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Updated: Jun 26, 2026
Peptide Scanning-assisted Identification of a Monoclonal Antibody-recognized Linear B-cell Epitope
Published on: March 24, 2017
Epitope mapping of a chimeric CD137 mAb: a necessary step for assessing the biologic relevance of non-human primate
Siaw-Lin Chan1, Caroline J Voskens, Wei Lin
1Department of Otorhinolaryngology-Head and Neck Surgery, University of Maryland School of Medicine, 685 West Baltimore Street, HSFI Rm332, Baltimore, MD 21201, USA.
Abstract:
Antibody based manipulation of the CD137 (4-1BB) co-signaling pathway is an attractive option for the treatment of cancer and autoimmune disease. We developed a chimeric anti-human CD137 monoclonal antibody (GG) and characterized its function. As a component of planned preclinical studies, we evaluated the binding of GG to activated peripheral blood mononuclear cells (PBMCs) from cynomolgus macaque and baboon against human. Interestingly, GG only recognized human CD137, while a commercial anti-CD137 mAb (4B4-1), recognized activated PBMCs from both human and non-human primates (NHP). Subsequent analysis revealed that the amino acid sequence of CD137 is largely conserved between primate species ( approximately 95% identical), with the extracellular domain differing by only 9-10 amino acids. Based on these data, we generated mutant constructs in the extracellular domain, replacing NHP with human CD137 sequences, and identified 3 amino acids critical for GG binding. These residues are likely part of a conformational epitope, as a peptide spanning this region is unable to block mAb binding. These data demonstrate that subtle sequence variations of defined co-stimulatory molecules amongst primate species can be employed as a strategy for mapping residues necessary for antibody binding to conformational epitopes.
Insights
A novel chimeric antibody targets human CD137 (4-1BB) but not non-human primates due to specific amino acid differences. This finding aids in mapping antibody binding sites on conformational epitopes for therapeutic development.
Area of Science:
- Immunology
- Molecular Biology
- Biotechnology
Background:
- Antibody therapies targeting the CD137 (4-1BB) co-signaling pathway show promise for cancer and autoimmune disease treatment.
- Developing specific antibodies requires understanding cross-species reactivity and molecular differences.
Purpose of the Study:
- To characterize a new chimeric anti-human CD137 monoclonal antibody (GG).
- To investigate the binding specificity of GG against human and non-human primate (NHP) CD137.
- To identify key amino acid residues responsible for species-specific binding.
Main Methods:
- Developed a chimeric anti-human CD137 monoclonal antibody (GG).
- Evaluated GG binding to activated peripheral blood mononuclear cells (PBMCs) from humans and NHPs (cynomolgus macaque, baboon).
- Compared GG binding with a commercial anti-CD137 antibody (4B4-1).
- Generated mutant CD137 constructs with NHP sequences replaced by human sequences to map critical residues.
Main Results:
- The chimeric antibody GG specifically recognized human CD137, unlike the commercial antibody 4B4-1 which bound both human and NHP CD137.
- CD137 extracellular domains share ~95% sequence identity between humans and NHPs, with minor differences.
- Identified 3 critical amino acids in the extracellular domain responsible for GG binding, likely forming a conformational epitope.
Conclusions:
- Subtle sequence variations in co-stimulatory molecules across primate species can be exploited to map antibody binding sites.
- This strategy is valuable for developing precisely targeted antibody therapeutics, especially for preclinical studies.
- Understanding species-specific epitopes is crucial for antibody drug development and efficacy.
