Wall teichoic acids (WTAs) are glycopolymers decorating the surface of Gram-positive bacteria and potential targets for antibody-mediated treatments against Staphylococcus aureus, including methicillin-resistant (MRSA) strains. Through a combination of glycan microarray, synthetic chemistry, crystallography, NMR, and computational studies, we unraveled the molecular and structural details of fully defined synthetic WTA fragments recognized by previously described monoclonal antibodies (mAbs 4461 and 4497). Our results unveiled the structural requirements for the discriminatory recognition of α- and β-GlcNAc-modified WTA glycoforms by the complementarity-determining regions (CDRs) of the heavy and light chains of the mAbs. Both mAbs interacted not only with the sugar moiety but also with the phosphate groups as well as residues in the ribitol phosphate (RboP) units of the WTA backbone, highlighting their significant role in ligand specificity. Using elongated WTA fragments, containing two sugar modifications, we also demonstrated that the internal carbohydrate moiety of α-GlcNAc-modified WTA is preferentially accommodated in the binding pocket of mAb 4461 with respect to the terminal moiety. Our results also explained the recently documented cross-reactivity of mAb 4497 for β-1,3/β-1,4-GlcNAc-modified WTA, revealing that the flexibility of the RboP backbone is crucial to allow positioning of both glycans in the antibody binding pocket.

中文翻译：

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不同金黄色葡萄球菌壁磷壁酸糖型的抗体识别

壁磷壁酸 (WTA) 是修饰革兰氏阳性菌表面的糖聚合物，是抗体介导的金黄色葡萄球菌治疗的潜在靶标，包括耐甲氧西林 (MRSA) 菌株。通过聚糖微阵列、合成化学、晶体学、NMR 和计算研究的结合，我们揭示了先前描述的单克隆抗体（mAb 4461 和 4497）识别的完全定义的合成 WTA 片段的分子和结构细节。我们的结果揭示了通过 mAb 重链和轻链的互补决定区 (CDR) 区分识别 α- 和 β-GlcNAc 修饰的 WTA 糖型的结构要求。两种 mAb 不仅与糖部分相互作用，而且与磷酸基团以及 WTA 骨架的核糖醇磷酸 (RboP) 单元中的残基相互作用，突出了它们在配体特异性中的重要作用。使用包含两个糖修饰的加长 WTA 片段，我们还证明了 α-GlcNAc 修饰的 WTA 的内部碳水化合物部分相对于末端部分优先容纳在 mAb 4461 的结合口袋中。我们的结果还解释了最近记录的 mAb 4497 与 β-1,3/β-1,4-GlcNAc 修饰的 WTA 的交叉反应性，揭示了 RboP 主链的灵活性对于允许在抗体中定位两种聚糖至关重要装订口袋。