Vi-specific B-cell receptor (Vi-BCR)

The Vi-specific B-cell receptor (Vi-BCR) is a membrane-bound immunoglobulin complex expressed on the surface of a specialized subset of human B cells that specifically recognizes the Vi capsular polysaccharide of Salmonella enterica serovar Typhi (S. Typhi) (PMID: 28912503). This receptor is central to the adaptive immune response against typhoid fever, as the Vi capsule is a major virulence factor that shields the bacterium from host immune detection (PMID: 30206165). Upon binding to the Vi antigen—a linear polymer of α-1,4-linked N-acetylgalactosaminuronic acid—the Vi-BCR initiates intracellular signaling pathways that drive B-cell activation, clonal expansion, and differentiation into plasma cells that secrete anti-Vi antibodies (PMID: 25135964). In clinical practice, the Vi-BCR is the primary target for typhoid vaccines, including unconjugated polysaccharide vaccines (e.g., Typhim Vi) and Vi-conjugate vaccines (e.g., Typbar-TCV) (PMID: 31813631). While plain polysaccharide vaccines act as T-cell independent antigens, conjugate vaccines recruit T-cell help to induce high-affinity antibodies and long-lived memory B cells, providing superior protection in infants and young children (PMID: 29033302). Monitoring the frequency and affinity of Vi-specific BCRs serves as a critical biomarker for evaluating vaccine immunogenicity and the duration of protective immunity (PMID: 33432156).

Other names

Vi capsular polysaccharide-specific B-cell receptorSalmonella Typhi Vi-specific BCRVi-antigen-specific BCRVi-specific B-cell surface immunoglobulin

Antigen-mediated cross-linking of the B-cell receptor (BCR) triggers intracellular signaling pathways (e.g., via Lyn, Syk, and PLCγ2) that lead to B-cell activation, clonal expansion, and differentiation into antibody-secreting plasma cells and memory B cells.