Mechanism Governing Association Between Viral Respiratory Infection Relapse Generation and Disease Progression in Persons with MS

Background: The purpose of this proposal is to determine how peripheral viral infection alters the natural history of multiple sclerosis (MS), which is directly aligned with the fiscal year 2022 Focus Area "Factors Contributing to Disease Course." It has been estimated that 85% of patients initially present with a relapsing-remitting disease course wherein they experience episodic neurological dysfunction (relapses) followed by periods of partial recovery (remission). Since 1965, data have repeatedly shown that within 5 weeks of contracting a respiratory infection, an estimated 27%-41% of relapsing-remitting MS patients will suffer a relapse. Indeed viral pathogens, including picornaviruses, influenza A virus, and, most recently, SARS-CoV-2 coronavirus have all been linked to infection-induced relapse, which may be associated with sustained disability. As such, uncovering the physiological and molecular mechanism(s) that govern infection-induced relapses is of great importance. Unfortunately, the effects of respiratory viral infection on MS pathogenesis remain obscure despite this type of infection doubling the risk for relapse. Until the mechanism by which infection exacerbates disease is determined, persons with MS will continue to be at risk for disease exacerbation when exposed to ubiquitous pathogens such as SARS-CoV-2. We have conducted experiments to address the role of viral infection on the pathogenesis of both relapsing and chronic models of EAE using mouse-adapted human influenza A virus (IAV). In all models tested, infection increased relapses, exacerbated symptoms, and increased pathology in the brain and, to a lesser extent, the spinal cord. Furthermore, our data indicate that IAV infection exacerbated EAE in a manner that was, in part, attributable to alterations to myelin-reactive T cells by acting on antigen-presenting cells. Herein, we hypothesize viral infection invokes changes to antigen-presenting cell effector function that in turn increase T cell reactivity causing them to differentially affect cells within the central nervous system (CNS). To test this hypothesis we have devised three specific aims. The specific aims and study design for each are as follows: Aim 1: Determine the effect of viral evasion proteins on APC/T cell interactions and encephalitogenic potential. Viral evasion proteins, such as IAV non-structural protein 1 (NS1), are known to alter interferon response and cytokine production in APCs. Study Design: Viral evasion proteins encoded by influenza A virus (NS1), murine hepatitis virus-1 (NS2), and SARS-CoV-2 (NSP13, NSP6 and ORF6) will be overexpressed in primary mouse bone marrow-derived dendritic cells (BMDCs) or human THP-1 cells. Control cells will be transfected with an empty plasmid. Subsequently, we will examine how expression alters the cytokine production, T cell reactivity, chemokine receptor expression, and encephalitogenic potential. Aim 2: Unravel the interactions between infection-primed myelin-specific T cell and CNS resident glia. Our preliminary data show that myelin-reactive T cells primed by IAV pulsed BMDCs have increased encephalitogenicity. Study Design: We will utilize primary mixed glial cultures and organotypic cerebellar slice cultures to establish how T cells primed by BMDCs expressing viral evasion proteins or pulsed with virus differentially cause glial activation and reductions in oligodendrocyte and neuron viability compared to controls cells. We will also test the hypothesis that these cells differentially affect glial reactivity and viability using snRNA-seq following adoptive transfer T cells primed under these conditions. Aim 3: Determine whether treatment with VX-765 during infection lowers relapse risk. Viral evasion proteins circumvent the endogenous production of type 1 interferons and their signaling, but in doing so activate the inflammasome causing release of bioactive proinflammatory cytokines such as IL-1β. Study Design: Relapsing EAE will be induced in mice, then after peak disease onset they will be inoculated with saline, IAV, or MHV-1. Mice will be treated with VX-765, a caspase 1 inhibitor or vehicle by intraperitoneal injection. We will test the ability for treatment to ameliorate infection induced relapse after infection. To elucidate the role of the inflammasome we will test whether infection can cause relapse in Asc-/- mice. Impact: We expect to identify a novel, but unifying, mechanism whereby viral pathogens influence relapse generation and the progression of disease. Establishing a role for viral evasion proteins in modulating adaptive immune responses should uncover molecular targets that may prove therapeutically efficacious in the prevention of infection-induced disease exacerbations and may slow disease progression in general. Finally, identifying specific interactions between T cells and glia should shed light on mechanisms that govern reductions in oligodendrocyte and neuronal viability, which could be capitalized upon to reduce disease or promote repair. Less