Induction of immunocontraceptive effects in both male and female mice immunized with GnRH vaccine

BACKGROUND: Gonadotropin‐releasing hormone (GnRH) plays a pivotal role in regulating the reproductive endocrine system. OBJECTIVE: An immunocontraception vaccine aimed at inhibiting the functions of GnRH is tested as a potential tool for controlling animal populations. METHODS: We developed a recombinant immunocontraceptive vaccine composed of GnRH‐I and GnRH‐II (GnRH I+II), which was conjugated with Salmonella typhimurium flagellin. Forty‐eight BALB/c mice aged 4 weeks were divided into four groups (each group had n = 12): non‐vaccinated male (NVM), non‐vaccinated female (NVF), vaccinated male (VM), and vaccinated female (VF). Mice in the vaccinated groups were vaccinated twice by intramuscular injection at 0 and 2 weeks with 300 μg of the recombinant GnRH protein complex per mouse. Mice in the non‐vaccinated groups were injected with saline and served as the unimmunized controls. Twenty‐four pairs of male and female mice were mated for 10–12 weeks after initial immunization in four groups: 6 NVF × 6 NVM, 6 VF × 6 NVM, 6 NVF × 6 VM, and 6 VF × 6 VM. Results: An increase (p < 0.001) in antibody titers in VM and VF mice was observed. The testosterone levels and the number of spermatocytes were lower (p < 0.001) in VM mice than those in the control mice. The progesterone levels and the number of corpora lutea were lower (p < 0.001) than those in the control mice. Mating results in both VM and VF mice confirmed a 60% reduction in pregnancy rates and offspring numbers. CONCLUSIONS: The recombinant GnRH vaccine can be used for birth control in both male and female animals.