Association of interleukin 28B polymorphism and mutations in the NS5A region of hepatitis C virus genotype 2 with interferon responsiveness

Background and Aim: The single nucleotide polymorphism (SNP) of interleukin 28B (IL28B) and the mutations in the NS5A region of hepatitis C virus (HCV) genotype 1 have been associated with response to interferon (IFN) therapy. However, these relationships in patients with HCV genotype 2 are not well understood. The aim of this study was to investigate whether the SNP of IL28B (rs8099917) and amino acid substitutions in the NS5A region in patients with HCV genotype 2 affect the response to IFN and ribavirin combination therapy. Methods: The study enrolled 286 patients with chronic hepatitis C genotype 2. Patients received pegylated-IFN-alpha 2b once each week plus oral ribavirin daily for 24 weeks. Results: Of the 286 patients, 215 (75.2%) achieved sustained virologic response (SVR). Rate of SVR was similar in patients with IL28B TT allele (76%) and those with TG or GG alleles (72%). Patients with SVR were younger than those without SVR (P<0.001). SVR was achieved in 65.9% of patients with wild-type IFN sensitivity-determining region (ISDR) and 83.5% of patients with mutant type (P<0.001). There were no significant differences in other factors, including sex, alanine aminotransferase, platelet count, HCV viral load, HCV genotype, and IL28B genotype. The factors related to SVR on multivariate analysis were age (P=0.019) and ISDR (P=0.003). Conclusions: ISDR sequence variations are significantly associated with IFN responsiveness in patients with HCV genotype 2. The SNP of IL28B was not associated with SVR in patients with HCV genotype 2.