Pseudomonas aeruginosa lipopolysaccharide O-antigen (P. aeruginosa O-antigen)

The O-antigen, specifically the long-chain O-specific antigen (OSA), is the outermost polysaccharide component of the lipopolysaccharide (LPS) molecule on the surface of the Gram-negative bacterium Pseudomonas aeruginosa (Rocchetta et al., 1999). It consists of repeating oligosaccharide units that define the bacterium's serotype and serve as a critical interface between the pathogen and the host immune system (King et al., 2009). Biologically, the O-antigen acts as a major virulence factor by protecting the bacterium from complement-mediated lysis and phagocytosis, while also facilitating environmental adaptation and biofilm formation (De Bentzmann & Plésiat, 2011). In therapeutic development, the O-antigen is a primary target for monoclonal antibodies and vaccines designed to induce opsonophagocytic killing and neutralize the pro-inflammatory effects of LPS (Que et al., 2014). Because P. aeruginosa exhibits significant structural diversity in its O-antigen across different strains, clinical strategies often target specific high-prevalence serotypes, such as O11, or utilize polyvalent formulations (Lam et al., 2011). Understanding the transition from smooth (O-antigen producing) to rough (O-antigen deficient) phenotypes is also vital, as this shift often occurs during chronic infections in cystic fibrosis patients to evade host detection (Pier, 2007).

Other names

O-specific antigenOSAB-band lipopolysaccharideO-polysaccharideO-side chainLPS O-antigen

Opsonophagocytic killing, Neutralization of endotoxin, Complement activation, Inhibition of bacterial adhesion