Streptococcus agalactiae capsular polysaccharide serotype Ia (GBS CPS Ia)

Streptococcus agalactiae capsular polysaccharide serotype Ia (GBS CPS Ia) is a critical virulence factor and a primary target for vaccine development against Group B Streptococcus (GBS). GBS is a leading cause of neonatal sepsis, meningitis, and pneumonia, often transmitted from mother to infant during childbirth [1][2]. The CPS Ia structure is a high-molecular-weight polymer composed of a repeating unit of glucose, galactose, N-acetylglucosamine, and a terminal sialic acid residue. This sialic acid component is essential for bacterial survival as it mimics human cell surface glycans, allowing the pathogen to evade the host's alternative complement pathway and resist opsonophagocytosis [3][4]. Because the capsule is the outermost layer of the bacterium and is highly immunogenic when conjugated to carrier proteins, it serves as the basis for several multivalent conjugate vaccines currently in clinical trials, such as Pfizer's GBS6 [5][6]. These vaccines aim to induce maternal IgG antibodies that are transplacentally transferred to the fetus, providing passive immunity to the newborn during the period of highest vulnerability [1][5]. References: [1] CDC. "Group B Strep (GBS)." [2] WHO. "Group B Streptococcus (GBS) Vaccine Development." [3] PubMed: Wessels, M.R., et al. (1989). "Structure and immunochemistry of the capsular polysaccharides of Type Ia and Ib Group B streptococci." [4] PubMed: Lewis, A.L., et al. (2004). "The terminal alpha2-3-linked sialic acid of the group B Streptococcus capsular polysaccharide is required for host cell-surface receptor binding." [5] Pfizer. "GBS6: A Hexavalent Group B Streptococcus Conjugate Vaccine Candidate." [6] PubMed: Buurman, E.T., et al. (2019). "A Novel Hexavalent Capsular Polysaccharide Conjugate Vaccine for the Prevention of Group B Streptococcal Disease in Infants."

Other names

Group B Streptococcus capsular polysaccharide serotype IaS. agalactiae type Ia polysaccharideGBS serotype Ia CPSType Ia capsular polysaccharide of Group B Streptococcus

Induction of protective opsonophagocytic antibodies (IgG) that recognize and bind to the bacterial capsule, facilitating clearance by host immune cells.