Virulence mechanisms regulating Candida-driven vaginal epithelial exfoliation

Vulvovaginal candidiasis (VVC), the only type of candidiasis regularly affecting individuals without co- morbidities, will afflict about half of all women at least twice in their lifetimes. Despite this serious clinical burden, we still don't understand why some women harbor Candida in the vaginal tract asymptomatically, while others suffer debilitating VVC symptoms such as pain (vulvodynia, dyspareunia) and vaginal discharge. Currently it is believed that VVC is driven by changes in the vaginal environment, largely discounting the potential contribution of fungal strain-specific virulence factors. Our recent work challenges this dogma and suggests that VVC Candida albicans isolates, compared to Colonizing isolates, drive more vaginal epithelial cell (vEC) exfoliation—which could drive VVC's inflammatory symptoms. These results reframe the Candida-VVC interaction to incorporate differential fungal virulence, highlight the importance of understanding vEC exfoliation in VVC, and demonstrate how in vitro assays with human vEC can inform human disease. This proposal will test the hypothesis that Candida causes vEC exfoliation via dysregulation of a small number of epithelial signaling pathways, including type I interferon (IFN-I) and integrin signaling, by specific fungal virulence factors. Aim 1 builds on our finding that IFN-I activation is crucial for limiting exfoliation. We will identify the pathway(s) that Colonizing strains use to turn on IFN-I signaling, test the effects of bacterial co-infection, and determine how IFN-I is differentially activated by VVC and Colonizing strains. Aim 2 will determine if there is differential integrin signaling in exfoliation and test for Candida-bacterial co-infection synergy, drawing on the established role of integrin signaling in Candida-oral epithelial and bacterial-vEC interactions. We will determine which pathway components are differentially regulated and which are required to stimulate exfoliation. Aim 3 will use transcriptomics of Candida-vEC interactions with multiple VVC and Colonizing strains, combined with targeted virulence candidate-based testing, to identify and test fungal virulence factors for their roles in vEC exfoliation, IFN-I and integrin signaling. This Aim will also, via two- species RNAseq, identify and functionally implicate epithelial signaling pathways triggered during exfoliation. The work is significant because 1) VVC is an important unmet clinical problem, 2) our novel approach focusing on epithelial exfoliation could transform how we view and study VVC, and 3) study of a phenotype that distinguishes VVC from Colonizing strains could identify fungal VVC isolate-specific virulence factors. The innovation of this proposal lies largely in expanding the current host-biased model of VVC pathology to include the contribution of Candida strain-specific fungal virulence factors. In addition, the novel assays we have developed and the VVC and Colonizing strains we have identified provide unique tools to investigate VVC. These mechanisms may point to ways to distinguish virulent from commensal Candida strains, leading to more sophisticated diagnostics and treatments and limiting overtreatment of healthy colonized women. Project Number: 1R01AI189500-01A1 | Fiscal Year: 2026 | NIH Institute/Center: National Institute of Allergy and Infectious Diseases (NIAID) | Principal Investigator: Robert Wheeler | Institution: UNIVERSITY OF MAINE ORONO, ORONO, ME | Award Amount: $777,795 | Activity Code: R01 | Study Section: Interspecies Microbial Interactions and Infections Study Section[IMII] View on NIH RePORTER: https://reporter.nih.gov/project-details/1R01AI18950001A1