Dendritic cell heterogeneity and its role in pulmonary fungal infection

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Project Summary The opportunistic fungal pathogen Aspergillus fumigatus is a major health concern in immunocompromised and critically ill patients, manifesting as a variety of pulmonary conditions ranging from acute to chronic. In these clinical syndromes, A. fumigatus elicits a diverse adaptive CD4 T cell response, but the mechanisms by which these varied responses are induced remains unknown. Conventional dendritic cells (cDCs) are crucial for sensing and initiating immune responses to this fungal pathogen and are the likely mediators of diverse T cell responses to A. fumigatus. Recent studies have established the transcriptional basis for cDC heterogeneity through single cell analyses, specifically demonstrating a division in the cDC2 population, which are considered the canonical antigen presenting cells, expressing MHC Class II and priming CD4 T cells. We now separate cDC2s into two novel subsets—cDC2A and cDC2B—based on differential expression of the transcription factors T-bet and RORγt, respectively. In addition, the anatomic positioning of cDC2s is known to facilitate spatial colocalization with pathogen-derived products allowing for efficient pathogen sensing, antigen uptake, and subsequent CD4 T cell activation. Based on the pathogenic properties of A. fumigatus and recent discoveries of cDC2 heterogeneity, our specific hypothesis is that cDC2A and cDC2B subsets will localize differently in lung and draining lymph node and facilitate different adaptive CD4 T cell response types to A. fumigatus. In this study, we investigate cDC2 subsets’ functionality in a clinically relevant murine model of invasive pulmonary aspergillosis. In Specific Aim 1, we will define the temporal and spatial dynamics of cDC2 subsets during acute A. fumigatus infection by applying high-content immunofluorescence methods and flow cytometry. We will also assess cDC2A and cDC2B functional properties in vitro. In Specific Aim 2, we will elucidate the direct impact of cDC2 subsets on adaptive immunity in A. fumigatus infection by implementing genetic tools to specifically ablate cDC2A and cDC2B subsets and establish their functional significance in vivo. In addition, by investigating spatial reorganization of other immune cell subsets in subset-specific ablation of cDC2A and cDC2B, we can identify their significance in cellular circuits governing lung immunity. This study employs and develops novel genetic tools, microscopy methods, and computational approaches to generate a systems level understanding of lung immunobiology and study host-pathogen interactions. Furthermore, this proposal is tailored for a physician-scientist in training, as it investigates the basic features of and mechanisms by which cDC2 subsets induce adaptive immunity to the clinically relevant pathogen A. fumigatus, with implications for anti-fungal therapeutic strategies and vaccine development.