Alcohol impairs interferon signaling and enhances full cycle hepatitis C virus JFH-1 infection of human hepatocytes.

Alcohol drinking and hepatitis C virus (HCV) infection frequently coexist in patients with chronic liver disease. There is limited information, however, about the impact of alcohol on host cell innate immunity and full cycle replication of HCV. This study investigated whether alcohol impairs the intracellular innate immunity in human hepatocytes, promoting HCV infection and replication. Alcohol treatment of human hepatocytes before, during and after viral infection significantly enhanced full cycle HCV replication. Alcohol suppressed intracellular expression of type I interferons (IFN-α/β) in human hepatocytes. Investigation of the mechanisms responsible for the alcohol action revealed that alcohol inhibited the expression of the IFN regulatory factors (IRF-5 and IRF-7), and signal transducer and activator of transcription (STAT-1 and STAT-2), the key positive regulators in type I IFN signaling pathway. In addition, alcohol induced the expression of suppressors of cytokine signaling (SOCS-2 and SOCS-3), the key negative regulators of IFN-α/β expression. These in vitro findings suggest that alcohol, through modulating the expression of key regulators in IFN signaling pathway, inhibits type I IFN-based intracellular innate immunity in hepatocytes, which may contribute to the chronicity of HCV infection and the poor efficacy of IFN-α-based therapy.