Rationally designed attenuated HCV variants for vaccine Development

HCV is a leading cause of liver disease and no vaccine is currently available for HCV. Live attenuated vaccines are considered very effective since they imitate the natural infection in a non pathogenic manner, but still induce efficient B and T cell anti-viral immunity. In this study we aim to rationally design and generat WT attenuated HCV variants.

We utilized novel bioinformatics tools to analyze HCV genomes from databases for identifng `silent` patterns of HCV mRNA folding, utilized this information to design HCV variants containing synonymous mutations that affect this structure. We designed HCV mutants that varies in number and positions of inserted mutations. To evaluate the effect of the synonymous mutations on viral fitness, we measured the ability of the HCV mutants to replicate and spread. Moreover, we evaluated the mutants` pathogenesis by measuring their effect on expression of host genes related to oncogenic pathways, and examined their invasion properties in Transwell and ECM degradation assays.

We observed an overall reduction of HCV replication in mutants compared to WT. The spread and replication levels of the mutants varied with correlation to the level and positions of mutations inserted. The pathogenesis of the mutants varied also with correlation to the level of viral replication, with minimal effect on oncogenic gene expression for the most attenuated viruses. The findings of this study highlight the potential of viral attenuation generated by synonymous mutations affecting viral mRNA folding to reduce viral fitness, as a potential tool for developing rationally designed live attenuated HCV-vaccine.