Identification of NS5B Resistance-Associated Mutations in Hepatitis C Virus Circulating in Treatment Naïve Vietnamese Patients.

Introduction: Treatment of HCV infection with peginterferon and ribavirin results in a low sustained virologic response rate, but has a number of undesirable adverse effects. Direct-acting antivirals (DAAs) offer a high efficacy, low risk, and a short treatment time. However, the existence of resistance-associated mutations, particularly in the NS5B polymerase, can attenuate the efficacy of DAAs. The objective of this study was to identify amino acid changes in the NS5B gene linked to DAA resistance in treatment-naive Vietnamese chronic hepatitis C patients. Methods: Blood samples and treatment data were collected from 100 HCV-infected patients hospitalized at the National Hospital for Tropical Diseases between January and December 2020; the plasma was then isolated and stored at -80°C for molecular analysis. The NS5B gene fragments of 100 samples were amplified with specified primers and the nucleotide sequences were obtained using the Sanger sequencing system. The nucleotide sequences were then analyzed and compared to identify substitutions in the NS5B region. Results: A total of 100 HCV isolates from patients were classified into three genotypes, including genotypes 1, 3, and 6. The NS5B sequence analysis revealed many amino acid mutations in all genotypes, although these mutations were not strongly associated with resistance to DAAs like S282T. Analytical data on ribavirin-resistance mutations revealed that Q309R was predominantly found in genotype 1a, D310N was mostly found in genotype 1b, and N244I, T329I, A333E were not observed. The following mutations were shown to be related with DAAs resistance: E237G, S282R, L320F, V321A, and V321I. Furthermore, NS5B-resistance mutations were not associated with clinical characteristics, long-term virological response, or improvements in clinical parameters (liver enzymes or liver fibrosis index). Conclusion: Although NS5B mutations were found in treatment-naive Vietnamese patients, changes in the NS5B gene did not appear to be highly correlated with HCV ribavirin and DAA antiviral resistance.