Highly Efficient JFH1-Based Cell-Culture System for Hepatitis C Virus Genotype 5a: Failure of Homologous Neutralizing-Antibody Treatment to Control Infection

Background. Recently, a hepatitis C virus (HCV) cell-culture system was developed that employed strain JFH1 ( genotype 2a), and JFH1-based intra-and intergenotypic recombinants now permit functional studies of the structural genes ( Core, E1, and E2), p7, and NS2 of genotypes 1-4. The goal was to adapt the system to employ genotype 5. Methods. Huh7.5 cells infected with SA13/JFH1, containing Core-NS2 of strain SA13 ( genotype 5a), were monitored for Core expression and for supernatant infectivity and HCV-RNA titers. Adaptive mutations of SA13/JFH1 were identified by sequence analysis of recovered genomes and reverse-genetic studies. Receptor blockage was performed with anti-CD81 and anti-SR-BI. For neutralization experiments, SA13/JFH1 or JFH1-based viruses of other genotypes were incubated with patient sera. Results. SA13/JFH1 with NS2 and NS3 mutations yielded infectivity titers > 10(5) TCID50/mL. Infection with SA13/JFH1 was inhibited by CD81 blocking and SR-BI blocking, respectively, and by preincubation with genotype 5a chronic-phase patient sera. Such sera had varying cross-genotype neutralization potential. However, preincubation and treatment with homologous neutralizing antibodies could not control SA13/JFH1 infection in culture. Conclusion. The SA13/JFH1 culture permits genotype 5a-specific studies of Core-NS2 function and interfering agents. The ability of HCV to spread in vivo during treatment with neutralizing antibodies was confirmed in vitro.