Epitope mapping of a chimeric CD137 mAb: a necessary step for assessing the biologic relevance of non‐human primate models |
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| Authors: | Siaw‐Lin Chan Caroline J Voskens Wei Lin Daniel G Schindler Agnes Azimzadeh Lai‐Xi Wang Rodney J Taylor Scott E Strome Dan H Schulze |
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| Institution: | 1. Department of Otorhinolaryngology‐Head and Neck Surgery, University of Maryland School of Medicine, 685 West Baltimore Street, HSFI Rm332, Baltimore, MD 21201, USA;2. Department of Pathology, University of Maryland School of Medicine, 10 S. Pine Street, MSTF Rm 856, Baltimore, MD 21201, USA;3. GTC Biotherapeutics Inc., 5 The Mountain Road, Framingham, MA 01701, USA;4. Department of Cardiac Surgery, University of Maryland School of Medicine, 10 S. Pine Street, MSTF Rm434C, Baltimore, MD 21201, USA;5. Department of Biochemistry and Molecular Biology, University of Maryland, IHV Basic Science/Vaccine, UMBI Medical Biotechnology Ctr, Room 8089, Baltimore, MD 21201, USA;6. Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 West Baltimore Street, HSFI Rm325D, Baltimore, MD 21201, USA |
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| 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 (～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. Copyright © 2009 John Wiley & Sons, Ltd. |
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| Keywords: | CD137 (4‐1BB) binding epitope non‐human primate monoclonal antibody co‐signaling |
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