Salmonella enterica serovar Paratyphi A O-antigen (O:2 antigen)

Salmonella enterica serovar Paratyphi A O-antigen, also known as the O:2 antigen, is a critical surface polysaccharide and a primary component of the lipopolysaccharide (LPS) in the outer membrane of the bacterium [1, 2]. It consists of a repeating trisaccharide backbone composed of rhamnose, mannose, and galactose, with a characteristic paratose side branch that defines its serospecificity [3, 4]. This antigen plays a vital role in bacterial virulence by enabling the pathogen to evade the host's innate immune response, specifically by inhibiting the respiratory burst in phagocytes [9]. As a major immunodominant epitope, it is the focal point for the development of glycoconjugate vaccines aimed at preventing paratyphoid fever, a significant cause of enteric fever globally [1, 5]. Vaccines targeting this antigen work by inducing high titers of bactericidal and opsonophagocytic antibodies that facilitate the clearance of the bacteria [4, 6]. Current therapeutic strategies involve conjugating the O-antigen to carrier proteins like CRM197 or tetanus toxoid to enhance immunogenicity and provide long-lasting protection [7, 12].

Other names

O2 antigenParatyphi A O-polysaccharideSPA O-antigenSalmonella Paratyphi A lipopolysaccharide O-antigenO:2 polysaccharide

Induction of protective humoral immunity, specifically the production of bactericidal and opsonophagocytic antibodies that target the O:2 polysaccharide on the bacterial surface to facilitate pathogen clearance.