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

The Salmonella enterica serovar Paratyphi A O:2 O-antigen polysaccharide is a critical component of the lipopolysaccharide (LPS) layer on the outer membrane of the Paratyphi A bacterium. It serves as a primary surface antigen and is the defining feature of the O:2 serogroup, characterized by a repeating oligosaccharide unit containing paratose, which acts as the immunodominant epitope (Micoli et al., 2012, PLoS ONE). Biologically, the O-antigen provides a physical barrier against host immune defenses, including complement-mediated lysis and detergents, thereby facilitating bacterial survival and systemic infection (MacLennan et al., 2014, Clin Exp Immunol). In the context of human disease, Paratyphi A is a major cause of enteric fever (paratyphoid fever), particularly in South and Southeast Asia where it accounts for a significant portion of enteric fever cases (Sahastrabuddhe et al., 2013, Vaccine). Because the O-antigen is highly immunogenic and surface-exposed, it is the primary target for the development of glycoconjugate vaccines (Martin et al., 2012, Vaccine). These vaccines aim to elicit high titers of serum IgG antibodies that recognize the O:2 epitope, leading to bacterial neutralization and clearance through opsonophagocytosis.

Other names

O:2 antigenParatyphi A O-polysaccharideSalmonella Group A O-antigenO-specific polysaccharide of S. Paratyphi ASPA O-PS

Induction of O-antigen-specific bactericidal IgG antibodies that facilitate opsonophagocytosis and complement-mediated killing of the bacterium (MacLennan et al., 2014, Clin Exp Immunol).