Production of infectious genotype 1a hepatitis C virus (Hutchinson strain) in cultured human hepatoma cells

Infections with hepatitis C virus (HCV) are marked by frequent viral persistence, chronic liver disease, and extraordinary viral genetic diversity. Although much has been learned about HCV since its discovery, progress has been slowed by a lack of permissive cell culture systems supporting its replication. Productive infections have been achieved recently with genotype 2a virus, but cirrhosis and liver cancer are typically associated with genotype 1 HCV, which is more prevalent and relatively resistant to IFN therapy. We describe production of infectious genotype 1a HCV in cells transfected with synthetic RNA derived from a prototype virus (H77-S). Viral proteins accumulated more slowly in H77-S transfected cells than in cells transfected with genotype 2a (JFH-1) RNA, but substantially more H77-S RNA was secreted into supernatant fluids. Most secreted RNA was noninfectious, banding in isopycnic gradients at a density of 1.04-1.07 gm/cm³, but infectivity was associated with H77-S particles possessing a density of 1.13-1.14 gm/cm³. The specific infectivity of H77-S particles (5.4 × 10⁴ RNA copies per focus-forming unit) was significantly lower than JFH-1 virus (1.4 × 10² RNA copies per focus-forming unit). Infection with either virus was blocked by CD81 antibody. Sera from genotype 1a-infected individuals neutralized H77-S virus, but had little activity against genotype 2a virus, suggesting that these genotypes represent different serotypes. The ability of this genotype 1a virus to infect cultured cells will substantially benefit antiviral and vaccine discovery programs.