HEPATITIS-C VIRUS AND LIVER-DISEASES

Hepatitis C virus (HCV) was identified molecularly and a procedure for its diagnosis was developed. In Japan, 70-80% of all cases of chronic liver disease, including hepatocellular carcinoma, are associated wit h HCV infection. Hepatitis C virus is a typical RNA virus with a high mutation rate. At least six Variants of HCV have been identified by th eir nucleotide sequences. These variants are still classified into thr ee types each containing at least two subtypes; that is, 1a (type I) a nd 1b(type II), 2a (type III) and 2b (type IV), and 3a (type V) and 3b (type VI). Type 1b (type II) is the predominant HCV in Japan. Even HC V cDNA clones isolated from a single patient showed mutations of HCV, especially in envelope-coding regions. Thus HCV may change during the course of chronic hepatitis due to the high mutation rate of HCV itsel f and elimination of some clones by immune reactions or interferon the rapy. These findings explain the higher rate of chronic HCV infection and indicate that production of an effective vaccine is difficult.