The respiratory immune system clears hundreds of airborne Aspergillus fumigatus spores (conidia) daily. Unchecked spore germination in the lung leads to invasive aspergillosis (IA), a major cause of infectious morbidity and mortality in immune compromised hosts. Beyond resident alveolar macrophages and recruited neutrophils, we identified a rapid influx of chemokine receptor CCR2-expressing monocytes following pulmonary A. fumigatus challenge. Recruited monocytes form monocyte-derived CD11b+ DCs, transport fungal antigen to draining lymph nodes, and facilitate the priming of fungus-specific CD4 T cells in the lung. Ablation of CCR2-expressing cells results in delayed fungal clearance and loss of fungus-specific CD4 T cell responses. To interrogate monocyte-mediated host defense mechanisms triggered by the direct encounter with fungal cells, we developed a novel fluorescent A. fumigatus strain to visualize fungal uptake and distinguish viable and inactivated fungal cells within host leukocytes in the lung. With this approach, we examine a model of monocyte function that links cell activation and effector mechanisms to fungal uptake and that integrates signals from C-type lectin (CTL) and Toll-like receptors (TLRs) via the adaptor proteins CARD9 and MyD88 and from the intracellular NOD-like receptor (NLR) NLRP3. The rationale for the proposed work is that it will provide a comprehensive view of monocytes and their derivatives in host defense against inhaled fungal spores. The hypothesis that underlies this proposal is that monocytes form a cellular antifungal effector system shaped by direct interactions with fungal cells and input from CTL, TLR, and NLR signaling pathways to direct innate and adaptive antifungal immune responses in the lung.
The aims will (1) define the mechanism of monocyte activation and contribution to fungal cell killing in immune competent and neutropenic hosts and (2) determine the relative contribution of CARD9-, MyD88-, and NLRP3-dependent signals on the outcome of infection, on monocyte-dependent innate and adaptive immune functions, and on orchestrating rapid neutrophil recruitment to infected airways. The experimental design will enable us to compare monocytes functionally with other immune cell subsets and to describe essential steps in the initiation of the immune response to A. fumigatus. The proposed studies serve as a model for in vivo fluorescence-based approaches that dissect the bilateral cellular outcomes of host-pathogen encounters.
Invasive aspergillosis causes significant mortality among patients with weakened immune systems. Monocytes represent an important white blood cell population that act against inhaled fungal organisms. This proposal seeks to define the mechanisms by which monocytes protect against opportunistic fungi in the lung and contribute to sterilizing immune responses. Knowledge gained from these studies will inform vaccination, cellular, and immune modulatory strategies with the aim of improving patient outcomes.
|Kowalski, Caitlin H; Beattie, Sarah R; Fuller, Kevin K et al. (2016) Heterogeneity among Isolates Reveals that Fitness in Low Oxygen Correlates with Aspergillus fumigatus Virulence. MBio 7:|
|Kasahara, Shinji; Jhingran, Anupam; Dhingra, Sourabh et al. (2016) Role of Granulocyte-Macrophage Colony-Stimulating Factor Signaling in Regulating Neutrophil Antifungal Activity and the Oxidative Burst During Respiratory Fungal Challenge. J Infect Dis 213:1289-98|
|Clark, Heather L; Jhingran, Anupam; Sun, Yan et al. (2016) Zinc and Manganese Chelation by Neutrophil S100A8/A9 (Calprotectin) Limits Extracellular Aspergillus fumigatus Hyphal Growth and Corneal Infection. J Immunol 196:336-44|
|Obar, Joshua J; Hohl, Tobias M; Cramer, Robert A (2016) New advances in invasive aspergillosis immunobiology leading the way towards personalized therapeutic approaches. Cytokine 84:63-73|
|Heung, Lena J; Hohl, Tobias M (2016) DAP12 Inhibits Pulmonary Immune Responses to Cryptococcus neoformans. Infect Immun 84:1879-86|
|Drummond, Rebecca A; Collar, Amanda L; Swamydas, Muthulekha et al. (2015) CARD9-Dependent Neutrophil Recruitment Protects against Fungal Invasion of the Central Nervous System. PLoS Pathog 11:e1005293|
|Rivera, Amariliz; Hohl, Tobias M (2015) Calnexin bridges the gap toward a pan-fungal vaccine. Cell Host Microbe 17:421-3|
|Lauvau, GrÃ©goire; Loke, P'ng; Hohl, Tobias M (2015) Monocyte-mediated defense against bacteria, fungi, and parasites. Semin Immunol 27:397-409|
|Jhingran, Anupam; Kasahara, Shinji; Shepardson, Kelly M et al. (2015) Compartment-specific and sequential role of MyD88 and CARD9 in chemokine induction and innate defense during respiratory fungal infection. PLoS Pathog 11:e1004589|
|Panea, Casandra; Farkas, Adam M; Goto, Yoshiyuki et al. (2015) Intestinal Monocyte-Derived Macrophages Control Commensal-Specific Th17 Responses. Cell Rep 12:1314-24|
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