Background & AimsHeterogeneity in the hepatitis C virus (HCV) protein NS5A influences its sensitivity to interferon-based therapy. Furthermore, NS5A is an important target for development of HCV-specific inhibitors. We aimed to develop recombinant infectious cell culture systems that express NS5A from isolates of the 7 major HCV genotypes, and determining their sensitivity to a specific NS5A inhibitor and to interferon-α.MethodsHuh7.5 hepatoma cells were transfected with RNA of genotype 1–7 NS5A recombinants. Viability was determined by measuring HCV replication and infectivity titers. Putative adaptive mutations were analyzed by reverse genetics. The activity of antiviral agents was determined ... More
Background & AimsHeterogeneity in the hepatitis C virus (HCV) protein NS5A influences its sensitivity to interferon-based therapy. Furthermore, NS5A is an important target for development of HCV-specific inhibitors. We aimed to develop recombinant infectious cell culture systems that express NS5A from isolates of the 7 major HCV genotypes, and determining their sensitivity to a specific NS5A inhibitor and to interferon-α.MethodsHuh7.5 hepatoma cells were transfected with RNA of genotype 1–7 NS5A recombinants. Viability was determined by measuring HCV replication and infectivity titers. Putative adaptive mutations were analyzed by reverse genetics. The activity of antiviral agents was determined in high-throughput infection assays.ResultsCells infected with viable HCV that expressed NS5A of genotypes 1–7 produced relatively high viral titers; most NS5A recombinants required introduction of specific adaptive mutations. The efficacy of the NS5A inhibitor BMS-790052 varied greatly, based on NS5A isolate, with median effective concentration (EC50) values ranging from 0.009 nmol/L to 14 nmol/L; the high sensitivity of genotype 1b NS5A to BMS-790052 reflected observations from clinical studies. Specific residues in NS5A domain I were associated with >100-fold variations in sensitivity between isolates of the same HCV subtype. The Y/T2065H mutation conferred resistance to BMS-790052 that varied among NS5A isolates. When infected cultures were incubated with interferon-α, all NS5A recombinants had EC50 values of ∼0.2 IU/mL, including an NS5A genotype 1b mutant with a putative sensitive-type, interferon sensitivity determining region.ConclusionsWe developed efficient in vitro systems in which recombinant viruses express HCV genotypes 1–7 NS5A; these permit genotype-and isolate-specific analyses of NS5A and the effects of antiviral compounds and resistance mutations. These culture systems will facilitate development of specific inhibitors against NS5A of different HCV variants.
