The binding of Chlamydia trachomatis and zinc to McCoy cells (mouse fibroblasts)

Zinc was found to have profoundly different effects upon the infection of McCoy cells (mouse fibroblasts) by two strains of Chlamydia trachomatis dependent upon the time and concentration of zinc exposure. Radiolabeled zinc-65 became McCoy cell-associated in a manner independent of incubation temperature, but highly dependent on incubation time and zinc concentration. This effect was maximal after 30 to 60 minutes of incubation. Correspondingly, incubation of a chlamydia inoculant with McCoy cells and supplemental zinc (10(-5) to 10(-4) M) for 1 h was associated with significantly (approximately twofold) more binding of the chlamydia to the McCoy cells compared with control media (8 X 10(-6) M Zn). More prolonged incubation of the chlamydia and McCoy cells with supplemental zinc was associated with significantly fewer chlamydia inclusions. Concentrations of 5 X 10(-4) M zinc or higher were also found to be toxic to the McCoy cells after 48 h of incubation. Brief exposure to supplemental zinc may augment infection of cells by chlamydia: however, more prolonged exposure to the same concentrations of zinc lessens cellular infection by chlamydia.