This renewal application is focused on understand the molecular mechanisms of hepatic innate immunity that controls the outcome of hepatitis C virus (HCV) infection. We have shown that retinoic acid inducible gene-I (RIG-I) initiates the hepatic innate immune response upon recognition and binding of the pathogen associated molecular pattern (PAMP) consisting of 5'triphosphate with poly-uridine (poly-U/UC) within the HCV RNA. During acute infection this recognition of transmission/founder (T/F) viral genome by RIG-I results in its modification and activation to bind the MAVS adaptor protein on mitochondria-associated membranes (MAM) and signal hepatic innate immune defenses that restrict infection. Our preliminary studies now reveal that T/F genomes from patients exhibit remarkable variation within their poly-U/UC motif, and that this variation imparts differential recognition and binding by RIG-I that allows escape from non-self recognition. Moreover, we have found that signaling by RIG-I is dependent on formation of a RIG-I translocon protein complex to facilitates RIG-I cytosol-to-membrane translocation for MAVS interaction and signaling. Our studies now reveal that these activities are governed by the reversible acteylation of RIG-I, and that this process is likely controlled through the HDAC6 protein as a RIG-I cofactor of innate immunity. We show that HCV evades hepatic innate immunity via MAM targeting by the NS3/4A viral protease to cleave MAVS and disrupt RIG-I signaling, thereby facilitating chronic infection, and this action is dependent on stable NS3/4A-MAVS interaction on the MAM. Ablation of this interaction restores innate immunity to prevent acute to chronic HCV transition. We hypothesize that regulation of the RIG-I pathway and hepatic innate immunity are major determinants controlling the acute to chronic transition of HCV infection. We will therefore conduct studies to: 1) Define the features of RIG-I and the HCV poly-U/UC motif that confer PAMP binding and innate immune signaling activation, and determine how PAMP variation among T/F genomes influences acute innate immune induction by HCV;2) Determine the role of reversible acetylation in RIG-I translocon assembly and function;3. Identify the cognate/reciprocal motifs of NS3/4A and MAVS that mediate interaction and control of the RIG-I pathway.

Public Health Relevance

Liver disease from microbial infection is a major public health concern. Hepatitis C virus (HCV) infects the liver to cause liver disease, liver cancer, and death. Our studies will define the virus and host components that control HCV infection outcome and liver disease.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
High Priority, Short Term Project Award (R56)
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Hepatobiliary Pathophysiology Study Section (HBPP)
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Koshy, Rajen
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University of Washington
Schools of Medicine
United States
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