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

The Group B Streptococcus (GBS) type III capsular polysaccharide (CPS) conformational epitope is a critical antigenic structure found on the surface of Streptococcus agalactiae, a leading cause of neonatal sepsis and meningitis. This epitope is characterized by a repeating unit of glucose, galactose, and N-acetylglucosamine, with a terminal sialic acid residue that is essential for its unique helical conformation and biological activity. The sialic acid residues mimic host cell surfaces, allowing the bacteria to evade the host's innate immune system by inhibiting the alternative complement pathway. As a therapeutic target, the type III CPS is the primary component of several conjugate vaccines currently in clinical development, where it is linked to carrier proteins to induce T-cell dependent immune responses. Antibodies directed against this specific conformational epitope provide protection by promoting opsonophagocytosis and subsequent bacterial killing. Because type III GBS is disproportionately associated with late-onset neonatal meningitis, targeting this epitope is a major focus for maternal immunization strategies aimed at providing passive immunity to newborns. Research indicates that the structural integrity of the polysaccharide, particularly its sialylation, is vital for the recognition by protective monoclonal antibodies.

Other names

Streptococcus agalactiae type III capsular polysaccharideGBS type III CPSType III GBS polysaccharide antigenSialylated type III GBS capsular polysaccharide

Induction of opsonophagocytic antibodies that facilitate the clearance of Streptococcus agalactiae by neutrophils and macrophages.