Hepatitis C virus (HCV) infection causes chronic liver diseases and is a global public health problem. Detailed analyses of HCV have been hampered by the lack of viral culture systems. Subgenomic replicons of the JFH1 genotype 2a strain cloned from an individual with fulminant hepatitis replicate efficiently in cell culture. Here we show that the JFH1 genome replicates efficiently and supports secretion of viral particles after transfection into a human hepatoma cell line (Huh7). Particles have a density of about 1.15-1.17 g/ml and a spherical morphology with an average diameter of about 55 nm. Secreted virus is infectious for Huh7 cells and infectivity can be neutralized by CD81-specific antibodies and by immunoglobulins from chronically infected individuals. The cell culture-generated HCV is infectious for chimpanzee. This system provides a powerful tool for studying the viral life cycle and developing antiviral strategies.

The absence of a robust cell culture model of hepatitis C virus (HCV) infection has severely limited analysis of the HCV life cycle and the development of effective antivirals and vaccines. Here we report the establishment of a simple yet robust HCV cell culture infection system based on the HCV JFH-1 molecular clone and Huh-7-derived cell lines that allows the production of virus that can be efficiently propagated in tissue culture. This system provides a powerful tool for the analysis of host-virus interactions that should facilitate the discovery of antiviral drugs and vaccines for this important human pathogen.CD81 ͉ Huh-7 ͉ viral entry ͉ viral spread ͉ interferon H epatitis C virus (HCV) is a noncytopathic positive-stranded RNA virus that causes acute and chronic hepatitis and hepatocellular carcinoma (1). The hepatocyte is the primary target cell, although various lymphoid populations, especially B cells and dendritic cells, may also be infected at lower levels (2-4). A striking feature of HCV infection is its tendency toward chronicity, with at least 70% of acute infections progressing to persistence (1), which is often associated with significant liver disease, including chronic active hepatitis, cirrhosis, and hepatocellular carcinoma (5). Thus, with Ͼ170 million people currently infected (5), HCV represents a growing public health burden.The HCV life cycle and host-virus interactions that determine the outcome of infection have been difficult to study, because cell culture and small animal models of HCV infection are not available. Thus, HCV infection studies to date have involved infected patients (6-8) and chimpanzees (9-12). The recent development of HCV replicon systems has also permitted the study of HCV translation and RNA replication in human hepatoma-derived Huh-7 cells in vitro (13,14), revealing some of the host-virus interactions that regulate these processes (15)(16)(17)(18)(19). Nonetheless, these replicons do not replicate efficiently without adaptive mutations (20, 21), nor do they produce infectious virions. Thus, the relevance of replicons to HCV infection is unclear, and they do not permit analysis of the complete viral life cycle.Wakita and colleagues (22, 23), however, have developed an HCV genotype 2a replicon (JFH-1) that replicates efficiently in Huh-7 cells, other human hepatocyte-derived cells (e.g., HepG2 and IMY-N9) (24), and nonhepatic cells (e.g., HeLa and HEK293) (25) without adaptive mutations. This group also recently reported that Huh-7 cells transfected with in vitro transcribed JFH-1 genomic RNA can secrete infectious viral particles. ʈ Unfortunately, the infection efficiency observed was low, and infectious particles could not be propagated in naïve ʈ).In contrast, we now report the establishment of a robust highly efficient in vitro infection system based on Huh-7-derived cell lines and the JFH-1 consensus clone. This system yields viral titers of 10 4 -10 5 infectious units per ml of culture supernatant; infection spreads throughout the culture within a few days a...