Selection of antigens for use in a virus-vectored immunocontraceptive vaccine: PH-20 as a case study

The European wild rabbit (Oryctolagus cuniculus) has become the major agricultural and environmental pest species in Australia. Current methods of rabbit control are lethal procedures which are increasingly questioned for their overall efficiency, applicability, specificity, cost and humaneness. New initiatives are required. One such initiative is virus-vectored immunocontraception. In this approach, the lagomorph-specific myxoma virus will be genetically engineered to include genes encoding components of rabbit gametes which can induce an immune response that causes infertility. Central to such a strategy is the ability to identify antigens capable of inducing an immunocontraceptive response. A strategy for identifying such antigens has been described previously. A case study of one sperm antigen, PH-20, is reported here. The issues involved in developing this antigen to the stage where it could be considered as a candidate for insertion into a recombinant myxoma virus with the ultimate goal of testing for immunocontraceptive efficacy are discussed. Techniques for inserting genes into myxoma virus have been described previously. The knowledge gained from research with this particular antigen are broadly applicable to other antigens used for both immunocontraceptive vaccines in general and, specifically, for virus-vectored immunocontraception.