Escherichia coli O-antigen serotypes O1A, O2, O6A, O25B (E. coli O-antigen (O1A, O2, O6A, O25B))

The Escherichia coli O-antigen is a highly variable polysaccharide component of the outer membrane lipopolysaccharide (LPS) that defines the serological identity of different strains. Serotypes O1A, O2, O6A, and O25B are specifically associated with Extra-intestinal Pathogenic Escherichia coli (ExPEC), which are the primary causative agents of invasive E. coli diseases such as urinary tract infections, sepsis, and bacteremia. These O-antigens play a critical role in bacterial survival within the host by providing a physical barrier against the host's innate immune system, particularly by inhibiting complement-mediated lysis and phagocytosis. In the context of drug development, these specific O-antigens serve as the primary targets for glycoconjugate vaccines designed to prevent ExPEC-related invasive disease. Vaccines like ExPEC4V and its successor ExPEC9V utilize these O-antigens conjugated to carrier proteins (such as Pseudomonas aeruginosa Exotoxin A) to elicit a robust, T-cell dependent immune response. The resulting antibodies are intended to provide opsonophagocytic protection, allowing the host immune system to recognize and eliminate the bacteria before they can cause systemic infection. This targeted approach is particularly relevant for elderly populations and patients undergoing elective surgery who are at high risk for E. coli bloodstream infections.

Other names

ExPEC O-antigensEscherichia coli Lipopolysaccharide O-side chainO-polysaccharideExtra-intestinal Pathogenic Escherichia coli surface antigens

Induction of serotype-specific opsonophagocytic antibodies that facilitate bacterial clearance by immune cells.