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.