Salmonella Typhimurium lipopolysaccharide O-antigen (LPS O-antigen (no widely-accepted, unique abbreviation specific to Salmonella Typhimurium O-antigen; general abbreviation is LPS O-antigen))

The Salmonella Typhimurium lipopolysaccharide O-antigen is the outermost, variable polysaccharide domain of the lipopolysaccharide (LPS) molecule on the bacterial surface. It is composed of repeating oligosaccharide subunits, whose sequence and modifications confer Salmonella serovar specificity and are a major determinant of immune recognition, virulence, and epidemiology. The O-antigen shields the bacterial cell from the actions of host innate immunity, including complement-mediated lysis, and impairs the ability of antibodies to access surface structures. It is highly immunogenic and serves as the major serological marker for diagnosis and for epidemiological surveillance; it is also a focus for vaccine and therapeutic antibody development. The structure is controlled by dedicated biosynthetic pathways, and can undergo phase variation and other modifications (e.g., acetylation, glucosylation), conferring the bacterium with the ability to evade host immunity and adapt to different niches. The diversity of O-antigen structures presents both opportunities and challenges for vaccine and therapeutic development.

Other names

Salmonella O-antigenO-antigen polysaccharideLPS O-antigenO-polysaccharide (OPS)Smooth LPS (S-LPS)

Opsonization and complement activation by antibodies targeting O-antigen; Induction of protective immune response (IgG, IgM); Disruption/destruction of bacterial membrane by membrane-active antibiotics (e.g., polymyxin B), which can have increased efficacy when O-antigen synthesis is disrupted; Binding and neutralization by bacteriophages (phage tailspike proteins recognize specific O-antigen types)