Carbohydrate depletion of immunoglobulin A1 by oral species of gram-positive rods.

Bacterial deglycosylation of immunoglobulin Al (IgA1), the dominant isotype of antibody in the oral cavity, probably provides both nutrition as well as protection to the oral bacterial community. Representative strains of oral gram-positive rods were tested for their ability to remove carbohydrates from IgA1. Detection of sialic acids was performed by means of high-performance liquid chromatography (HPLC) separation (Aminex HPX-87H) and ultraviolet light absorption at 190 nm, and neutral carbohydrates were measured by HPLC separation (Capcell Pak C-18 SG 120) and ultraviolet light absorption at 245 nm after derivatization. Four strains of Actinomyces naeslundii, two strains of Corynebacterium matruchotii and one of two strains of Actinomyces odontolyticus partially or totally removed sialic acid, while two strains of Propionibacterium propionicus and the other strain of A. odontolyticus did not. Complete correlation was observed between sialic acid removal, neuraminidase activity measured with fluorogenic substrate and with one exception, altered immunoelectrophoretic mobility of IgA1. Only limited removal of other carbohydrates was observed with poor correlation to exoglycosidase activities measured with chromogenic substrates. Desialylation increases the susceptibility of glycoproteins, including IgA1, to proteolysis. Therefore, the desialylation of IgA1 by oral gram-positive rods may facilitate the proteolytic activities of other oral bacteria, and the concerted action may positively influence the survival of the bacteria in the oral community.