In vivo interferon system assessed by 2′‐5′ oligoadenylate synthetase activity in chronic hepatitis C virus patients treated with pegylated interferon and ribavirin

Abstract

2',5' oligoadenylate synthetase (2-5AS), an enzyme induced by interferon, is an accurate indicator of the antiviral effect of interferon. We measured it during pegylated interferon based therapies in patients with chronic hepatitis C virus (HCV) in order to determine the dynamics of antiviral status in vivo and the relationship between the response to exogenous interferon and the outcome of therapy. A total of 160 patients with chronic HCV were treated with pegylated interferon alfa 2a or 2b or non-pegylated interferon, with or without ribavirin. Serum 2-5AS activity was measured by radioimmunoassay assay kits every 2 weeks. In 60 patients treated with pegylated interferon alfa 2a or 2b, 2-5AS levels increased to 7-40 times (average 235 pmol/dL) above the pretreatment levels (30 pmol/dL), which were significantly higher than the levels during non-pegylated interferon therapy. Ribavirin did not enhance 2-5AS levels. 2-5AS levels between sustained virological response (SVR) and non-SVR, including null responders to pegylated interferon plus ribavirin therapy were not significantly different. 2-5AS levels were significantly higher in patients treated with pegylated interferon than in those treated with non-pegylated interferon, suggesting that pegylated interferon is more potent at inducing interferon response genes resulting in an improved antiviral effect. Ribavirin did not appear to be related to interferon response gene induction.