Role of surface mannan in the adherence of Candida albicans to fibrin-platelet clots formed in vitro

An alkali-soluble extract from a cell wall preparation of Candida albicans was conjugated to sheep erythrocytes (SRBC) by using periodate oxidation or concanavalin A. Conjugated SRBC readily attached to a fibrin-platelet matrix, whereas nonconjugated SRBC did not. To determine the active component which promoted attachment of SRBC, the alkali-soluble fraction was treated with alpha-mannosidase, pronase, or glusulase or chemically degraded by acetolysis. The treated extract was then reconjugated with SRBC, and attachment was measured. When treated with alpha-mannosidase or degraded by acetolysis, the alkali-soluble extract failed to promote the adherence of SRBC to the fibrin-platelet matrix. Pronase- or glusulase-digested extract promoted attachment equally as well as untreated controls. In addition, when preabsorbed with antiserum to whole cells of C. albicans, the alkali extract abrogated the inhibition of adherence by antiserum, thus indicating its antigenicity. The extract consisted primarily of polysaccharide (72%) and contained a small amount of protein (less than 1%). Mannose and glucose (ratio, 3:1) were detected by gas-liquid chromatography. These data indicate that cell surface mannan may play an important role in the adherence of C. albicans to the fibrin-platelet matrices which form in vivo on the endocardium of heart valves.