Cross-Reactive HIV-1-Neutralizing Human Monoclonal Antibodies Identified from a Patient with 2F5-Like Antibodies

Abstract

The genes encoding broadly HIV-1-neutralizing human monoclonal antibodies (MAbs) are highly divergent from their germ line counterparts. We have hypothesized that such high levels of somatic hypermutation could pose a challenge for elicitation of the broadly neutralizing (bn) Abs and that identification of less somatically mutated bn Abs may help in the design of effective vaccine immunogens. In a quest for such bn Abs, phage-and yeast-displayed antibody libraries, constructed using peripheral blood mononuclear cells (PBMCs) from a patient with bn serum containing Abs targeting the epitope of the bn MAb 2F5, were panned against peptides containing the 2F5 epitope and against the HIV-1 gp140 JR-FL . Two MAbs (m66 and m66.6) were identified; the more mutated variant (m66.6) exhibited higher HIV-1-neutralizing activity than m66, although it was weaker than 2F5 in a TZM-bl cell assay. Binding of both MAbs to gp41 alanine substitution mutant peptides required the DKW 664-666 core of the 2F5 epitope and two additional upstream residues (L 660,663 ). The MAbs have long (21-residue) heavy-chain third complementarity-determining regions (CDR-H3s), and m66.6 (but not m66) exhibited polyspecific reactivity to self-and non-self-antigens. Both m66 and m66.6 are significantly less divergent from their germ line Ab counterparts than 2F5-they have a total of 11 and 18 amino acid changes, respectively, from the closest VH and V germ line gene products compared to 25 for 2F5. These new MAbs could help explore the complex maturation pathways involved in broad neutralization and its relationship with auto-and polyreactivity and may aid design of vaccine immunogens and development of therapeutics against HIV-1 infection.

A Cryptic Polyreactive Antibody Recognizes Distinct Clades of HIV-1 Glycoprotein 120 by an Identical Binding Mechanism

“…Different studies have suggested that antibody polyreactivity contributes to neutralization of HIV-1 (24,27,31,(55)(56)(57)(58). Several mechanisms have been proposed to explain the role of antibody polyreactivity in HIV-1 neutralization.…”

Neutralizing Epitopes in the Membrane-Proximal External Region of HIV-1 gp41 Are Influenced by the Transmembrane Domain and the Plasma Membrane

“…1 A) overlaps that of 4E10 (39). While the epitope for m66.6 overlaps substantially with that of 2F5, this MAb is less potent and broad, neutralizing only a subset of the 2F5-sensitive viruses (64). The heavy-chain variable domains of all four Nt Abs are highly mutated and possess an unusually long third complementaritydetermining region of the antibody heavy chain (CDR-H3).…”

“…Roughly half of the residues within this region are hydrophobic, and the MPER plays a crucial role in the fusion of the viral and cellular membranes (43). In addition, Nt epitopes within the MPER are targeted by two well-characterized broadly Nt (bNt) monoclonal Abs (MAbs) (4E10 and 2F5) (4,15,32,67) and two MAbs (Z13e1 and m66.6) that neutralize a range of viral isolates but are not bNt, making this region a promising target for vaccine efforts (39,64).…”

Immunisation with foamy virus Bet fusion proteins as novel strategy for HIV-1 epitope delivery

“…The antigens specifically reacted with 2F5, 4E10 and a serum against the E1 domain and were immunogenic in rats generating antibodies targeting an epitope overlapping with the 2F5 epitope; however, they did not prevent HIV-1 infection in a TZM-bl based neutralisation assay. The antigens comprised the HIV-1 MPER-derived E2 domain because the corresponding bnAb antibodies are characterised by strong somatic mutations which could benefit from prolonged antigen delivery by replicating vectors [67]. Additionally, some Bet hybrids contained the FPPR derived E1 domain and the E2 domain linked by a loop to stabilise a MPER conformation that increases 2F5 binding [56,53,57,54].…”