EFFICIENT IMMUNOCASTRATION OF MALE PIGLETS BY IMMUNONEUTRALIZATION OFGNRH USING A NEW GNRH-LIKE PEPTIDE

Active immunization to immunomodulate regulatory processes suffers fro m the disadvantage that the antigen is usually 'self' and therefore po orly immunogenic. This has been well illustrated by the long-standing experience with immunocastration vaccines targeting GnRH, a ten amino acid peptide. Not all animals vaccinated with these vaccines are equal ly affected, even after multiple vaccinations. This is a severe handic ap when immunocastration vaccines are applied to male piglets to circu mvent surgical castration. Surgical castration is universally practise d to prevent boar taint, produced in the testicles of mature boars. Al ternative immunocastration is only acceptable if all animals are equal ly affected using a minimum of vaccinations. Vaccines based on the GnR H peptide itself cannot meet these goals. We showed that using a GnRH- like peptide, a 20 amino acid tandem repeat of the amino acid sequence of the GnRH peptide, these goals can be attained. Using the tandem Gn RH peptide to vaccinate male piglets completely abolished the developm ent and endocrinological functioning of the testicles, in contrast to monomer GnRH. These results show that superior antigens can be made fo r effective immunomodulation by appropriate alteration of the antigen.