Elevated vaginal heparan sulfate correlates with impaired neutrophil killing of <i>Candida albicans</i> in women with vulvovaginal candidiasis

Recurrent vulvovaginal candidiasis (RVVC), primarily caused by the fungal pathogen <i>Candida albicans</i>, is a common infection affecting a significant number of women worldwide. Despite a robust inflammatory response by polymorphonuclear neutrophils (PMNs) with potent antifungal properties during symptomatic episodes, fungal clearance often fails, leading to persistent overgrowth and PMN-associated immunopathology. Studies in an established animal model demonstrated that elevated vaginal heparan sulfate (HS) interferes with PMN-<i>C. albicans</i> interactions, thereby impairing fungal clearance. This study investigated the presence and inhibitory effects of HS in women diagnosed with RVVC. Vaginal conditioned medium (VCM) was prepared from swab samples obtained from symptomatic VVC patients, women in asymptomatic remission, and healthy controls. Results from ELISA and immunostaining showed significantly elevated HS levels in VCM-containing vaginal secretions and epithelial cells from symptomatic women compared to those from asymptomatic and healthy controls. PMN killing assays further revealed significantly reduced antifungal activity in the presence of VCM from symptomatic women compared to asymptomatic and healthy control VCM, resulting in a significant negative correlation between vaginal HS concentrations and PMN antifungal activity. The inhibitory effect of HS was further confirmed <i>in vitro</i> by impaired PMN killing in control VCM spiked with purified HS, and by the restoration of PMN function following heparanase (HS lyase) treatment of both symptomatic VCM and HS-spiked controls. These findings support the results from the animal studies and provide the first clinical evidence that elevated HS in the vaginal environment contributes to PMN dysfunction, leading to persistent <i>C. albicans</i> colonization and VVC-associated immunopathology.