A COMPARISON OF THE IMMUNOGENICITY OF THE NATIVE AND DENATURED FORMS OF A PROTEIN

The effect of heat denaturation on the physicochemical and immunologic al properties of a model protein, ovalbumin, and its formaldehyde/lysi ne-treated form was investigated. Polyacrylamide gel electrophoresis a nd gel filtration showed that heat denaturation converted ovalbumin to high Mr polymers, whereas formaldehyde/lysine-treated ovalbumin remai ned monomeric with only a small proportion forming oligomers. NMR anal ysis demonstrated that non-denatured structures could easily be differ entiated from the denatured structures. Intraperitoneal immunization o f rabbits and mice showed that both native and denatured forms of oval bumin induced an immune response, but denatured forms of ovalbumin wer e found to be less immunogenic and to have a lower epitope density tha n native ovalbumin. Analysis of the antisera in crossed immunoelectrop horesis showed that they were specific for either native or denatured forms of ovalbumin. These findings were further investigated by ELISA and immunoaffinity chromatography, and the high specificity and low cr oss-reactivity was confirmed. We conclude that the immunogenic epitope s on denatured ovalbumin are different from those on ovalbumin, and th at these epitopes reflect a continuum of denatured conformations.