Development of a contraceptive vaccine for the marsupial brushtail possum (Trichosurus vulpecula) : lack of effects in mice and chickens immunised with recombinant possum ZP3 protein and a possum ZP3 antifertility epitope

Zona pellucida fertility-control vaccines are being developed in New Zealand to control an introduced marsupial pest, the brushtail possum (Trichosurus vulpecula). In this study recombinant possum ZP3 protein (rZP3) and a possum ZP3 peptide (amino acids 334–361) (both known to block fertility in possums) were examined for their potential to induce species-specific, or at least marsupial-specific, infertility. Laboratory mice (a ‘model’ eutherian mammal species) and domestic chickens (a ‘model’ bird species) immunised with possum rZP3 or possum-infertility ZP3 peptide in Freund’s adjuvants showed no reduction in a range of parameters indicative of reproductive performance. The lack of contraceptive effects on mouse and chicken fertility is an encouraging result in terms of rZP3 and ZP3 peptide specificity, and these promising antigens are to be expressed in a bacterial ghost vaccine system for mucosal delivery to possums and the effects on possum fertility evaluated. Ultimately, a much wider range of non-target species will need to be screened and tested once the antigens have been successfully formulated in their final delivery vehicle.