Synthetic, Zwitterionic Sp1 Oligosaccharides Adopt a Helical Structure Crucial for Antibody Interaction

Qingju Zhang, Ana Gimeno, Darielys Santana, Zhen Wang, Yury Valdés-Balbin, Laura M. Rodríguez-Noda, Thomas Hansen, Li Kong, Mengjie Shen, Herman S. Overkleeft, Vicente Vérez-Bencomo, Gijsbert A. van der Marel, Jesús Jiménez-Barbero, Fabrizio Chiodo, Jeroen D. C. Codée

Research output: Contribution to journalArticleAcademicpeer-review


The zwitterionic Streptococcus pneumoniae serotype 1 polysaccharide (Sp1) is an important anchor point for our immune system to act against streptococcal infections. Antibodies can recognize Sp1 saccharides, and it has been postulated that Sp1 can elicit a T-cell-dependent immune reaction as it can be presented by MHC-II molecules. To unravel the molecular mode of action of this unique polysaccharide we here describe the chemical synthesis of a set of Sp1 fragments, ranging from 3 to 12 monosaccharides in length. We outline a unique synthetic approach to overcome the major synthetic challenges associated with the complex Sp1 structure and provide a stereoselective route of synthesis for the oligosaccharide backbone as well as a strategy to introduce the carboxylic acid functions. Molecular dynamics (MD) simulations together with NMR spectroscopy studies reveal that the oligosaccharides take up helical structures with the nona- and dodecasaccharide completing a full helical turn. The 3D structure of the oligosaccharides coincides with the topology required for good interaction with anti-Sp1 antibodies, which has been mapped in detail using STD-NMR. Our study has revealed the Sp1 nona- and dodecasaccharides as promising synthetic antigens, displaying all (3D) structural elements required to mimic the natural polysaccharide and required to unravel the molecular mode of action of these unique zwitterionic polysaccharides.
Original languageEnglish
Pages (from-to)1407-1416
JournalACS Central Science
Issue number8
Publication statusPublished - 24 Jul 2019

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