Group B Streptococcus type III capsular polysaccharide (GBS type III CPS)

Group B Streptococcus type III capsular polysaccharide is a complex surface carbohydrate polymer found on the cell envelope of Group B Streptococcus (GBS) serotype III, a major pathogen in neonates. The polysaccharide’s repeating unit comprises a trisaccharide backbone of glucose, N-acetylglucosamine, and galactose, with a side branch consisting of sialic acid and galactose[5][1]. The presence of terminal sialic acid residues is critical for the polysaccharide’s function, inhibiting activation of the alternative complement pathway and enabling bacterial evasion of host immunity[3][4]. This molecule is the principal antigenic determinant used in the development of conjugate vaccines, which link the polysaccharide to a carrier protein to enhance immunogenicity and generate protective antibody responses[1][5][8]. These vaccines are under active development for the prevention of neonatal GBS disease, as higher maternal antibody levels against this polysaccharide reduce the risk of neonatal infection[8]. The capsular polysaccharide type III is considered a validated therapeutic target for vaccine strategies but is not a classic receptor, enzyme, or transporter; it is a bacterial surface carbohydrate virulence factor and antigen.

Other names

GBS type III polysaccharideGroup B Streptococcus serotype III capsuleGBSIII capsular polysaccharideGBS type III CPS

Induction of opsonizing, protective antibodies when delivered as a conjugate vaccine antigen[1][5][8].