Human synthetic peptide vaccine for contraception targeting sperm.

A vaccine targeting sperm is an interesting approach to contraception. The acceptability of a sperm antigen for contraceptive vaccine development is contingent upon its sperm-specificity, surface expression for antibody binding, and involvement in fertilization. Sperm-zona pellucida (ZP) binding is a pivotal step and constitutes an attractive site for immunointerception. Using phage display technology, we have identified a novel dodecamer peptide sequence, designated as YLP(12), that is present on sperm, and is involved in ZP binding and sperm capacitation/acrosome reaction in man/mouse. Extensive search in the human and mouse genome sequence databases did not indicate a complete identity with the YLP(12) nucleotide sequence. It is peptide mimetic with sperm receptor carbohydrate mimicking action that is involved in oocyte binding. The sperm-specific YLP(12) sequence is also involved in involuntary immunoinfertility in men, indicating its autoantigenicity, sperm-specificity, and involvement in fertility/infertility in humans. Vaccination of female animals with synthetic YLP(12) peptide causes a long-term reversible contraception by raising a sperm-specific immune response. The contraceptive effect could also be completely reversed voluntarily at any time by immunoneutralization of antibodies using intravaginal administration of the peptide. Thus, the novel synthetic YLP(12) peptide is an attractive candidate for contraceptive vaccine development, and diagnosis and treatment of immunoinfertility in humans.