Enhancement of antiviral immunity by small molecule antagonist of suppressor of cytokine signaling.

Suppressors of cytokine signaling (SOCSs) are negative regulators of both innate and adaptive immunity via inhibition of signaling by cytokines such as type I and type II IFNs. We have developed a small peptide antagonist of SOCS-1 that corresponds to the activation loop of JAK2. SOCS-1 inhibits both type I and type II IFN activities by binding to the kinase activation loop via the kinase inhibitory region of the SOCS. The antagonist, pJAK2(1001-1013), inhibited the replication of vaccinia virus and encephalomyocarditis virus in cell culture, suggesting that it possesses broad antiviral activity. In addition, pJAK2(1001-1013) protected mice against lethal vaccinia and encephalomyocarditis virus infection. pJAK2(1001-1013) increased the intracellular level of the constitutive IFN-beta, which may play a role in the antagonist antiviral effect at the cellular level. Ab neutralization suggests that constitutive IFN-beta may act intracellularly, consistent with recent findings on IFN-gamma intracellular signaling. pJAK2(1001-1013) also synergizes with IFNs as per IFN-gamma mimetic to exert a multiplicative antiviral effect at the level of transcription, the cell, and protection of mice against lethal viral infection. pJAK2(1001-1013) binds to the kinase inhibitory region of both SOCS-1 and SOCS-3 and blocks their inhibitory effects on the IFN-gamma activation site promoter. In addition to a direct antiviral effect and synergism with IFN, the SOCS antagonist also exhibits adjuvant effects on humoral and cellular immunity as well as an enhancement of polyinosinic-polycytidylic acid activation of TLR3. The SOCS antagonist thus presents a novel and effective approach to enhancement of host defense against viruses.

HSV-1-induced SOCS-1 expression in keratinocytes: use of a SOCS-1 antagonist to block a novel mechanism of viral immune evasion.

Keratinocytes are important for the acute phase of HSV-1 infection and subsequent persistence in sensory nervous tissue. In this study, we showed that keratinocytes (HEL-30) were refractory to IFN-gamma induction of an antiviral state to HSV-1 infection, while IFN-gamma did induce an antiviral state in fibroblasts (L929). This led us to examine the possible role of suppressor of cytokine signaling-1 (SOCS-1) in this refractiveness. RT-PCR analysis of SOCS-1 mRNA expression in HSV-1-infected cells showed a 4-fold increase for keratinocytes while having a negligible effect on fibroblasts. A similar pattern was observed at the level of SOCS-1 protein induction. Activation of STAT1alpha in keratinocytes was inhibited by HSV-1 infection. A direct effect of HSV-1 on the SOCS-1 promoter was shown in a luciferase reporter gene assay. We have developed a small peptide antagonist of SOCS-1, pJAK2(1001-1013), that had both an antiviral effect in keratinocytes against HSV-1 as well as a synergistic effect on IFN-gamma induction of an antiviral state. HSV-1 ICP0 mutant was inhibited by IFN-gamma in HEL-30 cells and was less effective than wild-type virus in induction of SOCS-1 promoter. We conclude that SOCS-1 plays an important role in the inhibition of the antiviral effect of IFN-gamma in keratinocytes infected with HSV-1. The use of SOCS-1 antagonist to abrogate this refractiveness could have a transformational effect on therapy against viral infections.