Expanding Excellence in Developmental Biology in Oklahoma Supplement: 3D Human Lung Tissue Model to Dissect Cellular Responses upon SARS-CoV-2 Infection

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Abstract SARS-CoV-2 infection is the causative agent of coronavirus disease 2019 (COVID-19), a global pandemic responsible for >6 million deaths worldwide. The mucociliary epithelium lining the human airways is the primary site of SARS-CoV-2 infection. Following viral exposure, the epithelium initiates responses to recruit immune cells to the site of infection and coordinate the innate immune response. A balance in the number of each cell type (i.e., ciliated, secretory) is critical to maintaining a healthy epithelium, and airway epithelial damage and changes in cell type abundance (termed remodeling) play important roles in the pathology associated with SARS-CoV-2 infection. However, our understanding of how immune cell interactions and emergent SARS-CoV-2 variants impact virus-induced damage and remodeling of the airway epithelium is limited. Our project will test the central hypothesis that myeloid cell responses and interactions with epithelial cells are major drivers of inflammation- mediated epithelial cell remodeling in SARS-CoV-2 infection of the upper airway. Using a novel in vitro 3D model of the human upper airway, composed of primary differentiated airway epithelial cells, lung fibroblasts, pulmonary microvascular endothelial cells and myeloid immune cells, combined with cutting edge scRNA-seq technology, our team will address the following unresolved questions regarding the host immune response to SARS-CoV-2. In Aim 1, we will determine how cross-talk between epithelial and innate myeloid cells in the initial stages of SARS-CoV-2 infection impacts the cell differentiation processes that drive pathological remodeling and damage of the airway epithelium. In Aim 2, we will determine if the SARS-CoV-2 ancestral strain and the Delta and Omicron variants elicit distinct host immune responses and pathogenic epithelial remodeling upon initial infection of the same host environment. The strengths of our novel 3D airway model include the ability to track the kinetics of the host cell response at defined times post-infection to capture early and later events and the ability to compare the impact of each SARS-CoV-2 variant on the same set of donor human cells. To accomplish this project, we have assembled a multi-disciplinary team with non-overlapping and synergistic expertise. Dr. Matthew Walters (Co-Project Lead), a lung cell biologist and virologist, will oversee the SARS-CoV-2 infection studies and characterize the epithelial remodeling phenotypes. Dr. Susan Kovats (Co-Project Lead), an immunologist with expertise in the pulmonary myeloid response to respiratory viruses, will oversee lung model construction and characterize the tissue immune response. Dr. Willard Freeman (Co-Investigator), an expert in transcriptome profiling, will oversee the scRNA-seq analyses. The data collected will form the basis of new multi- PI NIH R01 proposals with the goal to understand how different host environments (e.g., age across the lifespan, gender and chronic lung disease) modulate host immune responses and airway epithelium remodeling upon infection by respiratory viruses such as SARS-CoV-2, RSV and influenza virus.