Candida sp. are opportunistic fungal pathogens that colonize the skin and oral cavity and, when overgrown under permissive conditions, cause inflammation and disease. Previously, we identified a central role for the NLRP3 inflammasome in regulating IL-1β production and resistance to dissemination from oral infection with Candida albicans. Here we show that mucosal expression of NLRP3 and NLRC4 is induced by Candida infection, and up-regulation of these molecules is impaired in NLRP3 and NLRC4 deficient mice. Additionally, we reveal a role for the NLRC4 inflammasome in anti-fungal defenses. NLRC4 is important for control of mucosal Candida infection and impacts inflammatory cell recruitment to infected tissues, as well as protects against systemic dissemination of infection. Deficiency in either NLRC4 or NLRP3 results in severely attenuated pro-inflammatory and antimicrobial peptide responses in the oral cavity. Using bone marrow chimeric mouse models, we show that, in contrast to NLRP3 which limits the severity of infection when present in either the hematopoietic or stromal compartments, NLRC4 plays an important role in limiting mucosal candidiasis when functioning at the level of the mucosal stroma. Collectively, these studies reveal the tissue specific roles of the NLRP3 and NLRC4 inflammasome in innate immune responses against mucosal Candida infection.

Candida is an opportunistic fungal pathogen that colonizes the mucosal tract of humans. Pathogenic infection occurs in the presence of conditions causing perturbations to the commensal microbiota or host immunity. Early innate immune responses by the epithelium, including antimicrobial peptides (AMPs) and cytokines, are critical for protection against overgrowth. Reduced salivary AMP levels are associated with oral Candida infection and certain AMPs, including human beta-defensins 1 - 3, have direct fungicidal activity. Here we demonstrate that murine β-Defensin 1 (mBD1) is important for control of early mucosal Candida infection and plays a critical role in the induction of innate inflammatory mediators. Mice deficient in mBD1 exhibit elevated oral and systemic fungal burdens as compared to wild-type mice. Neutrophil infiltration to the sites of mucosal Candida invasion, an important step in limiting fungal infection, is significantly reduced in mBD1 deficient mice. These mice also exhibit defects in the expression of other antimicrobial peptides, including mBD2 and mBD4, which may have direct anti-Candida activity. We also show that mBD1 deficiency impacts the production of important anti-fungal inflammatory mediators including IL-1β, IL-6, KC, and IL-17. Collectively, these studies demonstrate a role for the mBD1 peptide in early control of Candida infection in a murine model of mucosal candidiasis, as well as on the modulation of host immunity through augmentation of leukocyte infiltration and inflammatory gene induction.