Resident microbes shape the vaginal epithelial glycan landscape

Abstract

AbstractEpithelial cells are covered in carbohydrates. This glycan coat or “glycocalyx” interfaces directly with microbes, providing a protective barrier against potential pathogens. Bacterial vaginosis is a condition associated with adverse health outcomes in which bacteria reside in direct proximity to the vaginal epithelium. Some of these bacteria, including Gardnerella, produce glycosyl hydrolase enzymes. However, glycans of the vaginal epithelial surface have not been studied in detail. Here we elucidate key characteristics of the vaginal epithelial glycan landscape and determine the impact of resident microbes on the surface glycocalyx. In BV, the glycocalyx was visibly diminished. We show that the “normal” vaginal epithelium displays sialylated N- and O-glycans by biochemical and mass spectrometric analysis. In contrast, BV-epithelial cell glycans were strikingly depleted of sialic acids, with underlying galactose residues exposed on the surface. Treatment of cells from BV-negative women with recombinant Gardnerella sialidases generated BV-like glycan characteristics. Together these data provide the first evidence that the vaginal epithelial glycocalyx is attacked by hydrolytic enzymes in BV. Given the widespread structural and functional roles of sialoglycans in biology and disease, these findings may point to a shared epithelial pathophysiology underlying the many adverse outcomes associated with BV.