Transfusional transmitted virus seroprevalence in asymptomatic HBsAg (+) hepatitis B carriers

BACKGROUND

The aim of this study was to evaluate the transfusional transmitted virus (TTV) seroprevalence in asymptomatic HBsAg (+) patients and to assess the influence of TTV on the course of these patients.

METHODS

Sixty asymptomatic HBV carriers were included and 31 healthy volunteers served as controls. Cases were followed at 6-month intervals for a total duration of 4 years.

RESULTS

In the asymptomatic carrier group, 31 patients (51.7%) had a history of surgery and 10 (16.7%) had a history of blood transfusions. TTV-DNA was detected in 45 of these patients (75%). In the control group, 12 patients (38.7%) had a history of surgery and 2 had (6.5%) a history of blood transfusions. TTV-DNA was found in 20 (64.5%) of these subjects. The incidence of TTV-DNA positivity was not significantly different between the two groups (P > 0.05).

CONCLUSION

In spite of the common occurrence of HBV and TTV, TTV-DNA was also detected in 64.5% of healthy controls. Furthermore, during 4 years of follow up, TTV had no detrimental effects on the course of asymptomatic HBV carriers. These results suggest that the hepatic injury due to TTV is insignificant in this group of patients.

High prevalence of transfusion-transmitted virus infection in patients with chronic liver diseases in an endemic area of hepatitis B and C virus

OBJECTIVE

To determine the prevalence and clinical impact of transfusion-transmitted virus (TTV) DNA in patients with chronic liver diseases in the Southeast Anatolia region of Turkey where hepatitis B and C viral infections are endemic.

SUBJECTS AND METHODS

Patients diagnosed with chronic liver disease by clinical, biochemical and histologic means were enrolled in the study. Serum samples of 60 patients (19 males, 41 females) with chronic liver diseases, and of 45 healthy volunteer blood donors as a control group were collected. The chronic liver disease group consisted of 11 patients with hepatitis B, 44 with hepatitis C and 5 with chronic liver disease of unknown etiology. Presence of TTV DNA was investigated by the polymerase chain reaction. Using a scoring system histological grading of inflammation and staging of fibrosis were performed only in the chronic hepatitis C group.

RESULTS

TTV DNA was detected in 47 (78%) patients with chronic liver disease and 5 (11%) volunteers in the control group. The difference was statistically significant (p < 0.001). Ten of the 11 (91%) patients with hepatitis B, 32 of 44 (73%) of those with hepatitis C-related chronic liver disease, and 5 of 5 (100%) of the patients with cryptogenic liver disease were positive for TTV DNA.

CONCLUSION

TTV is highly prevalent in patients with chronic liver diseases in Southeast Anatolia, Turkey but no pathogenic effect attributable to TTV infection was detected.

TT virus and hepatitis G virus infections in Korean blood donors and patients with chronic liver disease

AIM: To determine the prevalences of TTV and HGV infections among blood donors and patients with chronic liver disease in Korea, to investigate the association of TTV and HGV infections with blood transfusion, and to assess the correlation between TTV and HGV viremia and hepatic damage.

METHODS: A total of 391 serum samples were examined in this study. Samples were obtained from healthy blood donors (n = 110), hepatitis B surface antigen (HBsAg)-positive donors (n = 112), anti-hepatitis C virus (anti-HCV)-positive donors (n = 69), patients with type B chronic liver disease (n = 81), and patients with type C chronic liver disease (n = 19). TTV DNA was detected using the hemi-nested PCR. HGV RNA was tested using RT-PCR. A history of blood transfusion and serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were also determined.

RESULTS: TTV DNA was detected in 8.2% of healthy blood donors, 16.1% of HBsAg-positive donors, 20.3% of anti-HCV-positive donors, 21.0% of patients with type B chronic liver disease, and 21.1% of patients with type C chronic liver disease. HGV RNA was detected in 1.8% of healthy blood donors, 1.8% of HBsAg-positive donors, 17.4% of anti-HCV-positive donors, 13.6% of patients with type B chronic liver disease, and 10.5% of patients with type C chronic liver disease. The prevalence of TTV and HGV infections in HBV- or HCV-positive donors and patients was significantly higher than in healthy blood donors (P < 0.05), except for the detection rate of HGV in HBsAg-positive donors which was the same as for healthy donors. There was a history of transfusion in 66.7% of TTV DNA-positive patients and 76.9% of HGV RNA-positive patients (P < 0.05). No significant increase in serum ALT and AST was detected in the TTV- or HGV-positive donors and patients.

CONCLUSION: TTV and HGV infections are more frequently found in donors and patients infected with HBV or HCV than in healthy blood donors. However, there is no significant association between TTV or HGV infections and liver injury.

TT virus infection in patients on maintenance hemodialysis in Korea

BACKGROUND/AIMS

TT virus is a novel DNA virus that is associated with posttransfusion hepatitis. The prevalence, risk factors, and clinical significance of TT virus infection were evaluated in patients with chronic renal failure who are on hemodialysis.

METHODOLOGY

Nested polymerase chain reaction was used to test for TT virus DNA in the serum of patients on hemodialysis as well as in healthy controls.

RESULTS

TT virus DNA was detected in 15 (20.0%) of the 75 patients on hemodialysis and 10 (13.2%) of the 76 healthy controls (P > 0.05). In chronic renal failure patients on hemodialysis, the prevalence of TT virus did not differ according to the duration of hemodialysis or the amount of blood transfusion. The prevalence of TT virus was higher in IgG anti-hepatitis B core antibody-positive patients than IgG anti-hepatitis B core antibody-negative patients (27.5% vs. 4.2%, P = 0.03). Two (13.3%) of the 15 TT virus-positive and 6 (10.0%) of the 60 TT virus-negative patients showed elevated alanine aminotransferase levels (P > 0.05).

CONCLUSIONS

TT virus infection did not occur more frequently in patients on hemodialysis than in healthy controls. No relationship was found between TT virus infection and liver disease. The correlation between TT virus infection and IgG anti-hepatitis B core antibody suggests that TT virus may share some routes of transmission with hepatitis B virus.

TT virus infection in healthy children, children after blood transfusion, and children with non-A to E hepatitis or other liver diseases in Taiwan

Serum samples from healthy and diseased children were studied for the presence of TTV DNA by nested PCR using primer sets generated from N-22 region and from the untranslated region (UTR) of the viral genome. N-22 positive TTV DNA was detectable in 33 (27%) of 122 healthy children, 47 (73.4%) of 64 polytransfused thalassemic children, 37 (46.3%) of 80 children who received transfusion during cardiac surgery, 8 (42.1%) of 19 non-A to E hepatitis, 10 (33.3%) of 30 HBV carrier children, and 5 (15.6%) of 32 infants with biliary atresia. A much higher prevalence of TTV DNA with rates varying from 78-100% in the above study groups was observed using the UTR primers. For children with N-22 positive TTV DNA, biochemical assessment of isolated TTV viremia in thalassemic children or children transfused during surgery showed no convincing association between raised ALT levels and TTV viremia. Coinfection with TTV in chronic HCV-infected or HBV-infected children did not result in higher peak ALT levels during follow-up, suggesting that TTV has no synergistic pathogenic effect. The phylogenetic analysis of the N-22 positive TTV DNA isolates revealed that most isolates from healthy children, children transfused during surgery, and non-A to E fulminant hepatitis children were type 1 TTV. These results indicate that TTV infection in children was significantly associated with transfusion. TTV infection is highly prevalent in early childhood in Taiwan but plays a minimal role in the induction of hepatitis in children.

Prevalence of SENV-H viraemia among healthy subjects and individuals at risk for parenterally transmitted diseases in Germany

The prevalence of a newly described DNA virus (SENV-H) was examined in a population of 599 individuals by polymerase chain reaction (PCR). All individuals were assigned to a nonrisk or a risk group depending on the presence of historical or serological factors indicating an increased risk for parenterally transmitted diseases. In a group of 226 healthy blood donors, 38 (16.8%) were found to be SENV-H viraemic. The highest prevalence of SENV-H viraemia was observed among patients infected by HIV (28 of 63; 44.4%). Contrarily, of 78 individuals on maintenance haemodialysis, only 10 (12.8%) were found positive in the SENV-H PCR. Our results demonstrate that SENV-H viraemia is widespread in the general population. Therefore, it seems to be questionable if parenteral transmission is the main route for spreading SENV-H. The hepatitis-inducing capacity of SENV-H is unclear. However, taking our clinical and epidemiological data into account it seems unlikely that this virus is responsible for hepatitis.

[TT virus--characteristics, occurrence and routes of transmission]

Recent discovery of a novel DNA virus from the serum of a Japanese patient (T.T.) has prompted further studies directed on possible role of TT virus in the development of cryptogenic hepatitis. The TT is an unenveloped and circular DNA virus. TTV possesses single stranded DNA genome and comprises 3537 to 3853 nucleotides. TTV is similar to the Circoviridae and possesses three open reading frames. Phylogenetic analysis revealed up to 30% nucleotide sequence divergence in the 16 virus genotypes. TTV infection can be detected by polymerase chain reactions, in situ hybridization and by specific antibodies to TTV. TTV DNA has been identified in the serum of patients with cryptogenic hepatitis, hepatitis B and C, hepatocellular carcinoma as well as in healthy individuals. TTV has been found also in the peripheral blood leukocytes, bone marrow cells, liver biopsies as well as in feces and breast milk. Some animals including cattle, sheep, pigs and chicken appeared to have TTV viremia. Recent detection of TTV in nonblood products, such as saliva and feces suggest in addition to parenteral also nonparenteral routes of TTV transmissions including sexual and fecal-oral.

Insights into SEN virus prevalence, transmission, and treatment in community-based persons and patients with liver disease referred to a liver disease unit

To document the prevalence and routes of transmission of SEN virus (SEN-V) in community-based individuals and patients referred to a liver disease unit, stored serum samples obtained from 160 Canadian Inuit and 140 patients with liver disease were tested for SEN-V DNA by polymerase chain reaction. In the community-based population, SEN-V was present in 57 (36%) of 160 persons. SEN-V-positive individuals tended to be younger and were more often male. Liver enzyme levels and serologic markers for hepatitis A and B viruses were similar in SEN-V-positive and SEN-V-negative individuals. SEN-V was present in 30 (21%) of the 140 patients with liver disease. Age, sex, risk factors for viral acquisition, prevalence of symptoms, and liver biochemical and histological findings were similar in SEN-V-positive and SEN-V-negative patients. These results indicate that SEN-V infection is a common viral infection in both healthy individuals and patients with chronic liver disease, that transmission likely occurs via nonparenteral routes, and that SEN-V infection is not associated with higher rates of or more-severe liver disease in persons with preexisting liver disease.

The prevalence of TT virus in cancer patients

Transfusion-transmitted virus (TTV) is a recently discovered transfusion-transmissible DNA virus. Its frequency and clinical impact has not been established in cancer patients in Turkey. In this study, we determined the prevalence of TTV DNA positivity, and its relationship with history of transfusion, amount of transfusion, age and sex in patients with hematological and solid malignancies. Sixty-one patients (35 male and 26 female) followed up for various malignancies and 45 healthy subjects were included in the study. ITV DNA was assayed by the polymerase chain reaction (PCR). TTV DNA was detected in 18 of 61 patients (29.5%) and in 5 of 45 control subjects (11.1%). In cancer patients, the prevalence of TTV DNA positivity was higher to comparison with control group. In addition, the prevalence of TTV DNA positivity was significantly higher in 22 patients who had a history of blood transfusion in the last 6 months than 39 patients who had no current or past history of transfusion (40.9% vs 23.0% respectively). These results suggest that the prevalence of TTV DNA is high and the parenteral route is an important mode of transmission for TTV in cancer patients. In addition, the high prevalence and persistence of TTV in cancer patients with parenteral risk exposure could be related to the immunodeficiency due to cancer and high viral loads by parenteral route.

TT virus. A review of the literature

In 1997, a new DNA virus was cloned by a Japanese team and designated TT virus (TTV). This virus seemed to be associated with non-A, non-G post-transfusion hepatitis. It was isolated by polymerase chain reaction (PCR) and was presumed to be human Circoviridae. The virus is heterogenous; 16 different genotypes are currently registered, and it can be classified as a "swarm" of at least 5 different viruses. Depending on the PCR technique used, the prevalence of infection ranges from 1.9 to 36% among blood donors, from 11.5 to 71% in hemodialysis patients, from 47 to 82% among patients with non-A, non-B or non-C fulminant hepatic failure, and the most elevated percentage is found in hemophiliacs. Epidemiological studies have established that the routes of TTV infection might be parenteral, oral-fecal, and possibly salivary. Mother-to-infant transmission is controversial. TTV may play a role in the pathogenesis of non-A, non-B or non-C fulminant hepatic failure. Patients co-infected with hepatitis C virus (HCV) and TTV have a significantly higher histological grade score than patients with isolated HCV infection. Treatment with interferon seems to decrease TT viremia, according to results obtained outside the context of clinical trials. TTV seems to be a light pathogenic virus. Its widespread presence in the blood of infected subjects contrasts with the apparent absence of pathological symptoms. PCR standardization is needed to clearly establish its real prevalence worldwide.

[The SEN virus--will there be another letter in the alphabet of viral hepatitis?] ]

The SEN virus (SENV) is a small nonenveloped single-stranded DNA virus which is probably a circovirus. By phylogenetic analysis it is possible to differentiate genotypes SENV A-H. The pathway of transmission of infection is not known so far but the infection by this virus is frequent in recipients of blood transfusions and liver grafts and in intravenous drug addicts. This suggests possible parenteral transmission of infection. Other routes of transmission of the infection are also possible as the virus can be detected also in a significant proportion of young subjects without the risk of parenteral infection in the case-history. Whether SENV causes hepatitis has not been proved unequivocally so far. The prevalence of this infection does not differ significantly in patients with different liver diseases, acute or chronic viral or non-viral. SENV infection very probably does not influence the course of chronic hepatitis C.

Polymerase chain reaction-based prevalence of hepatitis A, hepatitis E and TT viruses in sewage from an endemic area

BACKGROUND/AIMS

Hepatitis A and E viruses (HAV, HEV) are transmitted enterically and are highly endemic in India. This study aims to evaluate prevalence of these and TT virus (TTV) in the sewage.

METHODS

Influent and effluent samples from a sewage treatment plant from Pune, India were collected twice a week for 1 year and subjected to nested polymerase chain reaction (PCR) for the detection of HAV RNA, HEV RNA and TTV DNA. HAV and HEV PCR products were sequenced. Effluent samples were not collected for 5 months as the plant was non-functional.

RESULTS

The overall prevalence was 24.42% (21/86, HAV), 10.98% (9/82, HEV) and 12.7% (8/63, TTV). Prevalence of HAV was significantly higher than HEV (P=0.023). During summer months, significantly higher HAV RNA positivity was noted (P<0.01). A substantial reduction in HAV RNA positivity (15/48 vs. 2/48, P=0.0008) was recorded for treated sewage samples. However, HEV RNA or TTV DNA positivity did not reduce significantly. Of the 17 HAV and HEV RNA negative sewage samples concentrated using ultracentrifugation, 13 and none were positive for HAV and HEV RNA, respectively. Phylogenetic analyses grouped these viruses in IB and Ia, respectively, the genotypes most prevalent in India.

CONCLUSIONS

Sewage may play an important role in maintaining hyper-endemicity of these infections. Sustained efforts are obligatory to render sewage less/non-infectious.

TT virus infection during childhood

BACKGROUND

TT virus (TTV) is widespread in the general population, however, the mode of its transmission and the mechanism of maintaining it in the general population are unclear.

STUDY DESIGN AND METHODS

To determine the possible mother-to-infant route of transmission, 54 infants bom to 50 anti-HCV-positive mothers were assessed longitudinally. Nucleotide sequences amplified by seminested PCR with primers targeting the N22 variable coding region of genotypes 1 through 6 were compared in mothers and their infants.

RESULTS

The prevalence of TTV DNA was 30 percent (15/50; 95% CI, 18-45) in mothers and 44 percent (24/54; 95% CI, 31-59) in their infants. TTV DNA was detected during a follow-up period in 13 (87%; 95% CI, 60-98) of 15 infants born to infected mothers and in 11 (28%; 95% CI, 15-45) of 39 infants bom to DNA-negative mothers. None of 38 cord blood samples, but one of 14 blood samples, obtained at 1 month of age had detectable TTV DNA. The lowest infection rate at the earliest ages and the subsequent increasing prevalence of infection (22% at 6 months and 33% [43% cumulative rate] at 2 years) is consistent with an age-dependent acquisition of TTV by nonparenteral routes. In 13-mother-infant pairs positive for TTV DNA, six showed a high degree of nucleotide sequence similarity (99.1-100%), whereas the remaining seven pairs differed more than 10 percent from each other (46.8-89.2%). The viral load of matemal blood was not a plausible risk factor for transmission. Genotype 1, of which pathogenicity failed to be shown by measurement of hepatic enzymes, was more rapidly cleared (88 vs. 8% other genotypes, p < 0.001) among infants.

CONCLUSIONS

These observations strongly suggest that the main factor for TTV acquisition in children involves their age-associated increase in environmental interactions with infectious materials. Genotype 1 might be involved in a weak or a limited pathologic role, which can possibly be diluted by other harmless genotypes.

Investigation of transfusion transmitted viruses in cases clinically suspected of posttransfusion hepatitis with undetermined ethiology

Transfusion transmitted viruses (TTV) were investigated in cardiac surgery cases who were previously transfused with blood and/or blood products and were suspected of having posttransfusion hepatitis (PTH) based on the results of physical examination, clinical findings, biochemical blood test results and in a smaller number, on radiological results. They were identified as having non-A-C hepatitis based on serological or molecular test methods. In this study, out of 90 cases suspected for PTH and non-A-C, 78 (86.7%) were male, 12 (13.3%) were female and their ages were between 17 and 67. Ninety healthy blood donors, who donated blood for the first time and had never had a transfusion, were selected as the control group. They had alanine aminotransferase (ALT) levels < 40 U, were seronegative for hepatitis B virus (HBV) and hepatitis C virus (HCV). Seventy-seven were immune, and 13 were seronegative for hepatitis A virus (HAV). In this study, TTV-deoxyribonucleic acid (DNA) investigation was performed by the polymerase chain reaction (PCR) method suggested by Takahashi et al. with 5' GCT ACG TCA CTA ACC ACG TG 3' (T801) and 5' CTG CGG TGT GTA AAC TCA CC 3' (T935) primers. TTV-DNA was found to be positive in 21 (23.3%) of the patient group and 4 (4.4%) of the control group (p < 0.05). In the patients determined to be TTV-DNA positive, the admission time following transfusion was a minimum of 3, and a maximum of 15 (average 7) weeks. The average ALT levels detected at the time of admission did not show a difference between TTV-DNA positive and negative cases (p > 0.05). However the ALT levels had a tendency to rise and reached their highest level nine weeks after transfusion in the TTV-DNA positive cases, although in two cases the ALT levels decreased to normal value after the 13th week. During the 24 month follow up of the TTV-DNA positives all cases except one were positive at the end of this period. The results of this study are the same as those reported in the literature suggesting that TTV-DNA, excluding the main viral agents which are known to cause PTH, can be determined in transfused PTH or non-transfused asymptomatic patients in varying ratios. In order to define the epidemiological properties and hepatic-extrahepatic pathologies more clearly we have looked for evidence of the viral agent, which probably contaminates both by transfusion and non-transfusion routes. It is suggested that, in addition to the case groups in this study, new clinical studies are necessary including transfused but non-PTH patients.

TTV, a new human virus with single stranded circular DNA genome

TT virus (TTV) was found in 1997 from a hepatitis patient without virus markers. However, the real impact of TTV on liver diseases remains uncertain to date. Due to the lack of suitable cell systems to support the growth of TTV, the biology of TTV is still obscure. This review tries to summarise the current status of TTV on aspects other than the taxonomic diversity of TTV. TTV was the first human virus with a single stranded circular DNA genome. TTV was considered to be a member of Circoviridae, but others suggested it conformed to a new family. TTV is distinct from ambisense viruses in the genus Circovirus, since the former genome is negative stranded. The genome structure of TTV is more related to chicken anaemia virus in the genus Gyrovirus, however, the sequence similarity is minimal except for a short stretch at 3816-3851 of TA278. Currently the working group is proposing the full name for TTV as TorqueTenoVirus and the TTV-like mini virus as TorqueTenoMiniVirus (TTMV) in a new genus Anellovirus (ring). TTVs are prevalent in non-human primates and human TTV can cross-infect chimpanzees. Furthermore, TTV sequences have been detected in chickens, pigs, cows and sheep. TTV can be transmitted by mother-to-child infection. However, within a year after birth, the prevalence reaches the same level for children born to both TTV-positive and TTV-negative mothers even without breast-feeding. The non-coding region surrounding a short 113 nt GC-rich stretch and occupying approximately one-third of the genome is considered to contain the putative replication origin. Three mRNAs are expressed by TTV, 3.0 and 1.2 and 1.0 kb species. A protein translated from the 3.0 kb mRNA is considered to be the major capsid protein as well as replicase. The nature of the proteins translated by the other two mRNAs are still putative.

Mother-to-child transmission of TT virus: sequence analysis of non-coding region of TT virus in infected mother-infant pairs

To investigate vertical transmission of TT virus, TTV-DNA was looked for in serum samples taken from 22 mothers and their 22 infants at birth and during nine months of follow-up. Sixteen mothers at delivery and six infants within nine months of age had TTV-DNA detected by the amplification of the non coding (NC) region. Two of these newborns had positive viremia at birth. Sequence analysis of the NC region of five mother-infant pairs revealed that the TTV strains detected at three and six months of age in two of the infants were closely related to that of their mothers, whereas two that became TTV-DNA positive at three moths had a different nucleotide sequence from that of their mothers. One of the two infants with detectable viremia at birth also had a different nucleotide sequence from her mother. These findings suggest that both in utero and perinatal transmission of TT virus may occur, and that the strain detected in the infants was not invariably dominant in the mothers at delivery.

Infectious hepatitis C, hepatitis G, and TT virus: review and implications for dentists

In the past 10 years, hepatitis C and G viruses have been identified, and in the last two years a further parenterally transmitted agent, termed TT virus (TTV), has been discovered. These viruses have a worldwide distribution and frequently cause chronic infection. The purpose of this article was to promote an understanding of these viral agents and their relevance in dental practice. Infected patients may develop a chronic carrier state without clinical disease or may develop liver disease, and may have related oral conditions. Dental providers will see a growing number of patients with HCV/HGV and possibly TTV infection. All of these patients require appropriate infection control measures during dental treatment.

Transmission of SEN virus from mothers to their babies

Sera from 30 women at high risk for infection, one half of which were SEN virus positive (SENV(+)), were collected at delivery to study SENV mother-to child transmission. Thirteen of their babies were positive for at least one SENV strain: one baby was SENV(+) at birth, eight became positive within 6 months from delivery, and four became positive in the following months. Our data indicate that vertical transmission of SENV does occur, presumably, at delivery, but it may not induce persistent viremia. This is supported by the fact that, generally, SENV is not detected at birth, by the high SENV homology in the sequences found in the mothers and in their children, by a lack of other risk factors for infection of the babies, and by the irregular detection of SENV in the follow-up. No clinical events surely linked to SENV infection were found, but transient elevations of alanine aminotransferase were observed in babies followed for a long period of time.

Early acquisition of TT virus in infants: possible minor role of maternal transmission

This study assessed the prevalence of TT virus (TTV) viremia in pregnant women and evaluated the role of maternal transmission in early acquisition of TTV in infants in Taiwan. Two groups of pregnant women were screened for TTV using polymerase chain reaction. The first group included 135 healthy pregnant women attending the obstetrics department for routine prenatal care and the second group from 25 GB virus-C/hepatitis G virus (GBV-C/HGV)-infected mothers. In both groups, when TTV infection was found in mothers, serial serum samples were collected for the infants at regular intervals until 1 year of age and were tested for TTV DNA. The results showed that 40% (54/135) of the women undergoing routine prenatal care and 56% (14/25) of GBV-C/HGV-infected pregnant women were positive for TTV DNA (P = 0.137). Of the 54 TTV-infected mothers in the routine prenatal group, 29 and their 30 infants received regular follow-up. The positive rate of TTV DNA in infants was 40% (12/30) in the routine prenatal group and 29% (4/14) in the group with GBV-C/HGV-infected mothers (P = 0.463). All but 2 of the 16 TTV-infected infants had normal serum alanine aminotransferase levels during follow-up. The phylogenetic analysis in 7 mother-infant pairs showed that the homology was diverse in each pair and a close genetic relatedness was found in 2 mother-infant pairs. In conclusion, TTV viremia is common in pregnant Taiwanese women and their infants. However, the results suggest that maternal transmission may play only a minor role in early acquisition of TTV in infants.

Genotypic distribution of TT virus (TTV) in a Czech population: evidence for sexual transmission of the virus

BACKGROUND

TTV is a new DNA virus distinguished by its high degree of strain heterogeneity. The geographic clustering of viral genotypes suggests frequent community transmission. While no specific human disease has yet been linked to it, a transmission mechanism that facilitates strain diversity may eventually select for a strain that will become pathogenic.

OBJECTIVE

This study was performed to examine the prevalence, genotypic distribution, and mode of transmission of TTV in detail.

STUDY DESIGN

Three groups of study subjects were recruited between October 1998 and January 2000 in Prague, Czech Republic. Group 1 included 152 injection drug users with liver disease; group 2 included 102 persons with liver disease who denied ever using injection drugs; group 3 included 111 prospective blood donors. TTV DNA was detected from blood by a semi-nested PCR assay, and a selected set of PCR products was genotyped by direct sequencing. Factors associated with TTV prevalence in groups 1 and 2 subjects were compared.

RESULTS

TTV was detected in 15.8, 13.7, and 13.5% of Groups 1, 2, and 3 subjects, respectively (P>0.05). The most common genotype was 2 (54%), followed by 1 (13%). The prevalence of TTV viremia was nearly three times higher in persons with a present or past history of hepatitis B compared to those without (P<0.05). TTV prevalence increased proportionately with the number of lifetime sex partners in both groups (P<0.05); it was highest (32%) among non-users of injection drugs who had five or more lifetime sex partners.

CONCLUSION

TTV prevalence in the Czech population is similar among blood donors, persons with liver disease, as well as in a high-risk population of injection drug users. TTV appears to be sexually transmitted.