Resistance of Zinc-Supplemented Candida albicans Cells to the Growth Inhibitory Effect of Calprotectin

Calprotectin is a neutrophil cytoplasmic protein with significant microbistatic activity. This protein may compete for zinc, or the metal may inactivate a different microbistatic activity of the protein. To distinguish between these possibilities, the sensitivity to calprotectin was determined for zinc-supplemented Candida albicans cells. The latter had increased growth in cultures containing either human empyema fluid as a source of calprotectin or purified calprotectin itself. This increased growth did not appear to be due to leakage of zinc into the medium. In other experiments, empyema fluid supernatants did not suppress C. albicans growth across a dialysis membrane; however, other studies suggested that it is difficult to significantly suppress C. albicans growth by zinc depletion unless the depleting agent remains in the cultures. These results indicate that calprotectin inhibits C. albicans growth through competition for zinc.