Group B Streptococcus serotype II capsular polysaccharide (GBS II CPS) (GBS II CPS)

Group B Streptococcus (GBS) serotype II capsular polysaccharide (CPS) is a critical virulence factor and a primary target for vaccine development against Streptococcus agalactiae (NIH, 2025). This complex polysaccharide forms a protective capsule that allows the bacterium to evade the host immune system by inhibiting opsonophagocytosis and complement activation (Wikipedia, 2023). Serotype II is one of the six most prevalent serotypes (Ia, Ib, II, III, IV, V) responsible for the majority of invasive GBS disease cases in neonates and pregnant women worldwide (Gavi, 2023). Therapeutic strategies targeting this antigen primarily involve conjugate vaccines, such as Pfizer's hexavalent GBS6, which link the polysaccharide to a carrier protein like CRM197 to enhance immunogenicity (Pfizer, 2023). These vaccines aim to induce high titers of serotype-specific IgG antibodies in pregnant women, which are then transplacentally transferred to the fetus to provide passive protection (NIH, 2023). This passive immunity is essential for preventing early-onset and late-onset neonatal sepsis, meningitis, and pneumonia (Medscape, 2024). Clinical trials have demonstrated that targeting the serotype II CPS can elicit robust, functional antibody responses that correlate with protection (Pfizer, 2023). As a vaccine target, it represents a significant opportunity to reduce the global burden of GBS-associated morbidity and mortality (Gavi, 2023).

Other names

Streptococcus agalactiae serotype II capsular polysaccharideGBS II CPSType II capsular polysaccharide of Group B StreptococcusGBS serotype II CPS

Induction of serotype-specific opsonophagocytic IgG antibodies that facilitate bacterial clearance by host immune cells.