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

Abstract

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.

Keywords: GnRH; contraceptive effect; female; immunocontraception; male; vaccine.