AIMS: Development of direct-acting antivirals (DAAs) has made antihepatitis C virus (HCV) treatment highly safe and effective. However, the emergence of resistant-associated variants (RAVs) after failure of DAA therapy affects retreatment outcomes. In particular, genotype 1 HCV with P32 deletion has been reported to be highly resistant to all approved non-structural protein (NS)5A inhibitors. However, analysis of RAVs in genotype 2 HCV has been limited. Accordingly, in this study, we evaluated the roles of genotype 2 HCV variants in antiviral drug efficacy. METHODS: We utilized HCV-2b/2a (JFH-1) chimeric virus (genotype 2a), which replicates more robustly than JFH-1. We constructed various genotype 2a JFH-1-based HCV cell culture systems with NS3 (D168E), NS5A (F28S, F28S/M31I, P32 deletion, and Y93H), and NS5B (S282 T) RAVs and analyzed the replication ability and sensitivity to various anti-HCV reagents. RESULTS: Genotype 2a-based HCV with NS5A-P32 deletion could not replicate even in long-term cultures. Genotype 2a-based HCV with NS5A-F28S/M31I showed significantly higher replication ability than the wild-type strain, and replication could not be suppressed, even with high concentrations of NS5A inhibitors, including pibrentasvir and velpatasvir (<1000-10 000 fold-resistance compared with the wild-type strain). However, genotype 2a-based HCV with NA5A-F28S/M31I was sensitive to HCV protease inhibitor, NS5B inhibitor, interferon-α, and ribavirin. Genotype 2a-based HCV with NS5B-S282 T was resistant to sofosbuvir, but was highly sensitive to ribavirin compared with the control. CONCLUSIONS: When undertaking retreatment for genotype 2a HCV-infected patients who fail to respond to DAAs, the optimized retreatment should be chosen according to the sensitivity of the emerging RAVs to anti-HCV drugs.
AIMS: Development of direct-acting antivirals (DAAs) has made antihepatitis C virus (HCV) treatment highly safe and effective. However, the emergence of resistant-associated variants (RAVs) after failure of DAA therapy affects retreatment outcomes. In particular, genotype 1 HCV with P32 deletion has been reported to be highly resistant to all approved non-structural protein (NS)5A inhibitors. However, analysis of RAVs in genotype 2 HCV has been limited. Accordingly, in this study, we evaluated the roles of genotype 2 HCV variants in antiviral drug efficacy. METHODS: We utilized HCV-2b/2a (JFH-1) chimeric virus (genotype 2a), which replicates more robustly than JFH-1. We constructed various genotype 2a JFH-1-based HCV cell culture systems with NS3 (D168E), NS5A (F28S, F28S/M31I, P32 deletion, and Y93H), and NS5B (S282 T) RAVs and analyzed the replication ability and sensitivity to various anti-HCV reagents. RESULTS: Genotype 2a-based HCV with NS5A-P32 deletion could not replicate even in long-term cultures. Genotype 2a-based HCV with NS5A-F28S/M31I showed significantly higher replication ability than the wild-type strain, and replication could not be suppressed, even with high concentrations of NS5A inhibitors, including pibrentasvir and velpatasvir (<1000-10 000 fold-resistance compared with the wild-type strain). However, genotype 2a-based HCV with NA5A-F28S/M31I was sensitive to HCV protease inhibitor, NS5B inhibitor, interferon-α, and ribavirin. Genotype 2a-based HCV with NS5B-S282 T was resistant to sofosbuvir, but was highly sensitive to ribavirin compared with the control. CONCLUSIONS: When undertaking retreatment for genotype 2a HCV-infectedpatients who fail to respond to DAAs, the optimized retreatment should be chosen according to the sensitivity of the emerging RAVs to anti-HCV drugs.