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Item Using gastrointestestinal organoids to study infectious diseases in humans and bats(Montana State University - Bozeman, College of Agriculture, 2021) Hashimi, Marziah; Chairperson, Graduate Committee: Diane Bimczok; This is a manuscript style paper that includes co-authored chapters.The gastrointestinal epithelium plays a critical role in protecting the gastrointestinal mucosa from invading microorganism such as bacteria or a viruses. Helicobacter pylori (H. pylori) infection of human gastric epithelium causes gastric cancer, which is the third leading cause of cancer-related mortality worldwide. Dendritic cells (DCs)--which are antigen presenting cells--are responsible for the activation of T cells. However, the mechanism by which DCs are recruited to the gastric epithelium is still unknown. We hypothesized that the DCs are recruited to the gastric epithelium in a chemokine- dependent manner. For my thesis work, I utilized human primary gastric epithelial organoids cells to test this hypothesis and evaluate the recruitment of DCs to the epithelium under normal conditions and upon H. pylori infection. Using monocyte-derived DCs in a chemotaxis assay, I showed that these cells are recruited to H. pylori-infected organoid supernatant. I showed that this recruitment is chemokine- dependent, as it was significantly decreased when a chemokine receptor inhibitor was included in the chemotaxis assay. COVID-19 is caused by severe respiratory syndrome coronavirus-2 (SARS-CoV-2). In addition to respiratory symptoms, COVID-19 patients can also have diarrhea and vomiting, indicating that SARS-CoV-2 may infect the gastrointestinal tract. Bats are thought to be the natural reservoirs for SARS-CoV-2, however there is no known bat gastrointestinal model to study SARS-CoV-2 infection. In the second part of my thesis, I developed Jamaican fruit bat (JFB), Artibeus jamaicensis) gastrointestinal organoids (JFB organoids). I successfully developed organoids from JFB stomach, proximal and distal intestine. I showed via histology and gene expression that developed organoids do indeed recapitulate their corresponding tissues from which they were derived. I also tested whether the JFB distal intestinal organoids were susceptible to SARS-CoV-2 infection. While they do not support the active replication of SARS-CoV-2 infection, they did show antiviral and pro-inflammatory responses. My results also showed that SARS-CoV-2 does not induce programmed cell death in the organoids.