ANALYSIS OF CANDIDA-ALBICANS ADHESION TO SALIVARY MUCIN

Clearance of Candida albicans from the oral cavity is thought to be me diated via specific receptor-ligand interactions between salivary cons tituents and the fungus. Since surfaces in the oral cavity are normall y coated with a saliva-derived pellicle, specific interactions between salivary constituents and C. albicans may also contribute to adhesion of C. albicans to the oral mucosa and dental prostheses. Therefore, t he purpose of this study was to identify salivary constituents to whic h C. albicans is capable of binding. A solid-phase overlay assay was u sed in which electrophoretically separated rat and human salivary cons tituents bound to membrane filters were incubated with radiolabelled C . albicans cells. C. albicans adhered to a single salivary component f rom each host. Correlation of cell-binding activity with specific mono clonal antibody (MAb)-binding activity indicated that the constituent bound by C. albicans in human saliva was low-molecular-weight mucin (M G2) and that in rat saliva was rat submandibular gland (RSMG) mucin. F urther studies showed an identical cell hybridization signal and MAb c olocalization by using RSMG ductal saliva and an aqueous RSMG extract in the solid-phase overlay assay. Analysis of cell binding to the aque ous extract of RSMG fractionated by anion-exchange chromatography demo nstrated that C. albicans binding was restricted to an acidic subfract ion of the RSMG extract, which also bound the RSMG mucin-specific MAb. The Candida-binding fraction contained predominantly RSMG mucin glyco protein and also a noncovalently associated, chloroform-extractable ma terial. Furthermore, we identified two strains of C. albicans which di ffered severalfold in the ability to bind RSMG mucin in the overlay as say. These results suggest that C. albicans binds to only a specific s ubfraction of RSMG mucin and that the two C. albicans strains tested d iffer in the ability to bind RSMG mucin subfractions.