The Broadly Neutralizing Anti-Human Immunodeficiency Virus Type 1 4E10 Monoclonal Antibody Is Better Adapted to Membrane-Bound Epitope Recognition and Blocking than 2F5

Abstract

The broadly neutralizing 2F5 and 4E10 monoclonal antibodies (MAbs) recognize epitopes within the membrane-proximal external region (MPER) that connects the human immunodeficiency virus type 1 (HIV-1) envelope gp41 ectodomain with the transmembrane anchor. By adopting different conformations that stably insert into the virion external membrane interface, such as helical structures, a conserved aromatic-rich sequence within the MPER is thought to participate in HIV-1-cell fusion. Recent experimental evidence suggests that the neutralizing activity of 2F5 and 4E10 might correlate with the MAbs' capacity to recognize epitopes inserted into the viral membrane, thereby impairing MPER fusogenic activity. To gain new insights into the molecular mechanism underlying viral neutralization by these antibodies, we have compared the capacities of 2F5 and 4E10 to block the membrane-disorganizing activity of MPER peptides inserted into the surface bilayer of solution-diffusing unilamellar vesicles. Both MAbs inhibited leakage of vesicular aqueous contents (membrane permeabilization) and intervesicular lipid mixing (membrane fusion) promoted by MPER-derived peptides. Thus, our data support the idea that antibody binding to a membrane-inserted epitope may interfere with the function of the MPER during gp41-induced fusion. Antibody insertion into a cholesterol-containing, uncharged virion-like membrane is mediated by specific epitope recognition, and moreover, partitioning-coupled folding into a helix reduces the efficiency of 2F5 MAb binding to its epitope in the membrane. We conclude that the capacity to interfere with the membrane activity of conserved MPER sequences is best correlated with the broad neutralization of the 4E10 MAb.It is generally accepted that a potentially successful human immunodeficiency virus (HIV) vaccine should be capable of eliciting a robust neutralizing antibody (NAb) response (15, 16). The isolation from infected asymptomatic individuals of several antibodies showing neutralizing activity against a broad spectrum of viral clades implies that triggering such an immunogenic response might conceivably be possible (15,16,74). The anti-gp41 2F5 and 4E10 monoclonal antibodies (MAbs) constitute a paradigm in this respect (21,34,48,49,56,68). These MAbs simultaneously exert broad and potent neutralizing activity across different HIV type 1 (HIV-1) strains and primary isolates (9,34,45,48,68,89), confer protection against viral infection when passively transferred to primate models (67), and increase the neutralization response upon passive immunization of humans (66,74). Thus, deciphering the molecular mechanisms underlying viral cross-neutralization by 2F5 and 4E10 poses a challenge for researchers working on HIV vaccine development (86).2F5 and 4E10 recognize conserved linear epitopes located within the membrane-proximal external region (MPER) of the HIV-1 gp41 fusogenic Env subunit (7,18,19,34,48,49,51,54,89). The crystal structures of the 2F5 and 4E10 Fabs in a complex with soluble epitope derivatives hav...

Induction of Antibodies Specific for Gp41 of HIV-1 by Gene Gun DNA Vaccination

“…Enhanced binding of mAb 2F5 and mAb 4E10 to their epitopes was observed in a lipid environment compared with free MPER peptides [23][24][25][26]. These findings raise the question, whether membranes or …”

Broadly neutralizing anti-HIV-1 antibodies disrupt a hinge-related function of gp41 at the membrane interface

“…2F5 and 4E10 may exploit the naturally occurring motion and flexibility at the MPER N terminus and hinge to extract buried hydrophobic residues to achieve tight binding. Taken together, these BNAbs may interfere with viral fusion by inhibiting membrane disruption at an early stage and/or by blocking interaction between the MPER and the other region(s) of gp41 at a late stage (24)(25)(26)(27)(28).…”

Aromatic residues at the edge of the antibody combining site facilitate viral glycoprotein recognition through membrane interactions

“…Since the initial findings by Grunder et al and Ofek et al (12,22), a number of publications have also shown that 2F5, 4E10, and Z13e1 improve binding to Env and epitope peptides in a lipid environment (21,23,24). In addition, it has become increasingly clear that 4E10 binds to lipids in the absence of the MPER (21,(23)(24)(25)(26)(27)(28)(29).…”

“…In addition, it has become increasingly clear that 4E10 binds to lipids in the absence of the MPER (21,(23)(24)(25)(26)(27)(28)(29). These studies have generated models of 4E10 epitope recognition (21,23), but they have not yet fully addressed which antibody region(s) bind lipid and, of particular importance for vaccine design, whether lipid interaction is an essential component of MPER-mediated neutralization.…”