Project description:We identified a small molecule compound, KIN1148, that directly binds RIG-I to drive IRF3 and NF B activation and expression of innate immune genes, cytokines and chemokines. KIN1148 activates RIG-I in an RNA- and ATP-independent manner and does not induce a canonical antiviral interferon (IFN) gene program traditionally associated with RIG-I activation. When administered in combination with a vaccine against influenza A virus (IAV), KIN1148 induces both neutralizing antibody and broadly cross-protective IAV-specific T cell responses compared to vaccination alone, which induces poor responses. In this study, we demonstrate that KIN1148 directly engages RIG-I to activate IRF3- and NFB-dependent innate immune responses, making it the first small molecule RIG-I agonist to be identified. Biochemical studies show that KIN1148 binds to RIG-I to drive RIG-I self-oligomerization and downstream signaling activation in an RNA- and ATP-independent manner. We further find that transcriptional programs induced by KIN1148 treatment exhibit shared and unique signatures to that induced by other methods of RIG-I activation, including Sendai virus (SeV) infection and PAMP RNA transfection. KIN1148 adjuvants a split virus (SV) vaccine at suboptimal dose to protect mice from lethal challenge with a recombinant highly pathogenic avian H5N1 influenza virus, A/Vietnam/1203/2004.
Project description:RIG-I is thought to be the most important sensor of influenza virus infection and plays critical roles in the recognition of cytoplasmic dsRNA and activation of type I IFNs and initiates the innate antiviral immune responses. How the binding of viral RNA to and activation of RIG-I are regulated remains enigmatic. Here, by an affinity proteomics approach with viral RNA as the bait, we found that IFI16, previously identified as a DNA sensor, was significantly induced both in vitro and in vivo during influenza virus infection. Using an IFI16 knockout cells and p204-deficient mice model, we demonstrated that IFI16 enhanced RIG-I-mediated production of type I IFNs and thereby inhibited viral replication during influenza virus infection. Furthermore, we showed that IFI16 regulated the RIG-I signaling by enhancing its transcriptional expression through recruitment of RNA Pol II to the RIG-I promoter. We also verified that IFI16 directly interacted with both viral RNA by HINa domain and associated with RIG-I through its PYRIN domain as well as promoted influenza virus-induced K63-linked polyubiquitination of RIG-I. In addition, we found that IFI16 lost its ability to inhibit viral replication in the absence of RIG-I in virus-infected cells. These results indicate that IFI16 is a key regulator of the RIG-I signaling during antiviral innate immune responses, which highlights a novel mechanism of IFI16 in IAV and other RNA viruses infection, expands our knowledge in antiviral innate immunity, and suggests its possible use as a new strategies to manipulate antiviral responses.
