Targeting IDO in SARS-CoV2-induced Alzheimer's Disease progression

Project Summary/Abstract Alzheimer's disease (AD) is a national health crisis, affecting many Americans with total annual payments projected to be more than $1 trillion by 2050. The risk for Alzheimer's disease (AD) is an interaction between inherited and environmental risk factors that, with age, drives pathology resulting in neurodegeneration and disease onset. Increasing epidemiological evidence indicates that ~80% of individuals infected with SARS-CoV2, and who develop Covid-19, experience neurological sequelae characterized by common etiological factors of Alzheimer's disease, including cognitive and neuropsychiatric deficits. Therefore, there is a strong possibility in SARS-CoV2 causation of neurological conditions, such as Alzheimer's disease, based on the biology and host immune responses to the virus. Biological factors intertwined with the overactivity of the CNS inflammatory response during Covid-19, impact the functional status of the CNS. For example, the bidirectional relationship between CNS inflammation and dysregulation of the kynurenine (KYN) pathway (KP) and its metabolites, such as kynurenic acid (KYNA) and quinolinic acid (QUIN), are found in the blood and cerebrospinal fluid of AD patients; and levels are correlated to severity of neurological and cognitive impairments associated with viral infections such as HIV. Importantly, disruption and dysregulation of KP metabolites in Covid-19 patients is correlated to disease severity and triggered by inflammation-induced indoleamine 2,3-dioxygenase (IDO). This indicates that dysregulation of critical KP metabolites and CNS inflammation by SARs-CoV2 may underlie maladaptive changes in the CNS that exacerbate the development of AD. Therefore, it is critical to elucidate the interplay between SARS-CoV2-induced KP dysregulation and CNS inflammation during Covid-19 and the impact on AD disease progression and neuropathogenesis. The long-term goal of this proposal is to investigate the infectious disease risk factors and mechanisms underlying the neuropathogenesis of AD during the progression of SARS-CoV2 neurological sequelae. Using mouse-adapted SARS-CoV2, we will address our overall objective: to delineate KP dysregulation during SARS-CoV2 CNS infection and progression of Alzheimer's neuropathology and neurocognitive decline correlative to CNS immune responses and encephalitic infection. The central hypothesis is that SARS-CoV2 is a significant risk factor for the onset and severity of AD, by triggering IDO activity thereby dysregulating KP metabolites in the periphery and CNS and exacerbating the subsequent cytokine storm to exacerbate AD neuropathology. To address this hypothesis, we will 1) distinguish AD-related cognitive decline exacerbated following SARS-CoV2 infection, 2) delineate SARS- CoV2 neuropathology, disease burden, and dual activation of host immunity and KP signaling in AD, and 3) elucidate specific IDO contributions in SARs-CoV2-mediated exacerbation of AD onset and severity. This proposal will provide an immune-KP focused approach to identify SARS-CoV2 on the impact of neurodegenerative processes in AD.