Induction of Autoantibodies to Zona Pellucida by Immunization with an 18mer Synthetic Peptide in Rabbits

For the development of a safe contraceptive vaccine, it is necessary to define B cell epitopes which could induce fertilization-blocking autoantibodies. In this study, an 18mer peptide (CTYILDPEKLTLRVPYKA) of rabbit ZPA which was recognized by a fertilization-blocking monoclonal antibody was chemically synthesized and conjugated with diphtheria toxoid (DT). The conjugate was injected into rabbits i.d. with complete Freund's adjuvant. As a control, DT was injected into rabbits in the same way. Mice were also immunized with the same synthetic peptide to induce heteroantibodies. Antisera from both rabbits and mice reacted not only with the cognate peptide but also with the isolated intact zona pellucida of rabbits. The immunohistochemical study showed that the antibodies had remained bound to the zona pellucida of the immunized rabbits in vivo. It is therefore concluded that the synthetic peptide could induce autoantibodies reactive to the auto-antigen of the zona pellucida in rabbits.