A Double-Mimetic Peptide Efficiently Neutralizes HIV-1 by Bridging the CD4- and Coreceptor-Binding Sites of gp120

HIV-1 entry into host cells requires the viral envelope glycoprotein (gp120) to bind sequentially to the cellular receptor CD4 and a coreceptor (CCR5 or CXCR4). While researchers have previously developed individual peptides that mimic CD4 or the CCR5 binding site to inhibit this process, these single-target inhibitors face limitations: CD4-mimetics can inadvertently promote infection when CD4 is scarce, and CCR5-mimetics often have low binding affinity on their own. This study investigates whether a fusion protein, a double-mimetic peptide, can simultaneously bind both sites to improve neutralization potency and overcome these individual weaknesses.

The authors created a series of fusion proteins (immunoadhesins) that combine a scorpion toxin-derived CD4-mimetic peptide (CD4mim6) with a sulfopeptide mimetic of the CCR5 amino terminus (CCR5mim3). They tested various linker lengths (1, 6, 11, and 16 amino acids) and orientations to determine the optimal configuration for bridging the two binding sites on a single gp120 monomer. The efficacy of these constructs was evaluated through HIV-1 neutralization assays, cell-surface binding studies, and immunoprecipitation of gp120.

The study demonstrates that double-mimetic peptides with linkers of 11 amino acids or longer are significantly more potent at neutralizing HIV-1 than either CD4-Fc or equimolar mixtures of the individual peptides. The researchers found that the CCR5-mimetic component effectively prevents the CD4-mimetic component from promoting infection in CD4-negative cells, a common drawback of CD4-based inhibitors. Furthermore, the data suggest that these constructs achieve high avidity by simultaneously engaging both the CD4- and coreceptor-binding sites on the same gp120 monomer, provided the linker is long enough to span the distance between these sites.