CHARACTERIZATION OF MUTANT STRAINS OF CANDIDA-ALBICANS DEFICIENT IN EXPRESSION OF A SURFACE DETERMINANT

Monoclonal antibody (MAb) 17E4 reacts with a surface carbohydrate dete rminant and agglutinates cells of Candida albicans. Using this MAb, we have isolated N-methyl-N'-nitro-N-nitrosoguanidine-induced nonaggluti nating mutants. Eleven of these were characterized for the presence an d expression of the surface antigen recognized by MAb 17E4 by immunobl ot analysis of whole cells and by fluorescence flow cytometry. Soluble cell wall extracts from five mutant strains were negative by immunobl ot analysis. The reactivities of the strains with several other MAbs a nd commercial antisera (Candida Check; Iatron Laboratories, Tokyo, Jap an) which also recognize carbohydrate determinants were examined by im munoblot analysis of whole cells. Mutant strains showed no or reduced expression of the MAb 17E4 antigen and could be placed into at least t wo distinct phenotypic classes. Recognition by the other MAbs tested s howed a similar pattern, while recognition by the commercial antisera was unchanged in the mutant strains. H-1 and C-13 nuclear magnetic res onance spectral analysis of mannan prepared from the wild type and non expressing mutant strain 4A showed that the spectra from the mutant st rain were simpler than those of the wild type. Most of the beta-1,2 li nkages and all of the C-1 phosphate linkages were absent in the 4A man nan spectra, which suggested that the mutant mannan lacked the phospha te-bound beta-1,2-linked mannooligosaccharides. The effect of the surf ace defect on the ability of mutant strain 4A to adhere and to invade host tissue was examined in two murine models. In ex vivo binding assa ys, strain 4A showed reduced binding to the marginal zone and increase d binding to the white pulp of splenic tissue, decreased binding to ki dney tissue, and no change in binding to liver tissue compared with th e wild type. In vivo, no difference was observed in translocation of t he wild type or strain 4A to liver following immunocompromising treatm ent of infant mice which had been challenged with either strain by the oral-intragastric route.