Study on infection mechanisms of hepatitis C virus

点击翻译按钮获取中文摘要

Studies of infection mechanisms of hepatitis C virus (HCV) have been hampered by the lack of conventional cell culture system which support replication of HCV. To overcome this problem, we have established a sensitive cell fusion assay system and also constructed pseudotype vesicular stomatitis virus (VSV) possessing HCV envelope protein on the surface of the virion instead of its own envelope G glycoprotein. The chimeric HCV E1 and E2 proteins consisting of the ectodomain of E1 or E2 envelope proteins and the transmembrane and cytoplasmic domains of VSV G glycoprotein were expressed on the cell surface. The induction of cell fusion requires both of the chimeric E1 and E2 proteins with low pH-dependent manner. The pseudotype virus possessing both of the chimeric E1 and E2 proteins exhibited significantly higher susceptibility than that possessing either of the glycoproteins individually. These results suggest that HCV requires both E1 and E2 proteins in the infection and enters a targe … More t cell via an endosomal pathway. In the endosome, a low pH-dependent conformation change of the E1 or/and E2 proteins occurs, which then triggers membrane fusion and the entry of the nucleocapsid into the cytoplasm. Treatment of HepG2 cells with pronase, heparinase, or heparitinase reduced the levels of cell fusion activity and infectivity of the pseudotype VSV suggesting that certain protein molecules and glycosaminoglycans on the cell surface play an important role in the infection with HCV. Recently, human CD81 (hCD81) has been shown to be a binding receptor of the E2 protein. However, there was no difference in cell fusion activity and susceptibility to pseudotype VSV between the mouse cell line expressing hCD81 and the parental cell line. These results suggest that hCD81 atone is not sufficient to allow infection of HCV and that another cofactor(s) might be required or that HCV infection may occur in an hCD81-independent manner.The infection mechanisms revealed in this study might offer an important information for future studies on cellular receptors for HCV and for the development of prophylactics and therapeutics for hepatitis C. Less