Role of immunomodulators IL-33 and SPRR in oropharyngeal candidiasis - PROJECT SUMMARY/ABSTRACT Fungal infections of the oral mucosa are a major complication for the immunocompromised host, including in neonates, cancer patients, and patients with HIV/AIDS. Candida albicans, an otherwise benign commensal of human oral cavity is the foremost causative agent of oropharyngeal candidiasis (OPC). Despite antifungal ther- apy, OPC causes considerable morbidity, nutritional deficits, and increased prevalence of esophageal cancer. Studies on the immunological mechanisms of protection from OPC have largely focused on the pro-inflammatory innate immune response. Signaling in oral epithelial cells through TH-17 cytokines IL-17A, IL-17F, IL-22 and STAT3 drive critical mucosal responses against Candida, recruiting neutrophils, triggering more cytokines, chem- okines, and antimicrobial peptides (AMP) resulting in acute tissue inflammation. Little is known about the anti- inflammatory or immunomodulatory signals that regulate inflammation, and aid in tissue repair. Thus, our knowledge on the global immunity within the fungi-infected mucosa remains incomplete. To obtain a comprehensive understanding of the host-pathogen responses during OPC, we used a next-gener- ation sequencing technology called Visium 10X Spatial Genomics which provided a “visual” landscape of global gene expression changes in infected tongue sections. While we did find the TH-1 and TH-17 associated pro- inflammatory genes highly upregulated, as expected; we also discovered the presence of type-2 immune re- sponses marked by the presence of anti-inflammatory M2 macrophages, and the immunomodulatory IL-33/ST2 axis. Furthermore, a novel family of epidermally produced small proline-rich proteins (SPRRs) were remarkably upregulated during OPC. Exogenous treatment with recombinant (rec) recIL-33 or recSPRR could eradicate OPC in mice. In fact, recSPRR proteins directly killed Candida in vitro by permeabilizing their cell membranes. The role of M2 macrophages, IL-33 or SPRRs have never been examined in the context of mucosal candidiasis. In Aim 1 we will investigate the mechanistic contributions of IL-33 both as a pleotropic alarmin with abilities to trigger inflammatory neutrophils, as well as a type-2 cytokine that can polarize macrophages to the anti-inflam- matory M2 type. IL-33’s effect on key drivers of protection including: Th17, Th1, immunosuppressive cytokines and Th2 will be tested in recIL-33 treated versus WT and IL-33 -/- infected mice. IL-33 increased upon recSPRR2a treatment, indicating that SPRR likely regulates IL-33 secretion from oral epithelial cells. To investi- gate the role of SPRRs in the host response to OPC (Aim 2), we will determine the oral fungal burden, cytokine- chemokine response (including IL-33), and the extent of infiltrating neutrophils and monocytes in WT and SPRR- /- mice. To unravel their potential epistasis with SPRR in oral infections, we will evaluate IL-17/IL-23, IL-6/STAT3, and IL-4, IL-13 in SPRR-/- and in recSPRR2a treated WT mice and use knockout oral keratinocyte cell lines of cytokines prioritized from the in vivo studies. Proposed studies will advance our knowledge on protective immun- ity during OPC that could be maneuvered for future development of novel immunotherapeutic interventions.
