Development of male contraceptive vaccine--a perspective.

This paper reviews the recent advances that have occurred in the area of development of a male contraceptive vaccine. The vaccine candidates considered for review are hormone/hormone receptor-based proteins including luteinizing hormone-releasing hormone (LHRH)/LH, follicle stimulating hormone (FSH), as well as LH and FSH receptor proteins. The review also highlights the advances in our basic understanding of gonadotrophin action which have led to development of these vaccines. Focus is mainly on studies in the non-human primate which may be directly relevant to projected studies in the human. The data indicate that the vaccines are well tolerated by the primate (including the human based on limited data) and do not give rise to any known toxic symptoms or immediate health hazards. The response to the immunogen has been uniform and it may be possible to increase antibody titres as well as prolong the immune response by adding acceptable immune stimulators to the adjuvant cocktail and developing better immunization schedules or immunogen delivery systems. Contraceptive vaccines for the male are a feasible proposition and attention should now be focussed on evaluating carefully the bioefficacy of antibodies raised to recombinant ovine FSHbeta or FSH receptor protein fragments in both human and non-human primates. The advantage of the FSH/FSH receptor over the LHRH/LH-based vaccine lies in the fact that the former does not require an exogenous testosterone supplement to maintain accessory gland function, libido etc. The LHRH/LH-based vaccine results in azoospermia, while the FSH vaccine causes the production of low numbers of poor quality spermatozoa which are incapable of impregnating cycling females.