Immunological castration using a gonadotrophin-releasing hormone analogue conjugated to PPD

The importance of gonadotrophin-releasing hormone/luteinizing hormone-releasing hormone (GnRH/LHRH) to reproductive function is illustrated when animals immunized with GnRH produce a high humoral immune response which can achieve a humane alternative to surgical castration. In this paper, the male rat was used as a model Rats were immunized with an analogue of GnRH—GnRH-glycys-in both its free form and conjugated to the carrier PPD. Pre-immunization priming with BCG was compared with non-BCG priming. The results showed that BCG priming, in the absence of adjuvant, allowed a sufficient reduction in testosterone levels to occur without severely affecting gonadal changes. Immunization in conjunction with adjuvant resulted in high antibody titres, a decrease in testosterone levels, gonadal atrophy and a reduction in spermatogenesis. Alteration of the dose levels of the analogue and the long-term effects of immunization on gondal function were also investigated.