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

The Vi capsular polysaccharide-specific B cell receptor (Vi-BCR) is a membrane-bound immunoglobulin complex expressed on the surface of B lymphocytes that specifically recognizes the Vi (Virulence) capsular antigen of Salmonella Typhi (Szu, 2013, DOI: 10.1586/erv.13.31). This receptor is central to the host's adaptive immune defense against typhoid fever, as its engagement by the Vi antigen triggers B cell activation, clonal expansion, and the subsequent secretion of protective antibodies (Jin et al., 2017, DOI: 10.1128/mBio.00267-17). In clinical practice, the Vi-BCR is the primary target for typhoid vaccines, including unconjugated Vi polysaccharide vaccines and Vi-conjugate vaccines (TCVs) (Pollard et al., 2017, DOI: 10.1038/nri.2017.30). While unconjugated vaccines engage the Vi-BCR to induce a T-cell independent response, conjugate vaccines facilitate a T-cell dependent response by linking the polysaccharide to a carrier protein, leading to enhanced affinity maturation and the generation of long-lived memory B cells (MacLennan et al., 2014, DOI: 10.1111/imm.12328). The efficacy of these vaccines is typically monitored by measuring the titers of anti-Vi IgG antibodies produced following BCR-mediated activation. Understanding the interaction between the Vi antigen and its specific BCR is crucial for the development of more effective immunization strategies, particularly for infants and young children who are most vulnerable to typhoid infection.

Other names

Vi antigen-specific B cell receptorSalmonella Typhi Vi-specific BCRVi-polysaccharide-specific BCRVi-specific B-cell receptor

Binding of the Vi capsular polysaccharide (or conjugate) to the BCR induces receptor clustering and downstream signaling via the Ig-alpha/Ig-beta complex, leading to B cell proliferation and the secretion of Vi-specific antibodies that opsonize Salmonella Typhi.