Hepatitis C virus has already infected more than 3% of the worldwide population and 80% of those infected develop persistent HCV infection (Cerny and Chisari, 1999; Theodore and Fried, 2000) . Persistent HCV infection often leads to chronic hepatitis, hepatic steatosis, cirrhosis, and hepatocellular carcinoma. Currently, there are still 1.5 million or more HCV carriers in Japan.