Vitronectin interacts with Candida albicans and augments organism attachment to the NR8383 macrophage cell line

Candida albicans is an increasingly important cause of mucocutaneous and bloodstream infections. The potential role of circulating adhesive glycoproteins such as vitronectin (Vn) in host defense against C. albicans is currently unknown. Accordingly, we investigated the binding of plasma-derived Vn with C. albicans strain 36082. Vn specifically bound to C. albicans in a concentration-dependent fashion. Higher affinity binding sites numbered 9.8 x 10(4) sites per organism, with a dissociation constant, Kd of 3.5 x 10(-7) M. Vn binding with C. albicans was significantly inhibited by heparin, suggesting interaction of the organism with Vn's glycosaminoglycan-binding region. To further determine which molecule(s) on the fungus interacted with Vn, C. albicans components were extracted, separated by SDS and blotted with radiolabeled Vn. These studies revealed that Vn binds to a 30 kDa molecule on C. albicans. Finally, we investigated the role of Vn in promoting interaction of C. albicans with phagocytic cells. Incubation of C. albicans in the presence of Vn significantly increased binding of the organism to cultured NR8383 macrophages compared to incubations performed in the absence of Vn. These data demonstrate that C. albicans interacts with the heparin-binding domain Vn and further suggest that Vn augments organism uptake by phagocytic cells.