Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia.
Tick-induced Allergies Research and Awareness Centre, Sydney, NSW 2065, Australia.
Proc Natl Acad Sci U S A. 2022 Jul 12;119(28):e2123212119. doi: 10.1073/pnas.2123212119. Epub 2022 Jul 8.
Humans lack the capacity to produce the Galα1-3Galβ1-4GlcNAc (α-gal) glycan, and produce anti-α-gal antibodies upon exposure to the carbohydrate on a diverse set of immunogens, including commensal gut bacteria, malaria parasites, cetuximab, and tick proteins. Here we use X-ray crystallographic analysis of antibodies from α-gal knockout mice and humans in complex with the glycan to reveal a common binding motif, centered on a germline-encoded tryptophan residue at Kabat position 33 (W33) of the complementarity-determining region of the variable heavy chain (CDRH1). Immunoglobulin sequencing of anti-α-gal B cells in healthy humans and tick-induced mammalian meat anaphylaxis patients revealed preferential use of heavy chain germline IGHV3-7, encoding W33, among an otherwise highly polyclonal antibody response. Antigen binding was critically dependent on the presence of the germline-encoded W33 residue for all of the analyzed antibodies; moreover, introduction of the W33 motif into naive IGHV3-23 antibody phage libraries enabled the rapid selection of α-gal binders. Our results outline structural and genetic factors that shape the human anti-α-galactosyl antibody response, and provide a framework for future therapeutics development.
人类缺乏产生 Galα1-3Galβ1-4GlcNAc（α-半乳糖）聚糖的能力，并且在接触到包括共生肠道细菌、疟原虫、西妥昔单抗和蜱蛋白等多种免疫原上的碳水化合物时会产生抗 α-半乳糖的抗体。在这里，我们使用 X 射线晶体学分析来自 α-半乳糖敲除小鼠和人类与聚糖结合的抗体，揭示了一个共同的结合基序，该基序围绕着位于互补决定区的重链（CDRH1）Kabat 位置 33 的胚系编码色氨酸残基（W33）为中心。对健康人类和蜱诱导的哺乳动物肉过敏患者的抗 α-半乳糖 B 细胞进行免疫球蛋白测序表明，在高度多克隆抗体反应中，优先使用编码 W33 的重链胚系 IGHV3-7。所有分析的抗体的抗原结合都严重依赖于胚系编码的 W33 残基的存在；此外，将 W33 基序引入到幼稚的 IGHV3-23 抗体噬菌体文库中，能够快速选择 α-半乳糖结合物。我们的研究结果概述了影响人类抗 α-半乳糖基抗体反应的结构和遗传因素，并为未来的治疗药物开发提供了框架。
