Analysis of drug-resistance-associated mutations and genetic barriers in hepatitis C virus NS5B sequences in China

The hepatitis C virus (HCV) NS5B protein is an RNA-dependent RNA polymerase that is required for viral genome replication and constitutes the most important target region for drugs being developed as direct-acting antivirals (DAAs) against HCV genotype 1. However, the extreme genetic variability leading to drug resistance mutations and genetic barriers has dramatically compromised the effectiveness of DAA therapy. The purpose of this study was to analyze the genetic variability of NS5B polymerase in HCV patients from different provinces of China to identify the impact of these resistance sites on genetic barriers. We analyzed 3489 NS5B sequences of HCV strains circulating in different regions of China, obtained from the GenBank database, 153 of which were from three cities in Sichuan Province (Yibin, Zigong and Zhangzhou). Sequence alignment was conducted using MEGA 6.0, the genetic information was translated into amino acids, and the percentage of polymorphic amino acid sites was calculated. The Vijver method was used to evaluate the occurrence of genetic barriers in HCV NS5B sequences. Blood samples were collected from 153 HCV patients from Sichuan for NS5B sequence analysis using real-time PCR and the Sanger method. Of the 17 antiviral drug resistance sites summarized from the published literature, nine were found in Chinese NS5B sequences, and C316Y was identified as the dominant mutation. Analysis of genetic barriers revealed that the probability of mutation to a drug-resistance-associated amino acid, in response to selective pressure from antiviral drugs was 100% at site 96 and 99.7% at site 282. Our study is the first to analyze the drug resistance sites and to evaluate genetic barriers in NS5B sequences that could affect the responsiveness of Chinese HCV patients to DAA therapy. The results provide a valuable basis for drug development and introduction of foreign-origin antiviral drugs in China that targeting the HCV NS5B region.