Salmonella Paratyphi A O:2 O-polysaccharide antigen (O:2 O-PS)

The Salmonella Paratyphi A O:2 O-polysaccharide antigen is the primary surface-exposed carbohydrate component of the lipopolysaccharide (LPS) in Salmonella enterica serovar Paratyphi A [2, 7]. It serves as a critical virulence factor and the immunodominant target for the host's humoral immune response during infection [4, 9]. Structurally, it consists of a repeating trisaccharide backbone of rhamnose, mannose, and galactose, with a characteristic paratose side chain that defines the O:2 serogroup specificity [2, 4]. Because S. Paratyphi A lacks the Vi capsular polysaccharide found in S. Typhi, the O:2 antigen is the central focus for developing paratyphoid vaccines [1, 3]. Current therapeutic strategies involve conjugating this polysaccharide to carrier proteins, such as CRM197 or tetanus toxoid, to enhance its immunogenicity and induce long-lasting T-cell dependent memory [3, 6]. These vaccines aim to elicit high titers of bactericidal antibodies that facilitate the clearance of the pathogen through opsonophagocytosis and complement activation [4, 7]. Clinical development of these conjugates is essential to address the rising global burden of paratyphoid fever and the emergence of multidrug-resistant bacterial strains [4, 10].

Other names

O:2 antigenO-specific polysaccharideSalmonella Paratyphi A O-antigenO:2 OAgO-polysaccharide (O:2)OSP

Induction of protective humoral immunity, specifically the production of bactericidal IgG antibodies that mediate opsonophagocytosis and complement-dependent killing of the bacteria [1, 3, 7].