Role of RIG-like receptors in virally induced CNS inflammation

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DESCRIPTION (provided by applicant): While glial cells are recognized for their roles in maintaining neuronal function, there is growing appreciation of the ability of resident brain cells to initiate and/or regulate inflammation following trauma or infection in the central nervous system (CNS). Astrocytes and microglia are uniquely positioned to detect and respond to invading pathogens of the CNS and previous studies have demonstrated the ability of these cells to produce key inflammatory mediators following exposure to members of the Mononegavirales order of viruses that are the causative agents of lethal human CNS diseases, notably rabies. However, the mechanisms by which resident cells of the CNS perceive such viral challenges have not been defined. Recently, several cytosolic DExD/H box RNA helicases have been described that can bind early viral replicative intermediates leading to the realization that retinoic acid-inducible gene I (RIG-I)-like helicases, function as intracellular receptors for RNA viruses. We have recently completed investigations showing that astrocytes and microglia can be infected with, and respond to, a model neurotropic rhabdovirus, vesicular stomatitis virus (VSV). Importantly, we have also completed a characterization of RIG-I-like receptor (RLR) expression in these resident glial cell types. In the experiments described in this R03 pilot study, we will assess the role of RLR proteins in the initiation and/or maintenance of inflammatory immune responses of glia to a model neurotropic rhabdovirus. We will employ isolated cultures of astrocytes and microglia derived from normal animals and mice genetically deficient in the expression of RLR to assess the relative importance of these novel receptors in cytokine production following in vitro exposure to VSV. Furthermore, we will administer VSV intranasally in wild type and RLR deficient mice animals and assess subsequent viral burden and inflammatory CNS damage following infection to determine the relative importance of RIG-I in the progression of infection and/or CNS inflammatory damage in an in vivo setting. Results from these studies are anticipated to reveal that this RLR molecule represents an important mechanism underlying the initiation and/or maintenance of immune responses during a model neurotropic viral infection and will contribute significantly to our understanding of the events that underlie the development of either protective host responses within the brain or the progression of damaging CNS inflammation. Importantly, these initial studies will provide a solid rationale for more comprehensive investigations into the regulation and role of this novel viral pattern recognition receptor during CNS infection for which future R01 mechanism funding will be sought. PUBLIC HEALTH RELEVANCE: Members of the Mononegavirales order of viruses are the causative agents of lethal human central nervous system diseases, notably rabies. However, the mechanisms by which resident brain cells recognize such viral challenges have not been defined. In the proposed studies, we will we will assess the role of retinoic acid-inducible gene I (RIG-I) in the progression of damaging brain inflammation following infection with a model neurotropic rhabdovirus.