Initiation of immune responses to SARS COV2 in the oral cavity and upper airway

Abstract Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19), a life-threatening illness with multi-system involvement in a subset of infected individuals. Oral and nasopharyngeal (NP) epithelial cells express the SARS-CoV-2 receptor ACE2, and infection of the oral/nasopharyngeal cavity (ONP) is likely an obligate step in the development of COVID-19. Immune responses first generated in the ONP are almost certainly crucial for viral clearance but may also play a central role in the development of hyperinflammatory injury observed in many infected individuals. We have used single cell (sc)- RNA sequencing from a racially diverse prospective cohort of COVID-19 patients to identify distinct subsets of ciliated epithelial cells within the NP that are direct targets for SARS-CoV-2 infection and have described innate anti-viral responses generated by those cells within both directly infected as well as non-infected bystander cells. Interestingly this analysis demonstrates that increased mortality is linked to blunted anti-viral gene response in the NP, suggesting that a successful innate response to viral infection in the nose is a critical component of a successful anti-viral response. In addition to the nose, there is strong evidence that SARS-CoV-2 can infect the oral epithelium. While there are several anatomic sites within the mouth that are likely involved in anti-viral responses, the gingival sulcus is a unique immunologically active location that is crucial for maintaining oral health. The gingival epithelium expresses both the SARS-CoV-2 receptor ACE2 as well as the host protease TMPRSS2 necessary for viral entry, but exhibits important immunological differences compared to the nasal epithelium including a bias towards IL-17 associated neutrophil responses. Thus, our overall hypothesis is that identifying and enhancing successful innate and adaptive cellular immune responses of the nasal and gingival epithelium will lead to novel therapeutic avenues for COVID-19. To address this hypothesis, propose the following aims: 1. Stratify cell states and viral dynamics across mucosal surfaces following SARS-CoV-2 infection and vaccination; 2. Compare memory T cell responses within the nose and gingiva that are associated with successful or pathogenic responses to SARS-CoV-2; and 3. Characterize the regulation of host innate immune defense mechanisms that are essential to limit propagation of SARS-CoV-2 infection within ONP epithelial cells. To accomplish these aims, we will analyze human ONP samples from individuals with COVID- 19, recovered from COVID-19, and vaccinated for COVID-19 using sc-RNA-seq, flow cytometry, and other molecular biology techniques. At completion, the project will define the protective innate and adaptive immune mechanisms operating in the ONP of patients infected with SARS-CoV-2, improve our overall understanding of viral induced immunity in the ONP, and provide insight into how these pathways influence disease pathogenesis.