Active component of a GnRH based vaccine binds to natural GnRH receptors in Dunning R3327-G cell line and human prostate carcinoma vesicles.

An alternative approach to immunization with native GnRH for the inhibition of gonadotropin secretion and gonadal function is the use of peptidomimetics such as peptides of GnRH that could serve as vaccines when these are joined to more immunogenic molecules. The GnRH sequence of many species is well-known. Reported consensual aminoacid sequence of mammals is: Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly. Most of the known GnRH sequences, including birds, fish and reptiles, have the Glycin amino acid residue at position 6. Glycin is the smallest amino acid, and confers flexibility to the polypeptide chain. Glycin substitution by Prolin, to confer rigidity, and the coupling to a Tetanic Toxoid T helper epitope (GnRHm1-TT), increases considerably the immune response towards the autolog GnRH when it is administered using an oily adjuvant. In the present study we also investigate the capacity of GnRHm1-TT (active component of a GnRH based vaccine) to bind the natural GnRH receptor in Dunning R3327-G cell line and vesicles of different tissues when administered without an adjuvant. Results showed that GnRHm1-TT do not lose the binding ability to natural GnRH receptor in vitro and in vivo. We also demonstrated that this molecule behaves as a GnRH agonist analog when administered intraperitoneally to Wistar rats.