Regulation of Interferon Regulatory Factor-3 by the Hepatitis C Virus Serine Protease
Persistent infections with hepatitis C virus (HCV ) are likely to depend on viral inhibition of host defenses. We show that the HCV NS3/4A serine protease blocks the phosphorylation and effector action of interferon regulatory factor-3 (IRF-3), a key cellular antiviral signaling molecule. Disruption of NS3/4A protease function by mutation or a ketoamide peptidomimetic inhibitor relieved this blockade and restored IRF-3 phosphorylation after cellular challenge with an unrelated virus.
... d virus. Furthermore, dominant-negative or constitutively active IRF-3 mutants, respectively, enhanced or suppressed HCV RNA replication in hepatoma cells. Thus, the NS3/4A protease represents a dual therapeutic target, the inhibition of which may both block viral replication and restore IRF-3 control of HCV infection. Persistent HCV infection is a leading cause of liver disease worldwide and is frequently refractory to current interferon (IFN)-based therapies (1, 2). HCV persistence is facilitated by the ability of the virus to incorporate adaptive mutations and to replicate as a population of genetically distinct quasispecies (3, 4), but is likely to result from specific disruption of host immune responses by HCV proteins (5-7). The HCV genome, a 9.6-kb single-stranded RNA of Fig. 1. HCV regulation of the IRF-3 pathway. (A) Organization of the genotype 1b HCV RNA replicating in Huh7 C5B2-3 cells (referred to as Huh7 2-3 cells) (19) and of the genotype 1a polyprotein expressed conditionally in UHCV11 cells. The NS3/4A coding region is shaded. (B) Immunostaining for IRF-3 in SenV-infected (SenV ϩ ) or mock-infected (SenV -) cells. From top to bottom, IRF-3 subcellular localization in control Huh7 cells, 2-3 cells, or interferon-cured 2-3c cells is shown (20), as are UHCV11 cells with (ϩHCV 1a) or without polyprotein expression (-HCV 1a). On the right are immunoblots for NS3 and actin in corresponding cell extracts. (C) Huh7 cells, Huh7 2-3 cells, or 2-3c cells were transfected with the indicated promoter-luciferase reporter constructs and then infected with SenV (black bars) or mock-infected (gray bars). Luciferase activities were determined in cell extracts (mean Ϯ S.D. from three experiments) (20).