Inhibition of bovine sperm-oocyte fusion by a monoclonal antibody recognising the TEC-2 epitope on bovine oocytes

The TEC-2 antigenic determinant is a carbohydrate epitope located on a glyc oprotein carrier molecule. In the mouse, this epitope is expressed on the z ona pellucida and plasma membrane of the oocyte and is associated with the ZP2 glycoprotein and involved in the secondary sperm receptor mechanism. On the bovine oocyte expression is confined to the plasma membrane. The aim o f this study was to determine the role the TEC-2 epitope plays during ferti lization in the bovine species using the monoclonal antibody TEC-02, Incuba ting oocytes with the TEC-02 antibody prior to fertilization inhibited clea vage in a dose-dependent manner-the cleavage rate decreased as the concentr ation of the antibody increased. Significantly more sperm were bound to ooc ytes exposed to TEC-02 (12 sperm/oocyte) compared to oocytes that were not incubated with the antibody (4 sperm/oocyte). Oocytes treated with the TEC- 02 antibody had a 7.5 +/- 3.2% fusion rate and no cortical granule exocytos is compared with oocytes not exposed to the antibody, with 86.5 +/- 5.8% of sperm-oocyte fusions and release of cortical granules, The block to sperm- oocyte fertilization observed in the pretreated group was overcome using in tracytoplasmic sperm injection as the method of fertilization that bypassed the fusion process. Although sperm were binding to the oolemma these resul ts suggest that fusion was not occurring and this may be due to the antibod y occupying TEC-2 epitope sites involved in the fusion process. In conclusi on, the TEC-2 epitope seems to be involved in sperm-oocyte interaction in t he bovine species and appears to be involved specifically during the fusion events of fertillization. (C) 1999 Wiley-Liss, Inc.