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Identification of Human Sperm Peptide Sequence Involved in Egg Binding for Immunocontraception1

Rajesh K. Naz,2,3 Xiaolong Zhu,3 and Arjun L. Kadam4
02/09/2011

Development of a vaccine based on sperm antigens represents a promising approach to contraception. The sperm-zona pellucida (ZP) interaction constitutes the most important event in the fertilization process, and the molecular sequences involved at this site may provide the most attractive candidates for immunocontraception. In the present study, using the phase peptide display technique, a novel dodecamer sequence, designated as YLP12, was identified that is involved in sperm-ZP recognition/ binding. The synthetic 12-mer peptide based on this sequence and its monovalent Fab' antibodies specifically and significantly (P< 0.05) inhibited human sperm-ZP binding. In Western blot and immunoprecipitation procedures, the YLP12 peptide recognized the ZP3 component of solubilized human ZP proteins. In the Western blot procedure involving 10 different human tissue extracts, the anti-YLP12 Fab' antibodies recognized a protein band of ~72 ± 2 kDa only in the testis lane. The peptide sequence was localized on the acrosomal region of the human sperm cell. These findings indicate that the novel testis-specific 12-mer YLP12 that is present in the acrosomal region and is involved in human sperm-ZP interaction may find applications in contraceptive vaccine development, as well as in diagnosis and treatment of male infertility mediated through sperm dysfunction.