Department of Chemical and Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel.
Department of Biomolecular Sciences, Weizmann Institute of Science, 76100 Rehovot, Israel.
J Mol Biol. 2021 Jul 23;433(15):167099. doi: 10.1016/j.jmb.2021.167099. Epub 2021 Jun 11.
Glycans decorate the cell surface, secreted glycoproteins and glycolipids, and altered glycans are often found in cancers. Despite their high diagnostic and therapeutic potential, however, glycans are polar and flexible molecules that are quite challenging for the development and design of high-affinity binding antibodies. To understand the mechanisms by which glycan neoantigens are specifically recognized by antibodies, we analyze the biomolecular recognition of the tumor-associated carbohydrate antigen CA19-9 by two distinct antibodies using X-ray crystallography. Despite the potential plasticity of glycans and the very different antigen-binding surfaces presented by the antibodies, both structures reveal an essentially identical extended CA19-9 conformer, suggesting that this conformer's stability selects the antibodies. Starting from the bound structure of one of the antibodies, we use the AbLIFT computational algorithm to design a variant with seven core mutations in the variable domain's light-heavy chain interface that exhibits tenfold improved affinity for CA19-9. The results reveal strategies used by antibodies to specifically recognize glycan antigens and show how automated antibody-optimization methods may be used to enhance the clinical potential of existing antibodies.
聚糖修饰细胞表面、分泌型糖蛋白和糖脂，且异常的聚糖通常存在于癌症中。然而，尽管它们具有很高的诊断和治疗潜力，但聚糖是极性且灵活的分子，这给高亲和力结合抗体的开发和设计带来了很大的挑战。为了了解糖基新抗原被抗体特异性识别的机制，我们使用 X 射线晶体学分析两种不同抗体对肿瘤相关碳水化合物抗原 CA19-9 的生物分子识别。尽管聚糖具有潜在的可变性，且两种抗体呈现出非常不同的抗原结合表面，但这两种结构都揭示了一个基本相同的扩展 CA19-9 构象，这表明这种构象的稳定性选择了抗体。从其中一个抗体的结合结构出发，我们使用 AbLIFT 计算算法设计了一个在可变域的轻链-重链界面有七个核心突变的变体，该变体对 CA19-9 的亲和力提高了十倍。结果揭示了抗体特异性识别糖基抗原所使用的策略，并展示了如何使用自动化抗体优化方法来增强现有抗体的临床潜力。
