Prevalence and clinical characteristics of TT virus (TTV) in patients with sporadic acute hepatitis of unknown etiology

Background/Aims: Recently, a novel DNA virus was isolated from the serum of a patient with post-transfusion non-A–G hepatitis and named TT virus. The aim of this study was to determine the prevalence and clinical characteristics of TT virus infection in patients with sporadic acute hepatitis of unknown etiology. Methods: TT virus was investigated in the serum of 66 patients with sporadic acute hepatitis non-A–G and 50 healthy controls by semi-nested PCR with previously published primers. Results: TT virus was detected in 17 (26%) of the 66 patients with sporadic acute hepatitis non-A–G and in a slightly higher rate (34%,17/50) in the control group. No significant differences in alanine aminotransferase or bilirubin concentrations were observed between the groups of patients with or without TT virus infection. Eighty per cent (12/15) of patients for whom follow up was possible had persistent viremia from 4 to 36 months, and 67% (8/12) of these patients had already normalized their levels of alanine aminotransferase. A phylogenetic tree constructed by the Neighbor Joining Method revealed that all isolates in this study were grouped within genotype 1a and 1b, without showing any association between genetic type and development of hepatic disease. Conclusions: Our results suggest that TT virus DNA is present not only in patients with sporadic acute hepatitis non-A–G but also in a large proportion of the general population. This virus was not likely to be the causative agent of hepatitis among the patients in this study.