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Restricted Access Thesis

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Danielle Dube


The pathogenic bacterium Helicobacter pylori has evolved glycan-mediated mechanisms to evade host immune recognition. For example, H. pylori incorporates Lewis blood group antigens at the terminus of lipopolysaccharides on its cell surface that mimic the groups found on human cells. This study tests the hypothesis that disruption of H. pylori glycan biosynthesis enhances immune recognition and response. To test this hypothesis, human adenocarcinoma-derived gastric epithelial cells and leukemia-derived THP-1 monocytes differentiated into dendritic cells were challenged with wildtype H. pylori alongside an array of H. pylori glycosylation mutants. Relative levels of immune response were measured via gastric cell granularity, bacterial viability, dendritic cell maturation, and cytokine production from both human host cell models. Gastric and bacterial cell health both diminished in cocultures of gastric cells with glycosylation mutants compared to cocultures of gastric cells with wildtype bacteria. The glycoprotein mutant D579 significantly increased gastric CXCL-8 production compared to wildtype bacteria, where the LPS mutant DWZK significantly decreased production. All other mutants varied significantly across replicates, suggesting the role of phase variation and gene redundancy in regulating bacterial cell surface glycosylation. Dendritic cell activation and IL-10 production either increased or did not change in the presence of glycosylation mutants compared to wildtype. The outcomes of this study demonstrate that H. pylori’s glycan presentation plays an important role in modulating the host immune response.


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