Immunogenicity of polyethylene glycol-modified superoxide dismutase and catalase

Modification of proteins with polyethylene glycol (PEG) has been shown to result in a decrease in immunogenicity. Superoxide dismutase (SOD) and catalase were modified with PEG and used to immunize mice. Antibody titers against the antigens were determined by ELISA. Mice immunized with PEG-SOD had antibody titers 0.03%–0.07% of that seen in mice with SOD, while mice immunized with PEG-catalase developed titers 0.02%–0.09% of that seen in mice with catalase. The modified enzymes retained the ability to react with preformed antibodies to the unmodified antigens. Antibodies to SOD reacted equally well with the PEG-SOD or SOD antigen. Antibodies to catalase reacted to PEG-catalase but at only 0.02% of the reaction with catalase antigen. In reciprocal studies, antisera against the PEG-proteins failed to react to an appreciable level with the corresponding unmodified protein. Modification with PEG resulted in a decrease in immunogenicity of both SOD and catalase.