Successful interaction between sperm and egg is an obvious essential aspect of fertility. Recently, technological advances have increased our understanding of the molecular mechanisms involved in such interaction; it is now appropriate to incorporate such advances into contraceptive design.
The aim of this proposal is to use recent information, derived from the study of mouse gametes, to (a) identify a human sperm protein that permits and regulates initial interaction between sperm and egg and (b) define the most appropriate portion of that protein for use in developing a contraceptive vaccine. This project will focus on p95, a 95 kD sperm protein that is a receptor for the oocyte-specific extracellular matrix protein ZP3. In the mouse, we have identified p95 as a tyrosine kinase receptor with characteristics similar to others in this family, such as insulin-R, EGF-R, and PDGF-R. We intend to clone and sequence the cDNA that encodes murine p95 as a tyrosine kinase receptor with characteristics similar to others in this family, such as insulin-R, EGF-R, and PDGF-R. We intend to clone and sequence the cDNA that encodes murine p95 and express the protein in a variety of systems. The bioactivity of expressed recombinant p95 will be assessed in functional assays. From the deduced amino acid sequence of p95, a peptide that corresponds to the entire extracellular domain will be generated, used as immunogen for the production of anti-p95 antibodies in mice, and mapped for immunogenic epitopes. These experiments will define the peptide(s) from p95's extracellular domain with strong immunogenic activity. Antibodies directed against this peptide will be generated and screened for inhibitory effects on fertilization in mice. Use of p95 as an immunocontraceptive is predicted to block gamete interaction at two related, but separate, sites: sperm-zona binding and triggering of acrosomal exocytosis. Based on our results, a candidate vaccine incorporating the most promising p95 peptide will be constructed and tested for induction of infertility in mice. Our initial data indicate the presence of a highly related p95 homolog in human sperm. Based on information derived for murine p95, we will clone the cDNA that encodes human p95, determine its nucleotide sequence, and express the protein product in functional form. Immunological and biochemical techniques will be used to define the role of human p95 in fertilization. Having demonstrated the structural and functional homology between human and mouse p95, we plan to test the contraceptive potential of human p95 by immunization of cynomolgous macaques.
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