TrypanosomiasisSleeping Sickness

David HumberDavid Humber

Department of Life SciencesDepartment of Life Sciences

University of East LondonUniversity of East London

Trypanosomes of Vertebrates

T.corviT.corvi CorvidsCorvids

T.cruziT.cruzi Humans, Humans, rodents, rodents, marsupialsmarsupials

T.brucei spT.brucei sp Man, ungulatesMan, ungulates

T.lewisiT.lewisi RodentsRodents

T.musculisT.musculis RodentsRodents

T.microtiT.microti VolesVoles

T.dionisiiT.dionisii BatsBats

T.equiperdumT.equiperdum EquidsEquids

Bone MarrowBone Marrow

Heart muscle,Heart muscle,

autonomic autonomic gangliaganglia

BloodBlood

BloodBlood

BloodBlood

Lymphoid tissueLymphoid tissue

Heart muscleHeart muscle

GenitalsGenitals

Species Host Site

African Sleeping SicknessNgana

South American Sleeping SicknessChagas Disease

African Sleeping Sickness

Parasite - Parasite - Trypanosoma brucei sspTrypanosoma brucei ssp• Trypanosoma brucei rhodesienseTrypanosoma brucei rhodesiense• Trypanosoma brucei gambienseTrypanosoma brucei gambiense

Vector - Tse Tse flyVector - Tse Tse fly• Glossina mortisans Glossina mortisans (Eastern Africa)(Eastern Africa)• Glossina palpalis Glossina palpalis (Western Africa)(Western Africa)

Learning Outcomes

The Parasite & VectorThe Parasite & Vector The Life CycleThe Life Cycle Clinical FeaturesClinical Features DiagnosisDiagnosis EpidemiologyEpidemiology Chemotherapy & ControlChemotherapy & Control VaccinationVaccination

Taxonomy

Phylum Phylum Sub-PhylumSub-Phylum ClassClass OrderOrder GenusGenus

MastigophoraMastigophora

SarcomastigophoraSarcomastigophora

ZoomastigophoraZoomastigophora

KinetoplastidaeKinetoplastidae

TrypanosomaTrypanosoma

? species of mammals, birds, reptiles and amphibians

The Parasite

Polymorphic spindle-shapedPolymorphic spindle-shaped• Proliferative long-slenderProliferative long-slender• IntermediatesIntermediates• Non-proloiferative short-stumpyNon-proloiferative short-stumpy

KinetoplastKinetoplast Flagella & undulating membraneFlagella & undulating membrane

TrypomastigoteProcyclic

Epimastigote

Parasitemia

African TrypanosomiasisThe Life Cycle

HumanHuman Tse flyTse fly

TrypomastigoteTrypomastigoteTrypomastigoteTrypomastigoteStumpyStumpy MetacyclicMetacyclic

IntermediateIntermediate EpimastigoteEpimastigote

SlenderSlender TrypomastigoteTrypomastigote

The Vectors

GlossinaGlossina

22 species - hatchet wing cell22 species - hatchet wing cell

Shady habitat (20-30Shady habitat (20-30ooC)C)

Viviparous - 12 offspringViviparous - 12 offspring

Diurnal feeders (1mg/sec)Diurnal feeders (1mg/sec)

Parasite development 10-14 daysParasite development 10-14 days

Animal Reservoirs

Sub species now thought to be Sub species now thought to be zoonoticzoonotic

Largely ungulatesLargely ungulates

Cattle & PigsWild game

Hyaena

African Sleeping Sickness

VirulenceVirulence ReservoirReservoir ZoonoticZoonotic VectorVector DistributiDistributi

onon

LessLess More More

Human/animalHuman/animal Human/animalHuman/animal

LessLess More More

G.palpalisG.palpalis G.mortisansG.mortisans

Western AfricaWestern Africa Eastern Eastern AfricaAfrica

T.b.gambiense T.b.rhodesiense

Clinical Features

Primary chancre - resolves 2-3 Primary chancre - resolves 2-3 weeksweeks

Initial symptoms - fever & Initial symptoms - fever & headachesheadaches

Day time sleepingDay time sleeping

Tremors & ConvulsionsTremors & Convulsions

Coma & DeathComa & DeathEnlarged cervical lymph nodes (T.b.g)Winterbottoms sign

Diagnosis

Direct microscopyDirect microscopy• Blood (Blood (T.b.r.T.b.r.))• Lymph node aspirate (Lymph node aspirate (T.b.g.T.b.g.))• Lumbar puncture (Late Lumbar puncture (Late T.b.r. & T.b.r. &

T.b.g.T.b.g.)) SerologySerology Animal inoculationAnimal inoculation

Epidemiology

50 million at risk50 million at risk

<20% under surveillance<20% under surveillance

20,000 new case/year20,000 new case/year

Devastating epidemicsDevastating epidemics

200 endemic foci200 endemic foci

Distribution of Disease & Vector

Chemotherapy

Early stage - most recoverEarly stage - most recover• SuraminSuramin• MelasporolMelasporol• PentamidinePentamidine

Late stage - upto 5% relapseLate stage - upto 5% relapse• Only Melasoprol & EflornithineOnly Melasoprol & Eflornithine

– 10% encephalitis - 5% fatal10% encephalitis - 5% fatal

Control

Destruction of animal reservoirDestruction of animal reservoir

Vector ControlVector Control

Diagnosis & treatmentDiagnosis & treatment

ParasitemiaParasitemia in African Sleeping

Sickness

0

2

4

6

8

10

0 10 20 30

Days after Infection

Lo

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ml

Variable Surface Glycoprotein

60kd (450aa) glycoprotein (CHO 7-17%) 60kd (450aa) glycoprotein (CHO 7-17%)

C-terminal anchored in membraneC-terminal anchored in membrane

Often as a dimer (alpha helix)Often as a dimer (alpha helix)

Densely clustered 10Densely clustered 1077molecules/parasitemolecules/parasite

Only epitopes in end third of N-terminal Only epitopes in end third of N-terminal exposedexposed

Presented as topographical arrayPresented as topographical array

T-independent antigenT-independent antigen

VSG

Constant & Variable regionsConstant & Variable regions

Random rearrangement of N terminal end Random rearrangement of N terminal end (2/3)(2/3)

Almost no homology between V VSG’sAlmost no homology between V VSG’s

Except cystein residues S-S bondsExcept cystein residues S-S bonds

Switching not initiated by IRSwitching not initiated by IR

But selectedBut selected

Production of VSG

Gene rearrangementGene rearrangement

Produces on expression linked copy (ELC)Produces on expression linked copy (ELC)

ELC transposed to telomeric end of ELC transposed to telomeric end of chromosome - replacing existing genechromosome - replacing existing gene

Displaced gene lostDisplaced gene lost

Switch occurs every 10Switch occurs every 1066 divisions divisions

100-1000 copie of different VSG’s in clone100-1000 copie of different VSG’s in clone

VSG Specific IR

3-4 days post infection strong IgM 3-4 days post infection strong IgM responseresponse

Trypanosome disappear within hoursTrypanosome disappear within hours

VSG specific IgG appears - not relevantVSG specific IgG appears - not relevant

IgM response often >IgGIgM response often >IgG

After several cycles VSG abs vanishAfter several cycles VSG abs vanish

But abs to invariant ags remain elevatedBut abs to invariant ags remain elevated

Trypanosome Elimination

Antibody mediatedAntibody mediated

Destruction by Kupffer cellsDestruction by Kupffer cells

Splenic macrophages minor role (cf Splenic macrophages minor role (cf malaria)malaria)

Uptake - C3b - C3bi - direct?Uptake - C3b - C3bi - direct?

C mediated lysis not importantC mediated lysis not important

Trypanosome destroyed within minutes Trypanosome destroyed within minutes

Immunoregulation

No secondary response to VSG’s unless No secondary response to VSG’s unless cured by chemotherapycured by chemotherapy

Failure of 1ry or 2ndry response prior to Failure of 1ry or 2ndry response prior to deathdeath

Non specific polyclonal activationNon specific polyclonal activation

Suppresser MacrophagesSuppresser Macrophages

Failure of Ag presentationFailure of Ag presentation

Anti idiotype responsesAnti idiotype responses

Resistance and Virulence

Spectrum of diseaseSpectrum of disease

T. bruceiT. brucei sub species sub species

Host differencesHost differences

Independant of VSGIndependant of VSG

Vaccination

Effective Antibody responseEffective Antibody response

Phagocytosis & killingPhagocytosis & killing

butbut

Cyclical parasitemiaCyclical parasitemia

Antigenic variation not predicableAntigenic variation not predicable