Impact of Host Genetic Variants on Natural History and Treatment of Hepatitis C Virus Infection

Abstract: Chronic hepatitis C Virus (HCV) infection causes liver disease and may progress to severe fibrosis, cirrhosis, and hepatocellular carcinoma. This thesis aimed to evaluate the impact of host genetics, i.e. genetic variants of PNPLA3, IL28B and ITPA, on liver disease severity and treatment outcome in HCV genotype 2 and 3 infected patients treated with pegylated interferon and ribavirin for either 12 or 24 weeks. In paper I, 359 patients were evaluated retrospectively with regards to the impact of the PNPLA3 genetic variants. No significant impact was observed on liver disease severity nor on treatment outcome, and the clinical need to screen Nordic HCV genotype 2 or 3 infected patients for these genetic variants seems low. In papers II and III, in post-hoc evaluation encompassing 339 Nordic HCV genotype 2 or 3 infected patients, genetic variants of the rs12979860 in proximity to IL28B were not associated with treatment outcome but the CCrs12979860 and the TTrs8099917 genetic variants (n=314) were found to be associated with more pronounced liver histopathology among HCV genotype 3 infected patients. Thus, these patients may benefit from early initiation of therapy. In paper IV, in a real life trial (n=737) enrolling HCV genotype 1-3 infected patients evaluated by means of transient elastography, CCrs12979860 was significantly associated with higher liver stiffness values among HCV genotype 3 infected patients; thus confirming the results of papers II and III in an independent cohort of patients. In paper V, in a post-hoc analysis of Nordic HCV genotype 2 or 3 infected patients treated with 800 mg ribavirin daily and interferon reduced ITPase (n=354) activity was significantly associated with increased likelihood of achieving sustained virological response. Thus the majority of patients having normal ITPase activity may benefit more from a higher weight-based dosing of ribavirin.