JFH1-based Core-NS2 genotype variants of HCV with genetic stability in vivo and in vitro: Important tools in the evaluation of virus neutralization

Background and Aims: HCV infection continues to be a major global health burden despite effective antiviral treatments. The urgent need for a protective vaccine is hindered by the scarcity of suitable HCV-permissive animal models tractable in vaccination and challenge studies. Currently, only antibody neutralization studies in infectious cell culture systems or studies of protection by passive immunization of human liver chimeric mice offer the possibility to evaluate the effect of vaccine-induced antibodies. However, differences between culture-permissive and in vivo–permissive viruses make it a challenge to compare analyses between platforms. To address this problem, we aimed at developing genotype-specific virus variants with genetic stability both in vitro and in vivo. Approach and Results: We demonstrated infection of human liver chimeric mice with cell culture–adapted HCV JFH1-based Core-NS2 recombinants of genotype 1–6, with a panel of 10 virus strains used extensively in neutralization and receptor studies. Clonal re-engineering of mouse-selected mutations resulted in virus variants with robust replication both in Huh7.5 cells and human liver chimeric mice, with genetic stability. Furthermore, we showed that, overall, these virus variants have similar in vitro neutralization profiles as their parent strains and demonstrated their use for in vivo neutralization studies. Conclusions: These mouse-selected HCV recombinants enable the triage of new vaccine-relevant antibodies in vitro and further allow characterization of protection from infection in vivo using identical viruses in human liver chimeric mice. As such, these viruses will serve as important resources in testing novel antibodies and can thus guide strategies to develop an efficient protective vaccine against HCV infection.