Group B Streptococcus serotype III capsular polysaccharide antigen (GBS III CPS)

Group B Streptococcus (GBS) serotype III capsular polysaccharide (CPS) is a critical virulence factor of Streptococcus agalactiae, particularly associated with late-onset neonatal meningitis and sepsis (Shabayek & Spellerberg, 2018). The CPS forms the outermost layer of the bacterium, providing a physical barrier that inhibits C3b deposition and subsequent phagocytosis by host immune cells (Lewis et al., 2004). Structurally, the serotype III CPS is characterized by a repeating pentasaccharide unit containing a terminal sialic acid residue, which mimics host glycans to evade immune detection. As a primary target for vaccine development, it is often conjugated to carrier proteins like CRM197 to enhance immunogenicity in vulnerable populations such as pregnant women (Kobayashi et al., 2021). Therapeutic strategies focus on eliciting opsonophagocytic antibodies that neutralize the protective effect of the capsule, allowing for effective bacterial clearance and providing passive immunity to newborns via transplacental antibody transfer (Hillier et al., 2019).

Other names

Streptococcus agalactiae serotype III capsular polysaccharideGBS type III polysaccharideType III capsular polysaccharide of Group B StreptococcusS. agalactiae serotype III CPS

Induction of serotype-specific opsonophagocytic IgG antibodies that facilitate bacterial clearance by the host immune system through complement-mediated phagocytosis.