Salmonella Paratyphi A O-antigen

The Salmonella Paratyphi A O-antigen is the dominant, serovar-specific polysaccharide component of the bacterium’s outer membrane lipopolysaccharide (LPS)[2][5]. It is composed of a repeating tetrasaccharide unit with a backbone of rhamnose, mannose, galactose, and a branch of paratose, linked through the core oligosaccharide to lipid A. O-acetylation of rhamnose and glucosylation of galactose are structural modifications that contribute to its immunogenic and antigenic properties[2][6]. This antigen plays a critical role in Salmonella’s evasion of host immunity—modulating phagocytosis, resistance to serum killing, and triggering protective immune responses[5]. The O-antigen is a main target for candidate paratyphoid vaccines and acts as a key biomarker for serological detection and monitoring. Variability in its structure can affect vaccine coverage and efficacy, highlighting the need for precise antigen characterization in vaccine development[4][6][7]. Synthetic oligosaccharide derivatives and O-antigen-conjugated vaccines utilizing this structure have shown promising immunogenicity and protective efficacy in preclinical models[6].

Other names

O:2 antigenParatyphi A O-polysaccharideS. Paratyphi A O-antigenOAg (when referencing O-antigen generically)

Induction of protective antibody responses (vaccines employing Paratyphi A O-antigen elicit IgG that promotes opsonization and clearance by host immunity) Antibody-mediated neutralization and complement activation against Salmonella Paratyphi A Used as immunogenic antigen in conjugate vaccine design