Group B Streptococcus Capsular Polysaccharides (None)

Group B Streptococcus (GBS) capsular polysaccharides (CPS) are high molecular weight carbohydrate polymers that form a capsule surrounding the bacterial cell. This capsule is a major virulence factor, enabling GBS to evade host immune defenses, particularly by inhibiting phagocytosis. The CPS defines the serotype of GBS and is essential for its pathogenicity. There are at least ten known GBS capsular serotypes: Ia, Ib, II, III, IV, V, VI, VII, VIII, and IX. The capsule’s primary function is to prevent opsonophagocytosis by masking underlying bacterial antigens from immune detection. Protective antibodies target specific epitopes within these polysaccharides—especially those containing sialic acid—which has driven development of conjugate vaccines using purified or synthetic versions of these structures.

Other names

GBS CPSGroup B Strep CPSStreptococcus agalactiae capsular polysaccharide

Antibodies targeting CPS promote opsonization and phagocytosis.