HEPATITIS C VIRUS

Hepatitis C is a flavivirus (of which yellow fever is the prototype) that causes non-A, non-B hepatitis. Flaviviruses (figure 5) are icosahedral, positive strand RNA viruses and gain an envelope from their host cell. The virus particle is about 30 to 60nm across. The genome of 9,600 bases codes for ten proteins. In many ways, the flaviviruses are similar to picornaviruses with the prominent exception that they are enveloped. The viral RNA does not have a 5’ cap or 3’ poly A tract. Translation of the viral RNA is mediated by the internal ribosome entry site (IRES).

There is one protein product from one open reading frame. The hepatitis C virus polyprotein is cleaved by both a virally-encoded protease activity and a cellular protease. The nascent protein contains a signal sequence that results in the translating ribosome attaching to the cytoplasmic surface of the endoplasmic reticulum. The envelope protein (E) thus crosses and embeds in the membrane and the signal sequence is removed by a cellular signal protease. This results in the remainder of the protein, the core protein, becoming cytoplasmic. It is cut by two viral proteases. The C-terminal domain of NS2 is a cysteine protease and cleaves at the NS2/NS3 junction. Another protease (NS3/4A serine protease) cleaves the remaining junctions.
Thus, the core protein is cut into NS1, NS2, NS3 and NS4 proteins. NS2 and NS4 are then cut again (to give NS2a, NS2b, NS4a and NS4b)
HCV binds to either the CD81 antigen or low density lipoprotein (LDL) receptor on hepatocytes via its E2 glycoprotein. There is also some evidence that it may bind to glycosaminoglycans.

tags:hepatitis C,virus hepatitis C,The hepatitis C virus polyprotein ,HCV,liver,