HEPATITIS C VIRUS AND ITS GENE STRUCTURE AND FUNCTION

Hepatitis C virus (HCV) is a member of the family Flaviviridae, and the principal cause of parenteral non A non B hepatitis. HCV is a single stranded, positive sense RNA virus whose genome contains a single open reading frame of about 10 kb in length which encodes a polyprotein of about 3000 amino acids. HCV is responsible for majority of the transfusion associated cases of hepatitis and a significant proportion of community-acquired hepatitis which leads to a range of clinical manifestations from an apparent carrier state to severe chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. Cell-free translation and cell culture transient expression studies revealed that HCV genome initially transcribed as a polyprotein is processed by cellular and viral proteases to produce the putative viral structural and nonstructural proteins. The preliminary map of the gene order for HCV was established: 5\u27 untranslated region (UTR)-core (C)-envelope 1 (E1)-E2-nonstructural 2(NS2)-NS3-NS4A-NS4B-NS5A-NS5B-UTR3\u27. Nonstructural proteins, NS2, NS3 and NS5, are believed to be a component of viral coded enzymes. Mutations in hypervariable region 1 (HVR1) of the E2 protein was considered to be a possible mechanism of chronicity of HCV infection. HCV infection can be monitored either by serodiagnosis or by genodiagnosis. Interferon seems to be considered as the sole drug for HCV treatment until now. In the history of virology, HCV was the first example that was identified by molecular cloning of its genome from infectious materials