Glycoconjugate vaccines so far licensed are generally composed of a native or size-reduced capsular polysaccharide conjugated to carrier proteins. Detailed information on the structural requirements necessary for CPS recognition is becoming the key to accelerating the development of next-generation improved glycoconjugate vaccines. Structural glycobiology studies using oligosaccharides (OS) complexed with functional monoclonal antibodies represent a powerful tool for gaining information on CPS immunological determinants at the atomic level. Herein, the minimal structural epitope of Haemophilus influenzae type b (Hib) CPS recognized by a functional human monoclonal antibody (hmAb) is reported. Short and well-defined Hib oligosaccharides originating from the depolymerization of the native CPS have been used to elucidate saccharide–mAb interactions by using a multidisciplinary approach combining surface plasmon resonance (SPR), saturation transfer difference-nanomagnetic resonance (STD-NMR), and X-ray crystallography. Our study demonstrates that the minimal structural epitope of Hib is comprised within two repeating units (RUs) where ribose and ribitol are directly engaged in the hmAb interaction, and the binding pocket fully accommodates two RUs without any additional involvement of a third one. Understanding saccharide antigen structural characteristics can provide the basis for the design of innovative glycoconjugate vaccines based on alternative technologies, such as synthetic or enzymatic approaches.

中文翻译：

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鉴定 b 型流感嗜血杆菌荚膜多糖保护性表位的多学科结构方法

迄今为止获得许可的糖缀合疫苗通常由与载体蛋白缀合的天然或尺寸减小的荚膜多糖组成。有关 CPS 识别所需结构要求的详细信息正在成为加速开发下一代改良糖复合物疫苗的关键。使用寡糖 (OS) 与功能性单克隆抗体复合进行的结构糖生物学研究是在原子水平上获取 CPS 免疫决定因素信息的有力工具。在此，报道了功能性人单克隆抗体 (hmAb) 识别的 b 型流感嗜血杆菌(Hib) CPS的最小结构表位。源自天然 CPS 解聚的短而明确的 Hib 寡糖已被用于通过结合表面等离振子共振 (SPR)、饱和转移差-纳米磁共振 (STD-NMR) 和X射线晶体学。我们的研究表明，Hib 的最小结构表位由两个重复单元 (RU) 组成，其中核糖和核糖醇直接参与 hmAb 相互作用，并且结合袋完全容纳两个 RU，而无需第三个 RU 的任何额外参与。了解糖抗原的结构特征可以为基于替代技术（例如合成或酶促方法）设计创新糖复合物疫苗提供基础。