بسم الله الرحمن بسم الله الرحمن الرحيمالرحيم

بسم الله الرحمن بسم الله الرحمن الرحيمالرحيم

((TTVTTV))

Manal M. BaddourManal M. Baddour

TTV

INTRODUCTIONINTRODUCTION

Nishizawa et al, 1997Nishizawa et al, 1997 Post-transfusion non-A to G hepatitisPost-transfusion non-A to G hepatitis Representational difference analysis Representational difference analysis TTVTTV 30 - 50 nm, 3,852 bases30 - 50 nm, 3,852 bases single stranded, negative sense, single stranded, negative sense,

covalently closed circular DNAcovalently closed circular DNA

TTV

Introduction, continued…..Introduction, continued…..

Parvoviridae, Circoviridae, Parvoviridae, Circoviridae, CircinoviridaeCircinoviridae

TA278, GH1, SANBAN, YONBAN, TA278, GH1, SANBAN, YONBAN, TUS01TUS01

Ubiquitous, global distributionUbiquitous, global distribution

TTV

EpidemiologyEpidemiology

The most remarkable feature of TTV The most remarkable feature of TTV is the extraordinarily high prevalence is the extraordinarily high prevalence of chronic viremia in apparently of chronic viremia in apparently healthy people, up to nearly 100% in healthy people, up to nearly 100% in some countries.some countries.

TTV infection of healthy blood donors TTV infection of healthy blood donors has been reported from many has been reported from many countries with varying prevalences:countries with varying prevalences:

TTV

InIn Asia; Asia; Japan, China, Mongolia, Russia, Japan, China, Mongolia, Russia, Taiwan, Thailand, Myanmar, Singapore, Taiwan, Thailand, Myanmar, Singapore, Pakistan, India, Nepal, New Zealand, Papua Pakistan, India, Nepal, New Zealand, Papua New Guinea and Saudi Arabia.New Guinea and Saudi Arabia.

In In AfricaAfrica; Egypt, Sudan, Congo, Nigeria, ; Egypt, Sudan, Congo, Nigeria, Tanzania and Gambia.Tanzania and Gambia.

In In EuropeEurope; Italy, France, UK, Scotland, ; Italy, France, UK, Scotland, Iceland, Netherlands and Finland.Iceland, Netherlands and Finland.

In the In the AmericasAmericas; USA, Equador, Colombia, ; USA, Equador, Colombia, Bolivia and Brazil.Bolivia and Brazil.

Epidemiology, continued…...Epidemiology, continued…...

TTV

Virus Genome and Virus Genome and ReplicationReplication

Long ORFLong ORF11 preceded by a short ORF preceded by a short ORF22 with an overlap.with an overlap.

ORFORF33 lacks an initiation codon. lacks an initiation codon. Novel 113 nt between 3’ and 5’ end Novel 113 nt between 3’ and 5’ end

arms forming a GC-rich stretch.arms forming a GC-rich stretch. The most conserved nucleotide The most conserved nucleotide

sequence is found in the non-coding sequence is found in the non-coding region just upstream from ORFregion just upstream from ORF22..

TTV

33 hyper-variable regions identified in a hyper-variable regions identified in a central position of ORF1. central position of ORF1.

Quasispecies to evade the immune Quasispecies to evade the immune surveillance of the host and establish surveillance of the host and establish persistent infection.persistent infection.

N-glycosylation site in the middle of ORF1.N-glycosylation site in the middle of ORF1. TATA box upstream of ORF1 & ORF2.TATA box upstream of ORF1 & ORF2. Poly A signal downstream.Poly A signal downstream.

Virus Genome, continuedVirus Genome, continued…..…..

TTV

Virus Genome, continued….Virus Genome, continued….

Rolling circle mechanism.Rolling circle mechanism. Three mRNAs were revealed in Three mRNAs were revealed in

bone marrow cells.bone marrow cells. Homologous recombination within Homologous recombination within

and among genotypes is and among genotypes is extensive. extensive.

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Sites of Viral Sites of Viral ReplicationReplication

LiverLiver Bone marrowBone marrow

PBMCsPBMCs Oropharyngeal Oropharyngeal

tissue or salivary tissue or salivary glandsglands

Viral GenotypesViral Genotypes Wide range of sequence divergence.Wide range of sequence divergence. Swarm of closely related viruses.Swarm of closely related viruses. 16 genotypes.16 genotypes. Variants, shared overall genetic structure Variants, shared overall genetic structure

and conserved a.a. motifs.and conserved a.a. motifs. Genotypes 1a & 1b most prevalent, ? Genotypes 1a & 1b most prevalent, ?

disease potential.disease potential. Quasispecies, genetic heterogeneity & Quasispecies, genetic heterogeneity &

viral evolution.viral evolution. Mixed infections with multiple strains. Mixed infections with multiple strains.

TTV

TTV in Body Fluids & TTV in Body Fluids & TissuesTissues

StoolStool SalivaSaliva BileBile UrineUrine Breast milkBreast milk SemenSemen TearsTears SweatSweat Throat swabsThroat swabs

KidneyKidney ProstateProstate Brain tissueBrain tissue Mammary tissueMammary tissue

TTV

Modes of TransmissionModes of Transmission

Blood transfusionBlood transfusion Fecal oral routeFecal oral route Community acquiredCommunity acquired NosocomialNosocomial VerticalVertical Air-borneAir-borne Salivary dropletsSalivary droplets SexualSexual

TTV

Detection and Detection and QuantificationQuantification

EMEM PCRPCR RTD-PCRRTD-PCR IgM anti-TTVIgM anti-TTV anti-TTVanti-TTV

TTV

Sequencing RFLPSequencing RFLP

Direct Di-deoxy chain mediated terminationDirect Di-deoxy chain mediated termination

Alignment Distance Alignment Distance

Phylogenetic Analysis ParsimonyPhylogenetic Analysis Parsimony Bootstrap resampling Maximum likelihoodBootstrap resampling Maximum likelihood

TypingTyping

TTV

TTV and Liver DiseaseTTV and Liver Disease

TTV DNA significantly detected in TTV DNA significantly detected in serum of patients with post-serum of patients with post-transfusion hepatitis and viral titre transfusion hepatitis and viral titre synchronized with ALT levels.synchronized with ALT levels.

In 5% of blood donors with In 5% of blood donors with elevated ALT but in only 0.7% with elevated ALT but in only 0.7% with normal normal

ALT.ALT.

TTV

With Liver Disease, continued….With Liver Disease, continued….

With HCVWith HCV TTV does not affect clinical, biological TTV does not affect clinical, biological

or histological features of HCV hepatitis.or histological features of HCV hepatitis. No effect on HCV response to IFN.No effect on HCV response to IFN.

TTV infected chronic HCV cases have TTV infected chronic HCV cases have lower HCV-RNA level.lower HCV-RNA level.

Serum TTV DNA titres are not Serum TTV DNA titres are not synchronized with serum ALT level.synchronized with serum ALT level.

TTV

With Liver Disease, With Liver Disease, continued…...continued…...

With HBVWith HBV Same as HCVSame as HCV

With fulminant hepatitisWith fulminant hepatitis No difference in clinical findings, No difference in clinical findings,

duration from onset to coma or results duration from onset to coma or results of lab tests.of lab tests.

Outcome for patients with fulminant Outcome for patients with fulminant hepatic failure worse in those with TTV hepatic failure worse in those with TTV infection.infection.

TTV

In Hepatocellular CarcinomaIn Hepatocellular Carcinoma

No significant differences in age, No significant differences in age, gender ratio, liver functions, tumor gender ratio, liver functions, tumor biology, other viral markers, biology, other viral markers, amount of alcohol intake or amount of alcohol intake or prognosis found between TTV prognosis found between TTV positive and negative cases.positive and negative cases.

TTV

In HCC, continued…...In HCC, continued…...

TTV does not seem to contribute to TTV does not seem to contribute to the development of HCC from the development of HCC from chronic liver disease, does not chronic liver disease, does not affect the features of non-A to G affect the features of non-A to G HCC and is not correlated with HCC and is not correlated with severity of liver disease.severity of liver disease.

No TTV DNA integration into host No TTV DNA integration into host DNA by Southern blotting.DNA by Southern blotting.

TTV

Hepatitis SurveillanceHepatitis Surveillance

““agents recently identified in agents recently identified in patients with viral hepatitis. patients with viral hepatitis. However, studies conducted to date However, studies conducted to date have shown have shown no associationno association between between these agents and acute and chronic these agents and acute and chronic hepatitis.”hepatitis.”

TTV

Pathology of Liver in TTV Pathology of Liver in TTV InfectionsInfections

By in situ hybridization, 3 staining By in situ hybridization, 3 staining patterns:patterns:

Nuclear, cytoplasmic and both i.e. Nuclear, cytoplasmic and both i.e. it is hepatotropic.it is hepatotropic.

No morphological changes or mild No morphological changes or mild changes suggesting a favorable changes suggesting a favorable outcome.outcome.

TTV

TTV in EgyptTTV in Egypt

46%46% of chronic HBV patients.of chronic HBV patients. 31% of chronic HCV patients.31% of chronic HCV patients. 36% of Schistosomal liver disease pts.36% of Schistosomal liver disease pts. 29% of blood donors.29% of blood donors. No difference in mean age, sex No difference in mean age, sex

distribution, history of blood distribution, history of blood transfusion or mean ALT level transfusion or mean ALT level between TTV +ve & -ve in each group.between TTV +ve & -ve in each group.

TTV

TTV in Egypt, continued….TTV in Egypt, continued….

85%85% of blood donors are TTV DNA of blood donors are TTV DNA positive positive

Genotypes 1 & 2 mainlyGenotypes 1 & 2 mainly

TTV

Association with other Association with other diseasesdiseases

No association with hematopoietic No association with hematopoietic malignancies.malignancies.

No role in posthepatitis aplastic No role in posthepatitis aplastic anemia.anemia.

No role in Behcet’s disease.No role in Behcet’s disease. No association with Kawasaki No association with Kawasaki

disease.disease. No link with rheumatoid arthritis.No link with rheumatoid arthritis.

TTV

Risk of Occupational Risk of Occupational InfectionInfection

Prevalence in workers in the medical Prevalence in workers in the medical field (doctors, dentists, nurses, field (doctors, dentists, nurses, laboratory technicians and office staff) laboratory technicians and office staff) similar to age matched controls.similar to age matched controls.

It appears that health care workers It appears that health care workers are not at increased risk of acquisition are not at increased risk of acquisition of TTV through their profession.of TTV through their profession.

TTV

Related VirusesRelated Viruses

TT virus like mini virus (TT virus like mini virus (TLMVTLMV))

Non-enveloped, single stranded negativeNon-enveloped, single stranded negative

sense, closed circular DNA virus.sense, closed circular DNA virus.

It is intermediate between TTV and CAV.It is intermediate between TTV and CAV. SENVSENV

Single stranded circular DNA viruses.Single stranded circular DNA viruses.

Some isolates have a possible associationSome isolates have a possible association

with posttransfusion hepatitis.with posttransfusion hepatitis.

TTV

The original hypothesis that TTV The original hypothesis that TTV might be an important cause of might be an important cause of cryptogenic hepatitis has not been cryptogenic hepatitis has not been borne out, although the possibility borne out, although the possibility that it might produce liver damage that it might produce liver damage under specific conditions has not under specific conditions has not been excluded. It has not been been excluded. It has not been etiologically linked to any other etiologically linked to any other human disease. Thus, TTV should human disease. Thus, TTV should be considered an “be considered an “orphanorphan” virus.” virus.

ConclusionConclusion

TTV

Discrimination of distinct TTV Discrimination of distinct TTV variants by direct sequencingvariants by direct sequencing

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PhylogramPhylogram