Calprotectin-mediated zinc chelation as a biostatic mechanism in host defence

The S-100 Ca2+ binding protein, calprotectin, isolated from neutrophil lysates, has been reported to exhibit zinc reversible biostatic activity in vitro. We verified these findings with C. albicans and investigated whether the growth inhibition resulted from zinc deprivation due to chelation by calprotectin. Calprotectin concentrations of 250 micrograms/ml significantly inhibited the growth of C. albicans. This was reversed by supplementing culture medium with 10 microM ZnSO4. Incubation of calprotectin in culture medium for 24 h prior to inoculation significantly reduced the minimum inhibitory concentration. When this latter medium was ultrafiltered to remove the calprotectin and then inoculated with C. albicans, significant growth inhibition was still present: again it was reversed by zinc. These findings implicate zinc chelation as a novel, potentially important host defence function of an abundant neutrophil protein.