Adaptation of the hepatitis C virus to cell culture.

A major breakthrough in the field of HCV research was the development of a system that supports the production of infectious virus particles. The key to this achievement was the molecular cloning of a genotype 2a genome, designated JFH1, which replicates to exceptionally high levels and at the same time supports virus particle assembly and release. A major drawback of this system was, however, the rather low yield of infectious particles obtained with the JFH1 genome as well as with most JFH1-derived virus chimeras. One approach to overcoming this hurdle is adaptation of the HCV genomes to cell culture. We found that both JFH1 and all chimeras, except one, can easily be adapted to cultured cells, increasing virus yields by up to three orders of magnitude. Surprisingly, adaptation is achieved by a multitude of mutations residing in both the structural and the nonstructural proteins. We therefore argue that a complex interaction between structural proteins and the HCV replicase takes place to allow efficient virus particle production.