Titers of anti-sperm antibodies in patient sera, follicular fluid, and/or cervical mucus have been shown to correlate with reduced fertility rats. This research project will develop a primate model for immunologic infertility based on Sperm Agglutination Antigen-1 (SAGA-1), a sperm glycoprotein that has been identified as a surface antigen involved in antibody-mediated infertility in humans. SAGA-1 was identified with a murine monoclonal antibody (mAb), S19, that agglutinates human spermatozoa, inhibits sperm-zona blinding, blocks sperm penetration of cervical mucus, and induces the shaking phenomena. SAGA-1 is also recognized by H6-3C4, a human sperm-agglutinating mAb produced using lymphocytes from an immunologically infertile women. The human H6-3C4 antibody and the function-inhibitory mAb S19 recognize carbohydrate epitopes present on the SAGA-1 glycoprotein. Microsequence analysis demonstrated that SAGA-1 is related to CDw52, a GPI-anchored protein first identified on lymphocytes and involved in signal transduction. The S19 and H6-3C4 carbohydrate epitopes are not present on the CDw252 glycoprotein. Therefore, SAGA-1 and CDw52 represent glycoforms, i.e. glycoprotein isoforms that have the same peptide sequence but possess different oligosaccharide side chains.
The specific aims of this research proposal includes studies to elucidate the carbohydrate structure of the SAGA-1 glycoform. The tissue-specific expression of the SAGA-1 S19 carbohydrate epitope will be investigated with immunochemical analyses. The putative role of SAGA-1 in sperm-zona/cell-extracellular matrix interactions will be examined using the human hemi-zona assay. To investigate SAGA-1 as an auto-, iso-, antigen involved in immunologic infertility, female macaques will be immunized with SAGA-1. Anti-SAGA-1 antibody titers in sera, cervical mucus, and oviductal fluid will be monitored and the effect(s) of these antibodies on sperm function will be determined in vitro. The proposed research will contribute to understanding the roles of SAGA-1 and the sperm glycocalyx in sperm-zona/cell-extracellular matrix interactions and will provide a non-human primate model for the study of antibody- mediated infertility.
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