Synthesis and Preliminary Immunological Evaluation of a Pseudotetrasaccharide Related to a Repeating Unit of the Streptococcus pneumoniae Serotype 6A Capsular Polysaccharide

• Published in: Frontiers in Molecular Biosciences
• Main Authors: Elena V. Sukhova, Dmitry V. Yashunsky, Ekaterina A. Kurbatova, Elina A. Akhmatova, Yury E. Tsvetkov, Nikolay E. Nifantiev
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2021-12-01
• Subjects: Streptococcus pneumoniae serotype 6A; capsular polysaccharide; conjugate vaccines; repeating unit; phosphodiester; synthesis
• Online Access: https://www.frontiersin.org/articles/10.3389/fmolb.2021.754753/full

2-Aminoethyl glycoside of the pseudotetrasaccharide α-d-Glcp-(1→3)-α-l-Rhap-(1→3)-d-Rib-ol-(5-P-2)-α-d-Galp corresponding to a repeating unit of the Streptococcus pneumoniae type 6A capsular polysaccharide has been synthesized. A suitably protected pseudotrisaccharide α-d-Glcp-(1→3)-α-l-Rhap-(1→3)-d-Rib-ol with a free 5-OH group in the ribitol moiety and a 2-OH derivative of 2-trifluoroacetamidoethyl α-d-galactopyranoside have been efficiently prepared and then connected via a phosphate bridge using the hydrogen phosphonate procedure. Preliminary immunological evaluation of this pseudotetrasaccharide and the previously synthesized pseudotetrasaccharide corresponding to a repeating unit of the capsular polysaccharide of S. pneumoniae serotype 6B has shown that they contain epitopes specifically recognized by anti-serogroup 6 antibodies and are able to model well the corresponding capsular polysaccharides. Conjugates of the synthetic pseudotetrasaccharides with bovine serum albumin were shown to be immunogenic in mice.