Anti-USP18 (full length) polyclonal antibody

Genetic polymorphisms in IFNL4 have been shown to predict responses to IFN-alpha-based therapy in hepatitis C virus (HCV)-infected patients. The IFNL4-Delta G genotype, which encodes functional IFN-lambda 4 protein, is associated with a poor treatment response. In the present study, we investigated the induction and biological effects of IFN-lambda 4 in HCV-infected hepatocytes and their association with responsiveness to IFN-alpha. We also studied the effects of direct-acting antiviral (DAA) treatment on IFN-lambda 4 expression and IFN-alpha responsiveness. HCV infection induced IFN-lambda 4 expression at mRNA and protein levels in primary human hepatocytes (PHHs). In hepatoma cells, IFNL4 gene transfection or recombinant IFN-lambda 4 protein treatment robustly increased the protein levels of ISG15 and USP18 in an IFNLR1-dependent manner and potently blocked IFN-alpha signalling. The ISG15/USP18-mediated IFN-alpha unresponsiveness was demonstrated by transfection of siRNAs targeting ISG15 and/or USP18. This potent IFN-lambda 4 effect was related to prolonged ISG expression after IFNL4 gene transfection. DAA treatment of HCV-infected PHHs reduced the expression of IFN-lambda s, including IFN-lambda 4, and restored IFN-alpha responsiveness. These results demonstrate that virus-induced IFN-lambda 4 potently blocks IFN-alpha signalling by inducing high protein levels of ISG15 and USP18. Moreover, the data clearly demonstrate that DAA therapy restores IFN-alpha responsiveness in HCV-infected cells.

The induction of innate and adaptive immunity is essential for controlling viral infections. Limited or overwhelming innate immunity can negatively impair the adaptive immune response. Therefore, balancing innate immunity separately from activating the adaptive immune response would result in a better antiviral immune response. Recently, we demonstrated that Usp18-dependent replication of virus in secondary lymphatic organs contributes to activation of the innate and adaptive immune responses. Whether specific mechanisms can balance innate and adaptive immunity separately remains unknown. In this study, using lymphocytic choriomeningitis virus (LCMV) and replication-deficient single-cycle LCMV vectors, we found that viral replication of the initial inoculum is essential for activating virus-specific CD8(+)T cells. In contrast, extracellular distribution of virus along the splenic conduits is necessary for inducing systemic levels of type I interferon (IFN-I). Although enforced virus replication is driven primarily by Usp18, B cell-derived lymphotoxin beta contributes to the extracellular distribution of virus along the splenic conduits. Therefore, lymphotoxin beta regulates IFN-I induction independently of CD8(+) T-cell activity. We found that two separate mechanisms act together in the spleen to guarantee amplification of virus during infection, thereby balancing the activation of the innate and adaptive immune system. (C) 2015 Elsevier Ltd. All rights reserved.