A modified GnRH peptide (CHWSYGLRPG-NH2) was conjugated to tetanus toxoid (TT) or diphtheria toxoid (DT) and formulated with Quil A saponin or a sustained release injectible PLGA (poly(lactide-co-glycolide)/triacetin). For the Quil A formulations, two administrations of TT conjugate at 3-weekly intervals were followed by two booster injections with the DT conjugate in entire ram lambs. With the PLGA formulations, only two injections were administered; the first containing TT and the second DT at 6-weekly intervals. Evaluation was carried out by comparing the specific antibody levels produced in relationship to hormone profiles and testicular changes. The Quil A formulation was considered the most effective, as it caused significant reduction in testosterone and follicle stimulating hormone levels, resulting in marked suppression of spermatogenesis.
Earl, E. R., Waterston, M. M., Aughey, E., Harvey, M. J., Matschke, C., Colston, A., & Ferro, V. A. (2006). Evaluation of two GnRH-I based vaccine formulations on the testes function of entire suffolk cross ram lambs. Vaccine, 24(16), 3172-3183. https://doi.org/10.1016/j.vaccine.2006.01.041