Identification of Five Interferon-Induced Cellular Proteins That Inhibit West Nile Virus and Dengue Virus Infections

Abstract

Interferons (IFNs) are key mediators of the host innate antiviral immune response. To identify IFNstimulated genes (ISGs) that instigate an antiviral state against two medically important flaviviruses, West Nile virus (WNV) and dengue virus (DENV), we tested 36 ISGs that are commonly induced by IFN-␣ for antiviral activity against the two viruses. We discovered that five ISGs efficiently suppressed WNV and/or DENV infection when they were individually expressed in HEK293 cells. Mechanistic analyses revealed that two structurally related cell plasma membrane proteins, IFITM2 and IFITM3, disrupted early steps (entry and/or uncoating) of the viral infection. In contrast, three IFN-induced cellular enzymes, viperin, ISG20, and double-stranded-RNA-activated protein kinase, inhibited steps in viral proteins and/or RNA biosynthesis. Our results thus imply that the antiviral activity of IFN-␣ is collectively mediated by a panel of ISGs that disrupt multiple steps of the DENV and WNV life cycles.West Nile virus (WNV) and dengue virus (DENV) are mosquito-borne flaviviruses that cause invasive neurological diseases and lethal hemorrhagic fever in humans, respectively (6, 32). Since its first incursion into New York City in 1999, WNV has rapidly spread throughout the continental United States and has recently reached South America (29, 34). In most cases, WNV infection of people resolves as an asymptomatic or a mild febrile illness. However, approximately 1% of infections result in severe neurological disorders, such as encephalitis and meningitis (27). Unlike WNV, for which people are only accidental hosts, DENV has fully adapted to humans (32). It has apparently lost the need for an enzootic cycle and causes a range of diseases in people, from acute febrile illness to life-threatening dengue hemorrhagic fever/dengue shock syndrome (6). Four distinct serotypes of DENV have spread throughout the tropical and subtropical parts of the world, with an estimated 50 to 100 million human cases annually and about 2.5 billion people worldwide being at risk of infection (32). Effective antiviral therapies and vaccines to treat or prevent WNV and DENV infections in humans are not yet available.Type I interferons (IFNs), represented by IFN-␣ and IFN-␤, have been demonstrated to play an essential role in defending against WNV and DENV infections. For example, mice with deficiencies in the induction of type I IFNs and the receptor or JAK-STAT signal transduction pathway of the cytokines are vulnerable to WNV and DENV infections (7,38,42,(49)(50)(51). In addition, a strain of WNV that fails to block the type I IFN signal transduction pathway is phenotypically attenuated in mice (23,50). Clinically, during acute DENV infection, innate immune responses play a key role in determining disease outcome (35), and resolution of WNV infection requires effective IFN-mediated innate host responses (23,43,53). Therefore, understanding how the IFN-mediated innate immune response functions is one of the critical frontiers in the molecular biology of WN...

Leukocyte immunoglobulin-like receptor B1 is critical for antibody-dependent dengue

“…At low antibody concentrations where ADE occurs, the inhibitory FcγRIIB is not coligated (9). Ligation of the activating FcγRs by DENV opsonized with subneutralizing levels of antibody would thus induce the expression of ISGs and hinder DENV replication (10). Here, we demonstrate that DENV employs a unique evasive mechanism by coligating LILRB1 to down-regulate the early antiviral responses triggered by activating FcγRs for ADE.…”

“…1 D and F-I). These included MX1, MX2, and viperin, which are potent inhibitors of DENV replication (10). The up-regulation of ISGs in THP-1.2R, however, was not due to h3H5 (SI Appendix, Fig.…”

Reduction in sphingosine kinase 1 influences the susceptibility to dengue virus infection by altering antiviral responses

“…Viperin (Helbig et al, 2013;Jiang et al, 2010), OAS1 (Lin et al, 2009;Perelygin et al, 2002), IRF7 (Chen et al, 2013) and CXCL10 have previously been ascribed antiviral functions against DENV infection. We further analysed and compared the kinetics of the induction of these genes in iMEFs and 1uMEFs.…”

Inhibitor of κB Kinase ϵ (IKKϵ), STAT1, and IFIT2 Proteins Define Novel Innate Immune Effector Pathway against West Nile Virus Infection

“…Our results now show that IFIT2 can restrict WNV growth in vitro and demonstrate that its expression within an IKK⑀-dependent innate immune effector pathway associates with the control of virus spread and pathogenesis in vivo. Although the magnitude of the increase of WNV-MAD replication in IFIT2 Ϫ/Ϫ cells was only 10-fold (one log), it is notable that this difference was statistically significant and caused by loss of a single ISG of several hundred known ISGs, many of which might restrict WNV infection (43). These observations indicate the importance of IFIT2 in controlling the growth of WNV and indeed may in part explain the immune protection and lack of pathogencity after infection by low virulence WNV strains such as WNV-MAD and others in animals (8,46,47).…”