Synthesis of phosphorylated fragments of Streptococcus pneumoniae type 19F capsular polysaccharide
作者:Giuseppina Soliveri、Anna Bertolotti、Luigi Panza、Laura Poletti、Christopher Jones、Luigi Lay
DOI:10.1039/b205684d
日期:2002.10.1
Serotype 19F is one of the most virulent of the Streptococcus pneumoniae serotypes, causing meningitis, otitis media, septicemia and pneumonia. Effective protection against infection is mediated by antibodies directed against its capsular polysaccharide (CPS), composed of the trisaccharide repeating units (→4-β-D-ManpNAc-(1→4)-α-D-Glcp-(1→2)-α-L-Rhap-1→) bridged by phosphate diesters. Unfortunately, CPSs are typical T-independent type 2 immunogens. Therefore, the conjugation of putative saccharide haptens to a protein carrier, which invokes T-cell involvement, has proved to be extremely effective in enhancing the immune response. In a project aimed at ascertaining the role played by the different structural factors in the immunogenicity of new vaccines against Streptococcus pneumoniae type 19F, we planned the synthesis of a family of trisaccharide repeating unit derivatives where the phosphate group is a) absent; b) linked only to the rhamnose unit; or c) linked only to the N-acetylmannosamine unit. Compound of type a) and c) also bear an appropriate spacer for conjugation to the protein carrier. Moreover, the synthesis of a dimer of the CPS repeating unit, in which a phosphate diester bridges two repeating units, was carried out.
血清型19F是肺炎链球菌中最具毒力的血清型之一,能够引起脑膜炎、中耳炎、脓毒血症和肺炎。对感染的有效保护是通过针对其荚膜多糖(CPS)的抗体介导的,该多糖由三糖重复单元(→4-β-D-ManpNAc-(1→4)-α-D-Glcp-(1→2)-α-L-Rhap-1→)通过磷酸二酯桥接而成。不幸的是,CPS通常是T细胞非依赖性2型免疫原。因此,将假定的糖类半抗原与蛋白质载体结合,以激发T细胞参与,已被证明在增强免疫应答方面极为有效。在一个旨在确定不同结构因素在新疫苗对肺炎链球菌19F型免疫原性中所起作用的项目中,我们计划合成一系列三糖重复单元衍生物,其中磷酸基团a) 缺失;b) 仅与鼠李糖单元相连;或c) 仅与N-乙酰甘露糖胺单元相连。a型和c型化合物还带有适当的连接 spacer,以便与蛋白质载体结合。此外,还进行了CPS重复单元二聚体的合成,其中磷酸二酯桥接两个重复单元。