Differential Efficacy of Protease Inhibitors Against HCV Genotypes 2a, 3a, 5a, and 6a NS3/4A Protease Recombinant Viruses

Background & AimsThe hepatitis C virus (HCV) genotype influences efficacy of interferon (IFN)-based therapy. HCV protease inhibitors are being licensed for treatment of genotype 1 infection. Because there are limited or no data on efficacy against HCV genotypes 2–7, we aimed at developing recombinant infectious cell culture systems expressing genotype-specific nonstructural (NS) protein 3 protease (NS3P).MethodsViability of J6/JFH1-based recombinants with genotypes 1–7 NS3P/NS4A was evaluated in Huh7.5 human hepatoma cells. Adaptive mutations were identified in reverse genetic studies. Efficacy of lead compound linear protease inhibitors VX-950 (telaprevir) and SCH503034 (boceprevir) and macrocyclic inhibitors TMC435350, ITMN-191 (danoprevir), and MK-7009 (vaniprevir) was determined in high-throughput infection assays.ResultsFor genotype(isolate) 2a(J6), 3a(S52), 5a(SA13), and 6a(HK6a), we developed culture systems producing supernatant infectivity titers of 3.5–4.0 log10 focus forming units/mL. Against 2a(J6), 5a(SA13), and 6a(HK6a), all inhibitors showed similar efficacy; macrocyclic inhibitors had ∼10-fold greater potency than linear inhibitors. However, compared with 2a recombinant J6/JFH1, efficacy against 3a(S52) was 16- to 70-fold lower for macrocyclic inhibitors and 2- to 7-fold lower for linear inhibitors. Testing of additional genotype 2a and 3a isolates showed that these differences were genotype specific. The resistance of 3a isolates was similar to J6/JFH1 with engineered resistance mutations originally observed for genotype 1 patients. In contrast, we found similar efficacy of NS5A inhibitor BMS-790052 and interferon-alfa2.ConclusionsNovel HCV culture systems with genotype specific NS3P/NS4A revealed similar efficacy of protease inhibitors against genotypes 2a, 5a, and 6a and comparatively low but varying efficacy against genotype 3a isolates. These systems will facilitate genotype-specific studies of HCV protease inhibitors and of viral resistance.