ANTIVIRALS, INTERFERON AND VACCINES EDWARD-BENGIE L. MAGSOMBOL, MD, FPCP, FPCC, DASNC Associate Professor in Microbiology

ANTIVIRALS, ANTIVIRALS, INTERFERON AND INTERFERON AND

VACCINESVACCINES

EDWARD-BENGIE L. MAGSOMBOL, EDWARD-BENGIE L. MAGSOMBOL, MD, FPCP, FPCC, DASNCMD, FPCP, FPCC, DASNC

Associate Professor in Associate Professor in MicrobiologyMicrobiology

AntiviralsAntiviralsAPPROACH TO ANTIVIRAL CHEMOTHERAPYAPPROACH TO ANTIVIRAL CHEMOTHERAPY1. Adsorption, Penetration and Uncoating1. Adsorption, Penetration and Uncoating = little is known about the specific = little is known about the specific

reactions involvedreactions involved = only amantadine, rimantadine used vs = only amantadine, rimantadine used vs

influenza Ainfluenza A = HIV, rhino, EBV now being researched on= HIV, rhino, EBV now being researched on

2. Replication of Viral Nucleic Acids2. Replication of Viral Nucleic Acids = attack enzymes which catalyze replication= attack enzymes which catalyze replication = not present in uninfected cells= not present in uninfected cells = all RNA viruses, pox, herpes and = all RNA viruses, pox, herpes and adenovirusadenovirus

AntiviralsAntiviralsAPPROACH TO ANTIVIRAL APPROACH TO ANTIVIRAL

CHEMOTHERAPYCHEMOTHERAPY

3.3. Integration of Viral Genomes into Cellular Integration of Viral Genomes into Cellular GenomesGenomes

= as part of multiplication cycle = as part of multiplication cycle (retrovirus and its integrase)(retrovirus and its integrase)

= tumorigenesis (papovavirus, herpes)= tumorigenesis (papovavirus, herpes)

4. Synthesis of Viral Messenger RNA’s4. Synthesis of Viral Messenger RNA’s = virus-encoded RNA polymerases, = virus-encoded RNA polymerases,

capping enzymescapping enzymes

AntiviralsAntivirals

APPROACH TO ANTIVIRAL APPROACH TO ANTIVIRAL CHEMOTHERAPYCHEMOTHERAPY

5. Synthesis of Viral Proteins5. Synthesis of Viral Proteins

= viral mRNA translation different from = viral mRNA translation different from host mRNAhost mRNA

6. Viral Morphogenesis6. Viral Morphogenesis

= enzymes which cleave precursors for = enzymes which cleave precursors for viral capsid CHONsviral capsid CHONs

= ex. viral proteases= ex. viral proteases

AntiviralsAntiviralsCLASSES OF ANTIVIRAL AGENTSCLASSES OF ANTIVIRAL AGENTS Synthetic Antiviral AgentsSynthetic Antiviral AgentsI. Analogues of Ribonucleosides and I. Analogues of Ribonucleosides and

DeoxyribonucleosidesDeoxyribonucleosides = nucleic acids base or derivatives= nucleic acids base or derivatives = included into nucleic acid, usually DNA= included into nucleic acid, usually DNA = interfere with nucleic acid function= interfere with nucleic acid function = selectively inhibit viral polymerases= selectively inhibit viral polymerases A. A. Idoxuridine and TrifluorothymidineIdoxuridine and Trifluorothymidine = analogues of thymidine, inhibits viral DNA = analogues of thymidine, inhibits viral DNA

formationformation = inhibit multiplication of herpesviruses= inhibit multiplication of herpesviruses = used for topical treatment of herpes simplex = used for topical treatment of herpes simplex

keratitiskeratitis = not used for systemic use because of toxicity= not used for systemic use because of toxicity

Herpes keratoconjunctivitisHerpes keratoconjunctivitis

Herpes simplexHerpes simplex



AntiviralsAntiviralsB. Vidarabine (Adenosine arabinoside, Ara-B. Vidarabine (Adenosine arabinoside, Ara-

A)A) = inhibits HSV and VZV multiplication= inhibits HSV and VZV multiplication = act as chain terminators; inhibit viral DNA = act as chain terminators; inhibit viral DNA

polymerase more than host DNA polymerasepolymerase more than host DNA polymerase = herpes simplex keratitis; herpes simplex = herpes simplex keratitis; herpes simplex

encephalitis (IV route)encephalitis (IV route)C. AcyclovirC. Acyclovir

= guanine linked to an open ring analogue of = guanine linked to an open ring analogue of ribose, deoxyriboseribose, deoxyribose

= thymine or cytosine derivative= thymine or cytosine derivative = phosphorylated by HSV and VZV TKinases= phosphorylated by HSV and VZV TKinases = topical or IV in mucocutaneous herpes simplex = topical or IV in mucocutaneous herpes simplex

in immunocompromised hosts and also in in immunocompromised hosts and also in genital genital

herpes simplex infectionsherpes simplex infections

CHICKENPOX (VARICELLA)CHICKENPOX (VARICELLA)

AntiviralsAntiviralsD. GanciclovirD. Ganciclovir= = close relative of acyclovir; inhibits HSV close relative of acyclovir; inhibits HSV

multiplicationmultiplication = better substrate for HSV TK than acyclovir= better substrate for HSV TK than acyclovir = best inhibitor of CMV multiplication in use= best inhibitor of CMV multiplication in use = probably not a strict chain terminator unlike = probably not a strict chain terminator unlike

acycloviracyclovir

E. Zidovudine (Azidothymidine, AZT, E. Zidovudine (Azidothymidine, AZT, RetrovirRetrovir))

= inhibits retrovirus reverse transcriptase= inhibits retrovirus reverse transcriptase= chain terminator because it does not possess a = chain terminator because it does not possess a

3’-OH group3’-OH group= demonstrated clinical efficacy in HIV= demonstrated clinical efficacy in HIV

CYTOMEGALOVIRUSCYTOMEGALOVIRUS

AIDSAIDS

AntiviralsAntiviralsF. Ribavirin (Virazole)F. Ribavirin (Virazole)= = analogue of purine precursor of 5-analogue of purine precursor of 5-

aminoimidazole 4-carboxamideaminoimidazole 4-carboxamide

= wide spectrum: good vs RNA and DNA viruses= wide spectrum: good vs RNA and DNA viruses

= target: virus-encoded nucleic acid = target: virus-encoded nucleic acid polymerasespolymerases

= affects elongation and initiation (less extent)= affects elongation and initiation (less extent)

= for severe RSV infection (aerosol) in children= for severe RSV infection (aerosol) in children

= reduce mortality on patients with Lassa fever= reduce mortality on patients with Lassa fever

RSV RSV infectioninfection

(bronchiolitis(bronchiolitis

))

RESPIRATORY SYNCYTIAL RESPIRATORY SYNCYTIAL VIRUS VIRUS


OthersOthers= analogues of thymidine = analogues of thymidine (BVdU)(BVdU) and and

cytosine cytosine (FIAC)(FIAC) - good vs herpesvirus - good vs herpesvirus DNA polymerases with low toxicityDNA polymerases with low toxicity

= 2’, 3’-dideoxynucleosides act as chain = 2’, 3’-dideoxynucleosides act as chain terminators in retrovirus infections terminators in retrovirus infections including HIVincluding HIV

= phosphonoformic acid = phosphonoformic acid (foscarnet)(foscarnet) and and phosphonoacetic acid phosphonoacetic acid (PAA)(PAA) – potent – potent highly specific inhibitors of HSV DNA.highly specific inhibitors of HSV DNA.

= toxic to bones and kidney= toxic to bones and kidney


OthersOthers

methyl phosphonate derivative (s)-methyl phosphonate derivative (s)-HPMPA HPMPA

= inhibits DNA viruses ex. herpes, = inhibits DNA viruses ex. herpes, pox, adeno and retropox, adeno and retro

PMEAPMEA- for retrovirus, HIV and tumor - for retrovirus, HIV and tumor formationformation

AntiviralsAntiviralsAmantadine and RimantadineAmantadine and Rimantadine= = effective inhibitors of influenza A effective inhibitors of influenza A

multiplicationmultiplication= affects penetration and uncoating= affects penetration and uncoating= also inhibits budding and virus particle = also inhibits budding and virus particle

releaserelease= FDA approved for prophylaxis vs = FDA approved for prophylaxis vs

influenza Ainfluenza A= CNS side effects worse for amantadine = CNS side effects worse for amantadine

than rimantadinethan rimantadine= useful for elderlies, immunocompromised, = useful for elderlies, immunocompromised,

allergies and in epidemicsallergies and in epidemics


Other Antiviral AgentsOther Antiviral Agents Isatin-B-thiosemicarbazoneIsatin-B-thiosemicarbazone= very potent inhibitor of Poxvirus= very potent inhibitor of Poxvirus

= at 3 mg/L – inhibits vaccinia multiplication = at 3 mg/L – inhibits vaccinia multiplication (90%)(90%)

= inhibits translation of late mRNA –> no viral = inhibits translation of late mRNA –> no viral capsid and CHON synthesis -> no progenycapsid and CHON synthesis -> no progeny

Marburan (n-methyl-IBT)Marburan (n-methyl-IBT) – a derivative of – a derivative of IBTIBT

= beneficial effects for smallpox contacts= beneficial effects for smallpox contacts

SMALLPOXSMALLPOX


2-2-HydroxylbenzylbenzimidazoHydroxylbenzylbenzimidazole (HBB) and Guanidinele (HBB) and Guanidine

= PICORNAVIRUSES (polio, echo, = PICORNAVIRUSES (polio, echo, coxsackie and coxsackie and FMD/enteroviruses)FMD/enteroviruses)

= interfere with replication of = interfere with replication of viral RNAviral RNA

= prevent the initiation of the = prevent the initiation of the synthesis of progeny (+) synthesis of progeny (+) strands by inhibiting protein 2Cstrands by inhibiting protein 2C

AntiviralsAntiviralsRifampicin and Rifamycin derivativesRifampicin and Rifamycin derivatives= = binds to bacterial RNA polymerasebinds to bacterial RNA polymerase

= prevent initiation of transcription= prevent initiation of transcription

= no binding to animal RNA polymerase= no binding to animal RNA polymerase

= inhibit multiplication of pox and adeno = inhibit multiplication of pox and adeno

= both early and late mRNAs are transcribed = both early and late mRNAs are transcribed

normally (viral polymerase not inhibited)normally (viral polymerase not inhibited)

= accumulation of immature virus particles = accumulation of immature virus particles that lack the normal dense spicule layer that lack the normal dense spicule layer


Arildone, Rhodanine, and Arildone, Rhodanine, and WIN 51711WIN 51711

= inhibit uncoating of = inhibit uncoating of Picornaviruses by making the Picornaviruses by making the virus more stable virus more stable

= does not affect absorption or = does not affect absorption or penetrationpenetration

AntiviralsAntiviralsInhibitors of ProteasesInhibitors of Proteases= precursors do not become the = precursors do not become the

functional functional

proteinsproteins

= = HIV protease:HIV protease: essential role in essential role in production of a functional virionproduction of a functional virion

= Saquinavir, indinavir, ritonavir, = Saquinavir, indinavir, ritonavir, nelfinavir, amprenavir – slip into the nelfinavir, amprenavir – slip into the hydrophobic active site of the hydrophobic active site of the enzymeenzyme

= combine with AZT and a 2= combine with AZT and a 2ndnd nucleoside analogue in tx of AIDSnucleoside analogue in tx of AIDS

AntiviralsAntiviralsPromising New ApproachesPromising New Approaches Inhibition of AdsorptionInhibition of Adsorption

= many viral receptors have been = many viral receptors have been identifiedidentified

Targeted Introduction of Toxins into Targeted Introduction of Toxins into Infected CellsInfected Cells

= directed against infected cells= directed against infected cells

= ricin or the Pseudomonas exotoxin = ricin or the Pseudomonas exotoxin to CD4--- attach to gp120 --- to CD4--- attach to gp120 --- internalized into infected cellinternalized into infected cell

AntiviralsAntivirals Introduction into Cells of Specific Introduction into Cells of Specific

Anti-Sense RNA SequencesAnti-Sense RNA Sequences

= = many mRNA splice junctions have many mRNA splice junctions have been sequencedbeen sequenced

Preventing Interactions Among Preventing Interactions Among Protein MoleculesProtein Molecules

= = add excess oligopeptides with the add excess oligopeptides with the same sequence as that of the same sequence as that of the interacting sequenceinteracting sequence

InterferonsInterferons natural antiviral compoundsnatural antiviral compounds substances that have antiviral properties substances that have antiviral properties

in adjacent, noninfected cellsin adjacent, noninfected cells

Types of InterferonsTypes of Interferons

Type I:Type I: (1) Interferon alpha (1) Interferon alpha = maximal = maximal

antiviral activityantiviral activity

(2) Interferon Beta(2) Interferon Beta = intermediate = intermediate

antiviral activityantiviral activity

Type II:Type II: Interferon GammaInterferon Gamma = more = more lymphokine than antivirallymphokine than antiviral

InterferonsInterferonsRegulation of Interferon Regulation of Interferon

ExpressionExpression= not expressed in a normal resting = not expressed in a normal resting

cellcell

= labile repressors bind to = labile repressors bind to promoter elements, block promoter elements, block transcriptiontranscription

= production of labile suppressors = production of labile suppressors drop in viral infection and allows drop in viral infection and allows interferon synthesis to occurinterferon synthesis to occur

InterferonsInterferonsMechanism of actionMechanism of action= synthesis, secretion, diffusion and binding = synthesis, secretion, diffusion and binding

to cellular receptorsto cellular receptors

= taken up by uninfected cells= taken up by uninfected cells

= viral replication (-) via cellular enzymes = viral replication (-) via cellular enzymes

Type IType I

= (-) viral protein synthesis (very specific)= (-) viral protein synthesis (very specific)

= 2 enzymes activated:= 2 enzymes activated:

1. 1. oligo-A synthetaseoligo-A synthetase adenine nucleotide adenine nucleotide viral mRNA digestion viral mRNA digestion

2. protein kinase2. protein kinase ->phosphorylates EF-2 -> ->phosphorylates EF-2 -> blocks CHON synthesisblocks CHON synthesis

= block other stages of replication including = block other stages of replication including buddingbudding

InterferonsInterferons

Type II :Type II :

= antiviral effects mediated by:= antiviral effects mediated by:

1. nitric oxide synthetase—1. nitric oxide synthetase—increased intracellular nitric increased intracellular nitric oxide levels oxide levels

2. upregulation of MHC I and II 2. upregulation of MHC I and II expressionexpression

3. activation of monocytes, 3. activation of monocytes, macrophages and NK cellsmacrophages and NK cells

InterferonInterferon

InterferonsInterferonsClinical Uses:Clinical Uses: IFN-A :IFN-A :

= treatment of viral infections: = treatment of viral infections: condylomata acuminata and chronic hepa condylomata acuminata and chronic hepa B and CB and C

= prophylactic or therapeutic agent in = prophylactic or therapeutic agent in immunocomp. hosts (VZV, HSV 1 and 2)immunocomp. hosts (VZV, HSV 1 and 2)

= prophylaxis vs CMV in renal transplant= prophylaxis vs CMV in renal transplant

= treatment of AIDS-associated Kaposi’s = treatment of AIDS-associated Kaposi’s sarcoma and hairy cell leukemiasarcoma and hairy cell leukemia

IFN-G:IFN-G: immunostimulant in oncologic and immunostimulant in oncologic and immunedeficiency disordersimmunedeficiency disorders

VaccinesVaccines

TYPES OF VACCINES:TYPES OF VACCINES: 1. Inactivated Virus Vaccines1. Inactivated Virus Vaccines = complete inactivation of = complete inactivation of

infectivity with minimum loss of infectivity with minimum loss of antigenicityantigenicity

= ex. a. UV irradiation= ex. a. UV irradiation b. photodynamic inactivation b. photodynamic inactivation and white light and white light

irradiationirradiation c. beta-propiolactonec. beta-propiolactone d. formaldehyde (most d. formaldehyde (most

effective)effective)

VaccinesVaccines

2.2. Attenuated Active Virus VaccinesAttenuated Active Virus Vaccines = Jenner’s smallpox , Theiler’s yellow fever = Jenner’s smallpox , Theiler’s yellow fever

virus, Sabin poliovirus, MMR, adenovirusvirus, Sabin poliovirus, MMR, adenovirus

= repeated passage of human pathogens in = repeated passage of human pathogens in

other host speciesother host species

= effective in small amounts: amplification = effective in small amounts: amplification

effect effect

= recombinant DNA technology has = recombinant DNA technology has

improved attenuationimproved attenuation

POLIO VACCINEPOLIO VACCINE

MEASLESMEASLES

VaccinesVaccines

3. Subunit Vaccines3. Subunit Vaccines

= viral proteins that elicit = viral proteins that elicit formation formation

of neutralizing Ab’sof neutralizing Ab’s

= smaller range of Ab’s (IgA, IgM) = smaller range of Ab’s (IgA, IgM)

producedproduced

= genes of these CHONs now can = genes of these CHONs now can be be

clonedcloned

VaccinesVaccines4. Viral Vectors4. Viral Vectors = genes of viral CHONs inserted into = genes of viral CHONs inserted into

avirulent avirulent

viral vectorsviral vectors

= thymidine kinase gene of Vaccinia virus = thymidine kinase gene of Vaccinia virus

= genes are expressed without disease and = genes are expressed without disease and

Ab’s are producedAb’s are produced

= HA gene of influenza, glycoprotein B gene = HA gene of influenza, glycoprotein B gene

of herpesvirus, surface Ag of HBVof herpesvirus, surface Ag of HBV

= major limitation is the infectivity of = major limitation is the infectivity of

vaccinia itselfvaccinia itself

THANK THANK YOUYOU

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ANTIVIRALS, INTERFERON AND VACCINES EDWARD-BENGIE L. MAGSOMBOL, MD, FPCP, FPCC, DASNC Associate Professor in Microbiology