Human immunodeficiency virus type 1 Tat binds to Candida albicans, inducing hyphae but augmenting phagocytosis in vitro

Tat, the human immunodeficiency virus type 1 (HIV-1) transactivating protei n, binds through its RGD-motif to human integrin receptors. Candida albican s, the commonest cause of mucosal candidiasis in subjects infected with HIV -1, also possesses RGD-binding capacity. The present Study reveals that Tat binds to C. albicans but not to C. tropicalis. Tat binding was markedly re duced by laminin and to a lesser extent by a complement C3 peptide containi ng the RGD motif, but not by a control peptide. The outgrowth of C. albican s was accelerated following binding of Tat, but phagocytosis of opsonizcd C . albicans was also increased after Tat binding. Thus, Tat binding promotes fungal virulence by inducing hyphae but may also reduce it by augmenting p hagocytosis. The net effect of Tat in vivo is difficult to judge but in vie w of the many disease-promoting effects of Tat we propose that accelerating the formation of hyphae dominates over the augmentation of phagocytosis.