Lipopolysaccharide core antigen of Gram-negative bacteria (LPS core antigen)

The lipopolysaccharide (LPS) core antigen is a conserved oligosaccharide region within the LPS molecule found on the outer membrane of all Gram-negative bacteria. The LPS consists of three regions: the lipid A anchor (the main endotoxin moiety), the core oligosaccharide (the "core antigen," attached to lipid A), and the distal O-antigen polysaccharide (highly variable and species-specific). The core region typically comprises a short array of unusual sugars (such as Kdo and heptoses) and is less variable than the O-antigen, making it an important cross-reactive antigenic target for immunodiagnostics and potential broad-spectrum Gram-negative vaccines. Functionally, the LPS core antigen is essential for maintaining membrane integrity, repelling harmful substances, and resisting host immune defenses. It also serves as a key antigenic marker for laboratory classification and serotyping of bacterial strains and species. When released during infection or bacterial lysis, LPS fragments with the core antigen can trigger severe innate immune responses, leading to fever, inflammation, or septic shock.

Other names

LPS core oligosaccharideCore region of lipopolysaccharideLipooligosaccharide (when O-antigen is missing, though this usually refers to a truncated LPS structure)Endotoxin core antigen (colloquial)

Outer membrane disruption: Drugs like polymyxins bind to the LPS core and lipid A, destabilizing the outer membrane and killing bacteria. Endotoxin neutralization: Experimental therapeutics (antibodies, peptides) may neutralize LPS or its core region to block inflammation.