CONTRACEPTIVE VACCINE DEVELOPMENT

Recent advances in antigen definition and production have made the development of a contraceptive vaccine more attainable. Such a vaccine must evoke an immune response that blocks an indispensable step in the reproductive process. Vaccine research involves many approaches to fertility prevention. Vaccines are being developed that could interrupt fertility by inhibition of gonadotrophin release, the function of follicle-stimulating hormone or the effects of human chorionic gonadotrophin (hCG); alternatively, they may prevent fertilization by interfering with the transport of spermatozoa or with sperm-zona pellucida binding. The most advanced prototype is a vaccine based on antibodies to beta hCG. Such vaccines are being studied for clinical efficacy. Many hurdles remain in contraceptive vaccine development. Since the antigens are peptides or small proteins, the resultant immune response is usually moderate, and better adjuvants and delivery systems must be developed to enhance and maintain the immune response. Improvement of the mucosal immune response may be necessary for vaccines incorporating sperm antigens. Research on vaccines that control fertility has resulted in a fascinating base of scientific knowledge that, it is hoped, can be converted into products that will allow another option for individuals who wish to control their fertility.