The major aim of this project is to study the mechanism of action of the salivary agglutinin, a high molecular weight glycoprotein which aggregates many strains of oral bacteria. Progress in these studies has produced 5 major findings: 1) agglutinin-coated bacterial-aggregates can specifically incorporate uncoated bacteria, suggesting that the agglutinin molecule may only possess specific binding sites for the naked bacterial surface, 2) formation of bacterial-aggregates by the agglutinin as a unique process, both qualitatively and quantitatively different from bacterial aggregations induced by lysozyme or zinc, 3) agglutinin found in submandibular saliva is identical to the protein in parotid saliva, and both species differ in behavior on Sepharose 4B-CL from the salivary adherence promoting factor found in submandibular saliva, 4) carbohydrate residues on the agglutinin can interact with specific lectins, thus allowing the use of these proteins as probes for the salivary molecule and 5) a series of monoclonal antibodies directed against the salivary agglutinin have been isolated. Utilizing this information, we will investigate the functional domains of the salivary agglutinin through a series of binding competition experiments to ascertain the extent of overlap amongst the epitopes seen by the monoclonals, and the lectin binding sites. Further, we will use these probes for an immunohistochemical investigation of salivary gland tissue, to determine the site of agglutinin synthesis and to extend these studies to salivary gland tumors, animal model systems and normal human (non-salivary gland) tissues. Other studies will center on the use of functional assays to further elucidate the interaction between the bacterial cell, the salivary protein and other ligands such as calcium, lysozyme and zinc. Finally, we will utilize our new probes to gain insights into the relationship between bacterial aggregation and bacterial adherence to hydroxyapatite surfaces, and the impact of these processes on dental diseases.
