BATHOPHENANTHROLINE DISULFONATE AND SOLUBLE CD4 AS PROBES FOR EARLY EVENTS OF HIV TYPE-1 ENTRY

We report here that a metalloprotease inhibitor, bathophenanthraline d isulfonate (Bphe-ds), neutralizes both laboratory-adapted and primary strains of HIV-1. Presaturation of Bphe-ds with zinc does not alter it s neutralizing activity, suggesting that the metal-chelating ability o f Bphe-ds is not required for neutralization. Bphe-ds blocks infection of CD4(+) cells at the stage of viral entry, not through a direct vir icidal effect, but by interfering with both binding and postbinding ev ents. This drug interacts with HIV-1 envelope, blocking almost complet ely the binding of three MAbs that recognize epitopes overlapping the CD4-binding site on gp120, but has no effect on the binding of MAbs di rected to the cellular receptor CD4. The exposure of epitopes in the V 2 and V3 but not C5 domains of gp120 is partially decreased in the pre sence of Bphe-ds, suggesting that the drug induces conformational chan ges in the envelope glycoprotein(s). Binding of both virions and solub le gp120 to CD4(+) cells is inhibited by this drug in a dose-dependent manner. This contrasted with the effects of soluble CD4, which actual ly increased binding of virions to cells at 4 degrees C, while inhibit ing the binding of soluble gp120. Bphe-ds also increases shedding of g p120 from cells infected with HIV-1(IIIB). Thus, Bphe-ds appears to be an envelope-directed inhibitor of HIV-1 that neutralizes HIV-1 infect ivity via multiple mechanisms.