丙型肝炎病毒（hepatitis C virus, HCV）感染可导致传染性丙型肝炎，是诱发肝硬化和肝癌的重要因素之一。HCV有7种基因型，各基因型对药物的应答差异严重影响对病人的治疗。缺乏代表各基因型HCV的细胞培养系统严重阻碍了HCV基础研究和抗病毒药物的研制。迄今，只发现基因2a型的JFH1克隆可在肝细胞系中自主复制。最近，我们鉴定了3个适应性突变，称LSG突变（F1464L，A1672S和D2979G），并建立了基于LSG的HCV基因1a、2a和2b型的体外感染性克隆。但是，适应性突变启动HCV在肝细胞系中复制的机制还不清楚。本项目将研究LSG和出现在不同感染性克隆中的突变（P1096L，N1927T和N1927S）启动无复制能力的HCV基因组在肝细胞系中复制的分子机制。此课题将综合解析适应性突变克服细胞限制因子，进行复制的分子机理，为建立普遍适用的HCV体外培养系统奠定基础。

Majority of hepatitis C virus (HCV) infection results in chronic hepatitis C, which is a leading cause of liver cirrhosis and liver cancer. HCV is classified into 7 genotypes, with differential sensitivity to current therapeutics. To date, only JFH1 (genotype 2a) clone was found to be able to replicate spontaneously in cultured human hepatoma cells and releases infectious virus. Basic HCV research required for vaccine and drug development has been hampered by the inability to culture patient isolates. Recently, we identified 3 cell culture adaptive mutations F1464L, A1672S, and D2979G (LSG), with which we successfully developed novel HCV genotype 1a, 2a, and 2b infectious culture systems. In this project, we aim to study the molecular mechanism of the LSG and other mutations P1096L, N1927T, and N1927S, identified from different adapted infectious HCV clones, in promoting replication-incompetent HCV genomes to replicate and establish persistent infection in hepatic cell lines. This project is expected to elucidate the mechanism of culture adaptive mutations in overcoming the barrier of host factors to establish a productive HCV infection in vitro, thus facilitating the development of infectious culture systems for other HCV isolates as well as a culture system universal for HCV genotypes.