Salmonella paratyphi A O-antigen polysaccharide (O:2 antigen)

Salmonella paratyphi A O-antigen polysaccharide is a critical somatic antigen located on the outer membrane of the Gram-negative bacterium Salmonella enterica serovar Paratyphi A [1, 12]. It is a key component of the lipopolysaccharide (LPS) and consists of a repeating trisaccharide backbone of rhamnose, mannose, and galactose, with a paratose side chain that defines the O:2 serospecificity [3, 8]. This polysaccharide plays a vital role in bacterial virulence and serves as the primary target for the development of conjugate vaccines against paratyphoid fever, a major cause of enteric fever in South and Southeast Asia [1, 4]. Because the O-antigen alone is T-cell independent and poorly immunogenic in infants, it is typically conjugated to carrier proteins like tetanus toxoid or CRM197 to induce a robust, T-cell dependent immune response [2, 9]. Current therapeutic strategies focus on bivalent vaccines that combine this O-antigen with the Vi antigen of Salmonella Typhi to provide broad protection against enteric fever [6, 7]. Clinical candidates such as O:2-CRM197 have demonstrated the ability to elicit antibodies with potent bactericidal activity against diverse clinical isolates [3, 16].

Other names

Salmonella Paratyphi A O-polysaccharideSPA O-antigenO:2 somatic antigenO-specific polysaccharide (OPS)Salmonella enterica serovar Paratyphi A lipopolysaccharide O-antigen

Induction of protective IgG antibodies that facilitate serum bactericidal activity and opsonophagocytosis against Salmonella Paratyphi A.