Synthesis and Immunological Studies of Oligosaccharides that Consist of the Repeating Unit of Streptococcus pneumoniae Serotype 3 Capsular Polysaccharide

Abstract

A highly convergent and efficient strategy was developed for the chemical synthesis of complex oligosaccharides of Streptococcus pneumoniae type 3 capsular polysaccharides that contain multiple glucuronic acid units. Once the oligoglucosides were efficiently and stereoselectively assembled, the designated glucose units were regioselectively oxidized to glucuronic acid in one step at the final synthetic stage, which helped avoid difficult glycosylations that involved glucuronic acid. The target oligosaccharides had a free amino group at the reducing terminus and varied caps at the non-reducing terminus to enable further modification and structure-activity relationship studies. Immunological evaluations of the oligosaccharide-tetanus toxoid conjugates showed that they elicited robust T-cell-dependent immunoglobulin G antibody responses and that the sugar chain length had a major impact on their immunological properties. In particular, the penta- and hexasaccharides were identified as promising antigens for vaccine development.

Synthesis of a Pentasaccharide Repeating Unit of Lipopolysaccharide Derived from Virulent E. coli O1 and Identification of a Glycotope Candidate of Avian Pathogenic E. coli O1

“…The resulting dialysates were lyophilized to provide 37 – 39 as white fluffy solids. The carbohydrate loading values [27] of these conjugates were determined by MALDI‐TOF MS analysis, and the results are shown in Table 1. According to MALDI TOF MS data (Supporting Information, Figure S1), 1 ‐BSA conjugate 37 contained 11.2 pentasaccharide residues per BSA molecule on average.…”

Synthesis of a Pentasaccharide Repeating Unit of Lipopolysaccharide Derived from Virulent E. coli O1 and Identification of a Glycotope Candidate of Avian Pathogenic E. coli O1

“…Forthe ELISA analysis of serum antibodies,bovine serum albumin (BSA)-glycan conjugates 37-39 were prepared by using the p-nitrophenol (PNP) activation method Angewandte Chemie (Scheme 6). [26] First, oligosaccharides 1-3 were reacted with known activated ester 32,w hich was used in large excess (7 equiv) to ensure the formation of monoamide-monoester products 33-35.Second, after size-exclusion column purification to remove any remaining reactant 32,compounds 33-35 were individually mixed with BSA (36)inphosphate-buffered saline solution (PBS,p H7.5, 4% DMF), and the reaction mixtures were kept at 25 8 8Cfor 18 hours to furnish the desired conjugates 37-39,which were dialyzed against distilled water to remove any remaining free sugars and salts.T he resulting dialysates were lyophilized to provide 37-39 as white fluffy solids.The carbohydrate loading values [27] of these conjugates were determined by MALDI-TOF MS analysis,a nd the results are shown in Table 1. According to MALDI TOFMS data (Supporting Information, Figure S1), 1-BSA conjugate 37 contained 11.2 pentasaccharide residues per BSA molecule To assess the antigenicity of APEC O1, ELISA tests using the synthetic glycoconjugates were conducted.…”

Synthetic Analogs of Streptococcus pneumoniae Capsular Polysaccharides and Immunogenic Activities of Glycoconjugates

“…Longer fragments of the serotype 3 CP (15) were synthesized, including up to four repeating units of this polysaccharide (compounds (23a-26a)) [89]. Among these ligands, there were oligosaccharides containing either glucose residue (23a, 24a) or glucuronic acid residue (25a, 26a) at the nonreducing end.…”