Chemical Synthesis Elucidates the Key Antigenic Epitope of the Autism‐Related Bacterium Clostridium bolteae Capsular Octadecasaccharide. (2nd September 2020)

• Record Type: Journal Article
• Authors: Cai, Juntao; Hu, Jing; Qin, Chunjun; Li, Lingxin; Shen, Dacheng; Tian, Guangzong; Zou, Xiaopeng; Seeberger, Peter H.; Yin, Jian
• Is Part Of: Angewandte Chemie. Volume 132:Number 46(2020)
• Page Start: 20710
• Page End: 20718
• Publication Date: 2020-09-02
• Subjects: carbohydrates -- glycoconjugates -- immunology -- polysaccharides -- total synthesis; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202007209
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: The gut pathogen Clostridium bolteae has been associated with the onset of autism spectrum disorder (ASD). To create vaccines against C. bolteae, it is important to identify exact protective epitopes of the immunologically active capsular polysaccharide (CPS). Here, a series of C. bolteae CPS glycans, up to an octadecasaccharide, was prepared. Key to achieving the total syntheses is a [2+2] coupling strategy based on a β‐d ‐Rha p ‐(1→3)‐α‐d ‐Man p repeating unit that in turn was accessed by a stereoselective β‐d ‐rhamnosylation. The 4, 6‐ O ‐benzylidene‐induced conformational locking is a powerful strategy for forming a β‐d ‐mannose‐type glycoside. An indirect strategy based on C2 epimerization of β‐d ‐quinovoside was efficiently achieved by Swern oxidation and borohydride reduction. Sequential glycosylation, and regioselective and global deprotection produced the disaccharide and tetrasaccharide, up to the octadecasaccharide. Glycan microarray analysis of sera from rabbits immunized with inactivated C. bolteae bacteria revealed a humoral immune response to the di‐ and tetrasaccharide, but none of the longer sequences. The tetrasaccharide may be a key motif for designing glycoconjugate vaccines against C. bolteae . Abstract : To identify exact protective epitopes of the immunologically active capsular polysaccharide (CPS) of autism‐related bacterium Clostridium bolteae, a series of the CPS glycans, up to an octadecasaccharide, was chemically synthesized for the first time. Glycan microarray analysis of rabbit sera against inactivated C. bolteae revealed that the tetrasaccharide fragment of CPS may be a key motif for designing glycoconjugate vaccines against C. bolteae .