Salmonella enterica serovar Enteritidis O-specific polysaccharide (SE OPS)

Salmonella enterica serovar Enteritidis O-specific polysaccharide (OPS), also known as the O-antigen, is a complex carbohydrate polymer located on the outermost surface of the bacterium as part of the lipopolysaccharide (LPS) layer. It is a critical virulence factor that defines the serogroup D1 classification and consists of a repeating tetrasaccharide unit containing the immunodominant sugar tyvelose. Biologically, the O-antigen acts as a protective shield that promotes serum resistance by preventing the host's complement system from depositing the membrane attack complex on the bacterial surface, thereby allowing the pathogen to evade innate immune clearance. Because of its high surface exposure and serovar specificity, the OPS is a primary target for the development of glycoconjugate vaccines and monoclonal antibodies. Therapeutic strategies focus on inducing high-titer IgG antibodies against the OPS to facilitate opsonophagocytosis and complement-mediated bacterial lysis, particularly to prevent invasive non-typhoidal Salmonella (iNTS) disease and self-limiting gastroenteritis.

Other names

O-antigenO-specific polysaccharideOPSOSPSE O-antigenLipopolysaccharide O-side chainCore-O-polysaccharide (COPS)

Induction of O-antigen-specific IgG antibodies to promote opsonophagocytosis and complement-mediated lysis of the bacterial cell.