A novel role for the inflammasome in the immunopathogenesis of Candida vaginitis

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DESCRIPTION (provided by applicant): Candida albicans, the primary causative agent of fungal vaginitis, will affect 75% of all women of reproductive age at least once in their lifetime. Static activity of commonly deployed antifungals and chronic infections are of growing concern; therefore, alternative therapies are crucially needed. Despite long-held beliefs that susceptibility to Candida vaginitis resulted from defects in adaptive immunity, it has recently been shown that the clinical immunopathology (i.e. itching, burning, pain, discomfort, redness of the vaginal mucosa) associated with Candida vaginitis is triggered by robust recruitment of polymorphonuclear leukocytes (PMN) to the vaginal epithelium. Using a mouse model of vaginitis, the S100 alarmins were identified as key signaling molecules in in this hallmark PMN response. However, recent studies using mice deficient in S100 alarmin production still responded with vigorous PMN recruitment when challenged with C. albicans. Therefore, a fundamental gap in knowledge still exists as to the alternative and/or complementary mechanism(s) by which neutrophils are recruited to the vaginal epithelium during Candida vaginitis. One possible process by which inflammation can be triggered at epithelial surfaces is by activation of the inflammasomes, a group of cytosolic cellular receptors that signal and initiate innate immune responses. Therefore, the objective of this proposal is to 1) demonstrate that the Nlrp3 inflammasome is a key early mediator of the innate inflammatory response and to 2) identify specific hypha-associated C. albicans virulence factors that result in inflammasome activation in the vaginal epithelium. Guided by strong preliminary data, these aims will test our central hypothesis that activation of the inflammasome induced by the C. albicans yeast-to-hypha transition during vaginitis potentiates exacerbated neutrophil influx and pro-inflammatory cytokine signaling in the vaginal epithelium. All aims will utilize a well-established mouse model of vaginitis to test our hypotheses. Under the first aim, genetic or pharmacologic blockade of discrete targets in the inflammasome signaling cascade will be utilized to elucidate signaling pathways contributing to Candida vaginitis. Successful disruption of inflammasome-dependent signaling will be assessed via measurement of inflammatory markers (PMNs, Interleukin-1b, S100 alarmins). In the second aim, morphogenesis-competent C. albicans strains deficient in specific hypha-associated virulence factors (secreted proteinases or adhesins) or strains locked in the yeast form but over-expressing these key identified hyphal virulence factors will be utilized to assess their required role for generating robust innate immune responses in vivo. This approach is innovative because it examines both host and fungal processes required for immune responses associated with Candida vaginitis and seeks to identify inflammasome function in the vaginal mucosa. This proposed work is significant because it will ultimately aid in the identification of novel signaling pathways that may serve as new therapeutic targets for such infections. This work will also provide a strong foundation on which the candidate can attain an independent academic research program. The candidate's immediate career goal is to successfully transition from a non-tenure track junior faculty member to a tenure-track Assistant Professor position studying the host innate immune response and molecular mechanisms associated with fungal vaginitis. His long-term career goal is to attain a tenured research faculty position to direct and maintain a well-funded, translational research team that studies innate immune mechanisms to fungal pathogens at the mucosal interface. In order to attain these career goals, aside from conducting the research described above, the candidate will assemble and maintain a supportive mentoring/consulting team that will aid in the successful completion of the research, hone the development of grantsmanship skills leading to effective funding opportunities, and accelerate the publication of high-impact data. Thus, these career goals fulfill the NIAID's mission to identify novel therapeutic approaches to combat fungal disease and to support junior investigators in making a career transition to independent faculty status under the K22 award mechanism.