The continuing occurrence of severe oropharyngeal and esophageal candidiasis in HIV+ and AIDS patients points to the need for a better understanding of the events that lead to disease. During immunosuppression, a shift in the microbial flora occurs that includes an increase in the number of fungi in saliva followed by invasion and inflammation of the oropharyngeal mucosa by Candida albicans. Intervention in this process requires a detailed knowledge of fungal factors that permit adherence and invasion. Using a reverse genetics approach towards identification of surface proteins of C. albicans that are important for adherence and invasion, the applicants have identified HWP1, a developmentally-regulated gene, which encodes a hypha-specific outer mannoprotein (Hwp1) with a cell surface-exposed proline and glutamine-rich putative ligand-binding domain at the N-terminus and C-terminus features that confer covalent integration into the beta-glucans of the cell wall of C. albicans hyphae. The N-terminal putative ligand binding domain resembles proteins such as small proline-rich proteins (sprp's) and the acidic salivary proteins (aprp's) that are substrates for epithelial cell transglutaminases, prompting the hypothesis that Hwp1 might mimic aprp's in being susceptible to transglutaminase-mediated crosslinking reactions, thereby leading to stabilized adhesion of C. albicans to the oral mucosa. The PI has created essential tools including isogenic strains with one or both copies of HWP1 deleted, a revertant strain in which HWP1 has been reintroduced into the double knockout strain, as well as a recombinant protein (rHwp1) and monospecific antibodies to rHwp1. These materials will be used to discover the role of HWP1 in stabilized adhesion using biochemical and molecular approaches, including site-specific mutagenesis, heterologous expression and animal studies. The long-term medical benefit of these studies will be the development of strategies to interfere with stabilized adhesion to, and invasion of , the oral mucosa by C. albicans. They will also contribute to the development of antifungal compounds by defining the characteristics of cell surface expression of pro-adhesive and pro- invasive proteins.
Showing the most recent 10 out of 16 publications
