Vi capsular polysaccharide of Salmonella enterica serovar Typhi (Vi antigen)

The Vi capsular polysaccharide of Salmonella enterica serovar Typhi is a linear homopolymer of variably O-acetylated α-1,4-linked N-acetylgalactosaminuronic acid residues. It forms a surface capsule that enhances bacterial virulence by evading complement-mediated immune responses, neutrophil chemotaxis and phagocytosis, and binding to the human DC-SIGN receptor on macrophages, which modulates inflammatory responses. The Vi antigen is the key protective component in subunit vaccines for typhoid fever. Genetic variation in capsule biosynthesis leads to distinct S. Typhi variants with different virulence[1][2][3][4][5][6].

Other names

Vi antigenVi capsuleVirulence capsular polysaccharideTyphoid capsule (rare)

Induction of immune response against Vi antigen (vaccines elicit anti-Vi antibodies, promoting opsonization and clearance of bacteria). Neutralization of capsule-mediated immune evasion.