Hepatitis C was first recognized as a form of viral hepatitis that was distinct from disease caused by hepatitis A virus and hepatitis B virus. The etiologic agent of hepatitis C was proposed to be a small, enveloped virus based on demonstrations of its transmissibility to chimpanzees, electron microscopic studies, and sensitive to chloroform. Successful molecular cloning of viral genome in the late 1980's led to the development of assay for serological diagnosis of HCV and it is currently estimated that at least 170 million people are chronically infected with the hepatitis C virus. HCV evades host antiviral defenses by mechanisms that remain to be identified and establishes a persistent infection in a majority of patients. Persistent infection of HCV is a leading cause of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. Therefore development of antiviral treatment for HCV is an urgent worldwide health problem. Although much has been learned about HCV genome organization, polyprotein processing, protein function and structure, many key questions remain to be answered. Major efforts of Japanese investigators should now be directed at establishing cellular system and animal models appropriate for dissecting the various steps in HCV replication cycle and strategies for blocking them.
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