Study on molecular mechanisms of hepatitis C virus infection.

尽管一些细胞表面分子如hCD81、LDL-R、SR-B1和DC-SIGN已被认为是丙型肝炎病毒受体的候选分子，但由于缺乏强大和可靠的体外细胞培养系统来传播丙型肝炎病毒，这些分子中是否有任何分子能够作为功能细胞受体发挥作用尚不清楚。作为研究丙型肝炎病毒感染的替代系统，以水疱性口炎病毒(HCVpv)和逆转录病毒(HCVpp)为基础的携带丙型肝炎病毒包膜糖蛋白的伪型病毒已被开发出来。我们先前已经证明，人成纤维细胞生长因子受体(HFGFR)4是基于与患者血清中的HCVpv、丙型肝炎病毒样颗粒和正品丙型肝炎病毒颗粒的特异性结合而与丙型肝炎病毒结合的受体。最近我们发现，在293T细胞和CHO细胞(HCVpv/CHO)中产生的HCVpv分别表现出hCD81依赖和非独立感染。HFGF2或抗hFGFR5抗体可抑制HCVpv/CHO对HepG2细胞的感染，hFGF2代表hFGFR5的胞外区与Ig G的铁区融合(hFGFR5/Fc)。HFGFR5在293T和Huh7细胞中的过表达增加了对HCVpv/CHO感染的易感性。相反，siRNA介导的hFGFR5在HepG2细胞中的敲除导致了HCVpv/CHO感染性的降低。此外，hFGFR5/Fc可抑制患者血清中真实的丙型肝炎病毒颗粒与HepG2细胞的结合。最后，hFGFR5(但不表达hFGFR4)在CHO细胞中的表达使其对HCVpv/CHO感染具有容许性。综上所述，这些结果提示hFGFR5可能以hCD81不依赖的方式参与了丙型肝炎病毒的内化过程。

Although several cell surface molecules such as hCD81, LDL-R, SR-B1, and DC-SIGN have been proposed as candidates for hepatitis C virus (HCV) receptor, it is still unclear if any of these molecules can play a role as a functional cellular receptor, due to the lack of robust and reliable in vitro cell culture systems to propagate HCV. As a surrogate system for the study of HCV infection, pseudotype viruses bearing HCV envelope glycoproteins based on vesicular stomatitis viruses (HCVpv) and retroviruses (HCVpp) have been developed. We have previously shown that human fibroblast growth factor receptor (hFGFR) 4 is a binding receptor for HCV based on the specific binding with HCVpv, HCV-like particles and authentic HCV particles in patient sera. Recently we found that HCVpv generated in 293T cells and CHO cells (HCVpv/CHO) exhibit hCD81-dependent and -independent infection, respectively. Infection of HCVpv/CHO to HepG2 cells was inhibited by hFGF2, a soluble protein representing the ectodomain of hFGFR5 fused with the Fe region of IgG (hFGFR5/Fc), or anti-hFGFR5 antibody. Overexpression of hFGFR5 in 293T and Huh7 cells enhanced the susceptibility to HCVpv/CHO infection. In contrast, siRNA-mediated knockdown of hFGFR5 in HepG2 cells resulted in the reduction of infectivity of HCVpv/CHO. Furthermore, binding of the authentic HCV particles in patient sera to HepG2 cells was inhibited by the hFGFR5/Fc. Finally, expression of hFGFR5 (but not hFGFR4) in CHO cells rendered them permissive for HCVpv/CHO infection. Together, these results suggest the possible involvement of hFGFR5 in the internalization process of HCV in a hCD81-independent fashion.