Extent of HCV NS3 protease variability and resistance-associated mutations assessed by next generation sequencing in HCV monoinfected and HIV/HCV coinfected patients.

HCV quasispecies variability represents the background for the selection of mutations and for the development of drug resistance. Natural aminoacid changes in NS3, associated with reduced protease inhibitor susceptibility, have been observed in treatment-naïve patients. Massively parallel sequencing has been used to analyze NS3 quasispecies in patients infected with HCV genotype 1, naive to anti-HCV treatment, with/without HIV-coinfection, to establish the genetic heterogeneity and the presence of amino acid substitutions at positions responsible for drug resistance. Genomes carrying substitutions represented either predominant or minority components of viral quasispecies, and were observed in 85.7% of patients. Multiple substitutions, frequently associated on the same haplotype, were observed in 46.4% of patients. High resistance combinations were not detected, neither on the same genome, nor in the whole quasispecies. Heterogeneity of HCV NS3 was lower in HIV-coinfected as compared to HCV-monoinfected patients, but factors underlying this difference remain to be established. Although the relevance of naturally occurring mutations with respect of resistance development and probability of success of direct acting antivirals is questioned, UDPS may be beneficial to help understanding viral dynamics, providing high resolution view of viral diversity.