Dehydration-rehydration vesicle methodology facilitates a novel approach to antibody binding to liposomes

Mouse monoclonal IgG1 specific for hepatitis B surface antigen and ovine polyclonal antibody raised against digoxin were covalently coupled by a diazotisation method to small unilamellar vesicles (SUV) composed of equimolar phospholipid and cholesterol supplemented with 6 mol% aminophenylstearylamine (APSA). Up to 33% of the antibody used was associated with vesicles, depending on the phospholipid and the antibody type used. Antibody-coated SUV were mixed with carboxyfluorescein (CF) or beta-galactosidase to generate multilamellar dehydration-rehydration vesicles (DRV) containing CF or active enzyme. In contrast, coupling of antibodies directly to beta-galactosidase-containing DRV resulted in total inactivation of the enzyme. About 85% of the SUV-bound antibody was recovered in DRV and of this, 78-82% was exposed on the liposomal surface, possibly because of reorientation of the APSA-antibody complex during DRV formation. Antibody-coated DRV remained stable in the presence of plasma at 37 degrees C and also under storage at 4 degrees C. Further, antibody coupled to such liposomes was capable of efficient interaction with the respective antigen. The present method allows the attachment of antibodies to the liposomal surface independently of entrapment of solutes, the activity of which is thus preserved, and could be adapted to alternative coupling procedures or ligands.