Mechanisms of vaccine immunity against coccidioidomycosis

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ABSTRACT Coccidioidomycosis is a re-emerging infection that NIH has prioritized for vaccine prevention. An experimental vaccine of live attenuated spores is highly protective after intranasal delivery. We propose to study this vaccine to define mechanisms by which lung epithelium regulates durable mucosal T cell immunity. Resistance against inhaled microbes is thought to reside within tissue-resident memory (TRM) cells, but little is known about how this intranasal vaccine induces lung TRM. Our preliminary data reveal that the vaccine elicits protective, Coccidioides endoglucanase 2 (C-Eng2) specific CD4+ T cells and that bronchiolar club cells and Ca++ calcineurin signaling in the cells are needed to mobilize inflammatory and T cells in response to vaccine. We also find that Microfold (M) cells descend from the bronchiolar club cells and facilitate T cell priming in response to the vaccine. From these preliminary data, we hypothesize that bronchiolar club cells and M cells regulate mucosal cellular immunity in response to intranasal vaccine. To test this hypothesis, we have created innovative tools: (i) transgenic mice to deplete epithelial cell subsets or their products to further define their role in inducing immunity; (ii) C-Eng2 specific tetramers to track and analyze protective CD4+ T cells and TRM in C57BL6 mice; and (iii) methods to isolate and culture human lung epithelial cells to translate results from mice to humans. We propose three aims to test our hypothesis. In Aim 1, we will elucidate early stages of the inflammatory response to intranasal vaccine regulated by bronchiolar club cells and M cells; in Aim 2, we will identify lung epithelial cell receptors - dectin-1, DUOX1 and DUOXA1 - and downstream PLCG2 that may sense intranasal vaccine and signal via Ca++ and calcineurin to mobilize mucosal immunity; and in Aim 3, we will define mechanisms of vaccine-induced durable mucosal immunity by studying lung TRM and the regulatory role of lung epithelium. In sum, we address the unmet need of vaccination against coccidioidomycosis. Our work is significant as it will define mechanisms by which a promising vaccine establishes T cell immunity at the lung mucosa. Results will identify tactics useful for other vaccine immunogens given intranasally, including subunit vaccines. The work will define correlates of immunity needed to advance this attenuated vaccine or next generation subunit vaccines against this high priority pathogen. The work will be done with state-of-the-art, cutting-edge tools. Our team of PI and Co-I’s will let us translate results from mouse to human, with tools and reagents for human lung epithelium.