Synthesis and immunological study of tetrasaccharide repeating units of capsular polysaccharide of Group B Streptococcus serotype VIII and their protein conjugates

This study reports the efficient synthesis of three tetrasaccharide derivatives of Group B Streptococcus (GBS) serotype VIII capsular polysaccharide with alternative glycan sequences and spacer chains through a convergent chemical glycosylation manner or a one-pot three-enzyme assembly protocol. Using bifunctional glutarate ester as the linker, these synthesized oligosaccharides were efficiently conjugated with recombinant ScpA193 protein, generating the resultant oligosaccharide-ScpA193 conjugates with desirable carbohydrate loading. ELISA analysis of the antisera obtained from mice inoculated with the synthetic glycoconjugates showed the elicitation of strong oligosaccharide-specific immunoglobulin G (IgG) antibodies, suggesting the potential of the synthesized oligosaccharides for use in the development of GBS vaccines.