HEPATITIS C VIRUS AND ITS GENE STRUCTURE AND FUNCTION

Hepatitis C virus (HCV)is a memberof the familyFlaviviridae,and the prin- cipal causeof parenteral non A non B hepatitis. HCVis a single stranded,positivesense RNA virus whosegenomecontainsa single open readingframe of about 10 kb in length whichencodesa polyproteinof about3000aminoacids. HCVis responsiblefor majorityof the transfusionassociatedcasesof hepatitis and a significantproportionof community-ac- quiredhepatitis whichleads to a range of clinicalmanifestationsfrom an apparentcarrier state to severe chronichepatitis, liver cirrhosis and hepatocellularcarcinoma.Cell-free translationand cellculture transientexpressionstudies revealedthat HCVgenomeinitially transcribed as a polyproteinis processedby cellular and viral proteasesto producethe putativeviralstructural and nonstructuralproteins.The preliminarymap of the geneorder for HCV was established: 5' untranslated region (UTR)-core(C)-envelope1 (E1)-E2- nonstructural2(NS2)-NS3-NS4A-NS4B-NS5A-NS5B-UTR3'. Nonstructuralproteins, NS2, NS3and NS5,are believedto be a componentof viral codedenzymes.Mutationsin hyper- variableregion 1 (HVR1)of the E2 proteinwas consideredto be a possiblemechanismof chronicityof HCVinfection.HCVinfectioncan be monitoredeither by serodiagnosis or by genodiagnosis. Interferonseemsto be consideredas the soledrug for HCVtreatmentuntil now. In the historyof virology,HCVwas the first examplethat was identifiedby molecular cloningof its genomefrom infectiousmaterials.