C. albicans infection i.e. candidiasis, produces recurrent, invasive oral lesions in a steadily increasing population of immunocompromised patients. The necessity of using toxic, systemic antimycotics in these patients has produced a renewed interest in developing alternative therapies for the treatment of candidiasis. Adhesion to epithelial cells, the first event in oral candidiasis, is mediated by a repertoire of adhesive molecules expressed on the surface of C. albicans cell wall. Previous studies suggests that the temporal escalation of non-covalent bond formation between candida adhesive molecules and epithelial cell surface molecules initially elicits a reversible adhesion which is quickly stabilized to become functionally irreversible. Additionally, saliva has been proposed to modulated candida adherence. These studies, however, have focused on characterization of C. albicans adhesive molecules; the host contribution to adhesion, i.e. the role of saliva and epithelial cell factors, have only been superficially characterized. Preliminary experiments in our laboratory indicate that an epithelial surface enzyme, transglutaminase, covalently cross-links inducible, morphotype specific, C. albicans cell wall protein to proteins on epithelial cell surfaces. [Additionally, the salivary proteins (proline-rich proteins > cystatin > amylase) react with transglutaminase and therefore, may compete with candida proteins for reactivity with transglutaminase.] Thus, we hypothesize that salivary proteins may modulate a transglutaminase catalyzed, covalent mechanism of adhesion by competing with candida cell wall proteins for transglutaminase catalyzed cross-linking to the epithelial cell surface. The objectives of this application are to confirm this hypothesis by utilizing the following specific aims: 1) Characterize the role of epithelial transglutaminase in stabilizing C. albicans adhesion to buccal epithelial cells; [2) Characterize the effect of salivary proteins on transglutaminase catalyzed mechanisms of adhesion; and 3) Characterize C. albicans transglutaminase reactive proteins (TRP) by transformation of non-adherent S. cerevisiae with TRP-cDNA: ] To our knowledge this is the first study of a covalent mechanisms in microbial adhesion. Conformation and characterization of this mechanism will provide knowledge adjunctive to the study of C. albicans adhesion. The results of this study may lead to alternative therapies for the treatment of candidal infection in immunocompromised patients.
