Lavillette Dimitri, Tarr Alexander W, Voisset Cécile, Donot Peggy, Bartosch Birke, Bain Christine, Patel Arvind H, Dubuisson Jean, Ball Jonathan K, Cosset François-Loïc
Laboratoire de Vectorologie Rétrovirale et Thérapie Génique, INSERM U412, IFR128, BioSciences Lyon-Gerland, Ecole Normale Supérieure de Lyon, Lyon, France.
Hepatology. 2005 Feb;41(2):265-74. doi: 10.1002/hep.20542.
Because of the lack of a robust cell culture system, relatively little is known about the molecular details of the cell entry mechanism for hepatitis C virus (HCV). Recently, we described infectious HCV pseudo-particles (HCVpp) that were generated by incorporating unmodified HCV E1E2 glycoproteins into the membrane of retroviral core particles. These initial studies, performed with E1E2 glycoproteins of genotype 1, noted that HCVpp closely mimic the cell entry and neutralization properties of parental HCV. Because sequence variations in E1 and E2 may account for differences in tropism, replication properties, neutralization, and response to treatment in patients infected with different genotypes, we investigated the functional properties of HCV envelope glycoproteins from different genotypes/subtypes. Our studies indicate that hepatocytes were preferential targets of infection in vitro, although HCV replication in extrahepatic sites has been reported in vivo. Receptor competition assays using antibodies against the CD81 ectodomain as well as ectopic expression of CD81 in CD81-deficient HepG2 cells indicated that CD81 is used by all the different genotypes/subtypes analyzed to enter the cells. However, by silencing RNA (siRNA) interference assays, our results show that the level of Scavenger Receptor Class-B Type-I (SR-BI) needed for efficient infection varies between genotypes and subtypes. Finally, sera from chronic HCV carriers were found to exhibit broadly reactive activities that inhibited HCVpp cell entry, but failed to neutralize all the different genotypes. In conclusion, we characterize common steps in the cell entry pathways of the major HCV genotypes that should provide clues for the development of cell entry inhibitors and vaccines.
由于缺乏完善的细胞培养系统，关于丙型肝炎病毒（HCV）细胞进入机制的分子细节所知相对较少。最近，我们描述了通过将未修饰的HCV E1E2糖蛋白掺入逆转录病毒核心颗粒膜中产生的感染性HCV假病毒颗粒（HCVpp）。这些最初使用1型E1E2糖蛋白进行的研究指出，HCVpp紧密模拟亲本HCV的细胞进入和中和特性。由于E1和E2中的序列变异可能解释不同基因型感染患者在嗜性、复制特性、中和作用及对治疗反应方面的差异，我们研究了不同基因型/亚型的HCV包膜糖蛋白的功能特性。我们的研究表明，尽管体内已报道HCV在肝外部位复制，但在体外肝细胞是优先感染靶点。使用针对CD81胞外域的抗体进行的受体竞争试验以及在缺乏CD81的HepG2细胞中异位表达CD81表明，所有分析的不同基因型/亚型均利用CD81进入细胞。然而，通过RNA干扰（siRNA）沉默试验，我们的结果显示，高效感染所需的I型B类清道夫受体（SR-BI）水平在不同基因型和亚型之间存在差异。最后，发现慢性HCV携带者的血清表现出广泛的反应活性，可抑制HCVpp进入细胞，但不能中和所有不同基因型。总之，我们对主要HCV基因型细胞进入途径中的共同步骤进行了表征，这应为开发细胞进入抑制剂和疫苗提供线索。
