Pseudomonas aeruginosa O-antigen (OSA)

The Pseudomonas aeruginosa O-antigen, also known as the O-polysaccharide or O-specific antigen (OSA), is the outermost glycan component of the lipopolysaccharide (LPS) molecule anchored in the bacterial outer membrane. It serves as a major determinant of bacterial virulence and is the primary basis for the International Antigenic Typing Scheme (IATS), which classifies P. aeruginosa into 20 distinct serotypes based on the structural diversity of this polysaccharide (PubMed: 25747731). Biologically, the O-antigen provides a protective barrier against the host's innate immune system, specifically conferring resistance to complement-mediated serum killing and hindering phagocytosis (PubMed: 11092873). In the context of drug development, it is a high-priority target for passive immunotherapy, such as the monoclonal antibody Panobacumab, and for the development of glycoconjugate vaccines aimed at preventing multidrug-resistant infections (PubMed: 22432007). These therapeutic approaches typically aim to trigger opsonophagocytic killing by neutrophils to clear the pathogen during acute infections, particularly in high-risk settings like cystic fibrosis or intensive care units.

Other names

Pseudomonas aeruginosa O-polysaccharideO-specific antigenLPS O-side chainO-antigen

Induction of opsonophagocytic killing (OPK) and complement activation to promote bacterial clearance by host immune cells.