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Abstract
Mycobacterium tuberculosis, the causative agent of the lung disease Tuberculosis (TB), is the world’s leading infectious killer. The BCG vaccine for Tuberculosis has been in use for almost 100 years, making it the oldest and currently the most widely distributed vaccine, but it fails to protect against pulmonary disease in adults. Because of the limitations of the BCG vaccine and an increase in multidrug resistant and extremely drug resistant TB, development of new vaccines are a cornerstone of the World Health Organization’s EndTB strategy. Our inability to decrease the burden of M. tuberculosis infection in the human population also reinforces the need for a better understanding of the host/pathogen relationship. Until recently, the efforts to understand this relationship have focused on interactions of M. tuberculosis with host alveolar macrophages, but previous work by our laboratory and others have shown that epithelial pneumocytes, the most numerous cell type in the lung alveolus, play a role during M. tuberculosis infection. Our laboratory has identified rv3351c as a gene important in epithelial cell infection. The goal of the research described in this dissertation was to characterize interactions and trafficking of ΔRv3351c within alveolar epithelial cells Our data suggest that ΔRv3351c bacilli, once internalized, are less able to survive and multiply intracellularly, and are thus less cytotoxic compared with the parent strain. The survival in these cells was dependent on the formation of lipid rafts on the host cell plasma membrane and inhibition of fusion of the mycobacterial containing compartment with the host cell lysosome. Thus, the role of Rv3351c in trafficking and survival of M. tuberculosis bacilli through epithelial cells may begin with modifications to the plasma membrane prior to attachment. We found that the localization of the Rv3351c protein to the membrane of Mtb, its ability to elicit antibodies in patients with active Tuberculosis, and its ability to reduce Mtb killing of A549 cells, makes it an attractive candidate for a mucosal subunit vaccine with other proteins that target alveolar epithelial cells