The research described in this thesis was aimed at the characterization of the Candida adhesin, and elucidation of the nature of the human epithelial cell receptor with which it combines. Previous data have shown that the fibrillar mannoprotein layer, produced when Candida albicans is grown in high concentrations of galactose, contains the proteinaceous adhesin. Different Candida species from leukoplakia patients were assayed for their ability to adhere to buccal cells. The results supported previous conclusions that there is a relationship between the ability of different Candida albicans strains to adhere to epithelial cells and their capacity for cell surface modification. Extracellular polymeric material (EPM) was isolated from culture supernates of C. albicans after growth in medium containing 500 mM galactose. When used to pretreat buccal epithelial cells, EPM inhibited adherence, which suggested that it contains an adhesin that binds to, and blocks epithelial cell receptors. Fractionation of EPM by affinity chromatography was performed. An index, the adhesion inhibition index (AII) was used to compare the various "lectin-like" components isolated from crude EPM. These studies indicated that use of different buccal cell donors gave different results, with the same C. albicans strain. Attempts to resolve EPM by SDS-polyacrylamide gel electrophonesis had previously proved unsuccessful. However here, success was achieved using the silver-stain technique. Chemical and enzymatic digestion of the EPM indicated that the protein portion , of the glycoprotein was more important than the carbohydrate at inhibiting adherence. N-Glycanase, papain, mild alkali treatment of EPM, followed by Synsorb-H-2 affinity adsorption chromatography, resulted in a purification of the yeast adhesin of more than 220 fold, relative to the crude EPM (on a protein weight basis). The nature of the epithelial cell receptor for C. albicans was investigated with potential receptor analogues such as sugars, lectins, monoclonal antibodies and saliva. The adhesion of C. albicans to the buccal cells of blood groups A and O, was found to be significant with respect to secretor status but not blood group. Caution should be shown in the interpretation of sugar inhibition tests. Nevertheless, N-acetyl-D- galactosamine was the most effective single sugar as an inhibitor of adhesion for buccal cell donors of blood group A; N-acetyl-D-galactosamine is the immunodominant blood group sugar for group A cells and the possibility exists that the blood group oligosaccharide on the buccal cell surface functions as the receptor for yeast adhesion. Further work would be needed to establish whether the purified adhesin had any therapeutic value in treating Candida infections.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:768662 |
| Date | January 1991 |
| Creators | Tosh, F. Donald |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/40982/ |
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