Murine Gammaherpesvirus 68 Encoding Open Reading Frame 11 Targets TANK Binding Kinase 1 To Negatively Regulate the Host Type I Interferon Response

Abstract

Upon viral infection, type I interferons, such as alpha and beta interferon (IFN-alpha and IFN-beta, respectively), are rapidly induced and activate multiple antiviral genes, thereby serving as the first line of host defense. Many DNA and RNA viruses counteract the host interferon system by modulating the production of IFNs. In this study, we report that murine gammaherpesvirus 68 (MHV-68), a double-stranded DNA virus, encodes open reading frame 11 (ORF11), a novel immune modulator, to block IFN-beta production. ORF11-deficient recombinant viruses induced more IFN-beta production in fibroblast and macrophage cells than the MHV-68 wild type or a marker rescue virus. MHV-68 ORF11 decreased IFN-beta promoter activation by various factors, the signaling of which converges on TBK1-IRF3 activation. MHV-68 ORF11 directly interacted with both overexpressed and endogenous TBK1 but not with IRF3. Physical interactions between ORF11 and endogenous TBK1 were further confirmed during virus replication in fibroblasts using a recombinant virus expressing FLAG-ORF11. ORF11 efficiently reduced interaction between TBK1 and IRF3 and subsequently inhibited activation of IRF3, thereby negatively regulating IFN-beta production. Our domain-mapping study showed that the central domain of ORF11 was responsible for both TBK1 binding and inhibition of IFN-beta induction, while the kinase domain of TBK1 was sufficient for ORF11 binding. Taken together, these results suggest a mechanism underlying inhibition of IFN-beta production by a gammaherpesvirus and highlight the importance of TBK1 in DNA virus replication.