Viral and immune-mediated CNS pathology during SARS-CoV-2 infection

Project Summary The COVID-19 pandemic has rampantly affected the population of the world and created lasting effects on the economy, health and psyche of the global community. Although it shares similarities with SARS-CoV-1, the full extent of the pathophysiology caused by SARS-CoV-2 is unclear. In particular, extrapulmonary manifestations effects of SARS-CoV-2 infection remain poorly understood. Case series from China and Europe suggest that the central nervous system is involved in the disease process in at least a subset of patients, with some reports estimating up to 30% of COVID-19 patients having neurological symptoms, including seizure, intractable headache, and impaired smell and taste. Although there are reports of neurological disease in in COVID-19 patients, it is unclear if SARS-CoV-2 invades the central nervous system (CNS). Studies of other coronaviruses, including SARS-CoV-1, demonstrate clear neurotropism as well as neuroinflammation associated with other members of this family of viruses. These studies raise the possibility that SARS-CoV-2 may cause neurological symptoms either through invasion of the CNS or through an increase in inflammatory cytokines within the CNS. We hypothesize that SARS-CoV-2 infections have neuroinvasive potential and lead to altered and hyperinflammatory immune states within the CNS of infected individuals. We further hypothesize that infection of the CNS exacerbates respiratory dysfunction through direct toxicity of ACE2 expressing neurons that are critical regulators of cardiopulmonary function. Our investigations will combine the power of human studies with those utilizing mouse models in which we can readily administer virus and assess for pathophysiology. Aim 1, we will determine the CNS immune responses in COVID-19 patients with neurological symptoms. Using a combination of single cell RNA-sequencing, cytokine profiling, viral sequencing and antibody validations, we will fully dissect out the inflammatory responses within the CNS compartment compared to the systemic circulation in COVID-19 patients. Using mouse models, in Aim 2, we will investigate the encephalitic potential of SARS-CoV-2. Using several complementary approaches to infect mice with SARS-CoV-2, we will introduce the virus into the central nervous system of mice. Using depletion antibodies and various knockout mice, we will identify which immune cells are required for neuropathology in these mice through survival studies, flow cytometry and immunofluorescent staining. Finally, in Aim 3, we will evaluate the effects of CNS infection on respiratory outcomes. Because of the known expression of ACE2 in the brainstem, and the brainstem's critical role in regulating cardiopulmonary functions, we suspect that CNS infection with SARS-CoV-2 will exacerbate SARS-CoV-2 respiratory disease. These three aims will help support our hypotheses of how SARS-CoV-2 infections can affect the CNS and respiratory compartments. We expect that our findings will uncover new strategies to treat patients diagnosed with COVID-19 and help gain new insight to understanding the biology of SARS-CoV-2 pathophysiology.