at the present growth rate, the world population is estimated to reach a phenomenal 8.9 billion people by the year 2050, posing a great risk of overpopulation. therefore, new strategies of contraception are required. a novel contraceptive strategy that is receiving considerable attention is that of immunocontraception. spermatozoa have proteins that are unique, cell specific, immunogenic and accessible to antibodies. the targeting of antibodies to gamete-specific antigens implicated in sperm function, sperm–egg binding and fertilisation could block sperm binding and thus fertilisation. the present review highlights the current status, relative merits and future directions for various sperm-based candidate antigens with regard to the development of a contraceptive vaccine.

This comparative study of the cDNA sequence of the zona pellucida C (ZPC) glycoprotein in murid rodents focuses on the nucleotide and amino acid sequence of the putative sperm-combining site. We ask the question: Has divergence evolved in the nucleotide sequence of ZPC in the murid rodents of Australia? Using RT-PCR and (RACE) PCR, the complete cDNA coding region of ZPC in the Australian hydromyine rodents Notomys alexis and Pseudomys australis, and a partial cDNA sequence from a third hydromyine rodent, Hydromys chrysogaster, has been determined. Comparison between the cDNA sequences of the hydromyine rodents reveals that the level of amino acid sequence identity between N. alexis and P. australis is 96%, whereas that between the two species of hydromyine rodents and M. musculus and R. norvegicus is 88% and 87% respectively. Despite being reproductively isolated from each other, the three species of hydromyine rodents have a 100% level of amino acid sequence identity at the putative sperm-combining site. This finding does not support the view that this site is under positive selective pressure. The sequence data obtained in this study may have important conservation implications for the dissemination of immunocontraception directed against M. musculus using ZPC antibodies.