Vaccine for human contraception targeting sperm Izumo protein and YLP12 dodecamer peptide

There is an urgent need to develop a better method of contraception which is non‐steroidal and reversible to control world population explosion and unintended pregnancies. Contraceptive vaccines (CV), especially targeting sperm‐specific proteins, can provide an ideal contraceptive modality. Sperm‐specific proteins can induce an immune response in women as well as men, thus can be used for CV development in both sexes. In this article, we will review two sperm‐specific proteins, namely Izumo protein and YLP₁₂ dodecamer peptide. Gene‐knockout studies indicate that Izumo protein is essential for sperm–egg membrane fusion. Vaccination with Izumo protein or its cDNA causes a significant reduction in fertility of female mice. The antibodies to human Izumo inhibit human sperm penetration assay. Recently, our laboratory found that a significant percentage of infertile women have antibodies to Izumo protein. The second sperm‐specific protein is YLP₁₂, a peptide mimetic sequence present on human sperm involved in recognition and binding to the human oocyte zona pellucida. Vaccination with YLP₁₂ or its cDNA causes long‐term, reversible contraception, without side effects, in female mice. Infertile, but not fertile, men and women have antibodies to YLP₁₂ peptide. Our laboratory has isolated, cloned, and sequenced cDNA encoding human single chain variable fragment (scFv) antibody from infertile men which reacts with YLP₁₂ peptide. The human YLP₁₂ scFv antibody may provide a novel passive immunocontraceptive, the first of its kind. In conclusion, sperm‐specific Izumo protein and YLP₁₂ peptide can provide exciting candidates for antisperm CV development.