[The association of TTV genetic variant with liver disease]

TT virus (TTV), a novel DNA virus, has been reported in non-A to non-G posttransfusion hepatitis patients. Among 61 Japanese patients with liver diseases of non-B and non-C etiology, TTV DNA was detected in 15(25%) patients. The N22 region of TTV was sequenced and compared with the published sequence. Four genetic groups corresponding to G1a, G1b, G2 and G4 were formed. TTV was detected persistently regardless of its genotype/subtype. However, G2 and G4 contained 10 to 100 folds lower in titer than G1. Co-existing multiple mutants and subtypes were identified in one case. Since changes of TTV DNA titer and appearance of deduced amino acid substitution was not linked to ALT levels, the association of TTV to chronic liver diseases seemed low.