Release of Candida albicans yeast antigens upon interaction with human neutrophils in vitro

Candida albicans is the leading cause of invasive candidosis. As conventional tests do not reliably detect invasive infection, attention has turned to the detection of C. albicans antigens circulating in blood. As antigen tests for invasive candidosis could be improved if C. albicans antigens released upon phagocytosis were defined, this study was undertaken to characterise antigens released during the interaction of yeasts and human neutrophils in vitro. An enzyme immunoassay developed previously to detect what were believed to be predominantly C. albicans cytoplasmic antigens in patients with invasive candidosis was used to follow the neutrophil-mediated release of yeast antigens. Serum opsonisation enhanced antigen release, which was rapid and essentially complete by 1 h. When fresh C. albicans yeasts were added to medium from cultures of neutrophils plus yeasts or neutrophils plus latex beads, additional yeast antigens were released. Medium from neutrophils plus yeasts or from yeasts alone had similar immunoblot patterns with rabbit antibodies to a C. albicans cytoplasmic antigen preparation, with the reactive antigens generally being of higher mol. wt than the reactive antigens in the antigen mixture used for preparation of the antiserum. The two supernates also had similar immunoblot patterns with rabbit anti-C. albicans cell-wall mannan antibodies. These results suggest that yeast surface antigens are released quickly during phagocytosis by neutrophils. Detection of such yeast surface antigens, possibly together with selected yeast cytoplasmic antigens, should improve the sensitivity of C. albicans antigen assays.