Detection of Pre-treatment mutations leading to resistance to direct hepatitis C virus blocking drugs in patients with chronic hepatitis C

Human is the only host of hepatitis C virus. This virus has a positive single stranded RNA and lipoprotein envelop that has 7 confirmed genotypes. According to studies, genotypes 1a, 3a and 1b are the most common genotypes in Iran. No effective vaccine against HCV infection has been developed instead, advances in antiviral treatment using drugs that directly affect specific viral genomic regions to inhibit virus replication have promising results, particularly in the treatment of genotype 1 of HCV virus as a hard to treat genotype. These drugs have been used in our country for few years to treat patients with chronic hepatitis C infection so, according to the mutation prone characteristic of HCV genome which could be resulted in drug resistance  monitoring of their effectiveness for early detection of resistant mutations has the great importance.The aim of this study was to determine the frequency of drug resistant mutations in NS5A and NS5B regions as targets of new hepatitis C antiviral drugs in patients with chronic HCV-1b infection who were under treatment with these drugs.

In this study, there were 29 volunteers with chronic HCV-1b infection who had failed to be treated with ribavirin and interferon but were considered “naïve” to direct acting anti-viral drugs. Viral genome was extracted from blood samples using Roche Viral RNA Extraction Kit. RT-PCR and nested PCR was performed by using specific external and internal primers separately by using the TaKaRa kit. The PCR products were sequenced and the results were verified by Bio Edit software version (7.9.5.3). Multiple alignment was performed by using CLUSTAL W software in MEGA version (6).

Resistance mutations against anti HCV drugs in this study were identified in 5 (17.24%) patients out of 29 patients against daclatasvir and ledipasvir drugs. However, all patients responded to anti-HCV therapy due to the absence of resistant mutations in NS5b region that is the viral genomic target region of sofosbovir, and this response was sustained at follow-up.

Use of Sofosbuvir in treatment of patients with chronic HCV-1b infection which is the most difficult to treat HCV genotypes, was very promising. Despite identification of resistant mutations against Daclatasvir and Ledipasvir the use of Sofosbuvir resulted in complete treatment of patients. However, due to the mutable nature of the virus, monitoring of occurrence of possible resistant mutations against Sofosbuvir is necessary to achieve HCV elimination in our country.