Salmonella typhi antigens (S. typhi antigens)

Salmonella typhi antigens are molecular components of the bacterium Salmonella enterica serovar Typhi, the causative agent of typhoid fever. The most clinically significant of these is the Vi capsular polysaccharide, which acts as a virulence factor by shielding the bacteria from the host's immune system, specifically preventing phagocytosis and complement-mediated lysis (Source: StatPearls, PMID: 32119431). Other key antigens include the O (somatic) and H (flagellar) antigens, which are historically used in diagnostic serology such as the Widal test (Source: CDC). These antigens serve as the primary targets for typhoid vaccines, including live-attenuated oral vaccines (Ty21a) and injectable Vi-based vaccines. Modern Vi conjugate vaccines (TCVs) link the polysaccharide to a carrier protein to enhance immunogenicity, particularly in infants and young children, providing long-lasting protection against infection (Source: WHO). Understanding these antigens is crucial for both the prevention of enteric fever and the development of rapid diagnostic tools in endemic regions.

Other names

Vi capsular polysaccharideO antigenH antigenSomatic antigenFlagellar antigenVi antigen

Induction of active immunity through the production of specific antibodies (e.g., anti-Vi IgG) that facilitate opsonophagocytosis and neutralization of the bacteria.