Interaction of Mycobacterium tuberculosis with upper airway mucosal cells

Project Summary The nasopharyngeal and respiratory mucosa represents a primary barrier to infection by inhaled organisms. Indeed, the earliest contact point between the airway pathogen Mycobacterium tuberculosis and the human body is the airway mucosa. As a result, M. tuberculosis has evolved to disseminate beyond the oral and respiratory mucosa to cause systemic disease, thus accounting for its global impact on human morbidity and mortality. Lining the airway mucosa are specialized epithelial cells that function to transcytose mucosal antigens from the mucosal surface to the basolateral space. These cells, known as microfold or M cells, overlie mucosal associated lymphatic tissue where macrophages and dendritic cells await to ingest and present antigens to B-cells and T-cells. We previously demonstrated that M. tuberculosis penetrates the mucosa via M cells by using a virulence factor called EsxA and a host receptor, scavenger receptor B1 (SR-B1). However, a major gap in our understanding of the impact of this very early event on the interaction of M. tuberculosis with the airway is that we do not fully understand M cell biology. Here, we will apply genetic, biochemical, immunologic, transcriptomic and animal approaches to determine the functional role of M-cells in mucosal and systemic immunity against M. tuberculosis. Thus, in the proposed research we will: (1) Determine the transcriptional profiles and functions of novel genes of primary human and mouse airway M cells at a single cell level under both homeostatic conditions and after experimental M. tuberculosis infection, (2) Identify and study unique cell-cell interactions of M cells with their adjacent epithelial and immune cells, (3) Characterize the mechanisms of binding and transcytosis of M. tuberculosis by airway M cells, (4) Determine the immunologic impact of M. tuberculosis transcytosis across airway M cells. The proposed work is expected to identify how M cells bind and transcytose M. tuberculosis and how this very early event in the life cycle of M. tuberculosis dictates the immunologic outcome of infection.