The Potential of the Zona Pellucida as a Target for Immunocontraception

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Abstract
PROBLEM: To investigate the contraceptive potential of the zona pellucida. METHOD: Generation of antibodies against native and recombinant zona glycoproteins which have then been assessed for their capacity to disrupt sperm-zona interaction in vivo and in vitro. The animal model selected for these studies was the common marmoset and the end points examined were antibody titre, ovarian cyclicity and fertility. RESULTS: The fact that antibodies against the major zona glycoprotein, ZP3, block both the primary and secondary phases of sperm-zona interaction suggests that this molecule might have potential for contraceptive vaccine development. Active immunization of marmoset monkeys with native porcine ZP3 or recombinant human ZP3 produced long term infertility but also precipitated a premature decline in the primordial follicle population. CONCLUSIONS: Future studies will have to determine whether a safe, effective vaccine can be engineered by coupling unique B-cell epitopes from ZP3 to foreign T-cell antigens.