The objective of producing vaccines which target elements of the reproductive system to control fertility has been pursued for many years. Of the many targets for such vaccines, several sperm-associated antigens have been proposed for antibody-mediated intervention before fertilization but the very abundance of antigen to be neutralized has been a barrier. Zona pellucida antigens associated with the surface of the oocyte have also been targeted and used successfully for control of 'wild' elephant populations but worries concerning immunopathologically-mediated tissue damage have been mooted. Vaccines using human chorionic gonadotropin (hCG) which is required for the implantation and maintenance of the fertilized egg, although of interest for the development of fertility control in human populations, has no relevance in the context of the present conference because external fertilization of fish eggs is independent. The pathways by which gonadotropin-releasing hormone (GnRH) secreted by the hypothalamus promote release of luteinizing (LH) and follicle-stimulating hormone 展开▼
