Characterization of 80 kDa human sperm antigen responsible for immunoinfertility

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 investigated for antifertility effects.

The purified 80 kDa HSA was used to immunize adult male and female rats. Rabbit anti 80 kDa HSA antibodies were used for immunofluorescent and immunohistochemical staining to demonstrate the presence of 80 kDa HSA on the sperm and to investigate its tissue distribution. The N-terminal sequence of native 80 kDa HSA and the peptides obtained by its endoproteinase Lys-C was determined.

Active immunization of male and female rats with 80 kDa HSA caused infertility in all the immunized animals. Immunofluorescent staining showed its localization on the head region of the human and rat spermatozoa. While immunohistochemical studies showed its localization in the testes and epididymis but not in other somatic tissues. Partial amino-acid sequence analysis showed no sequence homology with any of the known protein in the database.

80 kDa HSA is a promising candidate antigen for immunocontraception as it is characterized and found to cause infertility upon active immunization. specific to spermatozoa and is conserved.