MODIFICATION AT C6 OF THE TERMINAL GALACTOSYL RESIDUES OF COBRA VENOMFACTOR ABOLISHES ANTI-ALPHA-GAL ANTIBODY IMMUNOREACTIVITY WITHOUT AFFECTING FUNCTIONAL-ACTIVITY

The N-linked oligosaccharides of cobra venom factor (CVF) contain uniq ue terminal alpha-galactosylated Lewis X structures. We have previousl y shown that CVF immobilized on nylon membranes binds naturally occurr ing human anti-alpha-Gal antibody. The present study shows that solubl e CVF can effectively inhibit the binding of anti-alpha-Gal antibody t o CVF coated microtiter plates, indicating that the terminal alpha-gal actosyl residues of the functionally active CVF are accessible to anti -alpha-Gal antibody binding. Modification of the terminal galactosyl r esidues of CVF by treatment with galactose oxidase and in situ derivat ization of the generated aldehyde groups with hydrazides abolished the human anti-alpha-Gal antibody immunoreactivity without affecting the complement-activating activity. (C) 1998 Academic Press.