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Fertilization‐Related Sperm Antigens and their Immunocontraceptive Potentials

Vaccine(s) for contraception will provide an attractive alternative to contraception. There has been a renewed interest in defining fertilization‐related sperm antigens that can be used for the development of a contraceptive vaccine. The sperm‐zona pellucida (ZP) recognition and binding constitutes the most important event in the fertilization process, and the molecules involved at this site are attractive candidates for immunocontraception. Extensive research indicates that there are four sperm surface proteins that bind to oocyte ZP3 in humans and they belong to the four molecular regions of 95, 63, 51, and 14–18 kDa, respectively. Our laboratory is actively engaged in cloning and sequencing of cDNAs encoding for these sperm proteins and investigating the applications of recombinant (r) proteins in immunocontraception and infertility. Presently, the cDNAs encoding for the 14–18‐kDa proteins, designated the NZ‐1 and NZ‐2, respectively, and the 51‐kDa protein, designated fertilization antigen, have been cloned and sequenced. Active immunization with the rFA‐1 antigen caused a reversible block/inhibition in fertility of female mice by raising a sperm/testis‐specific immune response. FA‐1 antigen is also involved in human immunoinfertility, and a recent clinical trial indicates that it will have a clinical application in the treatment of immunoinfertile men. The long‐term goal is to employ various recombinant fertilization antigens and/or their bioeffective peptide epitopes in a single formulation, to generate an anti‐sperm vaccine that will be strongly immunogenic and highly efficacious for regulation of fertility.