Inhibition of sperm–egg binding and fertilisation in mice by a monoclonal antibody reactive to 57-kDa human sperm surface antigen
K. V. R. Reddy A B , G. Vijayalaxmi A , K. S. Rajeev A and C. Aranha AA Immunology Division, National Institute for Research in Reproductive Health, J.M. Street, Parel, Mumbai, India.
B Corresponding author. Email: shrichi@rediffmail.com
Reproduction, Fertility and Development 18(8) 875-884 https://doi.org/10.1071/RD06028
Submitted: 2 April 2006 Accepted: 7 August 2006 Published: 22 November 2006
Abstract
Monoclonal antibodies (mAbs) against spermatozoa are a popular approach to define sperm antigens involved in the process of fertilisation. The identification and characterisation of a 57-kDa fertility asssociated sperm antigen (FASA-57) from human spermatozoa was reported in an earlier paper by the authors. In the present report, studies to develop mAbs against partially purified FASA-57 are extended. From a panel of mAbs raised, one clone designated as 3H4B9 was selected and characterised because it recognised native FASA-57. Indirect immunofluorescence studies revealed that FASA-57 localised on the acrosome of non-acrosome-reacted human spermatozoa and on the equatorial region after the acrosome reaction. Spermatozoa from several other mammalian species were also found to express this antigen, suggesting its evolutionary conservation across the species. The antigen localised specifically in spermatogonial cells and luminal spermatozoa of the testis and epididymis. Western blot studies showed the presence of a FASA-57-like protein in the mouse brain also, indicating that testis and brain share antigenic similarities. Further, the role of FASA-57 in sperm–egg interaction was investigated using a mouse model. The mAb 3H4B9 inhibited sperm–egg binding and fusion in a dose-dependent manner with half-maximal inhibition at 2 µg mL–1. In conclusion, FASA-57 appears to play an important role in sperm–egg recognition, fusion and fertilisation. Therefore, FASA-57 could be used as a diagnostic marker in the evaluation of male infertility.
Acknowledgments
The authors are grateful to Dr Chander P. Puri, Director for his consistent encouragement throughout the study. This was partially supported by the Department of Biotechnology (Grant NO.DBT/PRO587/Med/09/115/97), and the Indian Council of Medical Research (Ref. No. NIRRH/MS/24/2004). We acknowledge Council of Scientific and Industrial Research for providing a Senior Research Fellowship to G.V.
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