Immune cell responses are not required to induce substantial hepatitis B virus antigen decline during pegylated interferon-alpha administration

Background 82 Aims: Pegylated interferon-alpha (PegIFN alpha) remains an attractive treatment option for chronic hepatitis B virus (HBV) infection because it induces higher rates of antigen loss and seroconversion than treatment with polymerase inhibitors. Although early HBsAg decline is recognised as the best predictor of sustained response to IFN-based therapy, it is unclear whether immune cell functions are required to induce significant antigenemia reduction in the first weeks of treatment. Aim of the study was to investigate whether PegIFN alpha can induce sustained human hepatocyte responsiveness and substantial loss of circulating and intrahepatic viral antigen loads in a system lacking immune cell functions. Methods: HBV-infected humanized uPA/SCID mice received either PegIFN alpha, entecavir (ETV), or both agents in combination. Serological and intrahepatic changes were determined by qRT-PCR and immunohistochemistry and compared to untreated mice. Results: After 4 weeks of treatment, median viremia reduction was greater in mice treated with ETV (either with or without PegIFN alpha) than with PegIFN alpha. In contrast, levels of circulating HBeAg, HBsAg, and intrahepatic HBcAg were significantly reduced (p = 0.03) only in mice receiving PegIFN alpha alone or in combination, as compared to mice receiving ETV monotherapy. Progressive antigen reduction was also demonstrated in mice receiving PegIFN alpha for 12 weeks (HBeAg = SI log; HBsAg = Delta 1.4 log; p<0.0001). Notably, repeated administrations of the longer-active PegIFN alpha could breach the impairment of HBV-infected hepatocyte responsiveness and induce sustained enhancement of human interferon stimulated genes (ISG). Conclusions: The antiviral effects of PegIFN alpha exerted on the human hepatocytes can induce sustained responsiveness and trigger substantial HBV antigen decline without claiming the involvement of immune cell responses. (C) 2013 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.