The HIV-Neutralizing Monoclonal Antibody 4E10 Recognizes N-Terminal Sequences on the Native Antigen

Abstract

Characterization of the epitope recognized by the broadly neutralizing anti-HIV Ab 4E10 has, heretofore, focused on a linear sequence from the gp41 pretransmembrane region (PTMR). Attempts to generate neutralizing Abs based on this linear epitope sequence have been unsuccessful. We have characterized the antigenic determinants on recombinant glycosylated full-length Ags, and nonglycosylated and truncated Ags recognized by 4E10 using epitope extraction and excision assays in conjunction with MALDI mass spectrometry. The mAb recognized the peptides 34LWVTVYYGVPVWK46 and 512AVGIGAVFLGFLGAAGSTMGAASMTLTVQAR542 located at the N-terminal region of gp120 and gp41, respectively. Immunoassays verified AV(L/M)FLGFLGAA as the gp41 epitope core. Recognition of the peptide from the gp41 PTMR was detected only in constructs in which the N termini of the mature envelope proteins were missing. In this region, the epitope core is located in the sequence 672WFDITNWLWY681. We hypothesize that the hydrophobic surface of the paratope functions as a “trap” for the viral sequences, which are responsible for insertion into the host cell membrane. As the N-terminal region of gp120, the fusogenic peptide of gp41, and the PTMR of gp41 show high sequence homology among various HIV strains, this model is consistent with the broadly neutralizing capabilities of 4E10.

The Membrane-Proximal External Region of the Human Immunodeficiency Virus Type 1 Envelope: Dominant Site of Antibody Neutralization and Target for Vaccine Design

“…Later, Zwick et al showed the 4E10 epitope comprises the linear sequence NWFDIT (aa 671 to 676), which is just C terminal to the 2F5 epitope in the MPER (273). As with 2F5, there is also conflicting information regarding the "full" 4E10 epitope, as a recent study suggested that 4E10 binds both FP at the N terminus of gp41 and the MPER epitope (95). Those authors hypothesized that the full 4E10 epitope was missing in previously reported studies because soluble gp41 does not include the FP.…”

Utilization of Immunoglobulin G Fc Receptors by Human Immunodeficiency Virus Type 1: a Specific Role for Antibodies against the Membrane-Proximal External Region of gp41

“…Several human monoclonal Abs that neutralize a broad spectrum of HIV-1 variants have attracted considerable interest for vaccine design. Epitopes for these monoclonal Abs include the receptor binding domain of gp120 in the case of b12 (71,86), a glycan-specific epitope on gp120 in the case of 2G12 (13,85,86), and two adjacent epitopes in the membrane-proximal external region (MPER) of g41 in the cases of 2F5 and 4E10 (3,11,38,93). At least three of these monoclonal Abs have been shown to interact with FcRs and to mediate ADCC (42,43).…”

Immunising with the transmembrane envelope proteins of different retroviruses including HIV-1

“…[41][42][43][44][45] In addition we had shown that the binding of 2F5 is enhanced when in addition to the peptide containing its epitope a peptide corresponding to the FPPR is present, suggesting that the interaction between both peptides induces a conformation allowing a better binding of 2F5. 46 Whether this conformation is also required to induce broadly neutralizing antibodies remains unclear.…”