Salmonella enterica Paratyphi A O:2 antigen

The Salmonella enterica Paratyphi A O:2 antigen is a serovar-specific O-antigen polysaccharide forming the outermost component of LPS (lipopolysaccharide) on the surface of Salmonella Paratyphi A, a Gram-negative bacterium responsible for paratyphoid fever[2][5]. The O:2 antigen consists of a trisaccharide backbone—rhamnose, mannose, and galactose—with serospecific branches of paratose and glucose, and partial O-acetylation, distinguishing it from other Salmonella O antigens[1][3][5]. This antigen is immunodominant, induces strong host antibody responses, and acts as a primary protective antigen being investigated for inclusion in conjugate vaccines to prevent Paratyphi A infections[1][3][4]. Experimental vaccine strategies utilize detoxified and highly purified O:2 polysaccharide in conjugation with carrier proteins or incorporate it into bacterial outer membrane vesicles to induce potent, functional immune protection. The O:2 antigen is also a determinant of serovar identity and plays roles in immune evasion and as a receptor for certain bacteriophages[2][5]. Deletion or mutation leads to bacterial death, highlighting its importance for bacterial viability and pathogenicity[2].

Other names

S. Paratyphi A O:2 antigenSalmonella Paratyphi A O antigenO:2-specific polysaccharideSalmonella Paratyphi A O-antigenGroup A O:2 antigen

Induction of antibody-mediated immunity (vaccination elicits antibodies against O:2 antigen conferring protection)[1][3][4][5]; Passive protection via serum bactericidal activity