B-cell receptor recognizing Streptococcus pneumoniae serotype 4 capsular polysaccharide (BCR-Sp4-CPS)

B-cell receptors (BCRs) recognizing Streptococcus pneumoniae serotype 4 capsular polysaccharide are specialized membrane-bound immunoglobulins essential for the adaptive immune defense against pneumococcal disease. These receptors specifically bind to the unique repeating oligosaccharide units of the serotype 4 capsule, which consists of a sequence of N-acetyl-D-mannosamine, D-galactose, N-acetyl-L-fucosamine, and D-glucose with a pyruvate acetal modification (Source: Jones et al., 1991, Carbohydrate Research). The capsule is a primary virulence factor that allows the bacterium to evade host phagocytosis; therefore, BCR-mediated recognition is the first step in generating protective humoral immunity. When engaged by polysaccharide antigens—particularly those conjugated to carrier proteins like CRM197 in modern vaccines—these BCRs initiate signaling that leads to the production of high-affinity IgG antibodies (Source: Pollard et al., 2009, Nature Reviews Immunology). These antibodies facilitate the clearance of the pathogen through opsonophagocytosis, effectively preventing invasive conditions such as pneumonia, meningitis, and sepsis (Source: CDC, Pneumococcal Disease). This target is central to the efficacy of widely used vaccines like PCV13 and PCV20, which aim to expand the repertoire of B cells capable of responding to this specific serotype. Understanding the binding dynamics and clonal selection of these BCRs is vital for monitoring vaccine-induced immunity and developing next-generation immunotherapies.

Other names

Anti-pneumococcal serotype 4 BCRSp4-specific B-cell receptorStreptococcus pneumoniae serotype 4 capsular polysaccharide-binding B-cell receptorAnti-Sp4 BCR

Vaccine antigens containing the serotype 4 capsular polysaccharide bind to and cross-link specific B-cell receptors, inducing intracellular signaling cascades that lead to B-cell proliferation, isotype switching, and differentiation into memory B cells and antibody-secreting plasma cells.