We propose to define how lung epithelial cells (EC) sense and respond to inhaled fungi. A person inhales a billion spores/day, but the modes by which fungi are sensed and restrained in lung are unclear. Our preliminary data reveal that EC regulate mucosal immunity to two primary pathogens, Blastomyces and Histoplasma. We find that EC NF-?B activation is essential, as are upstream signals of IL-1R, MyD88 and CARD9 and mobiliza- tion of innate lymphocytes that make IL-17 and GM-CSF. We posit that EC subsets, notably Club cells, sense fungi and regulate innate immunity, and that EC intrinsic signals via IL-1R and MyD88 drive NFkB-regulated products to trigger IL-17- and GM-CSF-producing innate lymphocytes, which recruit/activate myeloid effectors. The lung contains 6 EC subsets: alveolar, club (formerly clara), goblet, neuroendocrine, basal and ciliated columnar. We'll test the role of Club cells in regulating mucosal immunity by using transgenic mice that display a lineage-specific GFP reporter to track and analyze the behavior of this subset and, since our reporter mouse harbors cre recombinase, test its role in resistance by crossing the mouse with IKK2fl/fl or CRISPR/Cas9 mice to block NF-?B signaling. To learn how EC mobilize innate immunity to fungi, we will use two fungal pathogens that represent paradigmatic extracellular (Blastomyces) and intracellular (Histoplasma) pathogenic lifestyles that confront the epithelium of mammalian lungs.
Our aims are to: 1. Delineate the role and action of Club cells in sensing inhaled fungi. By using NF?B-eGFP reporter mice, advanced imaging and FACS analysis, we will track the timing and location of activation of EC and hemato- poietic cells in response to inhaled fungi. Transgenic mice will be used to dissect the roles of Club cells and their signaling pathways and downstream products in resistance, and CRISPR/Cas9 used to GFP tag, iso- late, profile and functionally interrogate specific functions of Club cells in regulating innate immunity. 2. Define how Club cells and products regulate ?? T cells and nTh17 cells to restrain inhaled fungi. We will define the regulatory role of Club cells and their signals on anti-fungal TCR ?? and nTh17 cells ? e.g. activa- tion or recruitment and cytokine production. The role of innate T cell IL-17A, GM-CSF and IL-22 will be dis- sected in promoting killing of fungi and fostering EC integrity. Soluble signals such as CCL20, IL-1, IL-6, IL- 18 & IL-23 that activate innate T cells in mice and humans will be defined, and the cell source(s) identified. Our work will reveal how lung Club cells regulate innate mucosal immunity to fungi offering conceptually new insight and powerful gene editing tools that will advance the field. By divining antifungal defense mechanisms, we will improve prospects for therapeutically targeting early events designed to optimize mucosal immunity to fungi and lung inflammation.
An average adult breathes ?10 liters of air every minute, resulting in about 10,000 liters breathed per day with an estimated 1 billion fungal spores! This proposal will elucidate how lung epithelium protects us from inhaled fungi by mobilizing and coordinating cellular and molecular elements of mucosal innate immunity.