A Coreceptor-Mimetic Peptide Enhances the Potency of V3-Glycan Antibodies

Abstract

Broadly neutralizing antibodies (bNAbs) target five major epitopes on the HIV-1 envelope glycoprotein (Env). The most potent bNAbs have median half-maximal inhibitory concentration (IC50) values in the nanomolar range, and the broadest bNAbs neutralize up to 98% of HIV-1 strains. The engineered HIV-1 entry inhibitor eCD4-Ig has greater breadth than bNAbs and similar potency. eCD4-Ig is markedly more potent than CD4-Ig due to its C-terminal coreceptor-mimetic peptide. Here we investigated whether the coreceptor-mimetic peptide mim6 improved the potency of bNAbs with different epitopes. We observed that when mim6 was appended to the C terminus of the heavy chains of bNAbs, this sulfopeptide improved the potency of all classes of bNAbs against HIV-1 isolates that are sensitive to neutralization by the sulfopeptide alone. However, mim6 did not significantly enhance neutralization of other isolates when appended to most classes of bNAbs, with one exception. Specifically, mim6 improved the potency of bNAbs of the V3-glycan class, including PGT121, PGT122, PGT128, and 10-1074, by an average of 2-fold for all HIV-1 isolates assayed. Despite this difference, 10-1074 does not induce exposure of the coreceptor-binding site, and addition of mim6 to 10-1074 did not promote shedding of the gp120 subunit of Env. Mixtures of 10-1074 and an Fc domain fused to mim6 neutralized less efficiently than a 10-1074/mim6 fusion, indicating that mim6 enhances the avidity of this fusion. Our data show that mim6 can consistently improve the potency of V3-glycan antibodies and suggest that these antibodies bind in an orientation that facilitates mim6 association with Env. IMPORTANCE HIV-1 requires both the cellular receptor CD4 and a tyrosine-sulfated coreceptor to infect its target cells. CD4-Ig is a fusion of the HIV-1-binding domains of CD4 with an antibody Fc domain. Previous studies have demonstrated that the potency of CD4-Ig is markedly increased by appending a coreceptor-mimetic sulfopeptide to its C terminus. We investigated whether this coreceptor-mimetic peptide improves the potency of broadly neutralizing antibodies (bNAbs) targeting five major epitopes on the HIV-1 envelope glycoprotein (Env). We observed that inclusion of the sulfopeptide dramatically improved the potency of all bNAb classes against isolates with more-open Env structures, typically those that utilize the coreceptor CXCR4. In contrast, the sulfopeptide improved only V3-glycan antibodies when neutralizing primary isolates, on average by 2-fold. These studies improve the potency of one class of bNAbs, show that coreceptor-mimetic sulfopeptides enhance neutralization through distinct mechanisms, and provide insight for the design of novel multispecific entry inhibitors.

The Potential of eCD4-Ig, Delivered by Adeno-Associated Virus (AAV) Vector as a Novel Vaccine for HIV/AIDS Infection

“…eCD4-Ig has the ability to expose the V3-loop of HIV Env hence its ability to enhance the potency of V3-loop antibodies, which are abundant but non-neutralizing in HIV-infected individuals. [18,21] The remarkable potency of eCD4-Ig also comes from its ability in mediating ADCC. An in vitro study by Davis-Gardner et al revealed that eCD4-Ig mediated killing of HIV-infected cells up to 10 times more efficiently by natural killer (NK) cells.…”

Antibody Conjugates for Targeted Therapy Against HIV-1 as an Emerging Tool for HIV-1 Cure

“…Improvement in potency was later observed when Gardner and colleagues designed eCD4-Ig, which is a fusion of a CCR5 mimetic peptide, mim1, to CD4-Ig. This construct can simultaneously bind to CD4- and coreceptor-binding site on HIV-1 Env, and was found to have an increased breadth and similar potencies as bNAbs ( 48 , 52 ). Subsequent variants of eCD4-Ig were designed with improved versions of mim1.…”

“…Indeed, the importance of bNAb carriers to potentiate improved potency of conjugated mim6 was exhibited by its conjugation to V3-targeting bNAbs. V3-targeting bNAbs conjugated with mim6 displayed a 2-fold increase in potency even against mim6-resistant HIV-1 isolates tested ( 48 ).…”