Characterization of mannoproteins from a virulent Candida albicans strain and its derived, avirulent strain.

Antigenic differences between a wild-type virulent strain of Candida albicans 4918 (wt) and its spontaneous avirulent mutant (m-10) were found with crossed-immunoelectrophoresis and western blotting. Mannoprotein fractions from yeast and mycelial forms were obtained by affinity chromatography on concanavalin A and analyzed with use of patient sera or sera from rabbits infected with live wt cells and boosted with whole extracts or rabbits immunized with purified wt cell wall preparations. A spike-formed precipitate was detected only with the wt yeast cells with crossed-electrophoresis and patient and rabbit sera. Otherwise serum from infected rabbits precipitated about equally the wt and m-10 cell wall mannoprotein antigens. The nature of this precipitate, with extremely slow electromobility in the first dimension and the possibility of its relation to some special immunodeterminant of the wt mannan molecule, is discussed. Likewise, when mycelial mannoproteins were analyzed by crossed-immunoelectrophoresis, a precipitate specific for wt cells was observed with rabbit anti-Candida sera. Also, a mannoprotein of approximately 47 kilodaltons was observed by western blotting only for wt mycelial cells. The observed antigenic differences between the virulent and the avirulent derived strain might be related to the greater adherence and infectivity of the wt strain.