Assessment of immunocontraceptive vaccine for population control: evaluation of a recombinant fusion GnRH vaccine in mice

Abstract

Abstract Gonadotropin-releasing hormone (GnRH) plays a pivotal role in regulating the reproductive endocrine system. Accumulated lines of evidence indicated that GnRH immunocontraception vaccine is a potential tool for control and management of animal population. However, the poor immunogenicity of GnRH peptide has limited its efficacy and field application. In the present study, a modified antigen, containing 8 GnRH repeats and immunostimulatory fusion protein, was formulated an oil-based MONTANIDE™ ISA 206 VG adjuvant to enhance the immunogenicity of the GnRH vaccine. The vaccine was vaccinated in 4-week-old male ICR mice (n = 10) and boosted twice, 4 and 8 weeks, respectively after the primary immunization. Mice injected with saline served as the unimmunized control (n = 10). Results demonstrated that the serum GnRH-specific antibody in vaccinated mice was significantly (p < 0.05) increased 5 weeks, peaked at 12 weeks, and remained high until 18 weeks after the primary immunization. In comparison with the control, vaccinated mice had significantly (p < 0.05) reduced serum testosterone concentration (0.856 ± 0.411 v.s. 160.77 ± 1. 865 ng/ml) and hampered development of testicles (weight and spermatogenesis) at 24 weeks after the primary immunization. Finally, a mating test indicated that the conception rate of female mice housed with vaccinated and unvaccinated males was 29% and 75%, respectively. The recombinant GnRH vaccine may be a potential approach for controlling animal population through immunocontraception.