Bacterial lipopolysaccharide O-antigen (O-antigen)

Bacterial lipopolysaccharide (LPS) O-antigens are the highly variable, outermost polysaccharide components of the LPS molecule found in the outer membrane of Gram-negative bacteria. They consist of repeating oligosaccharide units that extend from the bacterial surface, serving as a critical interface between the pathogen and the host environment. O-antigens play a vital role in bacterial pathogenesis by providing a physical barrier against host immune defenses, such as complement-mediated lysis and phagocytosis, and by facilitating motility and biofilm formation. Due to their high immunogenicity and surface exposure, O-antigens are primary targets for the development of serotype-specific vaccines and monoclonal antibodies. However, their extreme structural diversity across different bacterial strains and species presents a significant challenge for broad-spectrum therapeutic development, often necessitating multivalent or strain-specific approaches.

Other names

O-polysaccharideO-side chainO-specific polysaccharideO-antigenic determinantOPS

Drugs targeting O-antigens primarily work through neutralization of bacterial attachment, opsonization to enhance phagocytosis, and activation of the classical complement pathway to mediate bacterial killing. Vaccines induce the production of serotype-specific antibodies that bind to the O-antigen, preventing colonization and promoting immune clearance of the pathogen.