Peptide-coupled liposomes for homogeneous immunoassay of polyclonal antibodies against proteins

The concentration of anti-native insulin antibodies was measured by liposome immune lysis assay (LILA) using liposomes coupled with a peptide which corresponds to residues 19–30 of the B-chain of porcine insulin. Although native insulin was slightly soluble in the reaction solution used in binding the antigens to the liposomes, this peptide was readily soluble in the solution. Thus liposomes coupled with a sufficient amount of the antigen could be easily obtained. Antibodies against native insulin from several species bound to the peptide on the surface of the liposomes, and the antigen-antibody complexes activated the complement system. By using the peptide-coupled liposomes, the concentrations of antibodies against insulin from several species were measured by the LILA method without the limitation of the solubility of the antigens.