Prevalence and risk factor analysis of TTV infection in prostitutes

Hepatitis viruses (other than hepatitis B and C viruses) as causes of hepatocellular carcinoma: an update

Chronic hepatitis B and C virus infections are universally accepted as causes of hepatocellular carcinoma in humans. Hepatitis A and E viruses cause only acute self-limiting infections of the liver. Of the remaining hepatitis viruses - Delta hepatitis, hepatitis G (GB-C), TT and SEN - all have at some time been incriminated as causes of hepatocellular carcinoma. Delta hepatitis virus requires helper functions from hepatitis B virus to become invasive. Chronic Delta/hepatitis B viral co-infection runs a more severe course than that resulting from chronic hepatitis B virus infection alone, with progression to cirrhosis being more likely and more rapid. A substantial majority of the early studies did not find an increased incidence of hepatocellular carcinoma in co-infected individuals. But more recently, an increased incidence of the tumour has been recorded more often than no increase. Further studies are needed to draw a firm conclusion with regard to the hepatocarcinogenic effect of dual Delta/hepatitis B virus co-infection. With one exception, no published study (of 13) has incriminated chronic infection with hepatitis G virus as a cause of hepatocellular carcinoma. The dissenting study, published in 1999, was the only one performed in the United States. Fewer studies of the hepatocarcinogenic effect of TT virus have been performed. Apart from one study, published in 1999, no convincing evidence is available that supports a causal role for TT virus in hepatocarcinogenesis. The exception was in Japanese patients with high hepatitis C viral loads but independent of chronic hepatitis C virus infection. No evidence has been produced to indicate that SEN virus causes hepatocellular carcinoma.

Transfusion transmitted virus: A review on its molecular characteristics and role in medicine

The present review gives an updated overview of transfusion transmitted virus (TTV), a novel agent, in relation to its molecular characteristics, epidemiological features, modes of transmission, tissue tropism, pathogenesis, role in various diseases and its eradication from the body. TTV, a DNA virus, is a single stranded, non-enveloped, 3.8 kb long DNA virus with a small and covalently closed circular genome comprising 3852 bases. It was tentatively designated Circinoviridae virus. TTV genome sequence is heterogeneous and reveals the existence of six different genotypes and several subtypes. TTV has been reported to transmit not only via parenteral routes, but also via alternate routes. This virus has been detected in different non-human primates as well. At present, TTV is detected by polymerase chain reaction (PCR) with no other available diagnostic assays. It shows its presence globally and was detected in high percent populations of healthy persons as well as in various disease groups. Initially it was supposed to have strong association with liver disease; however, there is little evidence to show its liver tropism and contribution in causing liver diseases. It shows high prevalence in hemodialysis patients, pointing towards its significance in renal diseases. In addition, TTV is associated with several infectious and non-infectious diseases. Although its exact pathogenesis is not yet clear, TTV virus possibly resides and multiplies in bone marrow cells and peripheral blood mononuclear cells (PBMCs). Recently, attempts have been made to eradicate this virus with interferon treatment. More information is still needed to extricate various mysteries related to TTV.

Age-specific prevalence, transmission and phylogeny of TT virus in the Czech Republic

Background

TT virus is prevalent worldwide, but its prevalence and genotype distribution in Central and East-Europe has not been determined. The high prevalence of TTV in multiply-transfused patients points to the importance of a parenteral mode of transmission, but since more than half of the general population is infected other possible routes of transmission must be considered.

Methods

In our study, we investigated the epidemiology, transmission and phylogeny of TTV in the Czech Republic. The following groups were selected: a control group of 196 blood donors, 20 patients with hemophilia, 49 intravenous drug users, 100 sex workers, 50 penitentiary prisoners, 208 healthy children aged 1 to 14 years, 54 cord blood samples, 52 patients with non-A-E hepatitis, 74 patients with hepatitis C, and 51 blood donors with increased ALT levels. Primers specific for the non-coding region were used. The genotype distribution was studied in 70 TTV-positive samples.

Results

The prevalence rate of TTV among the Czech population was 52.6%. We have shown that TTV is not transmitted prenatally. Children were infected after birth with two peaks: one at the age of two years and the other after the beginning of primary school. Adults have shown a further increase in the TTV prevalence with age. The highest TTV prevalence was found in the group of patients who had received multiple blood transfusions. The TTV prevalence rate in subjects at an increased risk of sexual transmission was not significantly higher than in the general population. Genotypes G2 and G1 were most prevalent among the Czech population, followed by G8 and G3. The subjects positive for markers of HBV and/or HCV infection tested significantly more often TTV DNA positive, which is suggestive of a common route of transmission of these three infections.

Conclusions

This study on TTV prevalence, mode of transmission and age-specific prevalence is the most extensive study performed in Central and Eastern Europe. It showed insights into the epidemiology of TTV infection, but failed to associate TTV infection with clinical manifestations.

TT-virus infection in Japanese general population and in hemodialysis patients

To determine TT virus (TTV) prevalence and the persistence of viremia, we prospectively did cross-sectional and longitudinal studies using by the polymerase chain reaction to test the successive sera of 150 Japanese hemodialysis patients and compared these with those of 166 residents of a rural Japanese area endemic for hepatitis C virus (HCV). TTV DNA positivity was significantly higher in 50 (30.1%) of the residents than in 25 (16.7%) of the patients in 1997 (P < 0.05). TTV DNA positively in the patients was not associated with HCV RNA positivity and also increased with the number of blood transfusions and decreased with the duration of hemodialysis, but not significantly. Longitudinal study from 1997 to 1999 showed that persistent TTV DNA positivity was found significantly more often in 35 (21.1%) of the residents than in 13 (8.6%) of the patients (P < 0.05), and that persistent TTV DNA negativity was found significantly more often in 103 (68.7%) of the patients than in 91 (54.8%) of the residents (P < 0.05). Of the 25 patients and 50 residents TTV DNA positive in 1997, TTV DNA was eliminated more often in 12 (48.0%) patients than in 15 (30.0%) residents over the three years, but the difference was not significant. The route of TTV transmission might differ from HCV in that it could be nonparenteral. TTV was less prevalent in hemodialysis patients than residents, and the virus was more often eliminated by hemodialysis patients than by residents during the three-year observation period, possibly because of the effect of the hemodialysis procedure.

Transfusion-transmitted virus prevalence in subjects at high risk of sexually transmitted infection in Turkey

OBJECTIVE

To assess the possible sexual transmission of virus and to identify the prevalence of TTV viremia in Turkey and its association with other hepatotropic viruses.

METHODS

Serum samples were collected from 81 subjects (74 prostitutes and seven homosexual men) at high risk of sexually transmitted infection and from 81 healthy controls (74 females and seven males). Sera of patients and controls were tested for TTV, hepatitis A virus, hepatitis B virus, hepatitis C virus, and human immunodeficiency virus. Also, serum alanine and aspartate aminotransferases were measured.

RESULTS

The prevalence rates of TTV viremia in the risk group and control group were 86.4% and 82.7%, respectively. There was a statistical difference in mean age between TTV-infected and uninfected subjects (38.6 +/- 9.9 versus 32.2 +/- 6.1 years, respectively, P < 0.001). Prevalence rates of TTV infection in subjects with positive anti-HAV and positive anti-HBc were high when compared with subjects who were negative for these.

CONCLUSION

We suggest that TTV infection has a diverse route of transmission, and its prevalence increases with age; also, the prevalence rate of TTV is high in certain risk groups. The prevalence rates of TTV in the group at risk for sexual transmission (86.4%) and in the control group (82.7%) were among the highest ever reported in the world. Also, we suggest that TTV generally does not cause clinical disease, in spite of this high prevalence.

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.

Fecal excretion of a novel human circovirus, TT virus, in healthy children

The role of TT virus (TTV) as a human pathogen is unclear, as is the mode of TTV transmission. To determine the prevalence of TTV infection and the possible fecal-oral route of transmission, we analyzed fecal specimens from 67 healthy, nontransfused children for TTV DNA sequences by heminested PCR, using the NG and T primer sets. The overall prevalence of TTV fecal excretion was 22.4% (15 of 67), with the T primer set (19.4%) being more sensitive than the NG primer set (10.4%). TTV prevalence based on gender or ethnicity showed no significant differences. None of seven children in the 0- to 6-month age group had detectable TTV in feces. Of three sets of siblings, two unrelated sets of twins, ages 33 and 37 months, were negative for fecal TTV DNA, while the third set of siblings, ages 99 and 35 months, was positive. The absence of TTV in the feces of children younger than 6 months and the high prevalence (40%) in children 7 to 12 months of age is consistent with age-specific acquisition of TTV infection by the nonparenteral route. TTV genotypes 1, 3, 4, and 5 were represented in our study population. TTV-positive siblings had TTV genotypes 1 and 4, suggesting unrelated environmental sources of TTV infection. This observation suggests a possible time frame for TTV acquisition in children which coincides with increased interaction with their environment and increased susceptibility to infectious agents.