Salmonella enterica serovar Typhi Vi capsular antigen (None)

The Vi capsular antigen is a surface-expressed polysaccharide unique to *Salmonella enterica* serovar Typhi, the causative agent of typhoid fever. It is a major virulence factor that distinguishes S. Typhi from most other Salmonella serovars. The antigen is a linear polymer of α-1,4-linked 2-deoxy-2-N-acetylgalacturonic acid residues, variably O-acetylated at the C-3 position. It confers antiopsonic and antiphagocytic properties, reducing proinflammatory cytokine secretion and increasing resistance to oxidative killing. The Vi antigen is a validated target for licensed typhoid vaccines and an active focus area for next-generation vaccine development and antivirulence therapies.

Other names

Vi antigenVi polysaccharideVi capsule

Vi polysaccharide vaccine: Elicits anti-Vi antibodies that promote complement deposition and monocyte phagocytosis. Vi conjugate vaccines: Induce T-cell dependent immune response leading to improved antibody production and longer-lasting immunity.