Østerlid Kitt Emilie, Sorieul Charlotte, Unione Luca, Li Sizhe, García-Sepúlveda Cristian, Carboni Filippo, Del Bino Linda, Berni Francesca, Arda Ana, Overkleeft Herman S, van der Marel Gijsbert A, Romano Maria Rosaria, Jiménez-Barbero Jesús, Adamo Roberto, Codée Jeroen D C
Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands.
Center for Cooperative Research in Biosciences (CIC bioGUNE), Basque Research and Technology Alliance (BRTA), 48160 Derio, Bizkaia, Spain.
J Am Chem Soc. 2025 Jan 22;147(3):2829-2840. doi: 10.1021/jacs.4c16118. Epub 2025 Jan 10.
is a Gram-positive bacterium that is responsible for severe nosocomial infections. The rise of multidrug-resistant strains, which can pose significant health threats, prompts the development of new treatment interventions, and much attention has been directed at the development of prophylactic and therapeutic vaccination strategies. Capsular polysaccharides (CPs) are key protective elements of the cell wall and have been proposed as promising candidate antigens. Thirteen different CP serotypes have been identified to date, of which types 5 and 8 are the most prominent. CP8 is composed of trisaccharide repeating units that are built up from an -acetyl-4--acetyl-d-mannosaminuronic acid, that carries a C-4--acetyl, an -acetyl-α-d-fucosamine, and an -acetyl-α-l-fucosamine. Synthetic oligosaccharides are valuable tools to unravel the immunogenicity of bacterial oligosaccharides at the molecular level. However, the rare monosaccharides, -glycosidic linkages, and -acetylation represent significant challenges for the synthesis of CP8 fragments. Here the stereoselective assembly of well-defined CP8 fragments, comprising a trimer, hexamer, nonamer, and dodecamer, is presented. This is the first time that fragments larger than a single repeating trisaccharide, which has been proven to be insufficient for antigenic activity, have been assembled. Structural studies have revealed a linear conformation for the oligosaccharides, with each trisaccharide repeat tilted ∼90° with respect to the flanking repeats, which is stabilized by the acetyl groups that prevent rotation around the glycosidic linkages. The -acetyl groups in each repeating unit point in the same direction, generating a hydrophobic flank in the trisaccharide repeats. We applied the oligomers to generate model glycoconjugate vaccine modalities, which we then used to raise anti-CP8 antibodies. The antibody interaction and immunization studies have revealed a clear length dependent structure-activity relationship for the oligosaccharides, with an oligosaccharide of at least three repeating units required for an adequate immune response.
是一种革兰氏阳性细菌，可导致严重的医院感染。多重耐药菌株的出现对健康构成重大威胁，促使人们开发新的治疗干预措施，预防性和治疗性疫苗接种策略的开发受到了广泛关注。荚膜多糖（CPs）是细胞壁的关键保护成分，被认为是有前景的候选抗原。迄今为止已鉴定出13种不同的CP血清型，其中5型和8型最为突出。CP8由三糖重复单元组成，这些单元由一个携带C-4-乙酰基的α-乙酰基-4-α-乙酰基-D-甘露糖醛酸、一个α-乙酰基-α-D-岩藻糖胺和一个α-乙酰基-α-L-岩藻糖胺构成。合成寡糖是在分子水平上揭示细菌寡糖免疫原性的宝贵工具。然而，稀有单糖、α-糖苷键和α-乙酰化对CP8片段的合成构成了重大挑战。本文展示了明确的CP8片段（包括三聚体、六聚体、九聚体和十二聚体）的立体选择性组装。这是首次组装出大于单个重复三糖的片段，单个重复三糖已被证明对抗原活性不足。结构研究表明寡糖呈线性构象，每个三糖重复单元相对于侧翼重复单元倾斜约90°，这通过防止糖苷键旋转的乙酰基得以稳定。每个重复单元中的α-乙酰基指向同一方向，在三糖重复单元中形成一个疏水侧翼。我们应用这些寡聚物生成模型糖缀合物疫苗形式，然后用其产生抗CP8抗体。抗体相互作用和免疫研究揭示了寡糖明显的长度依赖性构效关系，至少需要三个重复单元的寡糖才能产生足够的免疫反应。
