DESCRIPTION (provided by applicant): During innate immune recognition of Candida, the organization of cell wall ligands and pattern recognition receptors is an important determinant of successful immune activation. The long-term goal of our research is to achieve a deeper understanding of the physical processes of receptor-ligand engagement that govern activation vs. evasion during innate immune fungal recognition. Our central hypothesis in this project is that nanoscale organization of immunogenic cell wall β-glucan and its receptor Dectin-1 provides a mechanistic basis for Dectin-1 signal initiation, and that spatiotemporal orchestration of antifungal is key to achieving adequate Dectin-1 responses. We anticipate that this work will provide mechanistic insight into how fungal pathogens conceal immunogenic ligands in attempt to escape detection and how pattern recognition receptors are coordinated to generate effective innate immunity against Candida. Grounded in previous results and our strong preliminary data, we will pursue this objective in three Specific Aims. In Aim 1, we will test the hypothesis that β glucan "masking" in Candida species minimizes nanoscale exposure geometry of this immunogenic ligand to evade immune recognition. Our approach will involve nanoscopic measurements of β-glucan exposure and assays to assess the functional significance of β-glucan exposure geometry. In Aim 2, we will test the hypothesis that Dectin-1 nanodomain rearrangements upon glucan engagement drive a process of nanoscale segregation from regulatory phosphatases that is stabilized by lipid domain separation. In Aim 3, we will test the hypothesis that mannan/DC-SIGN interactions drive signaling that coordinates long-range active transport of Dectin-1 into host-pathogen contacts. This recruitment process is especially important for Dectin-1 to efficiently find sparse glucan exposures, leading to DC activation. This application features innovative application of high-resolution imaging technologies and quantitative image analytical methods to an important problem in infectious disease. Our studies will move the field beyond current models of fungal recognition mechanisms that are limited by lack of information on the nanoscopic scale, allowing a more detailed and accurate understanding of the physical mechanisms of innate immunity against Candida species pathogens and how they may evade immunity. This project joins the PI's demonstrated expertise in fungal immunity, membrane biophysics and quantitative fluorescence imaging together with an interdisciplinary team that brings additional expertise in surface fabrication methods, nanobiology, mathematics and image bioinformatics. We anticipate that our work will advance the field through fundamentally new discoveries in fungal immunity and new therapeutic strategies for Candidiasis.

PUBLIC HEALTH RELEVANCE: Candida species are common fungal pathogens responsible for a spectrum of disease ranging from superficial mucocutaneous infections to life-threatening bloodstream infections, and innate immune host defense is an important element of immunity against Candida. Our proposed research is significant for public health and relevant to the NIAID mission because it will provide new mechanistic insight into innate immunity against Candida species pathogens, which will facilitate the discovery of new therapeutic targets for treating serious fungal infections in patients.