vaccines under development for many of the NTDs witha specific focus on those about to enter or that are currently in human clinical trialsSpecifically we report on the progress on dengue hookworm leishmaniasis schis-tosomiasis Chagas disease and onchocerciasis vaccines These products will besomeof the first with specific objectives to aid theworldrsquos poorest populations (Trans-lational Research 2013-1ndash12)

Abbreviations AIDS frac14 acquired immune deficiency syndrome CL frac14 cutaneous leishmaniasisDENV frac14 dengue virus DENV-1 frac14 dengue-1 virus DHF frac14 dengue hemorrhagic fever E frac14 enve-lope gene GLA-AF frac14 glucopyranosyl lipid A aqueous formulation GLA-SE frac14 glucopyranosyllipid A stable emulsion GSK frac14 GlaxoSmith-Kline HHV frac14 human hookworm vaccine HIV frac14 hu-man immunodeficiency virus IDRIfrac14 Infectious Disease Research Institute MLfrac14mucosalmuco-cutaneous leishmaniasis MPL-SE frac14 monophosphoryl lipid A stable emulsion Na-GST-1 frac14Necator americanus glutathione s-transferase 1 Na-APR-1(M74) frac14 Necator americanus as-partic protease 1 (M74) NIH frac14 National Institutes of Health NTD frac14 neglected tropical diseasePDPfrac14productdevelopment partnership PIVfrac14purified inactivated virus PKDLfrac14post-Kala-azardermal leishmaniasis prM frac14 membrane gene Sm-TSP-2 frac14 Schistosoma mansoni tetraspaninprotein 2 TDEN frac14 tetravalent dengue vaccine TLR frac14 toll-like receptor VL frac14 visceralleishmaniasis WRAIR frac14 Walter Reed Army Institute of Research

d Texas Childrenrsquos Hospital Center

al School of Tropical Medicine

on Tex

re involved in the development of

vaccines discussed in the article

st leishmaniasis Chagas disease

e read the journalrsquos policy on dis-

rest

espie contributed equally to the

Submitted for publication November 20 2012 revision submitted

March 15 2013 accepted for publication March 16 2013

Reprint requests Maria Elena Bottazzi PhD Sabin Vaccine Institute

amp Texas Childrenrsquos Hospital Center for Vaccine Development Na-

tional School of Tropical Medicine Baylor College of Medicine

Houston TX 77030 e-mail bottazzibcmedu

1931-5244$ - see front matter

2013 Mosby Inc All rights reserved

httpdxdoiorg101016jtrsl201303006

1

Table I Annual number of global deaths from

neglected parasitic and related tropical diseases

Disease Estimated no of deaths

Malaria 655000Schistosomiasis 280000 (Sub-Saharan Africa only)Hookworm infection 65000Leishmaniasis 51000Amoebiasis 40000Dengue 21000Chagas disease 14000Trichuriasis 10000Liver fluke and lung fluke 10000Total 11 million

Modified from reference3

Translational Research2 Beaumier et al - 2013

Human parasitic and related neglected tropical diseases(NTDs) are major causes of illness especially in thepoorest countries of Africa Asia Latin America andthe Caribbean Together these diseases cause morethan 1 million deaths annually (Table I) equivalent toalmost one half of the 18 million deaths that result glob-ally from (HIVAIDS) each year1 and almost as manyas the 14 million people who die annually from tuber-culosis2 However with the exceptions of falciparummalaria and schistosomiasis these human parasitic in-fections are not the leading causes of global mortality3

The 11 million deaths resulting from parasitic and re-lated NTDs account for only a portion of their health im-pact in addition to these deaths parasitic and relatedNTDs are major disablers and cause long-term andchronic disabilities among people who live in poverty(Table II)Today approximately 24 billion people roughly

one third of the worldrsquos population live on less than$2 per d and 13 billion live below theWorld Bank pov-erty figure of $125 per d4 South Asia and Sub-SaharanAfrica account for most of these individuals who live inextreme poverty4 Virtually all of them suffer from 1 ormore parasitic or related NTDs led by 4 major helminthinfectionsmdashie ascariasis hookworm infection trichur-iasis and schistosomiasismdashwith each disease affectingat least 400 million people In fact most of the lsquolsquobottom13 billionrsquorsquo are infected concomitantly with multiplehelminths especially hookworm and schistosomes inSub-Saharan Africa5 In addition tens of millions ofpeople living in extreme poverty are also infected withparasitic protozoa such as Entamoeba histolytica try-panosomes or Leishmania sppAlthough many of these parasitic and related NTDs

are not significant causes of mortality they neverthelessexert a huge health and socioeconomic impact becauseof their unique ability to impair childhood growth andnutrition and reduce agricultural worker productivitydrastically6 They also affect adversely the health ofgirls and women especially during pregnancy7 To-gether these effects translate into a huge economic bur-den resulting in billions of dollars lost annually6 Newerinformation suggests that schistosomiasis and possiblyother parasitic infections may also increase host suscep-tibility to HIVAIDS significantly8

The enormous disease and economic burdens fromparasitic and related NTDs provide a compelling reasonto treat or prevent these conditions as a means of liftingthe poorest people out of poverty and possibly asa back-door approach to reducing the global burden ofHIVAIDS One approach to global parasitic diseasecontrol and elimination is preventive chemotherapy orthe repeated use of anthelmintic drugs to at-risk popula-tions Through support from the governments of the

United States and United Kingdom as well as privatesupport from an Ending Neglected Diseases Fund andGlobal Network for NTDs and other sources the WorldHealth Organization estimates that more than 700 mil-lion people received preventive chemotherapy treat-ments in 20099 Preventive chemotherapy treatmentsare credited with great success toward the eliminationof lymphatic filariasis and trachoma as public healthproblems in several dozen countries9

Although preventive chemotherapy is leading to thecontrol or elimination of several important parasiticand related NTDs for some of the very high-prevalence diseases such as hookworm or schistosomi-asis it is anticipated that additional control tools will berequired including preventive vaccines10 Vaccines arealso urgently needed for dengue leishmaniasis Chagasdisease and possibly onchocerciasis10 Aside from thescientific hurdles to develop and test new NTD vac-cines there are important socioeconomic challengesto their development Because the major parasitic andrelated NTDs occur predominantly among the poorestpeople living in low- and middle-income countriesthere are fewmdashif anymdashmarket incentives to developnew products including vaccines10 Therefore mostof the NTD vaccines are currently being developed inthe nonprofit sector An important exception is denguewhich has also emerged in wealthy countries such asSingapore and the United States and in coastal citiesof Brazil and Southeast Asia where large numbers ofpeople with economic means also liveLeading the efforts in the development of NTD vac-

cines are nonprofit organizations called product devel-opment partnerships (PDPs) such as the SabinVaccine Institute PDP (httpwwwsabinorg) andIDRI (Infectious Disease Research Institute httpwwwidriorg) both headquartered in the United StatesBoth PDPs partner with developing country vaccinemanufacturers and contract research organizations

Table II Approximate number of cases of

neglected parasitic and related tropical diseases

DiseaseApproximate no of

cases globally

Ascariasis 800 millionHookworm 600 millionTrichuriasis 600 millionSchistosomiasis 400ndash600 millionAmoebiasis 480 millionMalaria 216 millionLymphatic filariasis 115 millionDengue 50ndash500 millionTrachoma 40 millionStrongyloidiasis 30ndash100 millionOnchocerciasis 26 millionLiver fluke infection 24 millionParagonimiasis 23 millionLeishmaniasis 12 millionChagas disease 10 million

Figures taken from either of two references references (3 and 10)or the information was combined

Translational ResearchVolume - Number - Beaumier et al 3

based in Brazil China India and Mexico Many ofthese manufacturers have aligned in a DevelopingCountry Vaccine Manufacturers Network (httpwwwdcvmnorg) In addition some of the developing coun-try manufacturers are themselves pursuing the develop-ment of NTD vaccines as is the Institut Pasteur whichhas advanced a schistosomiasis vaccine past phase 2 tri-als Still additional NTD vaccines are being developedat earlier stages by university laboratoriesHere we report on the progress of several human NTD

vaccines with an emphasis on those that are currently inclinical trials or at preclinical or process developmentstages that would allow them to enter trials soon Specif-ically we describe recent advances for vaccines that tar-get dengue hookworm leishmaniasis schistosomiasisChagas disease and onchocerciasis These activities aresummarized in Table III

DENGUE VACCINES

Dengue virus (DENV) a member of the genus Flavi-virus is the causative agent of dengue fever and themoresevere and potentially life-threatening dengue hemor-rhagic fever (DHF)dengue shock syndrome DENV isa vector-borne disease transmitted predominantly bythe mosquito Aedes agypti and also to a lesser extentAedes albopictus11 There are 4 genetically andimmunologically distinct serotypes dengue-1 virus(DENV-1) dengue-2 virus (DENV-2) dengue-3 virus(DENV-3) and dengue-4 virus (DENV-4) Althoughmost infections are subclinical dengue fever (alsoknown as break-bone fever) is a debilitating althoughself-limiting disease characterized by severe lsquolsquoflulikersquorsquo

symptoms myalgia headache nausea vomiting ar-thralgia rash and retrorbital pain12 In addition tothe aforementioned symptoms DHF has the hallmarkof plasma leakage caused by increased permeability ofthe vascular endothelium DHF has the potential to prog-ress into dengue shock syndrome and if left untreated(mostly by fluid replacement therapy) can be fatal13

DENVis endemic in South and Central America South-eastAsia and Sub-SaharanAfrica and has recently beenshown to have local transmission in the United States14

DENV infects 50 million peoplendash100 million peopleannually worldwide with 500000 cases of DHF notedyearly Although lifelong homotypic immunity occursafter infection with 1 serotype of DENV subsequentheterologous infections with the other serotypes isa risk factor for developing DHFdengue shocksyndrome1516 Because of this observation it is widelyhypothesized and supported throughout the literaturethat this pathology is an immunopathology caused byimmune reactions such as cross-reactive T cells andantibody-dependent enhancement17-23 There arecurrently no available drugs to cure dengue infectionand therefore development of an anti-dengue vaccinehas been a focus of utmost importance A challenge tothe creation of a dengue vaccine is that it must induceimmunity to all 4 serotypes because of theimmunopathology seen in subsequent heterologousinfections Although a dengue vaccine has beenpursued for decades one has yet to reach licensureHowever there are multiple vaccines developed onmultiple platforms currently in the clinic (Table III)

Live attenuated dengue vaccines The National Insti-tutes of Health (NIH) in the United States in collabora-tion with Johns Hopkins University has created liveattenuated vaccines for dengue using directedmutagenesis These vaccines were developed byadding attenuating mutations into the genomes ofeach virus in the 30 untranslated region Differentcombinations of candidates have been tested during15 phase 1 trials These previous trials illustrated thatvaccinations did result in seroconversion and werewell tolerated and safe The candidate vaccinesdeemed the most promising from these trials havebeen combined and formulated into tetravalentvaccines known as TetraVax-DV and 5 preparations ofTetraVax-DV are being tested There is currently anongoing phase 1 trial for TetraVax-DV in WashingtonDC Maryland and Vermont and 2 phase 1 trialsrecruiting both in Maryland and Vermont Lastplanned to begin is a phase 2 trial in Brazil andsponsored by Instituto Butantan2425

Another live attenuated dengue vaccine that has en-tered the clinic was developed by the Walter ReedArmy Institute of Research (WRAIR) in partnership

Table III Human parasitic and related neglected tropical disease vaccines advancing into clinical

development

Disease Vaccine candidate Organization Stage of development Production platform

Chagas disease Tc24 and TSA-1 Sabin PDP Preclinical Recombinant proteinDengue TetraVax-DV Johns Hopkins University

NIHInstituto ButantanPhase 1 clinical testing Live attenuated

TDEN USAMRMC Phase 1 clinical testing Live attenuatedDENVax CDCInviragen Phase 1 clinical testing Chimeric live attenuatedTV Sanofi Pasteur Phase 3 clinical testing Chimeric live attenuatedTDEN-PIV WRAIRGSK Phase 1 clinical testing Inactivated purified vaccineDENV-1 PIV WRAIR Phase 1 clinical testing Inactivated purified vaccineHBV-001 D1 Merck amp Co Phase 1 clinical testing Recombinant proteinTVDV NMRCVical Phase 1 clinical testing DNA

Hookworm Human hookworm vaccine Sabin PDP Phase 1 clinical testing Recombinant proteinLeishmaniasisVLCL LEISH-F1 IDRI Phases 1 and 2 clinical

testingRecombinant protein

VLCL LEISH-F2 IDRI Phases 1 and 2 clinicaltesting

Recombinant protein

VL LEISH-F3 IDRI Phase 1 clinical testing Recombinant proteinLutzomyia sand fly

antigens (CL)Sabin PDP Preclinical Recombinant protein

Onchocerciasis Multiple candidateantigens

Sabin PDPNYBC Preclinical Recombinant protein

Schistosomiasis Sm14 FIOCRUZ Phase 1 clinical testing Recombinant proteinBilhvax Sh28GST Institut Pasteur Lille Phase 2 clinical testing Recombinant proteinSm-TSP-2 Sabin PDP cGMP manufacture Recombinant proteinSmp80 (Calpain) Texas Tech Preclinical DNA

Abbreviations CDC Centers for Disease Control and Prevention cGMP cyclic guanosine monophosphate CL cutaneous leishmaniasis

DENV-1 PIV monovalent purified inactivated dengue virus-1 vaccine FIOCRUZ Fundac~ao Oswaldo Cruz GSK GlaxoSmith-Kline IDRI Infec-tious Disease Research Institute NIH National Institutes of Health NMRC Naval Medical Research Center NYBC New York Blood CenterPDP product development partnership Tc24 Trypanosoma cruzi 24-kDa antigen TSA thiol-specific antioxidant TSA-1 5 T cruzi surface tran-sialidase 1 (TSA-1) USAMRMC United States Army Medical Research and Materiel Command VL visceral leishmaniasis WRAIR Walter ReedArmy Institute of ResearchHave also shown efficacy against mucosalmucocutaneous leishmaniasis when used along with chemotherapy

Translational Research4 Beaumier et al - 2013

with GlaxoSmith-Kline (GSK) For this vaccine live vi-rus strains are attenuated by serial passage in a primarydog kidney cell line Many monovalent phase 1 trialsoccurred ultimately to downselect multiple liveattenuated dengue vaccine candidates into a tetravalentdengue vaccine candidates into a tetravalent denguevaccine formulation called TDEN These formulationshave been tested in pediatric trials in naive volunteersfollowed by phase 2 trials in adults in both the UnitedStates and Thailand and also in 12-year-oldsndash50-year-olds in Puerto Rico In these trials the vaccines ap-peared to be safe in both naive and immune volunteersand seroconversion was seen25

Chimeric live attenuated dengue vaccines Sanofi-Pasteur is currently the furthest along in the initiativeof developing a DENV vaccine Sanofi-Pasteurcurrently uses a live attenuated chimeric platform withthe yellow fever virus vaccine 17D (YFV-17D) asa backbone with its membrane (prM) and envelope Egenes replaced with those of the various serotypes of

dengue Previous pediatric and adult trials have shownthe vaccine to have no major safety issues result inhigh rates of seroconversion and it is able to induceTH1 responses25 Recently the results of SanofirsquosPhase 2b efficacy study in Ratchaburi Thailanddemonstrated an overall efficacy of approximately30 This lower efficacy value is a result of the lackof immune response to 1 of the serotypes26 Phase 3studies are currently ongoing25

The Centers for Disease Control and Prevention in theUnited States have also developed a chimeric denguevaccine DENVax which has been licensed to Invira-gen Inc This particular vaccine uses an attenuatedDENV-2 backbone and has its prM and E genesreplaced with those of the other serotypes of dengueSimilar to TDEN this strain has been attenuated byserial passage in primary dog kidney-53 cells25 DEN-Vax has completed a phase 1 trial in St Louis Missouriand another phase 1 trial is ongoing in Colombia Twoother phase 1 trials are currently recruiting with one

Translational ResearchVolume - Number - Beaumier et al 5

recruiting in Colorado Utah and Texas and the other inColombia Puerto Rico Singapore and Thailand27

Purified inactivated dengue vaccine The WRAIRGSK partnership is now pursuing a tetravalent vaccineusing purified inactivated versions of the viruses knownas TDEN-PIV These vaccines are made by growing thevirus in a VERO cell line (African Green Monkey epi-thelial cells) followed by formalin inactivation andthen formulated with alum or a proprietary GSKadjuvant TDEN-PIV with adjuvants AS03B orAS01E will be tested in Puerto Rico and Maryland inan actively recruiting phase 1 trial2829 In additionWRAIR has an ongoing phase 1 trial to testa monovalent purified inactivated DENV-1 vaccine inMaryland30

Recombinant protein dengue vaccine Merck amp Co ispursuing a recombinant protein dengue vaccine toDENV-1 (originally developed by Hawaii Biotech)The protein antigen in this vaccine HBV-001 D1 isa recombinant truncated form of the E protein of thevirus and is expressed using a Drosophila systemThis vaccine formulated with Alhydrogel hasbeen tested in a small phase 1 clinical trial in theUnited States in Missouri Results of this trial arepending2531

DNAvaccine for dengue The US Naval Medical Re-search Center is pursuing its dengue vaccine on a DNAplatform using the virusrsquos prM and E proteins as themain targets A DENV-1 monovalent phase 1 studywas completed Reactogenicity was low and 416seroconversion was observed at the high dose T-cellresponses were measured in terms of interferon-gamma and were detected in both low- and high-dosegroups in 50 and 833 of volunteers respectivelyB-cell ELISPOT responses were seen in 50 of thehigh-dose group and 33 of the low-dose groups25 Atetravalent DNA dengue vaccine from the US NavalMedical Research Center TVDV is currently ongoingin Maryland with the adjuvant Vaxfectin fromVical2532

HUMAN HOOKWORM VACCINE

Human hookworm is known to infect 600 millionpeoplendash700 million people worldwide and is seen pri-marily in Latin America Sub-Saharan Africa andSoutheast Asia33 In addition to its major clinical man-ifestation of iron deficient anemia hookworm infectionhas significant effects on children and pregnant womenIn children hookworm infection is associated with de-creases in physical and psychomotor maturation andin physical fitness along with reductions in develop-ment IQ and school participation and achievementsIn Sub-Saharan Africa one third of pregnant women

are infected with hookworm These pregnancies may re-sult in reduced birth weight and increased mortality inthe unborn child and also the mother3435 Hookwormis also responsible for 22 million disability-adjustedlife years These hookworm disability-adjusted lifeyears are half what is seen for malaria33 In fact co-infections with malaria and human hookworm usuallylead to significant confounding effects on anemia asdemonstrated by Brooker et al36

In 2001 theWorldHealth Assembly adopted a resolu-tion to decrease the global burden of soil-transmittedhelminthes and schistosomiasis by treating school-agechildren through mass drug administration Therehave been several difficulties for this resolutionrsquosapplication to human hookworm infections First therehas been difficulty in maintaining adequate coverageof mass drug administration in endemic areas In addi-tion there is evidence that at least 1 antihelminthicdrug mebendazole is largely ineffective against treat-ing hookworm and among the possibilities is thatdrug resistance may be occurring3738 Last evenwhen treating with an effective drug albendazolereinfection can occur within 6 months of treatmentwith the same burdens as those seen pretreatment38

Given the compelling evidence for a vaccine the Sa-bin Vaccine Institute PDP is developing a bivalent hu-man hookworm vaccine (HHV) (Table III) Necatoramericanus is the target of HHV because it is the caus-ative agent of approximately 85 of human hookworminfections The bivalent vaccine is intended to preventmoderate to heavy hookworm burden resulting from in-fection withN americanus39 It is targeted as a pediatricvaccine to be delivered with a maximum of 2 doses withExpanded Programme on Immunization vaccines or intandem with antihelminthic drugs3339

As a bivalent vaccine HHV consists of 2 antigensNecator americanus glutathione s-transferase 1 (Na-GST-1) and Necator americanus aspartic protease 1(M74) (Na-APR-1(M74)) both of which are candidateantigens derived from the adult stage of the worm Asthe adult worm feeds on the blood from the intestineof the host the hemoglobin from the blood is digestedinto heme by several proteases one of which is an as-partic protease 1 Because the heme is toxic to theworm it needs to be broken down further which is ac-complished by glutathione s-transferase 1 Thereforethis vaccine is designed to induce the production of neu-tralizing antibodies blocking hemoglobin breakdown aswell as preventing heme detoxification ultimatelystarving the organism3339

Na-GST-1 is produced as a recombinant protein of2316 kDa expressed in the yeast system Pichia pasto-ris Na-APR-1(M74) is a larger recombinant protein at4218 kDa and unlike Na-GST-1 it is a mutated version

Translational Research6 Beaumier et al - 2013

of the protein with its protease activity inactivated bythe mutation of 2 aspartic acid residues at positions97 and 284 to alanine residues39 The Na-APR-1(M74) recombinant protein is produced in partnershipwith Fraunhofer CMB and is expressed using agrobac-teria that is infiltrated into the tobacco plant Nicotianabenthamiana Both antigens are formulated on the alum-based adjuvant Alhydrogel39 In addition the aqueousformulation of glucopyranosyl lipid A aqueous formu-lation (GLA-AF) from IDRI will also be tested as anadditional adjuvant Both antigens have shown encour-aging preclinical data through a vaccinationchallengemodel in both canine and murine models usingAnclyostoma caninum and N americanus respec-tively3339

Currently the Na-GST-1 hookworm vaccine is under-going phase 1 testing as a monovalent vaccine in healthyadults in both Washington DC and Brazil (both ina nonendemic and an endemic area) with and withoutGLA-AF The Na-APR-1(M74) hookworm vaccine isintended to enter phase 1 trials in 2013 in the UnitedStates in healthy adult volunteers and later in popula-tions living in Brazil After successful completion ofboth phase 1 studies these 2 vaccines will be combinedinto a bivalent vaccine by both coadministration and co-formulation and tested in phase 2b and phase 3 efficacystudies in endemic areas of Sub-Saharan Africa andBrazil39

LEISHMANIASIS VACCINE

Leishmaniasis is a vector-borne disease that cur-rently threatens approximately 350 million people atrisk living in endemic areas with 20 species of the pro-tozoan parasite of the genus Leishmania known to bepathogenic in humans with a broad range of clinicalmanifestations which are determined not only by thespecies of the infecting parasite but also by the ge-netic makeup and general health of the infected hostThese manifestations include cutaneous leishmaniasis(CL) characterized by skin lesions mucosalmucocu-taneous leishmaniasis (ML) characterized by lesionsof the mucosa visceral leishmaniasis (VL) in whichlesions are disseminated to internal organs includingthe spleen and liver and post-Kala-azar dermal leish-maniasis (PKDL) caused by a persistence of parasitesin the skin following apparent successful treatment ofVL40 This along with the extensive number of vectorsand potential reservoirs for parasite transmissionmakes conventional control measures challenging41

Although treatment options have improved in recentyears becoming safer and more effective it is likelythat elimination will only be achieved through vacci-nation41 The concept of a leishmaniasis vaccine isstrengthened by the observation that most individuals

that have been infected and who recover from the in-fection become resistant to later clinical infection42

Resistance to infection has been associated witha TH1 immune response Increasing evidence suggestshowever that true protection from disease will requirethe involvement of both a TH1 and a TH2 immune re-sponse from vaccination4243 An ideal vaccine willallow for long-lasting immunity to Leishmania infec-tion thereby limiting the need for the use of chemo-therapy However despite an extensive vaccinedevelopment program no vaccine has gone on to li-censure and most have not progressed beyond the re-search and development phase42

The earliest of the first-generation vaccination at-tempts against leishmaniasis included deliberate inocu-lation from one person to another using virulentLeishmania from a cutaneous lesion a practice referredto as leishmanization41 This crude vaccination strategyallowed for the inoculum to be introduced onto an easilyconcealed area of the body thus sparing the person fromfacial or other disfiguring lesions42 From this crude in-noculation technique which has been largely aban-doned as a result of safety concerns vaccineevaluations have switched to trials involving wholekilled parasites as well as trials for inactivated whole-parasite vaccines attempts at the introduction(etc)4142 These early vaccines have been focused onCL and VL and clinical results from first-generationLeishmania vaccines have been inconsistent In addi-tion many of these preparations cannot be standardizedappropriately to be a viable option for licensure givencurrent regulatory considerations41

The work currently being done on the development ofsecond-generation vaccines against leishmaniasis relieson the use of adjuvanted recombinant DNA technolo-gies (Table III) It is believed that new strategies basedon these technologies will be easier to scale up formass dissemination in a cost-effective and reproduciblemanner and will be able to meet the current regulatoryrequirements for vaccines41 Many different recombi-nant proteins have been investigated for their use as pre-ventive and therapeutic vaccine candidates against CLVL PKDL and ML The first candidate of this type tomake it to phase 1 and phase 2 clinical trials wasLEISH-F1 from IDRI (Seattle Wash) LEISH-F1 iscomprised of 3 proteins that are conserved across vari-ous Leishmania species including Leishmania donovaniand Leishmania chagasi causative agents of NewWorld VL and Leishmania braziliensis a causativeagent of both ML and CL in the NewWorld The 3 pro-teins are L braziliensis elongation and initiation factorLeishmania major thiol-specific antioxidant and L ma-jor stress-inducible protein 1 The adjuvant of choicewith the LEISH-F1 vaccine is monophosphoryl lipid

Translational ResearchVolume - Number - Beaumier et al 7

A stable emulsion (MPL-SE) a powerful toll-like re-ceptor 4 (TLR-4) agonist that is derived from the lipo-polysaccharide of Salmonella enterica serovarMinnesota formulated as a stable emulsion Multiplephase 1 trials have been conducted with the LEISH-F1vaccine in the United States Colombia Brazil Peruand India targeting VL and CL and all have shownthe vaccine to be immunogenic safe and well toleratedin populations both with and without a seropositive sub-population leading researchers to believe that it wouldbe unnecessary to prescreen populations for their Leish-mania serostatus prior to administration of this vac-cine44 In addition the LEISH-F1 vaccine has alsodemonstrated some therapeutic significance in patientswith ML when used with chemotherapy45 With thegreat preliminary successes of the LEISH-F1 vaccineIDRI has redesigned this early vaccine candidate andhas taken their new construct (LEISH-F2) throughboth a phase 1 and a phase 2 trial The new candidate in-cludes a redesigned construct without the histidine tagon the N-terminus as well as the replacement ofLys274 with Gln in an effort to overcome possible reg-ulatory concerns and to aid in the manufacturing pro-cess43 The phase 1 trial included 3 injections 14 daysapart with LEISH-F2 (10 mg) 1 MPL-SE (25 mg) asan adjunct to standard chemotherapy in patients withPKDL46 Positive findings related to immunogenicityand safety from the phase 1 trial led to a phase 2 trialin which the efficacy safety and immunogenicity ofthe vaccine was studied after 3 administrations ofLEISH-F2 (10 mg) 1 MPL-SE (25 mg) to treat adultsand adolescents with CL compared with treatmentwith standard chemotherapy47 IDRI is also investigat-ing in a phase 1 trial of healthy adult volunteers theirnew LEISH-F3 vaccine for use against VL TheLEISH-F3 vaccine is a fusion polypeptide made by link-ing in tandem 2 Leishmania proteins residues 1ndash314 ofthe Leishmania infantumdonovani nonspecific nucleo-side hydrolase protein and residues 2-353 of L infantumsterol 24-c-methyltransferase protein The LEISH-F3vaccine is given at 20 mg with either 2 mg or 5 mg of glu-copyranosyl lipid A stable emulsion (GLA-SE) a novelTLR-4-based adjuvant and is compared with adminis-tration of unadjuvanted LEISH-F3 (20 mg)48 This firstphase 1 trial will enroll 36 adult volunteers in Washing-ton state A second phase 1 trial will then take place inIndia where IDRI will transfer its vaccine manufactur-ing process to Gennova Biopharmaceuticals4149

In addition to these advances by IDRI in recentyears other groups are investigating third-generationvaccines including DNA-based vaccines which haveshown great promise in animal models but have yet tobe made available to humans It is also believed that sal-ivary proteins of the sand fly vectors (Phlebotomus and

Lutzomyia spp) known to transmit Leishmania parasitesmay make good vaccine candidates as such manytransmission-blocking vaccines based on this idea arein early preclinical testing The Sabin Vaccine InstitutePDP working in partnership with the Vector MolecularBiology Section Laboratory of Malaria and VectorResearch National Institute of Allergy and InfectiousDiseases NIH (Rockville Md) is currently performingfeasibility studies for the selection preclinical testingand process development and scale-up of sand fly-derived (Lutzomyia spp) candidate antigens

SCHISTOSOMIASIS VACCINE

Human schistosomiasis is a disease manifestationcaused by a series of blood flukes or schistosomesand is most common in areas of extreme poverty inAfrica South America the Middle East and AsiaThese parasites are Schistosoma mansoni Schistosomahaematobium Schistosomamekongi Schistosoma japo-nicum and Schistosoma intercalatum More than 90of the infections are caused by either S haematobiumor S mansoni with almost all of these cases occurringin Sub-Saharan Africa and with the largest number ofcases outside of Africa occurring in Brazil Approxi-mately 200 million people are infected with 120 mil-lion displaying symptoms and 20 million afflictedwith severe disease Still other estimates suggest thatthe actual number of cases may be double or triplethat number because of egg-negative infections5051

S haematobium infections may result in urinary tractcomplications including fibrosis calcification andstructuring Infection with the other aforementioned or-ganisms may cause intestinal and hepatic fibrosis In ad-dition S haematobium eggs deposit in the uteruscervix and lower genital tract to cause female genitalschistosomiasis which is linked to a 3-foldndash4-fold in-crease in risk of acquiring HIVAIDS in Africa8

Currently the treatment for schistosomiasis is prazi-quantel Praziquantel administration is effective againstschistosomes but has its drawbacks such as a high fre-quency of reinfection risk of the development of drug-resistant organisms and the challenges of sustainingtreatment programs51 The availability of an antischisto-somiasis vaccine would be a powerful tool to add to thefight against the scourge of schistosomiasisRecent endeavors show promise for vaccines against

both S mansoni and S haematobium (Table III) The In-stitut Pasteur in Lille has developed Bilhvax a recombi-nant protein vaccine combined with alum that targetsthe schistosome molecule glutathione S-transferase 28kDa This vaccine recently completed phase 1 trials inhealthy male adults in Lille University Hospital inFrance Results reported include that there were no

Translational Research8 Beaumier et al - 2013

severe adverse events detected that were linked withvaccination Althoughminor adverse events were notedthey were limited to pain and swelling around the injec-tion site As a secondary end point the immune re-sponses were measured as a function of both humoraland cellular responses The antibody isotype profilewas predominated by immunoglobulin G1 Two doses(100 mg and 300 mg) of the vaccine were tested andboth induced specific antibody responses with no ap-preciable difference between both dosing strategiesWith regard to a cellular immune response TH2-typecytokines interleukin 13 and interleukin 5 were detectedafter in vitro stimulation of the donorrsquos mononuclearcells with schistosoma haematobium glutathioneS-transferase 28 kDa5253

Another promising vaccine candidate targets the fattyacid binding protein of S mansoni This particular re-combinant protein antigen is Sm14 and is adjuvantedwith GLA-SE A phase 1 clinical trial sponsored bythe Oswaldo Cruz Foundation (FIOCRUZ Brazil) incollaboration with Financiadora Estudos e Projetos forSm14 is currently ongoing in Rio de Janeiro Brazilat the Instituto de Pesquisa Clınica Evandro Chagas(IPEC)-FIOCRUZ This study is enrolling healthyadults who receive 3 doses of the vaccine at 50 mgSm14with 10 mg GLA-SE As this study is currently on-going no results are yet available54

A third encouraging vaccine antigen against S man-soni is S mansoni tetraspanin protein 2 (Sm-TSP-2)Sm-TSP-2 is being developed by the Sabin Vaccine In-stitute PDP and also uses recombinant protein technol-ogy and protein adjuvanted on alum Sm-TSP-2 isa member of the tetraspanin family of proteins and is ex-pressed in the tegument of the parasite In a murinemodel vaccination with Sm-TSP-2 demonstrated a pro-tective effect Although not yet in clinical trials it hasbeen manufactured in collaboration with Aeras (Mary-land) and has entered toxicology studies The clinicaldevelopment plan includes testing with and withoutthe inclusion of GLA-AF from IDRI The current planis to begin phase 1 safety trials in 201349

VACCINES ON THE CUSP ONCHOCERCIASIS ANDCHAGAS

Chagasdisease Chagasdisease in theAmericas repre-sents a substantial health burden and ranks among themost important NTDs in this region with 10 millionpeople believed to be infected55 The causative agentTrypanosoma cruzi is most commonly transmittedthrough the feces of the infected triatomine vectoralthough mother-to-child transmission transfusion andorgan transplantation-associated infection and infectionvia contaminated foods have also emerged as importantroutes of transmission56 Treatments are currently

available however they are costly require lengthyregimens and have the risk of severe adverse eventsThese drugs are also not approved for use in pregnantwomen which is problematic because of the high ratesof vertical transmission and congenital infection53

Current prevention efforts rely on vector control andalthough this has reduced disease incidence it is notbelieved that vector control measures alone will be ableto prevent transmission to humans57 Therefore a widerange of preventive vaccine formulations have beenevaluated throughout the years from the use of wholeparasites to purified or recombinant proteins to viralvectors and DNA vaccines57 Although there arechallenges associated with live vaccines a renewedinterest has been seen recently in live attenuatedvaccines such as the generation of T cruzi mutants forspecific genes Such genes are LYT1 which is believedto play a role in parasite infectivity mediating theescape of the parasite from the acidic parasitophorousvaculole into the cytosol and ECH1 and ECH2 (tandemenoyl-coenzymeA hydratase 1 and 2 genes) thought toplay a key role in amastigote energy metabolism5859

These live attenuated vaccines have been shown toprotect mice from infection55 It has been widely notedthat the outcome of many vaccines against T cruzi inanimal models depends heavily on the formulation usedand the immune response that is induced55 Regardlessof the vaccine platform chosen it is apparent thata strong cellular immune response will need to beinduced and encompass CD81 cell activation andcytotoxic activity to control T cruzi infection throughvaccination57 Many recent studies have been based onrecombinant protein technology recombinant viralvaccine vectors DNA vaccines and heterologousprime-boost vaccination strategies and have shownstrong protection against infection and increasedsurvival of mice It is now believed that for the controlof Chagas disease either a preventive vaccine against Tcruzi or a therapeutic vaccine could be of great value57

Both vaccine strategies would rely on a skewed im-mune response toward a TH1 type leading researchersto believe that the same antigens and vaccine formula-tions may be used for both the prevention of Chagas dis-ease as well as a therapeutic for an ongoing infectionRecent economic modeling has suggested that a thera-peutic vaccine for Chagas would be more cost-effective than a preventive vaccine55

Several different groups are conducting preclinicaltesting of candidate T cruzi vaccines57 The Sabin Vac-cine Institute PDP with the Instituto Carlos Slim de laSalud (Mexico DF Mexico) and in association withthe Laboratorio de Parasitologıa CIR UniversidadAutonoma de Yucatan (Merida Mexico) the Laborator-ios de Biologicos y Reactivos de Mexico (Birmex

Translational ResearchVolume - Number - Beaumier et al 9

Mexico City Mexico) the Centro de Investigacion y deEstudios Avanzados del Instituto Politecnico Nacional(Cinvestav Mexico City Mexico) and the Vector Mo-lecular Biology Section Laboratory of Malaria andVector Research National Institute of Allergy and In-fectious Diseases NIH (Rockville Md) is advancinga therapeutic vaccine from target selection through pro-cess development scale up and manufacturing Thisvaccine is intended to be a bivalent vaccine for the treat-ment of chronic Chagas disease comprised of 2 T cruzirecombinant proteins formulated on either Alhydrogelor Adju-Phos and coadministration with E6020 (EisaiCo Ltd Tokyo Japan) a novel TLR-4 agonist The 2selected novel antigens to advance through develop-ment are Tc24 a T cruzi 24 kDa antigen and TSA-1a T cruzi surface transialidase56 These antigens willbe expressed using a soluble expression system suchas yeast Escherichia coli or baculovirus The vaccineis intended to prevent or delay the onset of chagasic car-diomyopathy in patients with indeterminate Chagas dis-ease or in patients with early-stage disease and mayprevent further transmission of T cruzi56

Onchocerciasis Onchocerciasis transmitted by theblack fly of the genus Simulium is the second leadingcause of infectious blindness in humans worldwide withapproximately 120 million people at risk for the diseasein Africa and Latin America60 Vector and chemotherapyapproaches for onchocerciasis control have been ableto limit the extent and impact of this infection butneither strategy is a permanent solution61 Mountingevidence suggesting that humans can develop a naturallyacquired immunity against Onchocerca volvulus furtherstrengthens the argument for the development of anonchocerciasis vaccine62 The Edna McConnell ClarkFoundation has worked to complement the wealth ofonchocerciasis control programs (OnchocerciasisControl Programme the African Programme forOnchocerciasis Control and the OnchocerciasisElimination Program in the Americas) by dedicatingfunds for immunologic and molecular biologyapproaches to onchocerciasis research63 As a resultthere have been many gains made in the onchocerciasisfield especially in the area of vaccine developmentThese advances include the development of high-qualitycomplementary DNA libraries encompassing manystages of the Onchocerca volvulus life cycle63 It hasalso been shown clearly that mice humans and cattledevelop protective immunity against O volvuluslarvae60 In addition 44 recombinant proteins that werecloned by immunoscreening or other approaches haveyielded 14 potential antigens that have shown significantreduction (35ndash69) of L3 larval survival63

The Sabin Vaccine Institute PDP embarked in col-laboration with the New York Blood Center to estab-

lish a novel strategy of antigen selection that usesa scoring system to screen and rank proteins for effi-cacy in 2 complementary small animal models Fromthese efforts 8 top-ranking O volvulus protective an-tigens have emerged including Ov-CPI-2 a cysteineprotease inhibitor Ov-ALT-1 a filarial specific anti-gen Ov-RAL-2 a nematode-specific surface antigenOv-ASP-1 a homolog of venom allergen 5 and thePR-1 protein family Ov-103 a nematode-specific sur-face antigen Ov-RBP-1 a retinol binding protein Ov-CHI-1 a chitinase and Ov-B20 a nematode-specificsurface antigen60 Through continued efforts in re-search and development of these candidates it is thehope that at least 1 or 2 of these promising targetswould be suitable for a prophylactic vaccine and willmake it to the clinic in the coming years A prophylac-tic vaccine would be used as an additional componentof the already existing arsenal to control onchocercia-sis In addition a vaccine could aid in the reduction ofmicrofilariae burdens thus reducing the potential fortransmission60 Furthermore it would also not dependon current chemotherapy efforts with ivermectin In-stead the vaccine could be administered in communi-ties that have already gone through multiple rounds ofchemotherapy where resistance may become an issuethereby complementing this control measure in an ef-fort to reach the goal of the elimination of onchocerci-asis as a public health issue60

NEXT STEPS

During the next 5 years it is anticipated that severalNTD vaccines could advance into phase 2 and phase 3trials A major issue is what the lsquolsquoend gamersquorsquo will looklike in terms of subsequent steps for licensure andglobal access Most of the NTD vaccines outlinedhere will be among the first vaccine products targetedspecifically only for the bottom billion of the populationand are currently without major backing of a majorpharmaceutical company There are few if any prece-dents for achieving licensure and global access mile-stones without the benefit of major pharmaceuticalsupport Perhaps the closest comparison would be therecent successes of the Serum Institute of India (a devel-oping country vaccine manufacturer) in collaborationwith the Program for Appropriate Technology in Health(PATH Seattle WA a PDP) in producing a meningo-coccal A vaccine for the meningitis belt in Sub-Saharan Africa64

The scale andmagnitude of the major parasitic and re-lated NTDs discussed here are vast and therefore thevaccine development process may be potentially muchmore complex in terms of manufacturing partners li-censing strategies and World Health Organization

Translational Research10 Beaumier et al - 2013

prequalifications and uptake by the disease-endemiccountries most of which are among the most resourcepoor in the world Complicating the global access anduptake of the major NTD vaccines is the observationin preclinical testing that most of these candidate vac-cines are only protective in part similar to the RTSSmalaria vaccine as shown in recent clinical trials65

To date there is really not a clear road map for howsuch partially protective vaccines might be used along-side additional public health control measures such asantiparasitic drugs or in the case of malaria bed netsand other ancillary measures There are also importantquestions that will need to be answered regarding thebest system for incorporating NTD vaccines (egwhether efforts would focus on delivery alongside mea-sles or other infant vaccines as part of the ExpandedProgramme on Immunization or whether these productsmight be delivered in schools such as has been pro-posed with the human papillomavirus vaccine or evenin antenatal clinics) Toward this goal it is essentialthat in parallel with current development detaileddemand-forecasting exercises are performed to get a bet-ter sense of the needs of the end users in low- andmiddle-income countries and some of the major issuesrelated to global access and uptake The challenges ofwidespread distribution of NTD vaccines will be formi-dable but achieving such milestones would representimportant steps toward poverty reduction and achievingthe Millennium Development Goals

REFERENCES

1 AVERT Global HIV and AIDS estimates 2009 and 2010 Avail-

able at httpwwwavertorgworldstatshtm Accessed Novem-

ber 4 2012

2 World Health Organization Tuberculosis fact sheet 2012 Avail-

able at httpwwwwhointmediacentrefactsheetsfs104en

Accessed November 4 2012

3 Hotez PJ The Four Horsemen of the Apocalypse tropical medi-

cine in the fight against plague death famine and war Am J Trop

Med Hyg 2012873ndash10

4 A fall to cheer The Economist 2012 Available at httpwww

economistcomnode21548963 Accessed November 4 2012

5 Hotez PJ Bethony JM Oliveira SC Brindley PJ Loukas A Mul-

tivalent anthelminthic vaccine to prevent hookworm and schisto-

somiasis Expert Rev Vaccines 20087745ndash52

6 Hotez PJ Fenwick A Savioli L Molyneux DH Rescuing the bot-

tom billion through control of neglected tropical diseases Lancet

20093731570ndash5

7 Hotez PJ Empowering women and improving female reproduc-

tive health through control of neglected tropical diseases PLoS

Negl Trop Dis 20093e559

8 Mbabazi PS Andan O Fitzgerald DW Chitsulo L Engels D

Downs JA Examining the relationship between urogenital schis-

tosomiasis and HIV infection PLoS Negl Trop Dis 20115e1396

9 World Health Organization Neglected tropical diseases 2012

Available at httpwwwwhointghoneglected_diseasesen

indexhtml Accessed November 4 2012

10 Hotez P A handful of lsquoantipovertyrsquo vaccines exist for neglected

diseases but the worldrsquos poorest billion people need more Health

Aff 2011301080ndash7

11 Gubler DJ Aedes aegypti and Aedes aegypti-borne disease control

in the 1990s top down or bottom up Charles Franklin Craig lec-

ture Am J Trop Med Hyg 198940571ndash8

12 Kalayanarooj S Vaughn DW Nimmannitya S et al Early clinical

and laboratory indicators of acute dengue illness J Infect Dis

1997176313ndash21

13 Guzman MG Kouri G Dengue an update Lancet Infect Dis

2002233ndash42

14 Centers for Disease Control and Prevention Locally acquired

dengue Key West Florida 2009ndash2010 MMWR Morb Mortal

Wkly Rep 201059577ndash81

15 Halstead SB Immune enhancement of viral infection Prog Al-

lergy 198231301ndash64

16 Sangkawibha N Rojanasuphot S Ahandrik S et al Risk factors

in dengue shock syndrome a prospective epidemiologic study

in Rayong Thailand I The 1980 outbreak Am J Epidemiol

1984120653ndash69

17 Halstead SB Nimmannitya S Yamarat C Russell PK Hemor-

rhagic fever in Thailand recent knowledge regarding etiology

Jpn J Med Sci Biol 19672096ndash103

18 Kliks SC Nimmanitya S Nisalak A Burke DS Evidence that ma-

ternal dengue antibodies are important in the development of den-

gue hemorrhagic fever in infants Am J Trop Med Hyg 198838

411ndash9

19 Kliks SC Nisalak A Brandt WE Wahl L Burke DS Antibody-

dependent enhancement of dengue virus growth in human mono-

cytes as a risk factor for dengue hemorrhagic fever Am J Trop

Med Hyg 198940444ndash51

20 Kurane I Innis BL Nisalak A et al Human T cell responses to

dengue virus antigens proliferative responses and interferon

gamma production J Clin Invest 198983506ndash13

21 Kurane I Meager A Ennis FA Dengue virus-specific human T

cell clones serotype cross-reactive proliferation interferon

gamma production and cytotoxic activity J Exp Med 1989170

763ndash75

22 Mathew A Kurane I Green S et al Predominance of HLA-

restricted cytotoxic T-lymphocyte responses to serotype-cross-

reactive epitopes on nonstructural proteins following natural

secondary dengue virus infection J Virol 1998723999ndash4004

23 Mongkolsapaya J Dejnirattisai W Xu XN et al Original anti-

genic sin and apoptosis in the pathogenesis of dengue hemor-

rhagic fever Nat Med 20039921ndash7

24 National Institute of Allergy and Infectious Diseases Evaluating

the safety and immune response to two admixtures of a tetravalent

dengue virus vaccine 2012 Available at httpclinicaltrialsgovct2

showNCT01506570term5Tetravax-DVamprank53 Accessed No-

vember 4 2012

25 Thomas SJ Endy TP Vaccines for the prevention of dengue de-

velopment update Hum Vaccin 20117674ndash84

26 Sanofi-Pasteur Sanofi Pasteurrsquos dengue vaccine demonstrates

proof of efficacy 2012 Available at 5 wwwsanofipasteurcom

articles1118-sanofi-pasteurrsquos-dengue-vaccine-demonstrates-

proof-of-efficacyhtml Accessed November 2 2012

27 Inviragen Safety and immunogenicity study to assess DENVax

a live attenuated tetravalent vaccine for prevention of dengue fe-

ver 2011 Available at httpclinicaltrialsgovct2show

NCT01224639term5DENVaxamprank51 Accessed November

14 2012

28 US Army Medical Research and Materiel Command A two-

dose primary vaccination study of a tetravalent dengue virus

purified inactivated vaccine vs placebo in healthy adults 2012

Translational ResearchVolume - Number - Beaumier et al 5

recruiting in Colorado Utah and Texas and the other inColombia Puerto Rico Singapore and Thailand27

Purified inactivated dengue vaccine The WRAIRGSK partnership is now pursuing a tetravalent vaccineusing purified inactivated versions of the viruses knownas TDEN-PIV These vaccines are made by growing thevirus in a VERO cell line (African Green Monkey epi-thelial cells) followed by formalin inactivation andthen formulated with alum or a proprietary GSKadjuvant TDEN-PIV with adjuvants AS03B orAS01E will be tested in Puerto Rico and Maryland inan actively recruiting phase 1 trial2829 In additionWRAIR has an ongoing phase 1 trial to testa monovalent purified inactivated DENV-1 vaccine inMaryland30

Recombinant protein dengue vaccine Merck amp Co ispursuing a recombinant protein dengue vaccine toDENV-1 (originally developed by Hawaii Biotech)The protein antigen in this vaccine HBV-001 D1 isa recombinant truncated form of the E protein of thevirus and is expressed using a Drosophila systemThis vaccine formulated with Alhydrogel hasbeen tested in a small phase 1 clinical trial in theUnited States in Missouri Results of this trial arepending2531

DNAvaccine for dengue The US Naval Medical Re-search Center is pursuing its dengue vaccine on a DNAplatform using the virusrsquos prM and E proteins as themain targets A DENV-1 monovalent phase 1 studywas completed Reactogenicity was low and 416seroconversion was observed at the high dose T-cellresponses were measured in terms of interferon-gamma and were detected in both low- and high-dosegroups in 50 and 833 of volunteers respectivelyB-cell ELISPOT responses were seen in 50 of thehigh-dose group and 33 of the low-dose groups25 Atetravalent DNA dengue vaccine from the US NavalMedical Research Center TVDV is currently ongoingin Maryland with the adjuvant Vaxfectin fromVical2532

HUMAN HOOKWORM VACCINE

Human hookworm is known to infect 600 millionpeoplendash700 million people worldwide and is seen pri-marily in Latin America Sub-Saharan Africa andSoutheast Asia33 In addition to its major clinical man-ifestation of iron deficient anemia hookworm infectionhas significant effects on children and pregnant womenIn children hookworm infection is associated with de-creases in physical and psychomotor maturation andin physical fitness along with reductions in develop-ment IQ and school participation and achievementsIn Sub-Saharan Africa one third of pregnant women

are infected with hookworm These pregnancies may re-sult in reduced birth weight and increased mortality inthe unborn child and also the mother3435 Hookwormis also responsible for 22 million disability-adjustedlife years These hookworm disability-adjusted lifeyears are half what is seen for malaria33 In fact co-infections with malaria and human hookworm usuallylead to significant confounding effects on anemia asdemonstrated by Brooker et al36

In 2001 theWorldHealth Assembly adopted a resolu-tion to decrease the global burden of soil-transmittedhelminthes and schistosomiasis by treating school-agechildren through mass drug administration Therehave been several difficulties for this resolutionrsquosapplication to human hookworm infections First therehas been difficulty in maintaining adequate coverageof mass drug administration in endemic areas In addi-tion there is evidence that at least 1 antihelminthicdrug mebendazole is largely ineffective against treat-ing hookworm and among the possibilities is thatdrug resistance may be occurring3738 Last evenwhen treating with an effective drug albendazolereinfection can occur within 6 months of treatmentwith the same burdens as those seen pretreatment38

Given the compelling evidence for a vaccine the Sa-bin Vaccine Institute PDP is developing a bivalent hu-man hookworm vaccine (HHV) (Table III) Necatoramericanus is the target of HHV because it is the caus-ative agent of approximately 85 of human hookworminfections The bivalent vaccine is intended to preventmoderate to heavy hookworm burden resulting from in-fection withN americanus39 It is targeted as a pediatricvaccine to be delivered with a maximum of 2 doses withExpanded Programme on Immunization vaccines or intandem with antihelminthic drugs3339

As a bivalent vaccine HHV consists of 2 antigensNecator americanus glutathione s-transferase 1 (Na-GST-1) and Necator americanus aspartic protease 1(M74) (Na-APR-1(M74)) both of which are candidateantigens derived from the adult stage of the worm Asthe adult worm feeds on the blood from the intestineof the host the hemoglobin from the blood is digestedinto heme by several proteases one of which is an as-partic protease 1 Because the heme is toxic to theworm it needs to be broken down further which is ac-complished by glutathione s-transferase 1 Thereforethis vaccine is designed to induce the production of neu-tralizing antibodies blocking hemoglobin breakdown aswell as preventing heme detoxification ultimatelystarving the organism3339

Na-GST-1 is produced as a recombinant protein of2316 kDa expressed in the yeast system Pichia pasto-ris Na-APR-1(M74) is a larger recombinant protein at4218 kDa and unlike Na-GST-1 it is a mutated version

Translational Research6 Beaumier et al - 2013

of the protein with its protease activity inactivated bythe mutation of 2 aspartic acid residues at positions97 and 284 to alanine residues39 The Na-APR-1(M74) recombinant protein is produced in partnershipwith Fraunhofer CMB and is expressed using agrobac-teria that is infiltrated into the tobacco plant Nicotianabenthamiana Both antigens are formulated on the alum-based adjuvant Alhydrogel39 In addition the aqueousformulation of glucopyranosyl lipid A aqueous formu-lation (GLA-AF) from IDRI will also be tested as anadditional adjuvant Both antigens have shown encour-aging preclinical data through a vaccinationchallengemodel in both canine and murine models usingAnclyostoma caninum and N americanus respec-tively3339

Currently the Na-GST-1 hookworm vaccine is under-going phase 1 testing as a monovalent vaccine in healthyadults in both Washington DC and Brazil (both ina nonendemic and an endemic area) with and withoutGLA-AF The Na-APR-1(M74) hookworm vaccine isintended to enter phase 1 trials in 2013 in the UnitedStates in healthy adult volunteers and later in popula-tions living in Brazil After successful completion ofboth phase 1 studies these 2 vaccines will be combinedinto a bivalent vaccine by both coadministration and co-formulation and tested in phase 2b and phase 3 efficacystudies in endemic areas of Sub-Saharan Africa andBrazil39

LEISHMANIASIS VACCINE

Leishmaniasis is a vector-borne disease that cur-rently threatens approximately 350 million people atrisk living in endemic areas with 20 species of the pro-tozoan parasite of the genus Leishmania known to bepathogenic in humans with a broad range of clinicalmanifestations which are determined not only by thespecies of the infecting parasite but also by the ge-netic makeup and general health of the infected hostThese manifestations include cutaneous leishmaniasis(CL) characterized by skin lesions mucosalmucocu-taneous leishmaniasis (ML) characterized by lesionsof the mucosa visceral leishmaniasis (VL) in whichlesions are disseminated to internal organs includingthe spleen and liver and post-Kala-azar dermal leish-maniasis (PKDL) caused by a persistence of parasitesin the skin following apparent successful treatment ofVL40 This along with the extensive number of vectorsand potential reservoirs for parasite transmissionmakes conventional control measures challenging41

Although treatment options have improved in recentyears becoming safer and more effective it is likelythat elimination will only be achieved through vacci-nation41 The concept of a leishmaniasis vaccine isstrengthened by the observation that most individuals

that have been infected and who recover from the in-fection become resistant to later clinical infection42

Resistance to infection has been associated witha TH1 immune response Increasing evidence suggestshowever that true protection from disease will requirethe involvement of both a TH1 and a TH2 immune re-sponse from vaccination4243 An ideal vaccine willallow for long-lasting immunity to Leishmania infec-tion thereby limiting the need for the use of chemo-therapy However despite an extensive vaccinedevelopment program no vaccine has gone on to li-censure and most have not progressed beyond the re-search and development phase42

The earliest of the first-generation vaccination at-tempts against leishmaniasis included deliberate inocu-lation from one person to another using virulentLeishmania from a cutaneous lesion a practice referredto as leishmanization41 This crude vaccination strategyallowed for the inoculum to be introduced onto an easilyconcealed area of the body thus sparing the person fromfacial or other disfiguring lesions42 From this crude in-noculation technique which has been largely aban-doned as a result of safety concerns vaccineevaluations have switched to trials involving wholekilled parasites as well as trials for inactivated whole-parasite vaccines attempts at the introduction(etc)4142 These early vaccines have been focused onCL and VL and clinical results from first-generationLeishmania vaccines have been inconsistent In addi-tion many of these preparations cannot be standardizedappropriately to be a viable option for licensure givencurrent regulatory considerations41

The work currently being done on the development ofsecond-generation vaccines against leishmaniasis relieson the use of adjuvanted recombinant DNA technolo-gies (Table III) It is believed that new strategies basedon these technologies will be easier to scale up formass dissemination in a cost-effective and reproduciblemanner and will be able to meet the current regulatoryrequirements for vaccines41 Many different recombi-nant proteins have been investigated for their use as pre-ventive and therapeutic vaccine candidates against CLVL PKDL and ML The first candidate of this type tomake it to phase 1 and phase 2 clinical trials wasLEISH-F1 from IDRI (Seattle Wash) LEISH-F1 iscomprised of 3 proteins that are conserved across vari-ous Leishmania species including Leishmania donovaniand Leishmania chagasi causative agents of NewWorld VL and Leishmania braziliensis a causativeagent of both ML and CL in the NewWorld The 3 pro-teins are L braziliensis elongation and initiation factorLeishmania major thiol-specific antioxidant and L ma-jor stress-inducible protein 1 The adjuvant of choicewith the LEISH-F1 vaccine is monophosphoryl lipid

Translational ResearchVolume - Number - Beaumier et al 7

A stable emulsion (MPL-SE) a powerful toll-like re-ceptor 4 (TLR-4) agonist that is derived from the lipo-polysaccharide of Salmonella enterica serovarMinnesota formulated as a stable emulsion Multiplephase 1 trials have been conducted with the LEISH-F1vaccine in the United States Colombia Brazil Peruand India targeting VL and CL and all have shownthe vaccine to be immunogenic safe and well toleratedin populations both with and without a seropositive sub-population leading researchers to believe that it wouldbe unnecessary to prescreen populations for their Leish-mania serostatus prior to administration of this vac-cine44 In addition the LEISH-F1 vaccine has alsodemonstrated some therapeutic significance in patientswith ML when used with chemotherapy45 With thegreat preliminary successes of the LEISH-F1 vaccineIDRI has redesigned this early vaccine candidate andhas taken their new construct (LEISH-F2) throughboth a phase 1 and a phase 2 trial The new candidate in-cludes a redesigned construct without the histidine tagon the N-terminus as well as the replacement ofLys274 with Gln in an effort to overcome possible reg-ulatory concerns and to aid in the manufacturing pro-cess43 The phase 1 trial included 3 injections 14 daysapart with LEISH-F2 (10 mg) 1 MPL-SE (25 mg) asan adjunct to standard chemotherapy in patients withPKDL46 Positive findings related to immunogenicityand safety from the phase 1 trial led to a phase 2 trialin which the efficacy safety and immunogenicity ofthe vaccine was studied after 3 administrations ofLEISH-F2 (10 mg) 1 MPL-SE (25 mg) to treat adultsand adolescents with CL compared with treatmentwith standard chemotherapy47 IDRI is also investigat-ing in a phase 1 trial of healthy adult volunteers theirnew LEISH-F3 vaccine for use against VL TheLEISH-F3 vaccine is a fusion polypeptide made by link-ing in tandem 2 Leishmania proteins residues 1ndash314 ofthe Leishmania infantumdonovani nonspecific nucleo-side hydrolase protein and residues 2-353 of L infantumsterol 24-c-methyltransferase protein The LEISH-F3vaccine is given at 20 mg with either 2 mg or 5 mg of glu-copyranosyl lipid A stable emulsion (GLA-SE) a novelTLR-4-based adjuvant and is compared with adminis-tration of unadjuvanted LEISH-F3 (20 mg)48 This firstphase 1 trial will enroll 36 adult volunteers in Washing-ton state A second phase 1 trial will then take place inIndia where IDRI will transfer its vaccine manufactur-ing process to Gennova Biopharmaceuticals4149

In addition to these advances by IDRI in recentyears other groups are investigating third-generationvaccines including DNA-based vaccines which haveshown great promise in animal models but have yet tobe made available to humans It is also believed that sal-ivary proteins of the sand fly vectors (Phlebotomus and

Lutzomyia spp) known to transmit Leishmania parasitesmay make good vaccine candidates as such manytransmission-blocking vaccines based on this idea arein early preclinical testing The Sabin Vaccine InstitutePDP working in partnership with the Vector MolecularBiology Section Laboratory of Malaria and VectorResearch National Institute of Allergy and InfectiousDiseases NIH (Rockville Md) is currently performingfeasibility studies for the selection preclinical testingand process development and scale-up of sand fly-derived (Lutzomyia spp) candidate antigens

SCHISTOSOMIASIS VACCINE

Human schistosomiasis is a disease manifestationcaused by a series of blood flukes or schistosomesand is most common in areas of extreme poverty inAfrica South America the Middle East and AsiaThese parasites are Schistosoma mansoni Schistosomahaematobium Schistosomamekongi Schistosoma japo-nicum and Schistosoma intercalatum More than 90of the infections are caused by either S haematobiumor S mansoni with almost all of these cases occurringin Sub-Saharan Africa and with the largest number ofcases outside of Africa occurring in Brazil Approxi-mately 200 million people are infected with 120 mil-lion displaying symptoms and 20 million afflictedwith severe disease Still other estimates suggest thatthe actual number of cases may be double or triplethat number because of egg-negative infections5051

S haematobium infections may result in urinary tractcomplications including fibrosis calcification andstructuring Infection with the other aforementioned or-ganisms may cause intestinal and hepatic fibrosis In ad-dition S haematobium eggs deposit in the uteruscervix and lower genital tract to cause female genitalschistosomiasis which is linked to a 3-foldndash4-fold in-crease in risk of acquiring HIVAIDS in Africa8

Currently the treatment for schistosomiasis is prazi-quantel Praziquantel administration is effective againstschistosomes but has its drawbacks such as a high fre-quency of reinfection risk of the development of drug-resistant organisms and the challenges of sustainingtreatment programs51 The availability of an antischisto-somiasis vaccine would be a powerful tool to add to thefight against the scourge of schistosomiasisRecent endeavors show promise for vaccines against

both S mansoni and S haematobium (Table III) The In-stitut Pasteur in Lille has developed Bilhvax a recombi-nant protein vaccine combined with alum that targetsthe schistosome molecule glutathione S-transferase 28kDa This vaccine recently completed phase 1 trials inhealthy male adults in Lille University Hospital inFrance Results reported include that there were no

Translational Research8 Beaumier et al - 2013

severe adverse events detected that were linked withvaccination Althoughminor adverse events were notedthey were limited to pain and swelling around the injec-tion site As a secondary end point the immune re-sponses were measured as a function of both humoraland cellular responses The antibody isotype profilewas predominated by immunoglobulin G1 Two doses(100 mg and 300 mg) of the vaccine were tested andboth induced specific antibody responses with no ap-preciable difference between both dosing strategiesWith regard to a cellular immune response TH2-typecytokines interleukin 13 and interleukin 5 were detectedafter in vitro stimulation of the donorrsquos mononuclearcells with schistosoma haematobium glutathioneS-transferase 28 kDa5253

Another promising vaccine candidate targets the fattyacid binding protein of S mansoni This particular re-combinant protein antigen is Sm14 and is adjuvantedwith GLA-SE A phase 1 clinical trial sponsored bythe Oswaldo Cruz Foundation (FIOCRUZ Brazil) incollaboration with Financiadora Estudos e Projetos forSm14 is currently ongoing in Rio de Janeiro Brazilat the Instituto de Pesquisa Clınica Evandro Chagas(IPEC)-FIOCRUZ This study is enrolling healthyadults who receive 3 doses of the vaccine at 50 mgSm14with 10 mg GLA-SE As this study is currently on-going no results are yet available54

A third encouraging vaccine antigen against S man-soni is S mansoni tetraspanin protein 2 (Sm-TSP-2)Sm-TSP-2 is being developed by the Sabin Vaccine In-stitute PDP and also uses recombinant protein technol-ogy and protein adjuvanted on alum Sm-TSP-2 isa member of the tetraspanin family of proteins and is ex-pressed in the tegument of the parasite In a murinemodel vaccination with Sm-TSP-2 demonstrated a pro-tective effect Although not yet in clinical trials it hasbeen manufactured in collaboration with Aeras (Mary-land) and has entered toxicology studies The clinicaldevelopment plan includes testing with and withoutthe inclusion of GLA-AF from IDRI The current planis to begin phase 1 safety trials in 201349

VACCINES ON THE CUSP ONCHOCERCIASIS ANDCHAGAS

Chagasdisease Chagasdisease in theAmericas repre-sents a substantial health burden and ranks among themost important NTDs in this region with 10 millionpeople believed to be infected55 The causative agentTrypanosoma cruzi is most commonly transmittedthrough the feces of the infected triatomine vectoralthough mother-to-child transmission transfusion andorgan transplantation-associated infection and infectionvia contaminated foods have also emerged as importantroutes of transmission56 Treatments are currently

available however they are costly require lengthyregimens and have the risk of severe adverse eventsThese drugs are also not approved for use in pregnantwomen which is problematic because of the high ratesof vertical transmission and congenital infection53

Current prevention efforts rely on vector control andalthough this has reduced disease incidence it is notbelieved that vector control measures alone will be ableto prevent transmission to humans57 Therefore a widerange of preventive vaccine formulations have beenevaluated throughout the years from the use of wholeparasites to purified or recombinant proteins to viralvectors and DNA vaccines57 Although there arechallenges associated with live vaccines a renewedinterest has been seen recently in live attenuatedvaccines such as the generation of T cruzi mutants forspecific genes Such genes are LYT1 which is believedto play a role in parasite infectivity mediating theescape of the parasite from the acidic parasitophorousvaculole into the cytosol and ECH1 and ECH2 (tandemenoyl-coenzymeA hydratase 1 and 2 genes) thought toplay a key role in amastigote energy metabolism5859

These live attenuated vaccines have been shown toprotect mice from infection55 It has been widely notedthat the outcome of many vaccines against T cruzi inanimal models depends heavily on the formulation usedand the immune response that is induced55 Regardlessof the vaccine platform chosen it is apparent thata strong cellular immune response will need to beinduced and encompass CD81 cell activation andcytotoxic activity to control T cruzi infection throughvaccination57 Many recent studies have been based onrecombinant protein technology recombinant viralvaccine vectors DNA vaccines and heterologousprime-boost vaccination strategies and have shownstrong protection against infection and increasedsurvival of mice It is now believed that for the controlof Chagas disease either a preventive vaccine against Tcruzi or a therapeutic vaccine could be of great value57

Both vaccine strategies would rely on a skewed im-mune response toward a TH1 type leading researchersto believe that the same antigens and vaccine formula-tions may be used for both the prevention of Chagas dis-ease as well as a therapeutic for an ongoing infectionRecent economic modeling has suggested that a thera-peutic vaccine for Chagas would be more cost-effective than a preventive vaccine55

Several different groups are conducting preclinicaltesting of candidate T cruzi vaccines57 The Sabin Vac-cine Institute PDP with the Instituto Carlos Slim de laSalud (Mexico DF Mexico) and in association withthe Laboratorio de Parasitologıa CIR UniversidadAutonoma de Yucatan (Merida Mexico) the Laborator-ios de Biologicos y Reactivos de Mexico (Birmex

Translational ResearchVolume - Number - Beaumier et al 9

Mexico City Mexico) the Centro de Investigacion y deEstudios Avanzados del Instituto Politecnico Nacional(Cinvestav Mexico City Mexico) and the Vector Mo-lecular Biology Section Laboratory of Malaria andVector Research National Institute of Allergy and In-fectious Diseases NIH (Rockville Md) is advancinga therapeutic vaccine from target selection through pro-cess development scale up and manufacturing Thisvaccine is intended to be a bivalent vaccine for the treat-ment of chronic Chagas disease comprised of 2 T cruzirecombinant proteins formulated on either Alhydrogelor Adju-Phos and coadministration with E6020 (EisaiCo Ltd Tokyo Japan) a novel TLR-4 agonist The 2selected novel antigens to advance through develop-ment are Tc24 a T cruzi 24 kDa antigen and TSA-1a T cruzi surface transialidase56 These antigens willbe expressed using a soluble expression system suchas yeast Escherichia coli or baculovirus The vaccineis intended to prevent or delay the onset of chagasic car-diomyopathy in patients with indeterminate Chagas dis-ease or in patients with early-stage disease and mayprevent further transmission of T cruzi56

Onchocerciasis Onchocerciasis transmitted by theblack fly of the genus Simulium is the second leadingcause of infectious blindness in humans worldwide withapproximately 120 million people at risk for the diseasein Africa and Latin America60 Vector and chemotherapyapproaches for onchocerciasis control have been ableto limit the extent and impact of this infection butneither strategy is a permanent solution61 Mountingevidence suggesting that humans can develop a naturallyacquired immunity against Onchocerca volvulus furtherstrengthens the argument for the development of anonchocerciasis vaccine62 The Edna McConnell ClarkFoundation has worked to complement the wealth ofonchocerciasis control programs (OnchocerciasisControl Programme the African Programme forOnchocerciasis Control and the OnchocerciasisElimination Program in the Americas) by dedicatingfunds for immunologic and molecular biologyapproaches to onchocerciasis research63 As a resultthere have been many gains made in the onchocerciasisfield especially in the area of vaccine developmentThese advances include the development of high-qualitycomplementary DNA libraries encompassing manystages of the Onchocerca volvulus life cycle63 It hasalso been shown clearly that mice humans and cattledevelop protective immunity against O volvuluslarvae60 In addition 44 recombinant proteins that werecloned by immunoscreening or other approaches haveyielded 14 potential antigens that have shown significantreduction (35ndash69) of L3 larval survival63

The Sabin Vaccine Institute PDP embarked in col-laboration with the New York Blood Center to estab-

lish a novel strategy of antigen selection that usesa scoring system to screen and rank proteins for effi-cacy in 2 complementary small animal models Fromthese efforts 8 top-ranking O volvulus protective an-tigens have emerged including Ov-CPI-2 a cysteineprotease inhibitor Ov-ALT-1 a filarial specific anti-gen Ov-RAL-2 a nematode-specific surface antigenOv-ASP-1 a homolog of venom allergen 5 and thePR-1 protein family Ov-103 a nematode-specific sur-face antigen Ov-RBP-1 a retinol binding protein Ov-CHI-1 a chitinase and Ov-B20 a nematode-specificsurface antigen60 Through continued efforts in re-search and development of these candidates it is thehope that at least 1 or 2 of these promising targetswould be suitable for a prophylactic vaccine and willmake it to the clinic in the coming years A prophylac-tic vaccine would be used as an additional componentof the already existing arsenal to control onchocercia-sis In addition a vaccine could aid in the reduction ofmicrofilariae burdens thus reducing the potential fortransmission60 Furthermore it would also not dependon current chemotherapy efforts with ivermectin In-stead the vaccine could be administered in communi-ties that have already gone through multiple rounds ofchemotherapy where resistance may become an issuethereby complementing this control measure in an ef-fort to reach the goal of the elimination of onchocerci-asis as a public health issue60

NEXT STEPS

During the next 5 years it is anticipated that severalNTD vaccines could advance into phase 2 and phase 3trials A major issue is what the lsquolsquoend gamersquorsquo will looklike in terms of subsequent steps for licensure andglobal access Most of the NTD vaccines outlinedhere will be among the first vaccine products targetedspecifically only for the bottom billion of the populationand are currently without major backing of a majorpharmaceutical company There are few if any prece-dents for achieving licensure and global access mile-stones without the benefit of major pharmaceuticalsupport Perhaps the closest comparison would be therecent successes of the Serum Institute of India (a devel-oping country vaccine manufacturer) in collaborationwith the Program for Appropriate Technology in Health(PATH Seattle WA a PDP) in producing a meningo-coccal A vaccine for the meningitis belt in Sub-Saharan Africa64

The scale andmagnitude of the major parasitic and re-lated NTDs discussed here are vast and therefore thevaccine development process may be potentially muchmore complex in terms of manufacturing partners li-censing strategies and World Health Organization

Translational Research10 Beaumier et al - 2013

prequalifications and uptake by the disease-endemiccountries most of which are among the most resourcepoor in the world Complicating the global access anduptake of the major NTD vaccines is the observationin preclinical testing that most of these candidate vac-cines are only protective in part similar to the RTSSmalaria vaccine as shown in recent clinical trials65

To date there is really not a clear road map for howsuch partially protective vaccines might be used along-side additional public health control measures such asantiparasitic drugs or in the case of malaria bed netsand other ancillary measures There are also importantquestions that will need to be answered regarding thebest system for incorporating NTD vaccines (egwhether efforts would focus on delivery alongside mea-sles or other infant vaccines as part of the ExpandedProgramme on Immunization or whether these productsmight be delivered in schools such as has been pro-posed with the human papillomavirus vaccine or evenin antenatal clinics) Toward this goal it is essentialthat in parallel with current development detaileddemand-forecasting exercises are performed to get a bet-ter sense of the needs of the end users in low- andmiddle-income countries and some of the major issuesrelated to global access and uptake The challenges ofwidespread distribution of NTD vaccines will be formi-dable but achieving such milestones would representimportant steps toward poverty reduction and achievingthe Millennium Development Goals

REFERENCES

1 AVERT Global HIV and AIDS estimates 2009 and 2010 Avail-

able at httpwwwavertorgworldstatshtm Accessed Novem-

ber 4 2012

2 World Health Organization Tuberculosis fact sheet 2012 Avail-

able at httpwwwwhointmediacentrefactsheetsfs104en

Accessed November 4 2012

3 Hotez PJ The Four Horsemen of the Apocalypse tropical medi-

cine in the fight against plague death famine and war Am J Trop

Med Hyg 2012873ndash10

4 A fall to cheer The Economist 2012 Available at httpwww

economistcomnode21548963 Accessed November 4 2012

5 Hotez PJ Bethony JM Oliveira SC Brindley PJ Loukas A Mul-

tivalent anthelminthic vaccine to prevent hookworm and schisto-

somiasis Expert Rev Vaccines 20087745ndash52

6 Hotez PJ Fenwick A Savioli L Molyneux DH Rescuing the bot-

tom billion through control of neglected tropical diseases Lancet

20093731570ndash5

7 Hotez PJ Empowering women and improving female reproduc-

tive health through control of neglected tropical diseases PLoS

Negl Trop Dis 20093e559

8 Mbabazi PS Andan O Fitzgerald DW Chitsulo L Engels D

Downs JA Examining the relationship between urogenital schis-

tosomiasis and HIV infection PLoS Negl Trop Dis 20115e1396

9 World Health Organization Neglected tropical diseases 2012

Available at httpwwwwhointghoneglected_diseasesen

indexhtml Accessed November 4 2012

10 Hotez P A handful of lsquoantipovertyrsquo vaccines exist for neglected

diseases but the worldrsquos poorest billion people need more Health

Aff 2011301080ndash7

11 Gubler DJ Aedes aegypti and Aedes aegypti-borne disease control

in the 1990s top down or bottom up Charles Franklin Craig lec-

ture Am J Trop Med Hyg 198940571ndash8

12 Kalayanarooj S Vaughn DW Nimmannitya S et al Early clinical

and laboratory indicators of acute dengue illness J Infect Dis

1997176313ndash21

13 Guzman MG Kouri G Dengue an update Lancet Infect Dis

2002233ndash42

14 Centers for Disease Control and Prevention Locally acquired

dengue Key West Florida 2009ndash2010 MMWR Morb Mortal

Wkly Rep 201059577ndash81

15 Halstead SB Immune enhancement of viral infection Prog Al-

lergy 198231301ndash64

16 Sangkawibha N Rojanasuphot S Ahandrik S et al Risk factors

in dengue shock syndrome a prospective epidemiologic study

in Rayong Thailand I The 1980 outbreak Am J Epidemiol

1984120653ndash69

17 Halstead SB Nimmannitya S Yamarat C Russell PK Hemor-

rhagic fever in Thailand recent knowledge regarding etiology

Jpn J Med Sci Biol 19672096ndash103

18 Kliks SC Nimmanitya S Nisalak A Burke DS Evidence that ma-

ternal dengue antibodies are important in the development of den-

gue hemorrhagic fever in infants Am J Trop Med Hyg 198838

411ndash9

19 Kliks SC Nisalak A Brandt WE Wahl L Burke DS Antibody-

dependent enhancement of dengue virus growth in human mono-

cytes as a risk factor for dengue hemorrhagic fever Am J Trop

Med Hyg 198940444ndash51

20 Kurane I Innis BL Nisalak A et al Human T cell responses to

dengue virus antigens proliferative responses and interferon

gamma production J Clin Invest 198983506ndash13

21 Kurane I Meager A Ennis FA Dengue virus-specific human T

cell clones serotype cross-reactive proliferation interferon

gamma production and cytotoxic activity J Exp Med 1989170

763ndash75

22 Mathew A Kurane I Green S et al Predominance of HLA-

restricted cytotoxic T-lymphocyte responses to serotype-cross-

reactive epitopes on nonstructural proteins following natural

secondary dengue virus infection J Virol 1998723999ndash4004

23 Mongkolsapaya J Dejnirattisai W Xu XN et al Original anti-

genic sin and apoptosis in the pathogenesis of dengue hemor-

rhagic fever Nat Med 20039921ndash7

24 National Institute of Allergy and Infectious Diseases Evaluating

the safety and immune response to two admixtures of a tetravalent

dengue virus vaccine 2012 Available at httpclinicaltrialsgovct2

showNCT01506570term5Tetravax-DVamprank53 Accessed No-

vember 4 2012

25 Thomas SJ Endy TP Vaccines for the prevention of dengue de-

velopment update Hum Vaccin 20117674ndash84

26 Sanofi-Pasteur Sanofi Pasteurrsquos dengue vaccine demonstrates

proof of efficacy 2012 Available at 5 wwwsanofipasteurcom

articles1118-sanofi-pasteurrsquos-dengue-vaccine-demonstrates-

proof-of-efficacyhtml Accessed November 2 2012

27 Inviragen Safety and immunogenicity study to assess DENVax

a live attenuated tetravalent vaccine for prevention of dengue fe-

ver 2011 Available at httpclinicaltrialsgovct2show

NCT01224639term5DENVaxamprank51 Accessed November

14 2012

28 US Army Medical Research and Materiel Command A two-

dose primary vaccination study of a tetravalent dengue virus

purified inactivated vaccine vs placebo in healthy adults 2012

Translational Research6 Beaumier et al - 2013

of the protein with its protease activity inactivated bythe mutation of 2 aspartic acid residues at positions97 and 284 to alanine residues39 The Na-APR-1(M74) recombinant protein is produced in partnershipwith Fraunhofer CMB and is expressed using agrobac-teria that is infiltrated into the tobacco plant Nicotianabenthamiana Both antigens are formulated on the alum-based adjuvant Alhydrogel39 In addition the aqueousformulation of glucopyranosyl lipid A aqueous formu-lation (GLA-AF) from IDRI will also be tested as anadditional adjuvant Both antigens have shown encour-aging preclinical data through a vaccinationchallengemodel in both canine and murine models usingAnclyostoma caninum and N americanus respec-tively3339

Currently the Na-GST-1 hookworm vaccine is under-going phase 1 testing as a monovalent vaccine in healthyadults in both Washington DC and Brazil (both ina nonendemic and an endemic area) with and withoutGLA-AF The Na-APR-1(M74) hookworm vaccine isintended to enter phase 1 trials in 2013 in the UnitedStates in healthy adult volunteers and later in popula-tions living in Brazil After successful completion ofboth phase 1 studies these 2 vaccines will be combinedinto a bivalent vaccine by both coadministration and co-formulation and tested in phase 2b and phase 3 efficacystudies in endemic areas of Sub-Saharan Africa andBrazil39

LEISHMANIASIS VACCINE

Leishmaniasis is a vector-borne disease that cur-rently threatens approximately 350 million people atrisk living in endemic areas with 20 species of the pro-tozoan parasite of the genus Leishmania known to bepathogenic in humans with a broad range of clinicalmanifestations which are determined not only by thespecies of the infecting parasite but also by the ge-netic makeup and general health of the infected hostThese manifestations include cutaneous leishmaniasis(CL) characterized by skin lesions mucosalmucocu-taneous leishmaniasis (ML) characterized by lesionsof the mucosa visceral leishmaniasis (VL) in whichlesions are disseminated to internal organs includingthe spleen and liver and post-Kala-azar dermal leish-maniasis (PKDL) caused by a persistence of parasitesin the skin following apparent successful treatment ofVL40 This along with the extensive number of vectorsand potential reservoirs for parasite transmissionmakes conventional control measures challenging41

Although treatment options have improved in recentyears becoming safer and more effective it is likelythat elimination will only be achieved through vacci-nation41 The concept of a leishmaniasis vaccine isstrengthened by the observation that most individuals

that have been infected and who recover from the in-fection become resistant to later clinical infection42

Resistance to infection has been associated witha TH1 immune response Increasing evidence suggestshowever that true protection from disease will requirethe involvement of both a TH1 and a TH2 immune re-sponse from vaccination4243 An ideal vaccine willallow for long-lasting immunity to Leishmania infec-tion thereby limiting the need for the use of chemo-therapy However despite an extensive vaccinedevelopment program no vaccine has gone on to li-censure and most have not progressed beyond the re-search and development phase42

The earliest of the first-generation vaccination at-tempts against leishmaniasis included deliberate inocu-lation from one person to another using virulentLeishmania from a cutaneous lesion a practice referredto as leishmanization41 This crude vaccination strategyallowed for the inoculum to be introduced onto an easilyconcealed area of the body thus sparing the person fromfacial or other disfiguring lesions42 From this crude in-noculation technique which has been largely aban-doned as a result of safety concerns vaccineevaluations have switched to trials involving wholekilled parasites as well as trials for inactivated whole-parasite vaccines attempts at the introduction(etc)4142 These early vaccines have been focused onCL and VL and clinical results from first-generationLeishmania vaccines have been inconsistent In addi-tion many of these preparations cannot be standardizedappropriately to be a viable option for licensure givencurrent regulatory considerations41

The work currently being done on the development ofsecond-generation vaccines against leishmaniasis relieson the use of adjuvanted recombinant DNA technolo-gies (Table III) It is believed that new strategies basedon these technologies will be easier to scale up formass dissemination in a cost-effective and reproduciblemanner and will be able to meet the current regulatoryrequirements for vaccines41 Many different recombi-nant proteins have been investigated for their use as pre-ventive and therapeutic vaccine candidates against CLVL PKDL and ML The first candidate of this type tomake it to phase 1 and phase 2 clinical trials wasLEISH-F1 from IDRI (Seattle Wash) LEISH-F1 iscomprised of 3 proteins that are conserved across vari-ous Leishmania species including Leishmania donovaniand Leishmania chagasi causative agents of NewWorld VL and Leishmania braziliensis a causativeagent of both ML and CL in the NewWorld The 3 pro-teins are L braziliensis elongation and initiation factorLeishmania major thiol-specific antioxidant and L ma-jor stress-inducible protein 1 The adjuvant of choicewith the LEISH-F1 vaccine is monophosphoryl lipid

Translational ResearchVolume - Number - Beaumier et al 7

A stable emulsion (MPL-SE) a powerful toll-like re-ceptor 4 (TLR-4) agonist that is derived from the lipo-polysaccharide of Salmonella enterica serovarMinnesota formulated as a stable emulsion Multiplephase 1 trials have been conducted with the LEISH-F1vaccine in the United States Colombia Brazil Peruand India targeting VL and CL and all have shownthe vaccine to be immunogenic safe and well toleratedin populations both with and without a seropositive sub-population leading researchers to believe that it wouldbe unnecessary to prescreen populations for their Leish-mania serostatus prior to administration of this vac-cine44 In addition the LEISH-F1 vaccine has alsodemonstrated some therapeutic significance in patientswith ML when used with chemotherapy45 With thegreat preliminary successes of the LEISH-F1 vaccineIDRI has redesigned this early vaccine candidate andhas taken their new construct (LEISH-F2) throughboth a phase 1 and a phase 2 trial The new candidate in-cludes a redesigned construct without the histidine tagon the N-terminus as well as the replacement ofLys274 with Gln in an effort to overcome possible reg-ulatory concerns and to aid in the manufacturing pro-cess43 The phase 1 trial included 3 injections 14 daysapart with LEISH-F2 (10 mg) 1 MPL-SE (25 mg) asan adjunct to standard chemotherapy in patients withPKDL46 Positive findings related to immunogenicityand safety from the phase 1 trial led to a phase 2 trialin which the efficacy safety and immunogenicity ofthe vaccine was studied after 3 administrations ofLEISH-F2 (10 mg) 1 MPL-SE (25 mg) to treat adultsand adolescents with CL compared with treatmentwith standard chemotherapy47 IDRI is also investigat-ing in a phase 1 trial of healthy adult volunteers theirnew LEISH-F3 vaccine for use against VL TheLEISH-F3 vaccine is a fusion polypeptide made by link-ing in tandem 2 Leishmania proteins residues 1ndash314 ofthe Leishmania infantumdonovani nonspecific nucleo-side hydrolase protein and residues 2-353 of L infantumsterol 24-c-methyltransferase protein The LEISH-F3vaccine is given at 20 mg with either 2 mg or 5 mg of glu-copyranosyl lipid A stable emulsion (GLA-SE) a novelTLR-4-based adjuvant and is compared with adminis-tration of unadjuvanted LEISH-F3 (20 mg)48 This firstphase 1 trial will enroll 36 adult volunteers in Washing-ton state A second phase 1 trial will then take place inIndia where IDRI will transfer its vaccine manufactur-ing process to Gennova Biopharmaceuticals4149

In addition to these advances by IDRI in recentyears other groups are investigating third-generationvaccines including DNA-based vaccines which haveshown great promise in animal models but have yet tobe made available to humans It is also believed that sal-ivary proteins of the sand fly vectors (Phlebotomus and

Lutzomyia spp) known to transmit Leishmania parasitesmay make good vaccine candidates as such manytransmission-blocking vaccines based on this idea arein early preclinical testing The Sabin Vaccine InstitutePDP working in partnership with the Vector MolecularBiology Section Laboratory of Malaria and VectorResearch National Institute of Allergy and InfectiousDiseases NIH (Rockville Md) is currently performingfeasibility studies for the selection preclinical testingand process development and scale-up of sand fly-derived (Lutzomyia spp) candidate antigens

SCHISTOSOMIASIS VACCINE

Human schistosomiasis is a disease manifestationcaused by a series of blood flukes or schistosomesand is most common in areas of extreme poverty inAfrica South America the Middle East and AsiaThese parasites are Schistosoma mansoni Schistosomahaematobium Schistosomamekongi Schistosoma japo-nicum and Schistosoma intercalatum More than 90of the infections are caused by either S haematobiumor S mansoni with almost all of these cases occurringin Sub-Saharan Africa and with the largest number ofcases outside of Africa occurring in Brazil Approxi-mately 200 million people are infected with 120 mil-lion displaying symptoms and 20 million afflictedwith severe disease Still other estimates suggest thatthe actual number of cases may be double or triplethat number because of egg-negative infections5051

S haematobium infections may result in urinary tractcomplications including fibrosis calcification andstructuring Infection with the other aforementioned or-ganisms may cause intestinal and hepatic fibrosis In ad-dition S haematobium eggs deposit in the uteruscervix and lower genital tract to cause female genitalschistosomiasis which is linked to a 3-foldndash4-fold in-crease in risk of acquiring HIVAIDS in Africa8

Currently the treatment for schistosomiasis is prazi-quantel Praziquantel administration is effective againstschistosomes but has its drawbacks such as a high fre-quency of reinfection risk of the development of drug-resistant organisms and the challenges of sustainingtreatment programs51 The availability of an antischisto-somiasis vaccine would be a powerful tool to add to thefight against the scourge of schistosomiasisRecent endeavors show promise for vaccines against

both S mansoni and S haematobium (Table III) The In-stitut Pasteur in Lille has developed Bilhvax a recombi-nant protein vaccine combined with alum that targetsthe schistosome molecule glutathione S-transferase 28kDa This vaccine recently completed phase 1 trials inhealthy male adults in Lille University Hospital inFrance Results reported include that there were no

Translational Research8 Beaumier et al - 2013

severe adverse events detected that were linked withvaccination Althoughminor adverse events were notedthey were limited to pain and swelling around the injec-tion site As a secondary end point the immune re-sponses were measured as a function of both humoraland cellular responses The antibody isotype profilewas predominated by immunoglobulin G1 Two doses(100 mg and 300 mg) of the vaccine were tested andboth induced specific antibody responses with no ap-preciable difference between both dosing strategiesWith regard to a cellular immune response TH2-typecytokines interleukin 13 and interleukin 5 were detectedafter in vitro stimulation of the donorrsquos mononuclearcells with schistosoma haematobium glutathioneS-transferase 28 kDa5253

Another promising vaccine candidate targets the fattyacid binding protein of S mansoni This particular re-combinant protein antigen is Sm14 and is adjuvantedwith GLA-SE A phase 1 clinical trial sponsored bythe Oswaldo Cruz Foundation (FIOCRUZ Brazil) incollaboration with Financiadora Estudos e Projetos forSm14 is currently ongoing in Rio de Janeiro Brazilat the Instituto de Pesquisa Clınica Evandro Chagas(IPEC)-FIOCRUZ This study is enrolling healthyadults who receive 3 doses of the vaccine at 50 mgSm14with 10 mg GLA-SE As this study is currently on-going no results are yet available54

A third encouraging vaccine antigen against S man-soni is S mansoni tetraspanin protein 2 (Sm-TSP-2)Sm-TSP-2 is being developed by the Sabin Vaccine In-stitute PDP and also uses recombinant protein technol-ogy and protein adjuvanted on alum Sm-TSP-2 isa member of the tetraspanin family of proteins and is ex-pressed in the tegument of the parasite In a murinemodel vaccination with Sm-TSP-2 demonstrated a pro-tective effect Although not yet in clinical trials it hasbeen manufactured in collaboration with Aeras (Mary-land) and has entered toxicology studies The clinicaldevelopment plan includes testing with and withoutthe inclusion of GLA-AF from IDRI The current planis to begin phase 1 safety trials in 201349

VACCINES ON THE CUSP ONCHOCERCIASIS ANDCHAGAS

Chagasdisease Chagasdisease in theAmericas repre-sents a substantial health burden and ranks among themost important NTDs in this region with 10 millionpeople believed to be infected55 The causative agentTrypanosoma cruzi is most commonly transmittedthrough the feces of the infected triatomine vectoralthough mother-to-child transmission transfusion andorgan transplantation-associated infection and infectionvia contaminated foods have also emerged as importantroutes of transmission56 Treatments are currently

available however they are costly require lengthyregimens and have the risk of severe adverse eventsThese drugs are also not approved for use in pregnantwomen which is problematic because of the high ratesof vertical transmission and congenital infection53

Current prevention efforts rely on vector control andalthough this has reduced disease incidence it is notbelieved that vector control measures alone will be ableto prevent transmission to humans57 Therefore a widerange of preventive vaccine formulations have beenevaluated throughout the years from the use of wholeparasites to purified or recombinant proteins to viralvectors and DNA vaccines57 Although there arechallenges associated with live vaccines a renewedinterest has been seen recently in live attenuatedvaccines such as the generation of T cruzi mutants forspecific genes Such genes are LYT1 which is believedto play a role in parasite infectivity mediating theescape of the parasite from the acidic parasitophorousvaculole into the cytosol and ECH1 and ECH2 (tandemenoyl-coenzymeA hydratase 1 and 2 genes) thought toplay a key role in amastigote energy metabolism5859

These live attenuated vaccines have been shown toprotect mice from infection55 It has been widely notedthat the outcome of many vaccines against T cruzi inanimal models depends heavily on the formulation usedand the immune response that is induced55 Regardlessof the vaccine platform chosen it is apparent thata strong cellular immune response will need to beinduced and encompass CD81 cell activation andcytotoxic activity to control T cruzi infection throughvaccination57 Many recent studies have been based onrecombinant protein technology recombinant viralvaccine vectors DNA vaccines and heterologousprime-boost vaccination strategies and have shownstrong protection against infection and increasedsurvival of mice It is now believed that for the controlof Chagas disease either a preventive vaccine against Tcruzi or a therapeutic vaccine could be of great value57

Both vaccine strategies would rely on a skewed im-mune response toward a TH1 type leading researchersto believe that the same antigens and vaccine formula-tions may be used for both the prevention of Chagas dis-ease as well as a therapeutic for an ongoing infectionRecent economic modeling has suggested that a thera-peutic vaccine for Chagas would be more cost-effective than a preventive vaccine55

Several different groups are conducting preclinicaltesting of candidate T cruzi vaccines57 The Sabin Vac-cine Institute PDP with the Instituto Carlos Slim de laSalud (Mexico DF Mexico) and in association withthe Laboratorio de Parasitologıa CIR UniversidadAutonoma de Yucatan (Merida Mexico) the Laborator-ios de Biologicos y Reactivos de Mexico (Birmex

Translational ResearchVolume - Number - Beaumier et al 9

Mexico City Mexico) the Centro de Investigacion y deEstudios Avanzados del Instituto Politecnico Nacional(Cinvestav Mexico City Mexico) and the Vector Mo-lecular Biology Section Laboratory of Malaria andVector Research National Institute of Allergy and In-fectious Diseases NIH (Rockville Md) is advancinga therapeutic vaccine from target selection through pro-cess development scale up and manufacturing Thisvaccine is intended to be a bivalent vaccine for the treat-ment of chronic Chagas disease comprised of 2 T cruzirecombinant proteins formulated on either Alhydrogelor Adju-Phos and coadministration with E6020 (EisaiCo Ltd Tokyo Japan) a novel TLR-4 agonist The 2selected novel antigens to advance through develop-ment are Tc24 a T cruzi 24 kDa antigen and TSA-1a T cruzi surface transialidase56 These antigens willbe expressed using a soluble expression system suchas yeast Escherichia coli or baculovirus The vaccineis intended to prevent or delay the onset of chagasic car-diomyopathy in patients with indeterminate Chagas dis-ease or in patients with early-stage disease and mayprevent further transmission of T cruzi56

Onchocerciasis Onchocerciasis transmitted by theblack fly of the genus Simulium is the second leadingcause of infectious blindness in humans worldwide withapproximately 120 million people at risk for the diseasein Africa and Latin America60 Vector and chemotherapyapproaches for onchocerciasis control have been ableto limit the extent and impact of this infection butneither strategy is a permanent solution61 Mountingevidence suggesting that humans can develop a naturallyacquired immunity against Onchocerca volvulus furtherstrengthens the argument for the development of anonchocerciasis vaccine62 The Edna McConnell ClarkFoundation has worked to complement the wealth ofonchocerciasis control programs (OnchocerciasisControl Programme the African Programme forOnchocerciasis Control and the OnchocerciasisElimination Program in the Americas) by dedicatingfunds for immunologic and molecular biologyapproaches to onchocerciasis research63 As a resultthere have been many gains made in the onchocerciasisfield especially in the area of vaccine developmentThese advances include the development of high-qualitycomplementary DNA libraries encompassing manystages of the Onchocerca volvulus life cycle63 It hasalso been shown clearly that mice humans and cattledevelop protective immunity against O volvuluslarvae60 In addition 44 recombinant proteins that werecloned by immunoscreening or other approaches haveyielded 14 potential antigens that have shown significantreduction (35ndash69) of L3 larval survival63

The Sabin Vaccine Institute PDP embarked in col-laboration with the New York Blood Center to estab-

lish a novel strategy of antigen selection that usesa scoring system to screen and rank proteins for effi-cacy in 2 complementary small animal models Fromthese efforts 8 top-ranking O volvulus protective an-tigens have emerged including Ov-CPI-2 a cysteineprotease inhibitor Ov-ALT-1 a filarial specific anti-gen Ov-RAL-2 a nematode-specific surface antigenOv-ASP-1 a homolog of venom allergen 5 and thePR-1 protein family Ov-103 a nematode-specific sur-face antigen Ov-RBP-1 a retinol binding protein Ov-CHI-1 a chitinase and Ov-B20 a nematode-specificsurface antigen60 Through continued efforts in re-search and development of these candidates it is thehope that at least 1 or 2 of these promising targetswould be suitable for a prophylactic vaccine and willmake it to the clinic in the coming years A prophylac-tic vaccine would be used as an additional componentof the already existing arsenal to control onchocercia-sis In addition a vaccine could aid in the reduction ofmicrofilariae burdens thus reducing the potential fortransmission60 Furthermore it would also not dependon current chemotherapy efforts with ivermectin In-stead the vaccine could be administered in communi-ties that have already gone through multiple rounds ofchemotherapy where resistance may become an issuethereby complementing this control measure in an ef-fort to reach the goal of the elimination of onchocerci-asis as a public health issue60

NEXT STEPS

During the next 5 years it is anticipated that severalNTD vaccines could advance into phase 2 and phase 3trials A major issue is what the lsquolsquoend gamersquorsquo will looklike in terms of subsequent steps for licensure andglobal access Most of the NTD vaccines outlinedhere will be among the first vaccine products targetedspecifically only for the bottom billion of the populationand are currently without major backing of a majorpharmaceutical company There are few if any prece-dents for achieving licensure and global access mile-stones without the benefit of major pharmaceuticalsupport Perhaps the closest comparison would be therecent successes of the Serum Institute of India (a devel-oping country vaccine manufacturer) in collaborationwith the Program for Appropriate Technology in Health(PATH Seattle WA a PDP) in producing a meningo-coccal A vaccine for the meningitis belt in Sub-Saharan Africa64

The scale andmagnitude of the major parasitic and re-lated NTDs discussed here are vast and therefore thevaccine development process may be potentially muchmore complex in terms of manufacturing partners li-censing strategies and World Health Organization

Translational Research10 Beaumier et al - 2013

prequalifications and uptake by the disease-endemiccountries most of which are among the most resourcepoor in the world Complicating the global access anduptake of the major NTD vaccines is the observationin preclinical testing that most of these candidate vac-cines are only protective in part similar to the RTSSmalaria vaccine as shown in recent clinical trials65

To date there is really not a clear road map for howsuch partially protective vaccines might be used along-side additional public health control measures such asantiparasitic drugs or in the case of malaria bed netsand other ancillary measures There are also importantquestions that will need to be answered regarding thebest system for incorporating NTD vaccines (egwhether efforts would focus on delivery alongside mea-sles or other infant vaccines as part of the ExpandedProgramme on Immunization or whether these productsmight be delivered in schools such as has been pro-posed with the human papillomavirus vaccine or evenin antenatal clinics) Toward this goal it is essentialthat in parallel with current development detaileddemand-forecasting exercises are performed to get a bet-ter sense of the needs of the end users in low- andmiddle-income countries and some of the major issuesrelated to global access and uptake The challenges ofwidespread distribution of NTD vaccines will be formi-dable but achieving such milestones would representimportant steps toward poverty reduction and achievingthe Millennium Development Goals

REFERENCES

1 AVERT Global HIV and AIDS estimates 2009 and 2010 Avail-

able at httpwwwavertorgworldstatshtm Accessed Novem-

ber 4 2012

2 World Health Organization Tuberculosis fact sheet 2012 Avail-

able at httpwwwwhointmediacentrefactsheetsfs104en

Accessed November 4 2012

3 Hotez PJ The Four Horsemen of the Apocalypse tropical medi-

cine in the fight against plague death famine and war Am J Trop

Med Hyg 2012873ndash10

4 A fall to cheer The Economist 2012 Available at httpwww

economistcomnode21548963 Accessed November 4 2012

5 Hotez PJ Bethony JM Oliveira SC Brindley PJ Loukas A Mul-

tivalent anthelminthic vaccine to prevent hookworm and schisto-

somiasis Expert Rev Vaccines 20087745ndash52

6 Hotez PJ Fenwick A Savioli L Molyneux DH Rescuing the bot-

tom billion through control of neglected tropical diseases Lancet

20093731570ndash5

7 Hotez PJ Empowering women and improving female reproduc-

tive health through control of neglected tropical diseases PLoS

Negl Trop Dis 20093e559

8 Mbabazi PS Andan O Fitzgerald DW Chitsulo L Engels D

Downs JA Examining the relationship between urogenital schis-

tosomiasis and HIV infection PLoS Negl Trop Dis 20115e1396

9 World Health Organization Neglected tropical diseases 2012

Available at httpwwwwhointghoneglected_diseasesen

indexhtml Accessed November 4 2012

10 Hotez P A handful of lsquoantipovertyrsquo vaccines exist for neglected

diseases but the worldrsquos poorest billion people need more Health

Aff 2011301080ndash7

11 Gubler DJ Aedes aegypti and Aedes aegypti-borne disease control

in the 1990s top down or bottom up Charles Franklin Craig lec-

ture Am J Trop Med Hyg 198940571ndash8

12 Kalayanarooj S Vaughn DW Nimmannitya S et al Early clinical

and laboratory indicators of acute dengue illness J Infect Dis

1997176313ndash21

13 Guzman MG Kouri G Dengue an update Lancet Infect Dis

2002233ndash42

14 Centers for Disease Control and Prevention Locally acquired

dengue Key West Florida 2009ndash2010 MMWR Morb Mortal

Wkly Rep 201059577ndash81

15 Halstead SB Immune enhancement of viral infection Prog Al-

lergy 198231301ndash64

16 Sangkawibha N Rojanasuphot S Ahandrik S et al Risk factors

in dengue shock syndrome a prospective epidemiologic study

in Rayong Thailand I The 1980 outbreak Am J Epidemiol

1984120653ndash69

17 Halstead SB Nimmannitya S Yamarat C Russell PK Hemor-

rhagic fever in Thailand recent knowledge regarding etiology

Jpn J Med Sci Biol 19672096ndash103

18 Kliks SC Nimmanitya S Nisalak A Burke DS Evidence that ma-

ternal dengue antibodies are important in the development of den-

gue hemorrhagic fever in infants Am J Trop Med Hyg 198838

411ndash9

19 Kliks SC Nisalak A Brandt WE Wahl L Burke DS Antibody-

dependent enhancement of dengue virus growth in human mono-

cytes as a risk factor for dengue hemorrhagic fever Am J Trop

Med Hyg 198940444ndash51

20 Kurane I Innis BL Nisalak A et al Human T cell responses to

dengue virus antigens proliferative responses and interferon

gamma production J Clin Invest 198983506ndash13

21 Kurane I Meager A Ennis FA Dengue virus-specific human T

cell clones serotype cross-reactive proliferation interferon

gamma production and cytotoxic activity J Exp Med 1989170

763ndash75

22 Mathew A Kurane I Green S et al Predominance of HLA-

restricted cytotoxic T-lymphocyte responses to serotype-cross-

reactive epitopes on nonstructural proteins following natural

secondary dengue virus infection J Virol 1998723999ndash4004

23 Mongkolsapaya J Dejnirattisai W Xu XN et al Original anti-

genic sin and apoptosis in the pathogenesis of dengue hemor-

rhagic fever Nat Med 20039921ndash7

24 National Institute of Allergy and Infectious Diseases Evaluating

the safety and immune response to two admixtures of a tetravalent

dengue virus vaccine 2012 Available at httpclinicaltrialsgovct2

showNCT01506570term5Tetravax-DVamprank53 Accessed No-

vember 4 2012

25 Thomas SJ Endy TP Vaccines for the prevention of dengue de-

velopment update Hum Vaccin 20117674ndash84

26 Sanofi-Pasteur Sanofi Pasteurrsquos dengue vaccine demonstrates

proof of efficacy 2012 Available at 5 wwwsanofipasteurcom

articles1118-sanofi-pasteurrsquos-dengue-vaccine-demonstrates-

proof-of-efficacyhtml Accessed November 2 2012

27 Inviragen Safety and immunogenicity study to assess DENVax

a live attenuated tetravalent vaccine for prevention of dengue fe-

ver 2011 Available at httpclinicaltrialsgovct2show

NCT01224639term5DENVaxamprank51 Accessed November

14 2012

28 US Army Medical Research and Materiel Command A two-

dose primary vaccination study of a tetravalent dengue virus

purified inactivated vaccine vs placebo in healthy adults 2012

Translational ResearchVolume - Number - Beaumier et al 7

A stable emulsion (MPL-SE) a powerful toll-like re-ceptor 4 (TLR-4) agonist that is derived from the lipo-polysaccharide of Salmonella enterica serovarMinnesota formulated as a stable emulsion Multiplephase 1 trials have been conducted with the LEISH-F1vaccine in the United States Colombia Brazil Peruand India targeting VL and CL and all have shownthe vaccine to be immunogenic safe and well toleratedin populations both with and without a seropositive sub-population leading researchers to believe that it wouldbe unnecessary to prescreen populations for their Leish-mania serostatus prior to administration of this vac-cine44 In addition the LEISH-F1 vaccine has alsodemonstrated some therapeutic significance in patientswith ML when used with chemotherapy45 With thegreat preliminary successes of the LEISH-F1 vaccineIDRI has redesigned this early vaccine candidate andhas taken their new construct (LEISH-F2) throughboth a phase 1 and a phase 2 trial The new candidate in-cludes a redesigned construct without the histidine tagon the N-terminus as well as the replacement ofLys274 with Gln in an effort to overcome possible reg-ulatory concerns and to aid in the manufacturing pro-cess43 The phase 1 trial included 3 injections 14 daysapart with LEISH-F2 (10 mg) 1 MPL-SE (25 mg) asan adjunct to standard chemotherapy in patients withPKDL46 Positive findings related to immunogenicityand safety from the phase 1 trial led to a phase 2 trialin which the efficacy safety and immunogenicity ofthe vaccine was studied after 3 administrations ofLEISH-F2 (10 mg) 1 MPL-SE (25 mg) to treat adultsand adolescents with CL compared with treatmentwith standard chemotherapy47 IDRI is also investigat-ing in a phase 1 trial of healthy adult volunteers theirnew LEISH-F3 vaccine for use against VL TheLEISH-F3 vaccine is a fusion polypeptide made by link-ing in tandem 2 Leishmania proteins residues 1ndash314 ofthe Leishmania infantumdonovani nonspecific nucleo-side hydrolase protein and residues 2-353 of L infantumsterol 24-c-methyltransferase protein The LEISH-F3vaccine is given at 20 mg with either 2 mg or 5 mg of glu-copyranosyl lipid A stable emulsion (GLA-SE) a novelTLR-4-based adjuvant and is compared with adminis-tration of unadjuvanted LEISH-F3 (20 mg)48 This firstphase 1 trial will enroll 36 adult volunteers in Washing-ton state A second phase 1 trial will then take place inIndia where IDRI will transfer its vaccine manufactur-ing process to Gennova Biopharmaceuticals4149

In addition to these advances by IDRI in recentyears other groups are investigating third-generationvaccines including DNA-based vaccines which haveshown great promise in animal models but have yet tobe made available to humans It is also believed that sal-ivary proteins of the sand fly vectors (Phlebotomus and

Lutzomyia spp) known to transmit Leishmania parasitesmay make good vaccine candidates as such manytransmission-blocking vaccines based on this idea arein early preclinical testing The Sabin Vaccine InstitutePDP working in partnership with the Vector MolecularBiology Section Laboratory of Malaria and VectorResearch National Institute of Allergy and InfectiousDiseases NIH (Rockville Md) is currently performingfeasibility studies for the selection preclinical testingand process development and scale-up of sand fly-derived (Lutzomyia spp) candidate antigens

SCHISTOSOMIASIS VACCINE

Human schistosomiasis is a disease manifestationcaused by a series of blood flukes or schistosomesand is most common in areas of extreme poverty inAfrica South America the Middle East and AsiaThese parasites are Schistosoma mansoni Schistosomahaematobium Schistosomamekongi Schistosoma japo-nicum and Schistosoma intercalatum More than 90of the infections are caused by either S haematobiumor S mansoni with almost all of these cases occurringin Sub-Saharan Africa and with the largest number ofcases outside of Africa occurring in Brazil Approxi-mately 200 million people are infected with 120 mil-lion displaying symptoms and 20 million afflictedwith severe disease Still other estimates suggest thatthe actual number of cases may be double or triplethat number because of egg-negative infections5051

S haematobium infections may result in urinary tractcomplications including fibrosis calcification andstructuring Infection with the other aforementioned or-ganisms may cause intestinal and hepatic fibrosis In ad-dition S haematobium eggs deposit in the uteruscervix and lower genital tract to cause female genitalschistosomiasis which is linked to a 3-foldndash4-fold in-crease in risk of acquiring HIVAIDS in Africa8

Currently the treatment for schistosomiasis is prazi-quantel Praziquantel administration is effective againstschistosomes but has its drawbacks such as a high fre-quency of reinfection risk of the development of drug-resistant organisms and the challenges of sustainingtreatment programs51 The availability of an antischisto-somiasis vaccine would be a powerful tool to add to thefight against the scourge of schistosomiasisRecent endeavors show promise for vaccines against

both S mansoni and S haematobium (Table III) The In-stitut Pasteur in Lille has developed Bilhvax a recombi-nant protein vaccine combined with alum that targetsthe schistosome molecule glutathione S-transferase 28kDa This vaccine recently completed phase 1 trials inhealthy male adults in Lille University Hospital inFrance Results reported include that there were no

Translational Research8 Beaumier et al - 2013

severe adverse events detected that were linked withvaccination Althoughminor adverse events were notedthey were limited to pain and swelling around the injec-tion site As a secondary end point the immune re-sponses were measured as a function of both humoraland cellular responses The antibody isotype profilewas predominated by immunoglobulin G1 Two doses(100 mg and 300 mg) of the vaccine were tested andboth induced specific antibody responses with no ap-preciable difference between both dosing strategiesWith regard to a cellular immune response TH2-typecytokines interleukin 13 and interleukin 5 were detectedafter in vitro stimulation of the donorrsquos mononuclearcells with schistosoma haematobium glutathioneS-transferase 28 kDa5253

Another promising vaccine candidate targets the fattyacid binding protein of S mansoni This particular re-combinant protein antigen is Sm14 and is adjuvantedwith GLA-SE A phase 1 clinical trial sponsored bythe Oswaldo Cruz Foundation (FIOCRUZ Brazil) incollaboration with Financiadora Estudos e Projetos forSm14 is currently ongoing in Rio de Janeiro Brazilat the Instituto de Pesquisa Clınica Evandro Chagas(IPEC)-FIOCRUZ This study is enrolling healthyadults who receive 3 doses of the vaccine at 50 mgSm14with 10 mg GLA-SE As this study is currently on-going no results are yet available54

A third encouraging vaccine antigen against S man-soni is S mansoni tetraspanin protein 2 (Sm-TSP-2)Sm-TSP-2 is being developed by the Sabin Vaccine In-stitute PDP and also uses recombinant protein technol-ogy and protein adjuvanted on alum Sm-TSP-2 isa member of the tetraspanin family of proteins and is ex-pressed in the tegument of the parasite In a murinemodel vaccination with Sm-TSP-2 demonstrated a pro-tective effect Although not yet in clinical trials it hasbeen manufactured in collaboration with Aeras (Mary-land) and has entered toxicology studies The clinicaldevelopment plan includes testing with and withoutthe inclusion of GLA-AF from IDRI The current planis to begin phase 1 safety trials in 201349

VACCINES ON THE CUSP ONCHOCERCIASIS ANDCHAGAS

Chagasdisease Chagasdisease in theAmericas repre-sents a substantial health burden and ranks among themost important NTDs in this region with 10 millionpeople believed to be infected55 The causative agentTrypanosoma cruzi is most commonly transmittedthrough the feces of the infected triatomine vectoralthough mother-to-child transmission transfusion andorgan transplantation-associated infection and infectionvia contaminated foods have also emerged as importantroutes of transmission56 Treatments are currently

available however they are costly require lengthyregimens and have the risk of severe adverse eventsThese drugs are also not approved for use in pregnantwomen which is problematic because of the high ratesof vertical transmission and congenital infection53

Current prevention efforts rely on vector control andalthough this has reduced disease incidence it is notbelieved that vector control measures alone will be ableto prevent transmission to humans57 Therefore a widerange of preventive vaccine formulations have beenevaluated throughout the years from the use of wholeparasites to purified or recombinant proteins to viralvectors and DNA vaccines57 Although there arechallenges associated with live vaccines a renewedinterest has been seen recently in live attenuatedvaccines such as the generation of T cruzi mutants forspecific genes Such genes are LYT1 which is believedto play a role in parasite infectivity mediating theescape of the parasite from the acidic parasitophorousvaculole into the cytosol and ECH1 and ECH2 (tandemenoyl-coenzymeA hydratase 1 and 2 genes) thought toplay a key role in amastigote energy metabolism5859

These live attenuated vaccines have been shown toprotect mice from infection55 It has been widely notedthat the outcome of many vaccines against T cruzi inanimal models depends heavily on the formulation usedand the immune response that is induced55 Regardlessof the vaccine platform chosen it is apparent thata strong cellular immune response will need to beinduced and encompass CD81 cell activation andcytotoxic activity to control T cruzi infection throughvaccination57 Many recent studies have been based onrecombinant protein technology recombinant viralvaccine vectors DNA vaccines and heterologousprime-boost vaccination strategies and have shownstrong protection against infection and increasedsurvival of mice It is now believed that for the controlof Chagas disease either a preventive vaccine against Tcruzi or a therapeutic vaccine could be of great value57

Both vaccine strategies would rely on a skewed im-mune response toward a TH1 type leading researchersto believe that the same antigens and vaccine formula-tions may be used for both the prevention of Chagas dis-ease as well as a therapeutic for an ongoing infectionRecent economic modeling has suggested that a thera-peutic vaccine for Chagas would be more cost-effective than a preventive vaccine55

Several different groups are conducting preclinicaltesting of candidate T cruzi vaccines57 The Sabin Vac-cine Institute PDP with the Instituto Carlos Slim de laSalud (Mexico DF Mexico) and in association withthe Laboratorio de Parasitologıa CIR UniversidadAutonoma de Yucatan (Merida Mexico) the Laborator-ios de Biologicos y Reactivos de Mexico (Birmex

Translational ResearchVolume - Number - Beaumier et al 9

Mexico City Mexico) the Centro de Investigacion y deEstudios Avanzados del Instituto Politecnico Nacional(Cinvestav Mexico City Mexico) and the Vector Mo-lecular Biology Section Laboratory of Malaria andVector Research National Institute of Allergy and In-fectious Diseases NIH (Rockville Md) is advancinga therapeutic vaccine from target selection through pro-cess development scale up and manufacturing Thisvaccine is intended to be a bivalent vaccine for the treat-ment of chronic Chagas disease comprised of 2 T cruzirecombinant proteins formulated on either Alhydrogelor Adju-Phos and coadministration with E6020 (EisaiCo Ltd Tokyo Japan) a novel TLR-4 agonist The 2selected novel antigens to advance through develop-ment are Tc24 a T cruzi 24 kDa antigen and TSA-1a T cruzi surface transialidase56 These antigens willbe expressed using a soluble expression system suchas yeast Escherichia coli or baculovirus The vaccineis intended to prevent or delay the onset of chagasic car-diomyopathy in patients with indeterminate Chagas dis-ease or in patients with early-stage disease and mayprevent further transmission of T cruzi56

Onchocerciasis Onchocerciasis transmitted by theblack fly of the genus Simulium is the second leadingcause of infectious blindness in humans worldwide withapproximately 120 million people at risk for the diseasein Africa and Latin America60 Vector and chemotherapyapproaches for onchocerciasis control have been ableto limit the extent and impact of this infection butneither strategy is a permanent solution61 Mountingevidence suggesting that humans can develop a naturallyacquired immunity against Onchocerca volvulus furtherstrengthens the argument for the development of anonchocerciasis vaccine62 The Edna McConnell ClarkFoundation has worked to complement the wealth ofonchocerciasis control programs (OnchocerciasisControl Programme the African Programme forOnchocerciasis Control and the OnchocerciasisElimination Program in the Americas) by dedicatingfunds for immunologic and molecular biologyapproaches to onchocerciasis research63 As a resultthere have been many gains made in the onchocerciasisfield especially in the area of vaccine developmentThese advances include the development of high-qualitycomplementary DNA libraries encompassing manystages of the Onchocerca volvulus life cycle63 It hasalso been shown clearly that mice humans and cattledevelop protective immunity against O volvuluslarvae60 In addition 44 recombinant proteins that werecloned by immunoscreening or other approaches haveyielded 14 potential antigens that have shown significantreduction (35ndash69) of L3 larval survival63

The Sabin Vaccine Institute PDP embarked in col-laboration with the New York Blood Center to estab-

lish a novel strategy of antigen selection that usesa scoring system to screen and rank proteins for effi-cacy in 2 complementary small animal models Fromthese efforts 8 top-ranking O volvulus protective an-tigens have emerged including Ov-CPI-2 a cysteineprotease inhibitor Ov-ALT-1 a filarial specific anti-gen Ov-RAL-2 a nematode-specific surface antigenOv-ASP-1 a homolog of venom allergen 5 and thePR-1 protein family Ov-103 a nematode-specific sur-face antigen Ov-RBP-1 a retinol binding protein Ov-CHI-1 a chitinase and Ov-B20 a nematode-specificsurface antigen60 Through continued efforts in re-search and development of these candidates it is thehope that at least 1 or 2 of these promising targetswould be suitable for a prophylactic vaccine and willmake it to the clinic in the coming years A prophylac-tic vaccine would be used as an additional componentof the already existing arsenal to control onchocercia-sis In addition a vaccine could aid in the reduction ofmicrofilariae burdens thus reducing the potential fortransmission60 Furthermore it would also not dependon current chemotherapy efforts with ivermectin In-stead the vaccine could be administered in communi-ties that have already gone through multiple rounds ofchemotherapy where resistance may become an issuethereby complementing this control measure in an ef-fort to reach the goal of the elimination of onchocerci-asis as a public health issue60

NEXT STEPS

During the next 5 years it is anticipated that severalNTD vaccines could advance into phase 2 and phase 3trials A major issue is what the lsquolsquoend gamersquorsquo will looklike in terms of subsequent steps for licensure andglobal access Most of the NTD vaccines outlinedhere will be among the first vaccine products targetedspecifically only for the bottom billion of the populationand are currently without major backing of a majorpharmaceutical company There are few if any prece-dents for achieving licensure and global access mile-stones without the benefit of major pharmaceuticalsupport Perhaps the closest comparison would be therecent successes of the Serum Institute of India (a devel-oping country vaccine manufacturer) in collaborationwith the Program for Appropriate Technology in Health(PATH Seattle WA a PDP) in producing a meningo-coccal A vaccine for the meningitis belt in Sub-Saharan Africa64

The scale andmagnitude of the major parasitic and re-lated NTDs discussed here are vast and therefore thevaccine development process may be potentially muchmore complex in terms of manufacturing partners li-censing strategies and World Health Organization

Translational Research10 Beaumier et al - 2013

prequalifications and uptake by the disease-endemiccountries most of which are among the most resourcepoor in the world Complicating the global access anduptake of the major NTD vaccines is the observationin preclinical testing that most of these candidate vac-cines are only protective in part similar to the RTSSmalaria vaccine as shown in recent clinical trials65

To date there is really not a clear road map for howsuch partially protective vaccines might be used along-side additional public health control measures such asantiparasitic drugs or in the case of malaria bed netsand other ancillary measures There are also importantquestions that will need to be answered regarding thebest system for incorporating NTD vaccines (egwhether efforts would focus on delivery alongside mea-sles or other infant vaccines as part of the ExpandedProgramme on Immunization or whether these productsmight be delivered in schools such as has been pro-posed with the human papillomavirus vaccine or evenin antenatal clinics) Toward this goal it is essentialthat in parallel with current development detaileddemand-forecasting exercises are performed to get a bet-ter sense of the needs of the end users in low- andmiddle-income countries and some of the major issuesrelated to global access and uptake The challenges ofwidespread distribution of NTD vaccines will be formi-dable but achieving such milestones would representimportant steps toward poverty reduction and achievingthe Millennium Development Goals

REFERENCES

1 AVERT Global HIV and AIDS estimates 2009 and 2010 Avail-

able at httpwwwavertorgworldstatshtm Accessed Novem-

ber 4 2012

2 World Health Organization Tuberculosis fact sheet 2012 Avail-

able at httpwwwwhointmediacentrefactsheetsfs104en

Accessed November 4 2012

3 Hotez PJ The Four Horsemen of the Apocalypse tropical medi-

cine in the fight against plague death famine and war Am J Trop

Med Hyg 2012873ndash10

4 A fall to cheer The Economist 2012 Available at httpwww

economistcomnode21548963 Accessed November 4 2012

5 Hotez PJ Bethony JM Oliveira SC Brindley PJ Loukas A Mul-

tivalent anthelminthic vaccine to prevent hookworm and schisto-

somiasis Expert Rev Vaccines 20087745ndash52

6 Hotez PJ Fenwick A Savioli L Molyneux DH Rescuing the bot-

tom billion through control of neglected tropical diseases Lancet

20093731570ndash5

7 Hotez PJ Empowering women and improving female reproduc-

tive health through control of neglected tropical diseases PLoS

Negl Trop Dis 20093e559

8 Mbabazi PS Andan O Fitzgerald DW Chitsulo L Engels D

Downs JA Examining the relationship between urogenital schis-

tosomiasis and HIV infection PLoS Negl Trop Dis 20115e1396

9 World Health Organization Neglected tropical diseases 2012

Available at httpwwwwhointghoneglected_diseasesen

indexhtml Accessed November 4 2012

10 Hotez P A handful of lsquoantipovertyrsquo vaccines exist for neglected

diseases but the worldrsquos poorest billion people need more Health

Aff 2011301080ndash7

11 Gubler DJ Aedes aegypti and Aedes aegypti-borne disease control

in the 1990s top down or bottom up Charles Franklin Craig lec-

ture Am J Trop Med Hyg 198940571ndash8

12 Kalayanarooj S Vaughn DW Nimmannitya S et al Early clinical

and laboratory indicators of acute dengue illness J Infect Dis

1997176313ndash21

13 Guzman MG Kouri G Dengue an update Lancet Infect Dis

2002233ndash42

14 Centers for Disease Control and Prevention Locally acquired

dengue Key West Florida 2009ndash2010 MMWR Morb Mortal

Wkly Rep 201059577ndash81

15 Halstead SB Immune enhancement of viral infection Prog Al-

lergy 198231301ndash64

16 Sangkawibha N Rojanasuphot S Ahandrik S et al Risk factors

in dengue shock syndrome a prospective epidemiologic study

in Rayong Thailand I The 1980 outbreak Am J Epidemiol

1984120653ndash69

17 Halstead SB Nimmannitya S Yamarat C Russell PK Hemor-

rhagic fever in Thailand recent knowledge regarding etiology

Jpn J Med Sci Biol 19672096ndash103

18 Kliks SC Nimmanitya S Nisalak A Burke DS Evidence that ma-

ternal dengue antibodies are important in the development of den-

gue hemorrhagic fever in infants Am J Trop Med Hyg 198838

411ndash9

19 Kliks SC Nisalak A Brandt WE Wahl L Burke DS Antibody-

dependent enhancement of dengue virus growth in human mono-

cytes as a risk factor for dengue hemorrhagic fever Am J Trop

Med Hyg 198940444ndash51

20 Kurane I Innis BL Nisalak A et al Human T cell responses to

dengue virus antigens proliferative responses and interferon

gamma production J Clin Invest 198983506ndash13

21 Kurane I Meager A Ennis FA Dengue virus-specific human T

cell clones serotype cross-reactive proliferation interferon

gamma production and cytotoxic activity J Exp Med 1989170

763ndash75

22 Mathew A Kurane I Green S et al Predominance of HLA-

restricted cytotoxic T-lymphocyte responses to serotype-cross-

reactive epitopes on nonstructural proteins following natural

secondary dengue virus infection J Virol 1998723999ndash4004

23 Mongkolsapaya J Dejnirattisai W Xu XN et al Original anti-

genic sin and apoptosis in the pathogenesis of dengue hemor-

rhagic fever Nat Med 20039921ndash7

24 National Institute of Allergy and Infectious Diseases Evaluating

the safety and immune response to two admixtures of a tetravalent

dengue virus vaccine 2012 Available at httpclinicaltrialsgovct2

showNCT01506570term5Tetravax-DVamprank53 Accessed No-

vember 4 2012

25 Thomas SJ Endy TP Vaccines for the prevention of dengue de-

velopment update Hum Vaccin 20117674ndash84

26 Sanofi-Pasteur Sanofi Pasteurrsquos dengue vaccine demonstrates

proof of efficacy 2012 Available at 5 wwwsanofipasteurcom

articles1118-sanofi-pasteurrsquos-dengue-vaccine-demonstrates-

proof-of-efficacyhtml Accessed November 2 2012

27 Inviragen Safety and immunogenicity study to assess DENVax

a live attenuated tetravalent vaccine for prevention of dengue fe-

ver 2011 Available at httpclinicaltrialsgovct2show

NCT01224639term5DENVaxamprank51 Accessed November

14 2012

28 US Army Medical Research and Materiel Command A two-

dose primary vaccination study of a tetravalent dengue virus

purified inactivated vaccine vs placebo in healthy adults 2012

Translational Research8 Beaumier et al - 2013

severe adverse events detected that were linked withvaccination Althoughminor adverse events were notedthey were limited to pain and swelling around the injec-tion site As a secondary end point the immune re-sponses were measured as a function of both humoraland cellular responses The antibody isotype profilewas predominated by immunoglobulin G1 Two doses(100 mg and 300 mg) of the vaccine were tested andboth induced specific antibody responses with no ap-preciable difference between both dosing strategiesWith regard to a cellular immune response TH2-typecytokines interleukin 13 and interleukin 5 were detectedafter in vitro stimulation of the donorrsquos mononuclearcells with schistosoma haematobium glutathioneS-transferase 28 kDa5253

Another promising vaccine candidate targets the fattyacid binding protein of S mansoni This particular re-combinant protein antigen is Sm14 and is adjuvantedwith GLA-SE A phase 1 clinical trial sponsored bythe Oswaldo Cruz Foundation (FIOCRUZ Brazil) incollaboration with Financiadora Estudos e Projetos forSm14 is currently ongoing in Rio de Janeiro Brazilat the Instituto de Pesquisa Clınica Evandro Chagas(IPEC)-FIOCRUZ This study is enrolling healthyadults who receive 3 doses of the vaccine at 50 mgSm14with 10 mg GLA-SE As this study is currently on-going no results are yet available54

A third encouraging vaccine antigen against S man-soni is S mansoni tetraspanin protein 2 (Sm-TSP-2)Sm-TSP-2 is being developed by the Sabin Vaccine In-stitute PDP and also uses recombinant protein technol-ogy and protein adjuvanted on alum Sm-TSP-2 isa member of the tetraspanin family of proteins and is ex-pressed in the tegument of the parasite In a murinemodel vaccination with Sm-TSP-2 demonstrated a pro-tective effect Although not yet in clinical trials it hasbeen manufactured in collaboration with Aeras (Mary-land) and has entered toxicology studies The clinicaldevelopment plan includes testing with and withoutthe inclusion of GLA-AF from IDRI The current planis to begin phase 1 safety trials in 201349

VACCINES ON THE CUSP ONCHOCERCIASIS ANDCHAGAS

Chagasdisease Chagasdisease in theAmericas repre-sents a substantial health burden and ranks among themost important NTDs in this region with 10 millionpeople believed to be infected55 The causative agentTrypanosoma cruzi is most commonly transmittedthrough the feces of the infected triatomine vectoralthough mother-to-child transmission transfusion andorgan transplantation-associated infection and infectionvia contaminated foods have also emerged as importantroutes of transmission56 Treatments are currently

available however they are costly require lengthyregimens and have the risk of severe adverse eventsThese drugs are also not approved for use in pregnantwomen which is problematic because of the high ratesof vertical transmission and congenital infection53

Current prevention efforts rely on vector control andalthough this has reduced disease incidence it is notbelieved that vector control measures alone will be ableto prevent transmission to humans57 Therefore a widerange of preventive vaccine formulations have beenevaluated throughout the years from the use of wholeparasites to purified or recombinant proteins to viralvectors and DNA vaccines57 Although there arechallenges associated with live vaccines a renewedinterest has been seen recently in live attenuatedvaccines such as the generation of T cruzi mutants forspecific genes Such genes are LYT1 which is believedto play a role in parasite infectivity mediating theescape of the parasite from the acidic parasitophorousvaculole into the cytosol and ECH1 and ECH2 (tandemenoyl-coenzymeA hydratase 1 and 2 genes) thought toplay a key role in amastigote energy metabolism5859

These live attenuated vaccines have been shown toprotect mice from infection55 It has been widely notedthat the outcome of many vaccines against T cruzi inanimal models depends heavily on the formulation usedand the immune response that is induced55 Regardlessof the vaccine platform chosen it is apparent thata strong cellular immune response will need to beinduced and encompass CD81 cell activation andcytotoxic activity to control T cruzi infection throughvaccination57 Many recent studies have been based onrecombinant protein technology recombinant viralvaccine vectors DNA vaccines and heterologousprime-boost vaccination strategies and have shownstrong protection against infection and increasedsurvival of mice It is now believed that for the controlof Chagas disease either a preventive vaccine against Tcruzi or a therapeutic vaccine could be of great value57

Both vaccine strategies would rely on a skewed im-mune response toward a TH1 type leading researchersto believe that the same antigens and vaccine formula-tions may be used for both the prevention of Chagas dis-ease as well as a therapeutic for an ongoing infectionRecent economic modeling has suggested that a thera-peutic vaccine for Chagas would be more cost-effective than a preventive vaccine55

Several different groups are conducting preclinicaltesting of candidate T cruzi vaccines57 The Sabin Vac-cine Institute PDP with the Instituto Carlos Slim de laSalud (Mexico DF Mexico) and in association withthe Laboratorio de Parasitologıa CIR UniversidadAutonoma de Yucatan (Merida Mexico) the Laborator-ios de Biologicos y Reactivos de Mexico (Birmex

Translational ResearchVolume - Number - Beaumier et al 9

Mexico City Mexico) the Centro de Investigacion y deEstudios Avanzados del Instituto Politecnico Nacional(Cinvestav Mexico City Mexico) and the Vector Mo-lecular Biology Section Laboratory of Malaria andVector Research National Institute of Allergy and In-fectious Diseases NIH (Rockville Md) is advancinga therapeutic vaccine from target selection through pro-cess development scale up and manufacturing Thisvaccine is intended to be a bivalent vaccine for the treat-ment of chronic Chagas disease comprised of 2 T cruzirecombinant proteins formulated on either Alhydrogelor Adju-Phos and coadministration with E6020 (EisaiCo Ltd Tokyo Japan) a novel TLR-4 agonist The 2selected novel antigens to advance through develop-ment are Tc24 a T cruzi 24 kDa antigen and TSA-1a T cruzi surface transialidase56 These antigens willbe expressed using a soluble expression system suchas yeast Escherichia coli or baculovirus The vaccineis intended to prevent or delay the onset of chagasic car-diomyopathy in patients with indeterminate Chagas dis-ease or in patients with early-stage disease and mayprevent further transmission of T cruzi56

Onchocerciasis Onchocerciasis transmitted by theblack fly of the genus Simulium is the second leadingcause of infectious blindness in humans worldwide withapproximately 120 million people at risk for the diseasein Africa and Latin America60 Vector and chemotherapyapproaches for onchocerciasis control have been ableto limit the extent and impact of this infection butneither strategy is a permanent solution61 Mountingevidence suggesting that humans can develop a naturallyacquired immunity against Onchocerca volvulus furtherstrengthens the argument for the development of anonchocerciasis vaccine62 The Edna McConnell ClarkFoundation has worked to complement the wealth ofonchocerciasis control programs (OnchocerciasisControl Programme the African Programme forOnchocerciasis Control and the OnchocerciasisElimination Program in the Americas) by dedicatingfunds for immunologic and molecular biologyapproaches to onchocerciasis research63 As a resultthere have been many gains made in the onchocerciasisfield especially in the area of vaccine developmentThese advances include the development of high-qualitycomplementary DNA libraries encompassing manystages of the Onchocerca volvulus life cycle63 It hasalso been shown clearly that mice humans and cattledevelop protective immunity against O volvuluslarvae60 In addition 44 recombinant proteins that werecloned by immunoscreening or other approaches haveyielded 14 potential antigens that have shown significantreduction (35ndash69) of L3 larval survival63

The Sabin Vaccine Institute PDP embarked in col-laboration with the New York Blood Center to estab-

lish a novel strategy of antigen selection that usesa scoring system to screen and rank proteins for effi-cacy in 2 complementary small animal models Fromthese efforts 8 top-ranking O volvulus protective an-tigens have emerged including Ov-CPI-2 a cysteineprotease inhibitor Ov-ALT-1 a filarial specific anti-gen Ov-RAL-2 a nematode-specific surface antigenOv-ASP-1 a homolog of venom allergen 5 and thePR-1 protein family Ov-103 a nematode-specific sur-face antigen Ov-RBP-1 a retinol binding protein Ov-CHI-1 a chitinase and Ov-B20 a nematode-specificsurface antigen60 Through continued efforts in re-search and development of these candidates it is thehope that at least 1 or 2 of these promising targetswould be suitable for a prophylactic vaccine and willmake it to the clinic in the coming years A prophylac-tic vaccine would be used as an additional componentof the already existing arsenal to control onchocercia-sis In addition a vaccine could aid in the reduction ofmicrofilariae burdens thus reducing the potential fortransmission60 Furthermore it would also not dependon current chemotherapy efforts with ivermectin In-stead the vaccine could be administered in communi-ties that have already gone through multiple rounds ofchemotherapy where resistance may become an issuethereby complementing this control measure in an ef-fort to reach the goal of the elimination of onchocerci-asis as a public health issue60

NEXT STEPS

During the next 5 years it is anticipated that severalNTD vaccines could advance into phase 2 and phase 3trials A major issue is what the lsquolsquoend gamersquorsquo will looklike in terms of subsequent steps for licensure andglobal access Most of the NTD vaccines outlinedhere will be among the first vaccine products targetedspecifically only for the bottom billion of the populationand are currently without major backing of a majorpharmaceutical company There are few if any prece-dents for achieving licensure and global access mile-stones without the benefit of major pharmaceuticalsupport Perhaps the closest comparison would be therecent successes of the Serum Institute of India (a devel-oping country vaccine manufacturer) in collaborationwith the Program for Appropriate Technology in Health(PATH Seattle WA a PDP) in producing a meningo-coccal A vaccine for the meningitis belt in Sub-Saharan Africa64

The scale andmagnitude of the major parasitic and re-lated NTDs discussed here are vast and therefore thevaccine development process may be potentially muchmore complex in terms of manufacturing partners li-censing strategies and World Health Organization

Translational Research10 Beaumier et al - 2013

prequalifications and uptake by the disease-endemiccountries most of which are among the most resourcepoor in the world Complicating the global access anduptake of the major NTD vaccines is the observationin preclinical testing that most of these candidate vac-cines are only protective in part similar to the RTSSmalaria vaccine as shown in recent clinical trials65

To date there is really not a clear road map for howsuch partially protective vaccines might be used along-side additional public health control measures such asantiparasitic drugs or in the case of malaria bed netsand other ancillary measures There are also importantquestions that will need to be answered regarding thebest system for incorporating NTD vaccines (egwhether efforts would focus on delivery alongside mea-sles or other infant vaccines as part of the ExpandedProgramme on Immunization or whether these productsmight be delivered in schools such as has been pro-posed with the human papillomavirus vaccine or evenin antenatal clinics) Toward this goal it is essentialthat in parallel with current development detaileddemand-forecasting exercises are performed to get a bet-ter sense of the needs of the end users in low- andmiddle-income countries and some of the major issuesrelated to global access and uptake The challenges ofwidespread distribution of NTD vaccines will be formi-dable but achieving such milestones would representimportant steps toward poverty reduction and achievingthe Millennium Development Goals

REFERENCES

1 AVERT Global HIV and AIDS estimates 2009 and 2010 Avail-

able at httpwwwavertorgworldstatshtm Accessed Novem-

ber 4 2012

2 World Health Organization Tuberculosis fact sheet 2012 Avail-

able at httpwwwwhointmediacentrefactsheetsfs104en

Accessed November 4 2012

3 Hotez PJ The Four Horsemen of the Apocalypse tropical medi-

cine in the fight against plague death famine and war Am J Trop

Med Hyg 2012873ndash10

4 A fall to cheer The Economist 2012 Available at httpwww

economistcomnode21548963 Accessed November 4 2012

5 Hotez PJ Bethony JM Oliveira SC Brindley PJ Loukas A Mul-

tivalent anthelminthic vaccine to prevent hookworm and schisto-

somiasis Expert Rev Vaccines 20087745ndash52

6 Hotez PJ Fenwick A Savioli L Molyneux DH Rescuing the bot-

tom billion through control of neglected tropical diseases Lancet

20093731570ndash5

7 Hotez PJ Empowering women and improving female reproduc-

tive health through control of neglected tropical diseases PLoS

Negl Trop Dis 20093e559

8 Mbabazi PS Andan O Fitzgerald DW Chitsulo L Engels D

Downs JA Examining the relationship between urogenital schis-

tosomiasis and HIV infection PLoS Negl Trop Dis 20115e1396

9 World Health Organization Neglected tropical diseases 2012

Available at httpwwwwhointghoneglected_diseasesen

indexhtml Accessed November 4 2012

10 Hotez P A handful of lsquoantipovertyrsquo vaccines exist for neglected

diseases but the worldrsquos poorest billion people need more Health

Aff 2011301080ndash7

11 Gubler DJ Aedes aegypti and Aedes aegypti-borne disease control

in the 1990s top down or bottom up Charles Franklin Craig lec-

ture Am J Trop Med Hyg 198940571ndash8

12 Kalayanarooj S Vaughn DW Nimmannitya S et al Early clinical

and laboratory indicators of acute dengue illness J Infect Dis

1997176313ndash21

13 Guzman MG Kouri G Dengue an update Lancet Infect Dis

2002233ndash42

14 Centers for Disease Control and Prevention Locally acquired

dengue Key West Florida 2009ndash2010 MMWR Morb Mortal

Wkly Rep 201059577ndash81

15 Halstead SB Immune enhancement of viral infection Prog Al-

lergy 198231301ndash64

16 Sangkawibha N Rojanasuphot S Ahandrik S et al Risk factors

in dengue shock syndrome a prospective epidemiologic study

in Rayong Thailand I The 1980 outbreak Am J Epidemiol

1984120653ndash69

17 Halstead SB Nimmannitya S Yamarat C Russell PK Hemor-

rhagic fever in Thailand recent knowledge regarding etiology

Jpn J Med Sci Biol 19672096ndash103

18 Kliks SC Nimmanitya S Nisalak A Burke DS Evidence that ma-

ternal dengue antibodies are important in the development of den-

gue hemorrhagic fever in infants Am J Trop Med Hyg 198838

411ndash9

19 Kliks SC Nisalak A Brandt WE Wahl L Burke DS Antibody-

dependent enhancement of dengue virus growth in human mono-

cytes as a risk factor for dengue hemorrhagic fever Am J Trop

Med Hyg 198940444ndash51

20 Kurane I Innis BL Nisalak A et al Human T cell responses to

dengue virus antigens proliferative responses and interferon

gamma production J Clin Invest 198983506ndash13

21 Kurane I Meager A Ennis FA Dengue virus-specific human T

cell clones serotype cross-reactive proliferation interferon

gamma production and cytotoxic activity J Exp Med 1989170

763ndash75

22 Mathew A Kurane I Green S et al Predominance of HLA-

restricted cytotoxic T-lymphocyte responses to serotype-cross-

reactive epitopes on nonstructural proteins following natural

secondary dengue virus infection J Virol 1998723999ndash4004

23 Mongkolsapaya J Dejnirattisai W Xu XN et al Original anti-

genic sin and apoptosis in the pathogenesis of dengue hemor-

rhagic fever Nat Med 20039921ndash7

24 National Institute of Allergy and Infectious Diseases Evaluating

the safety and immune response to two admixtures of a tetravalent

dengue virus vaccine 2012 Available at httpclinicaltrialsgovct2

showNCT01506570term5Tetravax-DVamprank53 Accessed No-

vember 4 2012

25 Thomas SJ Endy TP Vaccines for the prevention of dengue de-

velopment update Hum Vaccin 20117674ndash84

26 Sanofi-Pasteur Sanofi Pasteurrsquos dengue vaccine demonstrates

proof of efficacy 2012 Available at 5 wwwsanofipasteurcom

articles1118-sanofi-pasteurrsquos-dengue-vaccine-demonstrates-

proof-of-efficacyhtml Accessed November 2 2012

27 Inviragen Safety and immunogenicity study to assess DENVax

a live attenuated tetravalent vaccine for prevention of dengue fe-

ver 2011 Available at httpclinicaltrialsgovct2show

NCT01224639term5DENVaxamprank51 Accessed November

14 2012

28 US Army Medical Research and Materiel Command A two-

dose primary vaccination study of a tetravalent dengue virus

purified inactivated vaccine vs placebo in healthy adults 2012

Translational ResearchVolume - Number - Beaumier et al 9

Mexico City Mexico) the Centro de Investigacion y deEstudios Avanzados del Instituto Politecnico Nacional(Cinvestav Mexico City Mexico) and the Vector Mo-lecular Biology Section Laboratory of Malaria andVector Research National Institute of Allergy and In-fectious Diseases NIH (Rockville Md) is advancinga therapeutic vaccine from target selection through pro-cess development scale up and manufacturing Thisvaccine is intended to be a bivalent vaccine for the treat-ment of chronic Chagas disease comprised of 2 T cruzirecombinant proteins formulated on either Alhydrogelor Adju-Phos and coadministration with E6020 (EisaiCo Ltd Tokyo Japan) a novel TLR-4 agonist The 2selected novel antigens to advance through develop-ment are Tc24 a T cruzi 24 kDa antigen and TSA-1a T cruzi surface transialidase56 These antigens willbe expressed using a soluble expression system suchas yeast Escherichia coli or baculovirus The vaccineis intended to prevent or delay the onset of chagasic car-diomyopathy in patients with indeterminate Chagas dis-ease or in patients with early-stage disease and mayprevent further transmission of T cruzi56

Onchocerciasis Onchocerciasis transmitted by theblack fly of the genus Simulium is the second leadingcause of infectious blindness in humans worldwide withapproximately 120 million people at risk for the diseasein Africa and Latin America60 Vector and chemotherapyapproaches for onchocerciasis control have been ableto limit the extent and impact of this infection butneither strategy is a permanent solution61 Mountingevidence suggesting that humans can develop a naturallyacquired immunity against Onchocerca volvulus furtherstrengthens the argument for the development of anonchocerciasis vaccine62 The Edna McConnell ClarkFoundation has worked to complement the wealth ofonchocerciasis control programs (OnchocerciasisControl Programme the African Programme forOnchocerciasis Control and the OnchocerciasisElimination Program in the Americas) by dedicatingfunds for immunologic and molecular biologyapproaches to onchocerciasis research63 As a resultthere have been many gains made in the onchocerciasisfield especially in the area of vaccine developmentThese advances include the development of high-qualitycomplementary DNA libraries encompassing manystages of the Onchocerca volvulus life cycle63 It hasalso been shown clearly that mice humans and cattledevelop protective immunity against O volvuluslarvae60 In addition 44 recombinant proteins that werecloned by immunoscreening or other approaches haveyielded 14 potential antigens that have shown significantreduction (35ndash69) of L3 larval survival63

The Sabin Vaccine Institute PDP embarked in col-laboration with the New York Blood Center to estab-

lish a novel strategy of antigen selection that usesa scoring system to screen and rank proteins for effi-cacy in 2 complementary small animal models Fromthese efforts 8 top-ranking O volvulus protective an-tigens have emerged including Ov-CPI-2 a cysteineprotease inhibitor Ov-ALT-1 a filarial specific anti-gen Ov-RAL-2 a nematode-specific surface antigenOv-ASP-1 a homolog of venom allergen 5 and thePR-1 protein family Ov-103 a nematode-specific sur-face antigen Ov-RBP-1 a retinol binding protein Ov-CHI-1 a chitinase and Ov-B20 a nematode-specificsurface antigen60 Through continued efforts in re-search and development of these candidates it is thehope that at least 1 or 2 of these promising targetswould be suitable for a prophylactic vaccine and willmake it to the clinic in the coming years A prophylac-tic vaccine would be used as an additional componentof the already existing arsenal to control onchocercia-sis In addition a vaccine could aid in the reduction ofmicrofilariae burdens thus reducing the potential fortransmission60 Furthermore it would also not dependon current chemotherapy efforts with ivermectin In-stead the vaccine could be administered in communi-ties that have already gone through multiple rounds ofchemotherapy where resistance may become an issuethereby complementing this control measure in an ef-fort to reach the goal of the elimination of onchocerci-asis as a public health issue60

NEXT STEPS

During the next 5 years it is anticipated that severalNTD vaccines could advance into phase 2 and phase 3trials A major issue is what the lsquolsquoend gamersquorsquo will looklike in terms of subsequent steps for licensure andglobal access Most of the NTD vaccines outlinedhere will be among the first vaccine products targetedspecifically only for the bottom billion of the populationand are currently without major backing of a majorpharmaceutical company There are few if any prece-dents for achieving licensure and global access mile-stones without the benefit of major pharmaceuticalsupport Perhaps the closest comparison would be therecent successes of the Serum Institute of India (a devel-oping country vaccine manufacturer) in collaborationwith the Program for Appropriate Technology in Health(PATH Seattle WA a PDP) in producing a meningo-coccal A vaccine for the meningitis belt in Sub-Saharan Africa64

The scale andmagnitude of the major parasitic and re-lated NTDs discussed here are vast and therefore thevaccine development process may be potentially muchmore complex in terms of manufacturing partners li-censing strategies and World Health Organization

Translational Research10 Beaumier et al - 2013

prequalifications and uptake by the disease-endemiccountries most of which are among the most resourcepoor in the world Complicating the global access anduptake of the major NTD vaccines is the observationin preclinical testing that most of these candidate vac-cines are only protective in part similar to the RTSSmalaria vaccine as shown in recent clinical trials65

To date there is really not a clear road map for howsuch partially protective vaccines might be used along-side additional public health control measures such asantiparasitic drugs or in the case of malaria bed netsand other ancillary measures There are also importantquestions that will need to be answered regarding thebest system for incorporating NTD vaccines (egwhether efforts would focus on delivery alongside mea-sles or other infant vaccines as part of the ExpandedProgramme on Immunization or whether these productsmight be delivered in schools such as has been pro-posed with the human papillomavirus vaccine or evenin antenatal clinics) Toward this goal it is essentialthat in parallel with current development detaileddemand-forecasting exercises are performed to get a bet-ter sense of the needs of the end users in low- andmiddle-income countries and some of the major issuesrelated to global access and uptake The challenges ofwidespread distribution of NTD vaccines will be formi-dable but achieving such milestones would representimportant steps toward poverty reduction and achievingthe Millennium Development Goals

REFERENCES

1 AVERT Global HIV and AIDS estimates 2009 and 2010 Avail-

able at httpwwwavertorgworldstatshtm Accessed Novem-

ber 4 2012

2 World Health Organization Tuberculosis fact sheet 2012 Avail-

able at httpwwwwhointmediacentrefactsheetsfs104en

Accessed November 4 2012

3 Hotez PJ The Four Horsemen of the Apocalypse tropical medi-

cine in the fight against plague death famine and war Am J Trop

Med Hyg 2012873ndash10

4 A fall to cheer The Economist 2012 Available at httpwww

economistcomnode21548963 Accessed November 4 2012

5 Hotez PJ Bethony JM Oliveira SC Brindley PJ Loukas A Mul-

tivalent anthelminthic vaccine to prevent hookworm and schisto-

somiasis Expert Rev Vaccines 20087745ndash52

6 Hotez PJ Fenwick A Savioli L Molyneux DH Rescuing the bot-

tom billion through control of neglected tropical diseases Lancet

20093731570ndash5

7 Hotez PJ Empowering women and improving female reproduc-

tive health through control of neglected tropical diseases PLoS

Negl Trop Dis 20093e559

8 Mbabazi PS Andan O Fitzgerald DW Chitsulo L Engels D

Downs JA Examining the relationship between urogenital schis-

tosomiasis and HIV infection PLoS Negl Trop Dis 20115e1396

9 World Health Organization Neglected tropical diseases 2012

Available at httpwwwwhointghoneglected_diseasesen

indexhtml Accessed November 4 2012

10 Hotez P A handful of lsquoantipovertyrsquo vaccines exist for neglected

diseases but the worldrsquos poorest billion people need more Health

Aff 2011301080ndash7

11 Gubler DJ Aedes aegypti and Aedes aegypti-borne disease control

in the 1990s top down or bottom up Charles Franklin Craig lec-

ture Am J Trop Med Hyg 198940571ndash8

12 Kalayanarooj S Vaughn DW Nimmannitya S et al Early clinical

and laboratory indicators of acute dengue illness J Infect Dis

1997176313ndash21

13 Guzman MG Kouri G Dengue an update Lancet Infect Dis

2002233ndash42

14 Centers for Disease Control and Prevention Locally acquired

dengue Key West Florida 2009ndash2010 MMWR Morb Mortal

Wkly Rep 201059577ndash81

15 Halstead SB Immune enhancement of viral infection Prog Al-

lergy 198231301ndash64

16 Sangkawibha N Rojanasuphot S Ahandrik S et al Risk factors

in dengue shock syndrome a prospective epidemiologic study

in Rayong Thailand I The 1980 outbreak Am J Epidemiol

1984120653ndash69

17 Halstead SB Nimmannitya S Yamarat C Russell PK Hemor-

rhagic fever in Thailand recent knowledge regarding etiology

Jpn J Med Sci Biol 19672096ndash103

18 Kliks SC Nimmanitya S Nisalak A Burke DS Evidence that ma-

ternal dengue antibodies are important in the development of den-

gue hemorrhagic fever in infants Am J Trop Med Hyg 198838

411ndash9

19 Kliks SC Nisalak A Brandt WE Wahl L Burke DS Antibody-

dependent enhancement of dengue virus growth in human mono-

cytes as a risk factor for dengue hemorrhagic fever Am J Trop

Med Hyg 198940444ndash51

20 Kurane I Innis BL Nisalak A et al Human T cell responses to

dengue virus antigens proliferative responses and interferon

gamma production J Clin Invest 198983506ndash13

21 Kurane I Meager A Ennis FA Dengue virus-specific human T

cell clones serotype cross-reactive proliferation interferon

gamma production and cytotoxic activity J Exp Med 1989170

763ndash75

22 Mathew A Kurane I Green S et al Predominance of HLA-

restricted cytotoxic T-lymphocyte responses to serotype-cross-

reactive epitopes on nonstructural proteins following natural

secondary dengue virus infection J Virol 1998723999ndash4004

23 Mongkolsapaya J Dejnirattisai W Xu XN et al Original anti-

genic sin and apoptosis in the pathogenesis of dengue hemor-

rhagic fever Nat Med 20039921ndash7

24 National Institute of Allergy and Infectious Diseases Evaluating

the safety and immune response to two admixtures of a tetravalent

dengue virus vaccine 2012 Available at httpclinicaltrialsgovct2

showNCT01506570term5Tetravax-DVamprank53 Accessed No-

vember 4 2012

25 Thomas SJ Endy TP Vaccines for the prevention of dengue de-

velopment update Hum Vaccin 20117674ndash84

26 Sanofi-Pasteur Sanofi Pasteurrsquos dengue vaccine demonstrates

proof of efficacy 2012 Available at 5 wwwsanofipasteurcom

articles1118-sanofi-pasteurrsquos-dengue-vaccine-demonstrates-

proof-of-efficacyhtml Accessed November 2 2012

27 Inviragen Safety and immunogenicity study to assess DENVax

a live attenuated tetravalent vaccine for prevention of dengue fe-

ver 2011 Available at httpclinicaltrialsgovct2show

NCT01224639term5DENVaxamprank51 Accessed November

14 2012

28 US Army Medical Research and Materiel Command A two-

dose primary vaccination study of a tetravalent dengue virus

purified inactivated vaccine vs placebo in healthy adults 2012

Translational Research10 Beaumier et al - 2013

prequalifications and uptake by the disease-endemiccountries most of which are among the most resourcepoor in the world Complicating the global access anduptake of the major NTD vaccines is the observationin preclinical testing that most of these candidate vac-cines are only protective in part similar to the RTSSmalaria vaccine as shown in recent clinical trials65

To date there is really not a clear road map for howsuch partially protective vaccines might be used along-side additional public health control measures such asantiparasitic drugs or in the case of malaria bed netsand other ancillary measures There are also importantquestions that will need to be answered regarding thebest system for incorporating NTD vaccines (egwhether efforts would focus on delivery alongside mea-sles or other infant vaccines as part of the ExpandedProgramme on Immunization or whether these productsmight be delivered in schools such as has been pro-posed with the human papillomavirus vaccine or evenin antenatal clinics) Toward this goal it is essentialthat in parallel with current development detaileddemand-forecasting exercises are performed to get a bet-ter sense of the needs of the end users in low- andmiddle-income countries and some of the major issuesrelated to global access and uptake The challenges ofwidespread distribution of NTD vaccines will be formi-dable but achieving such milestones would representimportant steps toward poverty reduction and achievingthe Millennium Development Goals

REFERENCES

1 AVERT Global HIV and AIDS estimates 2009 and 2010 Avail-

able at httpwwwavertorgworldstatshtm Accessed Novem-

ber 4 2012

2 World Health Organization Tuberculosis fact sheet 2012 Avail-

able at httpwwwwhointmediacentrefactsheetsfs104en

Accessed November 4 2012

3 Hotez PJ The Four Horsemen of the Apocalypse tropical medi-

cine in the fight against plague death famine and war Am J Trop

Med Hyg 2012873ndash10

4 A fall to cheer The Economist 2012 Available at httpwww

economistcomnode21548963 Accessed November 4 2012

5 Hotez PJ Bethony JM Oliveira SC Brindley PJ Loukas A Mul-

tivalent anthelminthic vaccine to prevent hookworm and schisto-

somiasis Expert Rev Vaccines 20087745ndash52

6 Hotez PJ Fenwick A Savioli L Molyneux DH Rescuing the bot-

tom billion through control of neglected tropical diseases Lancet

20093731570ndash5

7 Hotez PJ Empowering women and improving female reproduc-

tive health through control of neglected tropical diseases PLoS

Negl Trop Dis 20093e559

8 Mbabazi PS Andan O Fitzgerald DW Chitsulo L Engels D

Downs JA Examining the relationship between urogenital schis-

tosomiasis and HIV infection PLoS Negl Trop Dis 20115e1396

9 World Health Organization Neglected tropical diseases 2012

Available at httpwwwwhointghoneglected_diseasesen

indexhtml Accessed November 4 2012

10 Hotez P A handful of lsquoantipovertyrsquo vaccines exist for neglected

diseases but the worldrsquos poorest billion people need more Health

Aff 2011301080ndash7

11 Gubler DJ Aedes aegypti and Aedes aegypti-borne disease control

in the 1990s top down or bottom up Charles Franklin Craig lec-

ture Am J Trop Med Hyg 198940571ndash8

12 Kalayanarooj S Vaughn DW Nimmannitya S et al Early clinical

and laboratory indicators of acute dengue illness J Infect Dis

1997176313ndash21

13 Guzman MG Kouri G Dengue an update Lancet Infect Dis

2002233ndash42

14 Centers for Disease Control and Prevention Locally acquired

dengue Key West Florida 2009ndash2010 MMWR Morb Mortal

Wkly Rep 201059577ndash81

15 Halstead SB Immune enhancement of viral infection Prog Al-

lergy 198231301ndash64

16 Sangkawibha N Rojanasuphot S Ahandrik S et al Risk factors

in dengue shock syndrome a prospective epidemiologic study

in Rayong Thailand I The 1980 outbreak Am J Epidemiol

1984120653ndash69

17 Halstead SB Nimmannitya S Yamarat C Russell PK Hemor-

rhagic fever in Thailand recent knowledge regarding etiology

Jpn J Med Sci Biol 19672096ndash103

18 Kliks SC Nimmanitya S Nisalak A Burke DS Evidence that ma-

ternal dengue antibodies are important in the development of den-

gue hemorrhagic fever in infants Am J Trop Med Hyg 198838

411ndash9

19 Kliks SC Nisalak A Brandt WE Wahl L Burke DS Antibody-

dependent enhancement of dengue virus growth in human mono-

cytes as a risk factor for dengue hemorrhagic fever Am J Trop

Med Hyg 198940444ndash51

20 Kurane I Innis BL Nisalak A et al Human T cell responses to

dengue virus antigens proliferative responses and interferon

gamma production J Clin Invest 198983506ndash13

21 Kurane I Meager A Ennis FA Dengue virus-specific human T

cell clones serotype cross-reactive proliferation interferon

gamma production and cytotoxic activity J Exp Med 1989170

763ndash75

22 Mathew A Kurane I Green S et al Predominance of HLA-

restricted cytotoxic T-lymphocyte responses to serotype-cross-

reactive epitopes on nonstructural proteins following natural

secondary dengue virus infection J Virol 1998723999ndash4004

23 Mongkolsapaya J Dejnirattisai W Xu XN et al Original anti-

genic sin and apoptosis in the pathogenesis of dengue hemor-

rhagic fever Nat Med 20039921ndash7

24 National Institute of Allergy and Infectious Diseases Evaluating

the safety and immune response to two admixtures of a tetravalent

dengue virus vaccine 2012 Available at httpclinicaltrialsgovct2

showNCT01506570term5Tetravax-DVamprank53 Accessed No-

vember 4 2012

25 Thomas SJ Endy TP Vaccines for the prevention of dengue de-

velopment update Hum Vaccin 20117674ndash84

26 Sanofi-Pasteur Sanofi Pasteurrsquos dengue vaccine demonstrates

proof of efficacy 2012 Available at 5 wwwsanofipasteurcom

articles1118-sanofi-pasteurrsquos-dengue-vaccine-demonstrates-

proof-of-efficacyhtml Accessed November 2 2012

27 Inviragen Safety and immunogenicity study to assess DENVax

a live attenuated tetravalent vaccine for prevention of dengue fe-

ver 2011 Available at httpclinicaltrialsgovct2show

NCT01224639term5DENVaxamprank51 Accessed November

14 2012

28 US Army Medical Research and Materiel Command A two-

dose primary vaccination study of a tetravalent dengue virus

purified inactivated vaccine vs placebo in healthy adults 2012

Translational ResearchVolume - Number - Beaumier et al 11

Available at httpclinicaltrialsgovct2showNCT01666652

term5dengue1PIVamprank53 Accessed November 14 2012

29 US ArmyMedical Research andMateriel CommandA two-dose

primary vaccination study of a tetravalent dengue virus purified

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(DPIV-002) 2012 Available at httpclinicaltrialsgovct2

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showNCT01502358term5dengue1DNA1vaccineamprank52

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Hyg 199589538ndash41

39 Hotez PD Diemert D Bacon KM et al Decade of vaccine col-

laboration (DoVC) Human Hookworm Vaccine Case Study Vac-

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40 Das A Ali N Vaccine development against Leishmania donovani

Front Immunol 2012399

41 Duthie MS Raman VS Piazza FM Reed SG The development

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Int Immunopharmacol 2011111464ndash88

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protects against experimental leishmaniasis Vaccine 200927

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44 Chakravarty J Kumar S Trivedi S et al A clinical trial to evalu-

ate the safety and immunogenicity of the LEISH-F11MPL-SE

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cine 2011293531ndash7

45 Gomes R Teixeira C Oliveira F et al KSAC a defined Leish-

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46 Infectious Disease Research Institute Safety and immunogenicity

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48 Infectious Disease Research Institute Phase 1 LEISH-F3 Vaccine

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53 Riveau G Deplanque D Remoue F et al Safety and immunoge-

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54 OswaldoCruz Foundation Study to evaluate the sa fety of the vac-

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57 Quijano-Hernandez I Dumonteil E Advances and challenges to-

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