Superinfection of TT virus and hepatitis C virus among chronic haemodialysis patients

Background: The TT virus (TTV), a new DNA virus found in Japan from a patie nt with posttransfusion hepatitis non-A-non-G, is frequently positive in th e sera of patients with liver disease. It is not established whether this v irus causes liver damage. We studied the frequency of superinfection of thi s virus and hepatitis C virus (HCV) known to be endemic among haemodialysis patients, and the possible deleterious effect of TTV on HCV-induced chroni c liver disease. Methods: We used primers from a conservative region in the TTV genome (Okam oto, 1998) to detect TTV. Sera from 163 dialysis patients positive for anti -HCV and 77 dialysis patients negative for anti-HCV (control) were tested. Results: TT Virus positivity was 35% among HCV antibody (anti-HCV)-positive patients and 45.4% among anti-HCV-negative patients. TT Virus positivity w as unrelated to the length of haemodialysis or amounts of blood the patient s had received in the past. More anti-HCV-positive patients had a history o f transfusion, but TTV positivity was not as closely associated with transf usion as anti-HCV positivity. The severity of chronic liver disease was est imated from peak serum alanine aminotransferase levels in the preceding 6 m onths. Among anti-HCV positives, TTV-positive patients tended to have less active disease; at least there was no indication that TTV superinfection ag gravated chronic hepatitic C in longterm dialysis patients. Four of 35 anti -HCV-negative, TTV-positive patients had chronic active liver disease, whil e none of the anti-HCV-negative and TTV-negative patients did. Conclusions: TT Virus infection is prevalent among haemodialysis patients. Its transmission occurs not only by blood transfusion, but also by non-pare nteral infection. Superinfection of TTV does not exert deleterious effects on the liver disease induced by HCV. However, it may cause chronic hepatiti s in a limited number of patients, but remains dormant most of the time. Tr iple infection, HCV and TTV plus HBV or HGV (one case each), did not cause severe liver disease. (C) 1999 Blackwell Science Asia Pty Ltd.