Ied [31,32]. These compounds, which include the prototypic compound NBD556 and its derivatives, mimic the effects of CD4 by inducing the exposure of the coreceptor-binding site on gp120 [31,33]. Although NBD-556 inhibits HIV-1 infection of CD4+CCR5+ cells, it can replace CD4 and thus enhance HIV-1 infection of CD42CCR5+ cells [31]. In view of their capacity to enhance infectivity, any potential ap