Roles of glycoproteins and oligosaccharides found in human vaginal fluid in bacterial adherence

Adherence of type 1-piliated Escherichia coli to carbohydrate structures of vaginal mucosa plays a major role in the pathogenesis of ascending urinary tract infections in women. Colonization of the vaginal introitus is influe nced by interactions between pathogens, vaginal fluid, and vaginal epitheli um. In this study, the type and amount of carbohydrates and glycoproteins p resent in vaginal fluid were determined. Free and protein-bound oligosaccha rides in vaginal fluid specimens were analyzed by fluorophore-assisted carb ohydrate electrophoresis (FACE) and high-pressure liquid chromatography (HP LC). Two dimensional electrophoretic separations of vaginal fluid glycoprot eins were performed together with bacterial overlay assays. The results of FACE showed that the majority of the oligosaccharides are in the free state and the bound oligosaccharides are undetectable. HPLC analysis of free sug ars revealed glucose as the major sugar (3.3 +/- 0.3 mM), and the concentra tions of mannose and glucosamine were 0.065 +/- 0.04 and 0.02 +/- 0.001 mM, respectively. Radiolabaled E. call bound three vaginal fluid glycoproteins ,vith the following molecular masses and pIs: 82 kDa and pr 5.5, 55 kDa and pi 4.5, and 55 kDa and pi 6.5. The binding was inhibited by mannose and by deglycosylation of the proteins prior to the overlay assay. One of these p utative receptors was identified to be the heavy chain of secretory IgA (S- IgA). These data suggest that the free mannose in the fluid is less than th at required to affect E. coli-epithelial cell binding interactions and that S-IgA may bind E. coli in the vaginal introitus.