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Updated: Aug 30, 2025
Conformational Evaluation of HIV-1 Trimeric Envelope Glycoproteins Using a Cell-based ELISA Assay
Published on: September 14, 2014
Dependence on a variable residue limits the breadth of an HIV MPER neutralizing antibody, despite convergent
Cathrine Scheepers1,2, Prudence Kgagudi1,2, Nonkululeko Mzindle1,2
1Centre for HIV and STIs, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.
Abstract:
Broadly neutralizing antibodies (bNAbs) that target the membrane-proximal external region (MPER) of HIV gp41 envelope, such as 4E10, VRC42.01 and PGZL1, can neutralize >80% of viruses. These three MPER-directed monoclonal antibodies share germline antibody genes (IGHV1-69 and IGKV3-20) and form a bNAb epitope class. Furthermore, convergent evolution within these two lineages towards a 111.2GW111.3 motif in the CDRH3 is known to enhance neutralization potency. We have previously isolated an MPER neutralizing antibody, CAP206-CH12, that uses these same germline heavy and light chain genes but lacks breadth (neutralizing only 6% of heterologous viruses). Longitudinal sequencing of the CAP206-CH12 lineage over three years revealed similar convergent evolution towards 111.2GW111.3 among some lineage members. Mutagenesis of CAP206-CH12 from 111.2GL111.3 to 111.2GW111.3 and the introduction of the double GWGW motif into CAP206-CH12 modestly improved neutralization potency (2.5-3-fold) but did not reach the levels of potency of VRC42.01, 4E10 or PGZL1. To explore the lack of potency/breadth, viral mutagenesis was performed to map the CAP206-CH12 epitope. This indicated that CAP206-CH12 is dependent on D674, a highly variable residue at the solvent-exposed elbow of MPER. In contrast, VRC42.01, PGZL1 and 4E10 were dependent on highly conserved residues (W672, F673, T676, and W680) facing the hydrophobic patch of the MPER. Therefore, while CAP206-CH12, VRC42.01, PGZL1 and 4E10 share germline genes and show some evidence of convergent evolution, their dependence on different amino acids, which impacts orientation of binding to the MPER, result in differences in breadth and potency. These data have implications for the design of HIV vaccines directed at the MPER epitope.
Insights
Broadly neutralizing antibodies targeting HIV
Area of Science:
- Immunology and Virology
- Structural Biology
Background:
- Broadly neutralizing antibodies (bNAbs) targeting the HIV gp41 membrane-proximal external region (MPER) are crucial for viral neutralization.
- Antibodies like 4E10, VRC42.01, and PGZL1 share germline genes and a convergent evolution motif (111.2GW111.3) for enhanced potency.
Purpose of the Study:
- To investigate why the CAP206-CH12 antibody, despite sharing germline genes and showing convergent evolution, has limited neutralization breadth and potency.
- To map the epitope of CAP206-CH12 and compare it to other MPER-directed bNAbs.
Main Methods:
- Longitudinal sequencing of the CAP206-CH12 lineage.
- Mutagenesis of CAP206-CH12 to introduce the GWGW motif.
- Viral mutagenesis to map the CAP206-CH12 epitope.
Main Results:
- Mutagenesis of CAP206-CH12 to 111.2GW111.3 modestly improved potency but did not match other bNAbs.
- CAP206-CH12 binds to a variable residue (D674), while other bNAbs bind conserved residues (W672, F673, T676, W680).
- Differences in epitope binding orientation explain the variations in breadth and potency among these MPER-directed antibodies.
Conclusions:
- Shared germline genes and convergent evolution do not guarantee broad neutralization if epitope binding orientation differs.
- The dependence on variable versus conserved residues dictates the neutralization capabilities of MPER-directed antibodies.
- Findings inform the design of HIV vaccines targeting the MPER epitope.
