Identification of mutations within the sequence of interferon sensitivity determining region (ISDR) of virus genotype 1b in chronic hepatitis C patients who are virologically nonresponsive to ifn+ribavirin therapy

2. SUMMARY "Identification of mutations within the sequence of interferon sensitivity determining region (ISDR) of virus genotype lb in chronic hepatitis C patients who are virologically nonresponsive to IFN+Ribavirin therapy" Hepatitis C Virus (HCV) infection which affects 170 million people in the world, carries a risk of chronicity in up to 50-85 % and developing cirrhosis in 20 % of patients. Among the latter about 3.5-10 million of them have an increased risk of hepatocellular carcinoma. AntiHCV positivity is approximately 3 % in the world and 0.3-4 % in Turkey according to different resources. Besides, prevalance of HCV in chronic liver diseases is 13- 27 % in Turkey. Identifying the mechanisms that lead to theraphy failure in chronic HCV infection and improvement of effective therapy protocols are required. "Double stranded RNA activated protein kinase" binding region (PKR-binding region) was reported to be effective in IFN+Ribavirin treatment for international chronic HCV therapies. NS5A protein encoded from the HCV genome nonstructural 5A (NS5A) gene has a PKR-binding region that blocks the dimerization of PKR, resulting in the prevention of cell death and continuation of virus proliferation. Some of the mutations in this region are shown to prevent PKR enzyme binding and virus proliferation and thus lead to cell death in yeast. In this study, sera samples from three complete responders (CR), five biochemical responders (BR) and 11 nonresponders (NR) that were infected by genotype lb HCV and received IFN+Ribavirin therapy in Dokuz Eylul University Hospital were studied. HCV- NS5A (coding PKR binding region) gene was amplified through RNA extraction, RT-PCR and nested PCR and the PCR products were sequenced for mutation analysis. Finally, 86 aminoacid mutations were detected, 14 (16 %) of them were within the ISDR and 72(84%) of them were within the carboxy terminal domain of the protein. 12 (86 %) of 14 aminoacid mutations in the ISDR were detected in the BR group. ISDR aminoacid mutation number in BR patient group is statistically more significant than that in the NR patient group (p=0.012). According to this study, ISDR aminoacid mutations are important predictor factors for biochemical responses in IFN+Ribavirin therapy of genotype lb infected chronic HCV patients. Key Words: Chronic HCV, genotype lb, IFN+Ribavirin, PKR-binding region, ISDR