Salmonella enterica Typhi Vi capsular polysaccharide (Vi antigen)

The Vi capsular polysaccharide is a high-molecular-weight linear homopolymer of α-1,4-linked 2-deoxy-2-N-acetylgalactosaminuronic acid residues, variably O-acetylated at the C3 position, anchored to the surface of Salmonella enterica Typhi via a unique terminal lipid structure. This antigen forms a protective capsule critical for virulence: it enables S. Typhi to evade neutrophil phagocytosis, block complement activation, and modulate host immune responses by binding to specific host receptors such as DC-SIGN on macrophages and prohibitin-related complexes on intestinal epithelial cells. Its antiphagocytic and anti-inflammatory properties facilitate immune evasion, intracellular survival, and pathogenesis. The purified Vi antigen is a clinically validated component of several typhoid vaccines and is used as both a therapeutic and diagnostic target

Other names

Vi antigenVi capsular polysaccharideVi CPSVi polysaccharide

Vaccines: Induce anti-Vi antigen antibody responses, conferring protective immunity by neutralizing S. Typhi and preventing infection. Modulates host immune recognition: Prevents complement deposition, inhibits neutrophil phagocytosis, impairs neutrophil chemotaxis, reduces inflammatory signaling in epithelial cells, binds DC-SIGN to promote anti-inflammatory macrophage responses