Prevalence of TTV in an area endemic for hepatitis C virus and in patients with non a to G hepatitis

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Background: TT virus (TTV), a non-enveloped single stranded DNA virus, was identified as candidate for a new hepatitis virus. Little is known about its pathogenicity and routes of transmission. In this study, we investigated TTV infection in inhabitants of an area endemic for hepatitis C virus (HCV) and in patients with non A to G hepatitis and in healthy blood donors, and analyzed prevalence and transmission routes of TTY infection. Materials and methods: TTV infection was studied in 290 inhabitants, including 41 couples, who participated in a mass screening in HCV hyper-endemic area, furthermore in 45 patients with non A to G hepatitis, and in 50 healthy blood donors. TTV DNA was determined by polymerase chain reaction (PCR) with the set of primer reported by Okamoto et al. TTV DNA sequences were determined by dideoxy chain termination method and were analyzed by phylogenetic analysis. Result: TTY DNA was detected in 166 of 290 (57.2%) inhabitants in HCV hyper-endemic area, 20 of 45 (44.4%) patients with non A to G hepatitis, 11 of 50 (22%) healthy blood donors by Okamoto's primer set. In inhabitants in HCV hyper-endemic area, TTV infection was not related to the positive rate of other hepatitis virus markers (anti-HBc, HCV RNA, HGV RNA, antiHGV). The prevalence of TTV tended to be higher in inhabitants who had blood transfusion (P<0,07). In only TTV positive inhabitants, 7 cases had elevations of ALT level, although its degree is not severe. Among TTV positive inhabitants, there were no specific aminoacid sequences between patients of liver diseases and asymptomatic carriers, and also in phylogenetic analysis, no specific difference exists among two groups. In 41 couples, 15 couples (36.6%) were both positive for TTV DNA, 18 couples (43.9%) were either positive, 8 couples (19.5%) were neither positive. There was no couple that the genetic distance between husband and wife was close. Conclusion: The prevalence of TTV DNA showed high rate (57.2%) in HCV endemic area. The prevalence of TTY tends to be higher in inhabitants who had blood transfusion, however these strains reported here are distinct phylogenically. This raises the possibility that the TTV spreading in the study area originated from multiple locations. And we consider that TTV infection is rarely associated with liver diseases, because most of TTV positive inhabitants reveal normal ALT level. In transmission route, our results indicated that TTV is not likely to transmit sexually.