B-cell receptor specific for Group B Streptococcus type III capsular polysaccharide (BCR-GBS-III-CPS)

The B-cell receptor specific for Group B Streptococcus (GBS) type III capsular polysaccharide is a membrane-bound immunoglobulin complex that recognizes the specific repeating carbohydrate units of Streptococcus agalactiae serotype III (Wessels et al., 1989, J Exp Med). This receptor is essential for the adaptive immune response against GBS, which is a leading cause of life-threatening neonatal infections including sepsis and meningitis (Baker et al., 2003, Arch Dis Child). When the receptor binds to the type III capsular polysaccharide (CPS), it initiates intracellular signaling that drives the production of protective IgG antibodies capable of opsonizing the bacteria for phagocytic clearance (Kobayashi et al., 2019, Lancet Infect Dis). In the context of drug development, this receptor is the primary target for conjugate vaccines, such as Pfizer's GBS6, which utilize the CPS antigen to stimulate long-lasting humoral immunity (Pfizer, 2023, ClinicalTrials.gov). Because the CPS is a T-cell independent antigen, therapeutic candidates often conjugate the polysaccharide to a carrier protein like CRM197 to ensure robust B-cell activation and memory formation through T-cell recruitment. Successful engagement of this receptor in pregnant women allows for the transplacental transfer of protective antibodies to the neonate, providing passive immunity during the first months of life.

Other names

GBS type III CPS-specific B-cell receptorAnti-GBS III BCRStreptococcus agalactiae type III capsular polysaccharide receptorB-cell receptor for GBS serotype III

Antigen binding to the B-cell receptor triggers a signaling cascade that leads to B-cell proliferation, differentiation into antibody-secreting plasma cells, and the generation of immunological memory.