Characterization of a monoclonal antibody to a novel glycan-dependent epitope in the V1/V2 domain of the HIV-1 envelope protein, gp120

• Published in: Molecular immunology Vol. 62; no. 1; pp. 219 - 226
• Main Authors: Doran, Rachel C., Morales, Javier F., To, Briana, Morin, Trevor J., Theolis Jr, Richard, O’Rourke, Sara M., Yu, Bin, Mesa, Kathryn A., Berman, Phillip W.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.11.2014
• Subjects: AIDS Vaccines - immunology; AIDS Vaccines - isolation & purification; Amino Acid Sequence; Animals; Antibodies, Monoclonal - chemistry; Antibodies, Monoclonal - immunology; Antibodies, Neutralizing - immunology; Antibodies, Neutralizing - isolation & purification; asparagine; Cells, Cultured; Epitope; Epitope Mapping; epitopes; Epitopes - chemistry; Epitopes - immunology; glycopeptides; Glycosylation; Gp120; HEK293 Cells; HIV; HIV Envelope Protein gp120 - chemistry; HIV Envelope Protein gp120 - genetics; HIV Envelope Protein gp120 - immunology; HIV infections; Human immunodeficiency virus 1; Humans; immune response; immunization; Mice; Mice, Inbred BALB C; Molecular Sequence Data; molecular weight; monoclonal antibodies; Monoclonal antibody; mutagenesis; Mutagenesis, Site-Directed; neutralization; polysaccharides; Polysaccharides - immunology; Protein Structure, Tertiary; recombinant proteins; V1/V2 domain; vaccines; Gp120; Glycosylation; Monoclonal antibody; Epitope; HIV; V1/V2 domain
• ISSN: 0161-5890; 1872-9142; 1872-9142
• DOI: 10.1016/j.molimm.2014.06.025

•Monoclonal antibody, 4B6, recognizes a glycan-dependent epitope in HIV gp120.•4B6 binding is dependent on a glycan at position N130 in the V1/V2 domain of gp120.•Glycan-dependent antibodies to gp120 can arise from a short immunization schedule.•Glycan-dependent antibodies to gp120 may be more common than previously expected.•Structural studies may provide insight as to why 4B6 lacks neutralization activity. Recent studies have described several broadly neutralizing monoclonal antibodies (bN-mAbs) that recognize glycan-dependent epitopes (GDEs) in the HIV-1 envelope protein, gp120. These were recovered from HIV-1 infected subjects, and several (e.g., PG9, PG16, CH01, CH03) target glycans in the first and second variable (V1/V2) domain of gp120. The V1/V2 domain is thought to play an important role in conformational masking, and antibodies to the V1/V2 domain were recently identified as the only immune response that correlated with protection in the RV144 HIV-1 vaccine trial. While the importance of antibodies to polymeric glycans is well established for vaccines targeting bacterial diseases, the importance of antibodies to glycans in vaccines targeting HIV has only recently been recognized. Antibodies to GDEs may be particularly significant in HIV vaccines based on gp120, where 50% of the molecular mass of the envelope protein is contributed by N-linked carbohydrate. However, few studies have reported antibodies to GDEs in humans or animals immunized with candidate HIV-1 vaccines. In this report, we describe the isolation of a mouse mAb, 4B6, after immunization with the extracellular domain of the HIV-1 envelope protein, gp140. Epitope mapping using glycopeptide fragments and in vitro mutagenesis showed that binding of this antibody depends on N-linked glycosylation at asparagine N130 (HXB2 numbering) in the gp120 V1/V2 domain. Our results demonstrate that, in addition to natural HIV-1 infection, immunization with recombinant proteins can elicit antibodies to the GDEs in the V1/V2 domain of gp120. Although little is known regarding conditions that favor antibody responses to GDEs, our studies demonstrate that these antibodies can arise from a short-term immunization regimen. Our results suggest that antibodies to GDEs are more common than previously suspected, and that further analysis of antibody responses to the HIV-1 envelope protein will lead to the discovery of additional antibodies to GDEs.