Escherichia coli O1a antigen (O1a)

The Escherichia coli O1a antigen is a specific subtype of the O-antigen, which constitutes the outermost polysaccharide portion of the lipopolysaccharide (LPS) on the surface of Gram-negative bacteria. It serves as a critical virulence factor for extraintestinal pathogenic E. coli (ExPEC), particularly those associated with the ST95 clonal group, which is a leading cause of neonatal meningitis, neonatal sepsis, and adult bloodstream infections. The O1a antigen provides the bacteria with serum resistance by protecting them from complement-mediated lysis and opsonophagocytosis by the host's immune system. Due to its high prevalence in invasive clinical isolates and its essential role in bacterial survival within the host, the O1a antigen is a primary target for the development of multivalent glycoconjugate vaccines. These vaccines, such as the experimental ExPEC9V and ExPEC10V candidates, aim to induce high titers of functional antibodies that facilitate bacterial killing and clearance. Although some clinical programs have faced challenges in efficacy trials, the O1a antigen remains a high-priority target for preventing life-threatening invasive E. coli infections.

Other names

Escherichia coli O1A antigenO1a O-antigenO1a polysaccharideO1a LPSE. coli O1a antigen

Induction of opsonophagocytic and bactericidal antibodies that target the O1a antigen on the bacterial surface, leading to complement-mediated killing and phagocytosis.