Cellular and molecular mechanisms involving SLAMF1 during pulmonary fungal infection

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PROJECT SUMMARY/ABSTRACT Lung cellular resistance against microbes requires a signaling network involving stroma and innate myeloid and lymphoid cells. To date, the signaling receptors and pathways are incompletely understood. Signaling Lymphocyte Molecule Family (SLAMF) receptors are widely expressed among hematopoietic cells and lung epithelial cells making them ideal candidates to orchestrate phagocyte killing of microbes. We recently reported that during pulmonary infection with the fungus Blastomyces dermatitidis (Bd), SLAMF1 is required for innate immunity and dispensable for priming vaccine-induced CD4+ Tcells. In preliminary data, we found that SLAMF1 is required for killing of the yeast by neutrophils and monocytes in vivo, but the receptor is dispensible for killing in vitro. These findings suggest that extrinsic, SLAMF1 dependent signals activate phagocytes to kill yeast in vivo. In this application, we propose to elucidate where and how SLAMF1 receptors endow phagocytes with the ability to kill yeast in vivo during pulmonary fungal infection. We hypothesize that innate lymphocytes and CCR2+ monocytes are required for SLAMF1-mediated neutrophil activation. We also posit that SLAMF1 mediates its function through homophilic (SLAMF1:SLAMF1) interactions between innate lymphocytes and monocytes or through direct sensing of the yeast by SLAMF1. We provide strong preliminary data to support our hypotheses. By using a panel of antibodies directed against 17 pulmonary leukocyte populations, we found SLAMF1 staining on CD4+TCR+, TCR+, MAIT cells and Ly6Chi CCR2+ monocytes at 16 hours post-infection. Our workplan in Aim 1 offers approaches that will elucidate the requirement of SLAMF1 on lymphoid, myeloid or stromal cells for activation of neutrophil killing of yeast. In Aim 2, we will define the mode of SLAMF1 action by distinguishing between SLAMF1 homophilic interactions among cells that express the receptor vs. direct sensing of yeast by SLAMF1. Our work will identify new mechanisms of receptor-mediated activation of innate effector cells and lay the groundwork for subsequent studies to advance detailed mechanistic insight into how SLAMF1 orchestrates signaling and activation of neutrophils, as these cells are the most potent effector to combat fungal and other microbial pathogens. This knowledge will provide the basis for developing and designing new strategies for therapeutic treatments against fungi, and other pathogenic microbes that require innate immunity for pathogen restraint.