NS3 genetic variability in hepatitis C virus genotype-1b isolates from liver specimens and blood samples of treatment naïve patients with chronic hepatitis C

Background: Two distinct inhibitors of the hepatitis C virus (HCV) protease have been approved for the treatment of patients infected with HCV genotype-1. These molecules are highly efficient in suppressing HCV replication but their use is limited by the emergence of viral mutants resistant to them after a very short time of treatment. By the analysis of blood samples, it was shown that viral strains resistant to protease inhibitors (PI) may pre-exist to treatment. Aim of this study was to investigate the presence of viral variants resistant to PIs in isolates from liver and blood of HCV patients naïve to any antiviral therapy. Methods: Liver and blood HCV-1b isolates from 10 patients with chronic hepatitis were analysed by cloning and sequencing procedures. Results: The analyses of 10-15 clones from liver isolates of each patient showed that 7/10 cases had single or multiple mutations potentially conferring resistance to PIs. On the contrary, the analysis of the corresponding blood samples excluded the presence of these mutations in all cases but one, which had the Q80R mutation in all clones from both liver and plasma samples. No PI resistant variant was detected in isolates from either liver or plasma of 3 patients. Conclusions: Naturally occurring HCV variants resistant to PIs are commonly present at intrahepatic level and this clearly explains their usual, very early emergence under treatment. However, the identification of these variants as circulating viral populations appears to be occasional in untreated patients.