Computer-aided design and physiological testing of a luteinising hormone-releasing hormone analogue for 'adjuvant-free' immunocastration.

An analogue of LHRH containing an extension of Gly-Cys at the carboxyl-terminus has been designed to permit reproducible coupling to a suitably modified carrier via a thioether bond. Potential energy calculations indicated that this analogue adopted a conformation in solution virtually identical to the type II' turn around Gly-6-Leu-7 predicted for native LHRH. Intradermal administration of a conjugate of this analogue with purified protein derivative of tuberculin to male rats previously primed with BCG vaccine rapidly led to complete testicular regression. This adjuvant-free immunisation protocol may represent an alternative to castration for the veterinary control of reproductive function.