Cryptococcus neoformans in a pathogenic yeast that causes life- threatening meningoencephalitis in immunocompromised patients. The incidence of crytococcosis has increased dramatically in recent years as a consequence of the AIDS epidemic. The major capsular polysaccharide, glucuronoxylomannan (GXM), is serotype determinant of these organisms. The capsular polysaccharides are important contributors to the virulence of C. Neoformans. GXM is antiphagocytic and poorly immunogenic. In vitro, GNX inhibits leukocyte migration, enhances HIV infection in human lymphocytes, and promotes L-selectin shedding from neutrophils. The sensitivity and resolution of the analysis of GXM structure have improved due to the introduction of 1H Nuclear Magnetic Resonance Spectroscopy (NMR) in one and two dimensions. A database of 1H NMR chemical shifts has been established for the structural triad based on three -(1-3)-D- mannosyl residues. The chemical shifts of the mannosyl residues of the various triads serve as reporter groups for the identification and quantitation of seven structural triads as they occur in any GXM. The data-chemical shifts relative intensities, and peak areas of the reporter groups-are being placed in a relational database program.
The specific aims for the next period are: (1) To use the data to create a chemotyping scheme based on the quantitative distribution of the mannosyl triads in GXMS; (2) To use the data in aim one to develop a computer based neural network for the rapid chemotyping of C. Neoformans; (3) To determine the solution conformation of GXMs by high fields, multiple dimensional NMR since the immune response to C. Neoformans is intimately related to the three dimensional structure of GXM; (4) To determine the exact linkage dispositions of the 0-acetyl substituent, and indispensable component of the conformational epitope recognized by antibodies; (5) To characterize the individual Factor Specific antibodies obtained by tandem-column affinity chromatography using-GXM-affinity matrices; (6) To determine the fine structures of the mannoproteins from C. Neoformans Cap67: (7) To determine if polysaccharide is covalently linked to the cell wall of C. Neoformans. This information will be used to foster more precise investigations of the pathology, treatment, mechanisms of virulence, and prevention of cryptococcosis.
Showing the most recent 10 out of 19 publications
