Effect of iron depletion on cell-wall antigens of Candida albicans

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Abstract
Cell walls were isolated from stationary-phase cultures of Candida albicans grown at 25°C or 37°C, in iron-depleted and iron-sufficient conditions. Proteins solubilised from cell-wall fractions were separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Approximately 40 protein bands were detected by Coomassie blue staining in all wall extracts, regardless of temperature or other growth condition. Sera from patients with oral or systemic candidosis, from whom the isolates were obtained, and pooled normal human serum were examined for the presence of IgG and IgM antibodies to cell-wall proteins by Western blotting. Patient sera recognised more antigens than pooled normal human serum. In particular, an antigen of 44 kda was detected by IgG antibodies in the sera of patients and two antigens of 41 and 14 kda were detected by their IgM antibodies when the sera were used as probes against walls from iron-depleted cells, but not from iron-sufficient cells, grown at 25°C. Two antigens of 45 and 40 kda were detected by IgM antibodies in the sera of patients tested against walls from iron-depleted but not from iron-sufficient cells grown at 37°C. IgG antibodies did not distinguish between these wall preparations from cells grown at 37°C. These results suggest that the specific cell-wall proteins induced during growth in iron-depleted conditions, as well as other proteins, were immunogenic and were recognised by the patients' antibodies.