Host inflammatory response to SARS-CoV-2

Each year, humans encounter a variety of seasonal corona viruses that cause minor symptoms similar to the common cold. In contrast, SARS-CoV-2, which is responsible for COVID-19 (coronavirus disease 2019), has caused more than 110,000 deaths in the United States alone as of June 4, 2020. For unknown reasons, COVID- 19 disease severity is extremely variable, with many infected individuals experiencing mild symptoms including sore throat, headache, and cough or no symptoms at all. However, a significant number of infected individuals experience severe disease, including acute respiratory distress syndrome, renal failure, cardiac arrest, and gastrointestinal distress. Importantly, SARS-CoV-2 infection can trigger a hyperactive immune response that results in a cytokine storm, which is a massive release of pro-inflammatory molecules that can cause fatal tissue damage and likely causes the most severe disease symptoms. What triggers and regulates a cytokine storm is unclear, and studies are needed to reveal the processes by which SARS-CoV-2 induces inflammation, and how SARS-CoV-2 infection imparts COVID19 disease. Thus, the overarching goal of this proposal is to determine how inflammatory responses to SARS-CoV-2 are generated. To address this goal, we propose the following Specific Aims: 1. Define the inflammatory cytokine response induced by SARS-CoV-2. We will evaluate cytokine production from cells infected with SARS-CoV-2 using cell lines derived from lung and immune cells that populate the lung. Additionally, because severe COVID-19 patients present with elevated levels of the cytokine IL-1β and because IL-1β is released following the inflammatory form of cell death known as pyroptosis, we will assess the ability of SARS-CoV-2 to stimulate pyroptosis. We will then use CRISPR-based gene knockout and pharmacologic inhibitors to map the molecular pathways required for production and release of the observed cytokines. 2. Determine the inflammatory transcriptome across infected and bystander cells in propagating and amplifying inflammatory responses to CoV2. Using single cell RNA sequencing, we will assay mixed populations of cells with infected and non-infected (bystander) cells to determine how virus infection imparts inflammatory gene expression and how inflammatory signals from infected cells affect neighboring uninfected cells to amplify the inflammatory response. Sequencing and bioinformatics analyses will be conducted by the Gale lab transcriptomics and computational biology team, and results will be validated by complimentary techniques. From these studies, we expect to reveal the inflammatory cytokine signaling events following SARS-CoV-2 infection. These studies will also provide biomarkers to identify patients susceptible to cytokine storm and will identify gene or gene network/pathway targets to inform strategies to treat COVID-19 disease.