Expression of heterologous proteins flanked by NS3-4A cleavage sites within the hepatitis C virus polyprotein.

Hepatitis C virus (HCV) contributes substantially to human morbidity and mortality world-wide. The development of HCV genomes expressing heterologous proteins has enhanced the ability to study viral infection, but existing systems have drawbacks. Recombinant viruses often require adaptive mutations to compensate for reduced viral titers, or rely on an artificial genomic organization that uncouples viral protein expression from recombinant gene expression. Here, we sought to exploit the viral polyprotein processing machinery to express heterologous proteins within the context of the HCV polyprotein. We show that HCV genotypes 2a and 1b permit insertion of reporter proteins between NS5A and NS5B with minimal impact on viral fitness. Using this strategy we constructed reporter genomes exhibiting a wide dynamic range, simplifying analysis of HCV infection in primary hepatocytes. Expression of heterologous proteins within the HCV genome offers new opportunities to analyze HCV infection in experimental systems without perturbing functions of individual viral proteins.