Characterization of 80 kDa human sperm antigen responsible for immunoinfertility

PROBLEM: An 80 kDa human sperm antigen (80 kDa HSA) has been identified by western blot technique using serum of an immunoinfertile woman as a probe. The 80 kDa HSA has been subsequently purified from sperm extract and invest igated for antifertility effects. METHOD OF STUDY: The purified 80 kDa HSA was used to immunize adult male an d female rats. Rabbit anti 80 kDa HSA antibodies were used for immunofluore scent and immunohistochemical staining to demonstrate the presence of 80 kD a HSA on the sperm and to investigate its tissue distribution. The N-termin al sequence of native 80 kDa HSA and the peptides obtained by its endoprote inase Lys-C was determined. RESULTS: Active immunization of male and female rats with 80 kDa HSA caused infertility in all the immunized animals. Immunofluorescent staining showe d its localization on the head region of the human and rat spermatozoa. Whi le immunohistochemical studies showed its localization in the testes and ep ididymis but not in other somatic tissues. Partial amino-acid sequence anal ysis show ed no sequence homology with any of the known protein in the data base. CONCLUSIONS: 80 kDa HSA is a promising candidate antigen for immunocontrace ption as it is characterized and found to cause infertility upon active imm unization, specific to spermatozoa and is conserved.