Anti-Le a monoclonal antibody SPM 522 recognizes an extended Le a epitope

• Published in: Bioorganic & medicinal chemistry Vol. 56; p. 116628
• Main Authors: Jegatheeswaran, Sinthuja, Guillemineau, Mickael, Giovane, Richard, Borrillo, Louis, Liao, Liang, Kuir, Deng, Auzanneau, France-Isabelle
• Format: Journal Article
• Language: English
• Published: England 15.02.2022
• Subjects: Antibodies, Monoclonal - chemistry; Antibodies, Monoclonal - immunology; Carbohydrate Conformation; Carbohydrate Sequence; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Epitopes - immunology; Glycoconjugates - chemical synthesis; Glycoconjugates - chemistry; Glycoconjugates - immunology; Humans; Molecular Structure; Structure-Activity Relationship; Lewis A; LewisALewisX; SPM522 epitope; ELISA; Tumor-associated carbohydrate antigens
• DOI: 10.1016/j.bmc.2022.116628

Insights into the differential binding characteristics of anti-Le and anti-Le Le monoclonal antibodies (mAbs) provide information to develop Le Le -based cancer immunotherapeutics while avoiding anti-Le autoimmune reactions. We characterized the epitope recognized by anti-Le mAb SPM 522. We synthesized the Le 6-aminohexyl glycoside and report experimental evidence of a minor conformation in solution. The Le and three other 6-aminohexyl glycosides were conjugated to BSA and titration experiments with SPM 522 show that: 1. SPM 522 binds to Le Le better than to Le ; 2. the non-reducing Le galactosyl residue is essential to binding. Competitive ELISA experiments using a panel of tri- to pentasaccharide fragments of Le Le as well as Le analogues indicate that: 1. the Le β-d-galactosyl α hydrophobic patch is crucial to binding; 2. the Le fucosyl residue contributes to binding; 3. the Le d-galactosyl residue also contributes to binding. These results indicate that anti-Le mAb SPM 522 recognizes the Le [1,3]-β-d-Gal tetrasaccharide. We propose that a major recognition element is the extended hydrophobic surface defined by the Le -β-d-Gal residue extending to the α faces of the β-d-GlcNAc and β-d-Gal residues.