bHepatitis C virus (HCV) NS3 protease inhibitors (PIs) are important components of novel HCV therapy regimens. Studies of PI resistance initially focused on genotype 1. Therefore, knowledge about the determinants of PI resistance for the highly prevalent genotypes 2 to 6 remains limited. Using Huh7.5 cell culture-infectious HCV recombinants with genotype 1 to 6 NS3 protease, we identified protease positions 54, 155, and 156 as hot spots for the selection of resistance substitutions under treatment with the first licensed PIs, telaprevir and boceprevir. Treatment of a genotype 2 isolate with the newer PIs vaniprevir, faldaprevir, simeprevir, grazoprevir, paritaprevir, and deldeprevir identified positions 156 and 168 as hot spots for resistance; the Y56H substitution emerged for three newer PIs. Substitution selection also depended on the specific recombinant. The substitutions identified conferred cross-resistance to several PIs; however, most substitutions selected under telaprevir or boceprevir treatment conferred less resistance to certain newer PIs. In a single-cycle production assay, across genotypes, PI treatment primarily decreased viral replication, which was rescued by PI resistance substitutions. The substitutions identified resulted in differential effects on viral fitness, depending on the original recombinant and the substitution. Across genotypes, fitness impairment induced by resistance substitutions was due primarily to decreased replication. Most combinations of substitutions that were identified increased resistance or fitness. Combinations of resistance substitutions with fitness-compensating substitutions either rescued replication or compensated for decreased replication by increasing assembly. This comprehensive study provides insight into the selection patterns and effects of PI resistance substitutions for HCV genotypes 1 to 6 in the context of the infectious viral life cycle, which is of interest for clinical and virological HCV research.
With more than 100 million chronic infections causing approximately 500,000 deaths annually, hepatitis C virus (HCV) is a major global health and economic burden (1, 2). The six epidemiologically important genotypes differ in ϳ30% of their sequence and in their sensitivity to antiviral regimens (3-6). In Europe, the Americas, Asia, and Australasia, genotypes 1, 2, and 3 are most prevalent. While genotypes 4, 5, and 6 are more restricted to specific geographical regions in Africa and Asia, they account for 20% of global HCV infections and have spread beyond these primary geographical locations (1, 2, 7).The development of directly acting antivirals (DAAs) has revolutionized HCV therapy. The main components of interferonfree regimens introduced in the clinic are inhibitors of the HCV nonstructural (NS) proteins NS3 protease (NS3P), NS5A,8,9). Even though DAA-based therapy regimens could cure most patients in clinical trials, failure rates of 5 to 10% are to be expected in real life, due primarily to the development of DAA resistance (4,8). Given the large ...