Related TT viruses in chimpanzees

Torque Teno Sus Virus (TTSuV) Prevalence in Wild Fauna of Northern Italy

Torque teno sus virus (TTSuV) is a non-enveloped circular ssDNA virus which frequently infects swine and has been associated with hepatic, respiratory, and autoimmune disorders. TTSuV’s pathogenic role is still uncertain, and clear data in the literature on virus reservoirs are lacking. The aims of this study were to investigate the presence of potentially zoonotic TTSuV in wild animals in Northern Italy and to evaluate their role as reservoirs. Liver samples were collected between 2016 and 2020 during four hunting seasons from wild boars (Sus scrofa), red deer (Cervus elaphus), roe deer (Capreolus capreolus), and chamois (Rupicapra rupicapra). Samples originated from areas in Northern Italy characterized by different traits, i.e., mountains and flatland with, respectively low and high farm density and anthropization. Viral identification was carried out by end-point PCR with specific primers for TTSuV1a and TTSuVk2a species. TTSuV prevalence in wild boars was higher in the mountains than in the flatland (prevalence of 6.2% and 2.3%, respectively). In wild ruminants only TTSuVk2a was detected (with a prevalence of 9.4%). Our findings shed light on the occurrence and distribution of TTSuV in some wild animal species, investigating their possible role as reservoirs.

Two new species of betatorqueviruses identified in a human melanoma that metastasized to the brain

The role of viral infections in the etiology of brain cancer remains uncertain. Prior studies mostly focused on transcriptome or viral DNA integrated in tumor cells. To investigate for the presence of viral particles, we performed metagenomics sequencing on viral capsid-protected nucleic acids from 12 primary and 8 metastatic human brain tumors. One brain tumor metastasized from a skin melanoma harbored two new human anellovirus species, Torque teno mini virus Emory1 (TTMV Emory1) and Emory2 (TTMV Emory2), while the remaining 19 samples did not reveal any exogenous viral sequences. Their genomes share 63-67% identity with other TTMVs, and phylogenetic clustering supports their classification within the Betatorquevirus genus. This is the first identification of betatorqueviruses in brain tumors. The viral DNA was in its expected non-integrated circular form, and it is unclear if the viruses contributed to tumor formation. Whether the viruses originated from blood, or the primary skin tumor could not be ascertained. Overall, our results demonstrate the usefulness of viral metagenomics to detect previously unknown exogenous virus in human brain tumors. They further suggest that active viral infections are rare events in brain tumors, but support a follow-up larger scale study to quantify their frequency in different brain tumor subtypes.

New species of Torque Teno miniviruses infecting gorillas and chimpanzees

Anelloviridae family is comprised of small, non-enveloped viruses of various genome lengths, high sequence diversity, sharing the same genome organization. Infections and co-infections by different genotypes in humans are ubiquitous. Related viruses were described in number of mammalian hosts, but very limited data are available from the closest human relatives - great apes and non-human primates. Here we report the 100% prevalence determined by semi-nested PCR from fecal samples of 16 captive primate species. Only the Mandrillus sphinx, showed the prevalence only 8%. We describe three new species of gorillas׳ and four new species of chimpanzees׳ Betatorqueviruses and their co-infections in one individual. This study is also first report and analysis of nearly full length TTMV genomes infecting gorillas. Our attempts to sequence the complete genomes of anelloviruses from host feces invariably failed. Broader usage of blood /tissue material is necessary to understand the diversity and interspecies transmission of anelloviruses.

Global occurrence of Torque teno virus in water systems

Bacterial indicator organisms are used globally to assess the microbiological safety of waters. However, waterborne viral outbreaks have occurred in drinking water systems despite negative bacterial results. Using viral markers may therefore provide more accurate health risk assessment data. In this study, fecal, wastewater, stormwater, surface water (fresh and salt), groundwater, and drinking water samples were analyzed for the presence or concentration of traditional indicators, innovative indicators and viral markers. Samples were obtained in the United States, Italy, and Australia and results compared to those reported for studies conducted in Asia and South America as well. Indicators included total coliforms, Escherichia coli, enterococci, male-specific coliphages, somatic coliphages and microviradae. Viral markers included adenovirus, polyomavirus, and a potential new surrogate, Torque teno virus (TTV). TTV was more frequently found in wastewaters (38-100%) and waters influenced by waste discharges (25%) than in surface waters used as drinking water sources (5%). TTV was also specific to human rather than animal feces. While TTV numbers were strongly correlated to other viral markers in wastewaters, suggesting its utility as a fecal contamination marker, data limitations and TTV presence in treated drinking waters demonstrates that additional research is needed on this potential viral indicator.

Whole genome sequencing and phylogenetic analysis of feline anelloviruses

Torque teno felis virus (FcTTV) was detected in the cat population in the Czech Republic. A total of 110 serum samples were tested by a nested PCR technique using specific primers, situated in the highly conserved untranslated region of the virus genome. The frequency of feline TT virus in the Czech Republic was found to be 33.63%. Sequencing of PCR product from several virus strains showed that all of them are closely related and belong to the same virus species. Whole genome sequencing of three strains was performed to compare overall genetic heterogeneity of feline TT viruses. One of these three strains showed more that 10% difference at the nucleotide level. Furthermore we didn't find any correlation between FcTTV infection and sex or health status of examined animals.

Preliminary epitope mapping of Torque teno sus virus 1 and 2 putative capsid protein and serological detection of infection in pigs

The aim of this work is to identify antigenic regions within the ORF1 protein of Torque teno sus virus 1 (TTSuV1) and Torque teno virus sus 2 (TTSuV2) that could be used as antigens to detect virus-specific antibodies following infection in pigs. Protein sequences of TTSuV ORF1 genes were analysed to predict linear antigenic epitopes. Synthesized peptides were analysed for serological reactivity with swine sera. Such an antigenic region was identified at the C terminus of the ORF1 protein of both viruses and showed serological reactivity with 78 % (TTSuV1) and 88 % (TTSuV2) of swine sera. An ELISA with an immunodominant peptide as antigen was used to examine the sera of piglets, aged 4–20 weeks, and adults. Results indicated that TTSuV1- and TTSuV2-specific antibodies were detectable at 4 weeks. Antibody titres increased from week 10 and peaked at week 20. A relatively high antibody titre persisted to adulthood.

Torque teno sus virus 1 and 2 viral loads in postweaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS) affected pigs

Torque teno viruses (TTV) are small, non-enveloped viruses with a circular single-stranded DNA genome, which are considered non-pathogenic. However, TTVs have been eventually linked to human diseases. TTVs infecting pigs, Torque teno sus virus 1 (TTSuV1) and 2 (TTSuV2), have been recently associated to porcine circovirus diseases (PCVD). To get more insights into such potential disease association, the aim of this study was to quantify TTSuV1 and TTSuV2 viral loads in serum of pigs affected by two PCVDs, postweaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS). Such study was carried out by means of a newly developed real-time quantitative PCR (qPCR) method. Both TTSuVs were highly prevalent among studied pigs. TTSuV2 viral loads were significantly higher in PMWS affected animals, further supporting the previously suggested association between TTSuV2 and PMWS. On the contrary, TTSuV1 prevalence and loads were not related with the studied PCVDs.

Sequence analysis of a Torque teno canis virus isolated in China

In the present study, a total of 158 fecal samples were collected from diarrheal dogs younger than 1 year old in pet clinic in China. 20 specimens (20/158, 13%) were positive for Torque teno canis virus DNA using detection PCR. One representative positive isolate designated LDL was randomly selected, cloned and sequenced. The complete genome of the LDL Chinese strain was 2799 nucleotides in length and contains three open reading frames (ORFs), which encode 576 (ORF1), 101 (ORF2), and 243 (ORF3) aa. Compared with the human and other animal TTV genomes, the genome of the LDL strain is clearly smaller and shares 95% identity with Japanese cf-TTV10 strain (AB076002). Phylogenetic analysis showed that the present Chinese Torque teno canis virus LDL strain was also closely clustered with the previous Japanese cf-TTV10 strain, and formed a different branch together with Torque teno sus viruses 1 and 2 compared with other Torque teno viruses, Torque teno mini virus, and Torque teno midi virus. Our study demonstrated that Torque teno canis virus is present in China.

Prevalence and age distribution of porcine torque teno sus virus (TTSuV) in the Czech Republic

Torque teno sus viruses (TTSuV) were detected in the pig population in the Czech Republic by a nested PCR technique. The prevalence of individual TTSuV was found to be 42.9% (TTSuV1) and 46.7% (TTSuV2). The prevalence for TTSuV 1 and TTSuV2 was determined to be 52.7% and 60.6% in piglets at weaning, 90.9% and 63.6% in gilts, and 75% and 87.5% in sows, respectively. Both virus species were detected in 12% of newborn piglets, which suggests possible transplacental transmission. Sequencing of several virus strains showed that the sequenced TTSuV strains belong to two different species of viruses. The average similarity on the nucleotide levels between these two species was 43.3%.

Age-related tissue distribution of swine Torque teno sus virus 1 and 2

Torque teno viruses (TTVs) are small, non-enveloped viruses with a circular single-stranded DNA genome, belonging to the family Anelloviridae. In swine, two genetically distinct species have been identified, Torque teno sus virus 1 (TTSuV1) and 2 (TTSuV2). The aim of the present work was to study the tissue distribution of TTSuV1 and TTSuV2 in pigs of different ages, including foetuses at the second and last thirds of gestation, and animals at 5 days and 5, 15 and 24 weeks of age. Investigated tissues included brain, lung, mediastinal and mesenteric lymph nodes, heart, liver, spleen, kidney and bone marrow. Viral DNA from tissue extractions were tested by a comparative PCR for the presence of TTSuVs. Overall, TTSuV1 and TTSuV2 species were found in all tissues tested, with variations depending on age, and following similar infection dynamics in all tissues, increasing progressively in prevalence and virus load over time. The highest prevalence was found at 5 weeks of age and maintained afterwards, and the highest loads of virus in the different tissues were seen in the oldest animals (15 and 24 weeks of age). No animals were negative to TTV, including foetuses. In conclusion, the present study indicated that swine TTSuV1 and TTSuV2 can be found virtually in all body tissues of the pig. Both swine TTV species were present in high levels in almost all older animals, while viral negative tissues were only found in 5-week-old and 5-day-old pigs, and foetuses.

Development of a real-time TaqMan PCR assay for the detection of porcine and bovine Torque teno virus

AIMS

The goal of this study was to develop and to optimize molecular tools to detect the presence of Torque teno virus (TTV) in swine and cattle. A novel real-time polymerase chain reaction (PCR) using a TaqMan probe was developed to detect both genogroups of TTV strains.

METHODS AND RESULTS

Oligonucleotide primers and hybridization probes were designed based on sequence analysis of the noncoding region, a highly conserved part of the genome. The real-time PCR assay specifically detected bovine and porcine TTV DNA without cross-amplification of other common pathogens. The assay was compared with conventional PCR and nested-PCR assays for the detection of porcine genogroups 1 and 2 and bovine TTV on plasma and faecal samples, and the assay was found faster, more reliable and reduced the risk of false positive results.

CONCLUSIONS

The real-time PCR assay provided better detection results for the two TTV genogroups in both swine and cattle compared to the conventional PCR assays.

SIGNIFICANCE AND IMPACT OF THE STUDY

This new TaqMan PCR assay will be a useful tool for the detection of animal TTV strains, to evaluate the viral load from animal host and finally to identify the presence of these viruses in the agri-food continuum.

Analysis of the entire genomes of torque teno midi virus variants in chimpanzees: infrequent cross-species infection between humans and chimpanzees

Humans are frequently infected with three anelloviruses which have circular DNA genomes of 3.6-3.9 kb [Torque teno virus (TTV)], 2.8-2.9 kb [Torque teno mini virus (TTMV)] and 3.2 kb [a recently discovered anellovirus named Torque teno midi virus (TTMDV)]. Unexpectedly, human TTMDV DNA was not detectable in any of 74 chimpanzees tested, although all but one tested positive for both human TTV and TTMV DNA. Using universal primers for anelloviruses, novel variants of TTMDV that are phylogenetically clearly separate from human TTMDV were identified from chimpanzees, and over the entire genome, three chimpanzee TTMDV variants differed by 17.9-20.3 % from each other and by 40.4-43.6 % from all 18 reported human TTMDVs. A newly developed PCR assay that uses chimpanzee TTMDV-specific primers revealed the high prevalence of chimpanzee TTMDV in chimpanzees (63/74, 85 %) but low prevalence in humans (1/100). While variants of TTV and TTMV from chimpanzees and humans were phylogenetically interspersed, those of TTMDV were monophyletic for each species, with sequence diversity of <33 and <20 % within the 18 human and three chimpanzee TTMDV variants, respectively. Maximum within-group divergence values for TTV and TTMV were 51 and 57 %, respectively; both of these values were substantially greater than the maximum divergence among TTMDV variants (44 %), consistent with a later evolutionary emergence of TTMDV. However, substantiation of this hypothesis will require further analysis of genetic diversity using an expanded dataset of TTMDV variants in humans and chimpanzees. Similarly, the underlying mechanism of observed infrequent cross-species infection of TTMDV between humans and chimpanzees deserves further analysis.

Classification of TTV and related viruses (anelloviruses)

Ten years after the identification of the first partial sequences of Torque teno virus (TTV), more than 200 full-length related genomes have been characterized in humans and in several animal species. As suspected in the earlier stages of their description, a considerable genetic variability characterizes TTV and related viruses, the current members of the floating genus Anellovirous. Since information related to anelloviruses diversity is in constant evolution, the challenge in their taxonomic classification is to take into account all pertinent parameters, along with the taxonomic situation of other viruses having circular single-stranded DNA genomes. Past, present and future phylogenetic and taxonomic considerations are exposed.

TT viruses in animals

Infection with TT virus (Torque teno virus, TTV), a small, nonenveloped virus with a circular, single-stranded DNA genome classified in the floating genus Anellovirus, is not restricted to humans. Using highly conserved primers derived from the untranslated region of the human TTV genome, a variety of TTV-like viruses have been found circulating in nonhuman primates such as chimpanzees, macaques, and tamarins. TTV variants in nonhuman primates are species-specific, although some genetic groups of human and chimpanzee TTVs cluster to make human/chimpanzee clades. TTVs from macaques and tamarins are increasingly divergent from TTV variants infecting humans and chimpanzees. TTV-like mini virus (TTMV) infections have also been detected in chimpanzees, with genotypes distinct but interspersed with human TTMV genotypes. Pets are also naturally infected with species-specific TTVs, and several isolates have been found in cats and dogs. In addition, other mammals such as tupaias and pigs have species-specific TTVs: swine TTVs are found among pigs worldwide. The genomic organization and proposed transcriptional profiles of TTVs infecting nonhuman primate and other mammalian species are similar to those of human TTVs, and co-evolution of TTVs with their hosts has been suggested. To date, TTVs infecting nonhuman primates and other mammalian species have been under-examined. It is likely that essentially all animals are naturally infected with species-specific TTVs.

Identification and genomic characterization of a novel human torque teno virus of 3.2 kb

In the process of searching for the recently described small anelloviruses 1 and 2 (SAVs) with the genomic DNA length of 2.2 or 2.6 kb in human sera, we isolated a novel virus with its genomic organization resembling those of torque teno virus (TTV) of 3.8-3.9 kb and torque teno mini virus (TTMV) of 2.8-2.9 kb. The entire genomic sequence of three isolates (MD1-032, MD1-073 and MD2-013), which comprised 3242-3253 bases and exhibited 76-99 % identities with the SAVs within the overlapping sequence, was determined. Although the MD1-032, MD1-073 and MD2-013 isolates differed by 10-28 % from each other over the entire genome, they segregated into the same cluster and were phylogenetically distinguishable from all reported TTVs and TTMVs. These results suggest that SAVs are deletion mutants of the novel virus with intermediate genomic length between those of TTV and TTMV and that the novel virus can be classified into a third group of the genus Anellovirus.

Molecular detection of bovine and porcine Torque teno virus in plasma and feces

Torque teno virus (TTV) is frequently detected in humans, livestock and some companion animals. Very little is known about presence of TTV in Canadian livestock and the goal of this study was to evaluate the presence of TTV in swine and cattle using molecular tools. TTV DNA was detected and confirmed by sequencing in the plasma of 90.5% and in the feces of 60.3% of the animals tested in a single swine herd as well as 80.9% and 1.1% in the plasma of individuals from general Quebec swine and cattle populations, respectively. The impact of the TTV presence in livestock population for the agri-food chain should be further investigated.

Torque teno virus (TTV): current status

Torque teno virus (TTV), currently classified into the family Circoviridae, genus Anellovirus, was first found in a patient with non-A-E hepatitis. TTV has a single stranded circular DNA of approximately 3.8 kb. TTVs are extraordinarily diverse, spanning five groups including SANBAN and SEN viruses. Torque teno mini virus (TTMV) with approximately 2.9 kb genome also has wide variants. Recently, two related 2.2- and 2.6-kb species joined this community. Recombinations between variants are frequent. This extensive TTV diversity remains unexplained; it is unclear how TTVs could be viable, and why they require such genetic variation. An unequivocal culture system is still not available. TTVs are ubiquitous in > 90% of adults worldwide but no human pathogenicity of TTV has been fully established. Epidemiological surveys need to specify the variants being studied and clinical targets, and must calibrate the sensitivity of the assay used. Potentially interesting observations include a higher viral load in patients with severe idiopathic inflammatory myopathies, cancer and lupus. Active replication was also found in infants with acute respiratory diseases. TTV/TTMV-related viruses were found in chimpanzees, apes, African monkeys and tupaias, and also in chickens, pigs, cows, sheep and dogs. Experimentally, rhesus monkeys were persistently infected by TTV, but only 1/53 chimpanzees. TTV transcribes three species of mRNAs, 3.0-, 1.2- and 1.0-kb in the ratio of 60:5:35. Recently, at least three mRNAs were shown in chicken anaemia virus. The genomic region -154/-76 contains a critical promoter. TTV seems to have at least three proteins; however, the definite functions of these proteins await further research work.

Pig anelloviruses are highly prevalent in swine herds in France

A survey of anelloviruses in swine herds from Britanny, France, is reported. By using PCR targeted to the conserved untranslated region, prevalences of 93 and 73 % were found among 15 herds and 33 animals, respectively. The lung was the organ found to be positive most frequently among the five organs tested from 32 animals. The highest identity levels of our nucleotide sequences were found with pig isolates from Japan and with an isolate from Tupaia belangeri. Interestingly, when aligning all available swine isolates from France and Japan, at least two phylogenetic groups were identified, each one containing clones from France and Japan. Some animals carried clones from both groups, demonstrating intra-individual variability. Despite the putative harmlessness of anelloviruses, the potential inoculum carried by pigs must be further evaluated as a sanitary threat.

Isolation of multiple TT virus genotypes from spleen biopsy tissue from a Hodgkin's disease patient: genome reorganization and diversity in the hypervariable region

We report the isolation of 24 novel genotypes of TT viruses from a surgically removed spleen of a patient with Hodgkin's disease. The sequence analysis of our 24 isolates revealed the remarkable heterogeneity of TT virus isolates not only from the same patient but also from the same biopsy material. These isolates belong to four phylogenetic groups of TT viruses. Nucleotide sequence analyses revealed five distinct genotypes (tth3, tth4, tth5, tth6, and tth7). The limited variation in sequence identity of the other isolates defines the latter as variants of four of these genotypes. A group of 6 isolates (the tth7 group) revealed a reorganization of open reading frame 1 (ORF1) leading to one larger and a varying number of smaller ORFs. The nucleotide difference of the full-length genomes was less than 1%. A variation of 69 to 97% in amino acids of a second group of 8 isolates (the tth3 group) was restricted to the hypervariable region of ORF1, indicating the existence of a quasi-species. These isolates differed by less than 2% in the remainder of their nucleotide sequences. An alignment of these isolates with 79 previously reported TT virus genotypes permits the proposal of TT virus genera and species within the family Anelloviridae in analogy to a previous proposal for the papillomaviruses (family Papillomaviridae).

New prevalence estimate of TT virus (TTV) infection in low- and high-risk population from São Paulo, Brazil

The prevalence of TT virus (TTV) infection was investigated by Polymerase Chain Reaction (PCR) in low- (blood donors and healthy children/adolescents) and high-risk (hemophiliacs) groups from São Paulo, Brazil. Primers based on the untranslated region (UTR) of the viral genome proved to be much more ubiquitous, leading to much higher frequencies for both groups (>or= 81%) than the earlier N22-PCR directed to the open reading frame 1 (blood donors, 5.5%, and hemophiliacs, 42.3%). The UTR-PCR also revealed an interesting profile for healthy children/adolescents: very high prevalence at the early years and significant decrease in male teenagers. The N22-PCR, in turn, demonstrated higher frequency in hemophiliacs treated with fresh blood products (58%), than in those treated with virus-inactivated clotting factors (9.4%) and blood donors (5.5%).

Novel TTV variants isolated in an epidemic of hepatitis of unknown etiology

TT virus (TTV) is a recently discovered single-stranded DNA virus that has been reported to be associated with elevated transminase levels in the patients with posttransfusion hepatitis of unknown etiology. TTV prevalence is very high in the common population and its pathogenicity remains unclear. In this study, we performed an epidemiological study to investigate the infection rate of TTV and its role in an epidemic of unknown-etiology hepatitis. Moreover, two TTV isolates named L01 and L02 were cloned from the serum of a patient with unknown-etiology hepatitis. Eighty-one subjects were included in the study and were divided into two groups: 18 in the case group and 63 in the control group. TTVDNA was detected by nested PCR from sera samples. The infection rates of TTV in case and control groups were 33.3 and 38.9%, respectively. There was no significant difference between the two groups. Homology analysis showed that L01 had a very poor homology with other TTV isolates and L02, and L02 was 75.5% identical to JA10. The result does not support TTV as a causative agent in this epidemic. The genetic divergence between L01 and other TTV isolates beyond genotype, so it represents a new genotype of TTV.

Phylogenetic classification of TT virus groups based on the N22 region is unreliable

Evolutionary studies on the recently discovered TT virus (TTV) are currently focused on approximately 220 nts of the N22 region, since this is the region for which most sequence information is available. Regarding the extensive sequence heterogeneity in this region, within group classification can be sufficiently reliable, however, between group classification becomes problematic. We observed high divergence at the nucleotide level between distant related strains (TTV groups) preventing unambiguous alignments, saturation in transitions within TTV groups and considerable phylogenetic noise due to conflicting signals within distinct genotypes. Consequently, analysing all TTV groups in one tree, using this 220 nt region provides unreliable results. Also within genotype analysis can produce conflicting results. On the other hand, this region is still suitable to some extent for within TTV group phylogenetic analysis. We suggest that care should be taken in future TTV phylogenetic analysis, in particular, larger and more conserved regions should be sequenced to allow between group comparisons.

High frequency of mixed TT virus infections in healthy adults and children detected by a simplified heteroduplex mobility assay

Recombinant plasmids carrying 199 base pairs (bp) inserts from the non coding region (nucleotides (nt) 6-204) of the TT virus (TTV) genome were used to standardize an heteroduplex mobility assay able to detect mixed infections of a single individual with several TTV isolates. In this simplified heteroduplex mobility assay, polymerase chain reaction (PCR) products were analyzed directly by polyacrylamide gel electrophoresis, without requirement for post-PCR denaturation and annealing steps of the amplicons. The assay was used to test TTV positive serum samples collected from healthy 1-7 years old children, 11-17 years old adolescents, and 24-39 years old blood donors living in Rio de Janeiro, Brazil, as well as TTV positive samples from Amazonian Indians. The results showed a very high frequency of multiple infection in all groups, with 20/30 (67%), 31/33 (94%), 35/38 (92%), and 34/37 (92%) of the samples collected from children, adolescents, blood donors, and Amazonian Indians, respectively, containing more than one TTV genotype.

Prevalence and genotypic distribution of TT virus in Athens, Greece

The prevalence of TT virus (TTV) infection in various population groups from Athens, Greece, was assessed by the polymerase chain reaction (PCR) using two primer sets from distinct regions of the genome: the conventional set derived from the open reading frame-1 (ORF-1) and the new, highly sensitive set targeting the region that includes the TATA signal localized upstream of ORF-2. Based on both primer sets, TTV DNA was detected in 42/50 (84.0%) healthy individuals, 42/50 (84.0%) chronic hepatitis C patients, 31/39 (79.5%) acute non-A-E hepatitis patients (group I), 14/16 (87.5%) renal failure patients with acute non-A-E hepatitis (group II), 47/50 (94.0%) intravenous drug users (IVDU), 36/50 (72.0%) hemophiliacs, and 21/31 (67.7%) hemodialysis patients. The presence of TTV was not associated with any particular risk group, and no differences were observed in relation to demographic, biochemical and virological characteristics between TTV DNA-positive and -negative patients. TTV did not seem to have a profound effect on the course of chronic C or acute non-A-E hepatitis either. Phylogenetic analysis revealed that TTV strains circulating in the greater metropolitan area of Athens belong not only to the G1 and G2 genotypes that are encountered worldwide, but also to G3 and to G5 that are found mainly in Europe and Asia, respectively. Further studies will shed light on the role of this highly prevalent virus.