Biological Activity of the Carrier as a Factor in Immunogen Design for Haptens

Immunoanalytical methods are frequently employed in the detection of hazardous small molecular weight compounds. However, antibody development for these molecules is a challenge, because they are haptens and cannot induce a humoral immune response in experimental animals. Immunogenic forms of haptens are usually prepared by conjugating them to a protein carrier which serves as an immune stimulator. However, the carrier is usually considered merely as a bulk mass, and its biological activity is ignored. Here, we induced an endocytic receptor, transferrin receptor, by selecting its ligand as a carrier protein to enhance antibody production. We conjugated aflatoxin, a potent carcinogenic food contaminant, to transferrin and evaluated its potential to stimulate antibody production with respect to ovalbumin conjugates. Transferrin conjugates induced aflatoxin-specific immune responses in the second immunization, while ovalbumin conjugates reached similar antibody titers after 5 injections. Monoclonal antibodies were successfully developed with mice immunized with either of the conjugates.