Endotoxin-polymyxin complexes in an improved enzyme-linked immunosorbent assay for IgG antibodies in blood donor sera to gram-negative endotoxin core glycolipids.

Common or cross-reactive epitopes of Gram-negative endotoxins are found in the inner-core glycolipid region of the outer membrane lipopolysaccharides (LPS). Hydrophobic LPS from rough mutants of Gram-negative bacteria, lacking serotype polysaccharide O-antigen chains, did not bind satisfactorily to polystyrene microplates for ELISA detection of cross-reactive IgG anti-endotoxin antibodies. When these LPS molecules were reacted with the cationic polypeptide polymyxin B, complexes were formed which were stable when coated on microplates. LPS-polymyxin complexes allowed optimisation of conditions for an ELISA for IgG antibodies to the core glycolipid region of endotoxins which could be used for screening large numbers of blood donor sera.