Immunocontraceptive potential of a recombinant chimeric protein composed by a single gonadotropin-releasing hormone molecule and B subunit of Escherichia coli heat-labile enterotoxin in a mice model

Abstract

The present study aimed to evaluate the immunocontraceptive potential of a chimera containing gonadotropin-releasing hormone (GnRH) and the B subunit of Escherichia coli heat-labile enterotoxin (LTB) as a carrier molecule in male BALB/c mice. Mice were randomly divided into six experimental groups, according to the antigen/control inoculation: GnRH/LTB with adjuvant; commercial vaccine; GnRH/LTB; LTB with adjuvant; LTB; and PBS as control group. The humoral immune response was evaluated by indirect ELISA and the contraceptive potential was assessed through histological analysis of the animals' gonads and serum testosterone. Vaccinated groups respond with production of anti-GnRH/LTB antibodies. GnRH/LTB associated with adjuvant induced significant (P < 0.05) higher IgG titer after 14 days after the prime vaccination, keeping high titer up to 126 days. The histology results showed that chimeric antigen caused changes in spermatogenesis, and in the gonads tissue. In addition, this group had significantly lower testosterone levels than the control group (P < 0.05). The chimera produced through the fusion of a single GnRH molecule with LTB as a carrier are capable of inducing the humoral immune response, blocking endocrine functions related to reproduction, and causing tissue alterations in the gonads of male mice.