Immunization with Sperm Antigens to Induce Contraception

Abstract

Contraceptive vaccines (CV) may provide a viable and valuable alternative that could fulfill most, if not all, of the properties of an ideal contraceptive. The molecules for CV development target either gamete production [luteinizing hormone-releasing hormone (LHRH)/GnRH, FSH], gamete function [sperm antigens and oocytes Zona pellucida (ZP)], or gamete outcome (HCG). Sperm are an exciting target and several antigens have been actively explored for CV development. Vaccines based on recombinant sperm proteins, synthetic peptides, and naked DNA have shown reversible contraceptive effects without any serious side effects in various species of animals. No sperm vaccine has been tried in humans so far. Besides these specific concerns associated with each contraceptive vaccine, progress has been restricted due to the variability of immune response after active immunization, attain reasonably high antibody titers, especially in the genital tract and uncertainty regarding how long the bioeffective antibodies will remain in circulation. It is envisaged that these concerns may be obliterated by the passive immunization approach using the performed antibodies. The antibody therapies are successful against various infectious diseases, both in animals and humans. Phage display technology has been widely used to obtain a variety of engineered antibodies, including single chain variable fragment (scFv) antibodies. Using this technology, recently, our laboratory has isolated, produced, and characterized fully functional human scFv antibodies against specific human sperm antigens. These human antibodies are being examined for their utility as novel immunocontraceptive.