Inhibition of fertility in rabbits by monoclonal antibodies against sperm

Monoclonal antibodies were prepared against rabbit sperm antigens by fusing P3-X63-Ag8-653 mouse myeloma cells with lymphocytes from Ba!b/c mice immunized with Tergito! NP4O deter-gent-so!ubiized rabbit epididymal sperm. Ascites fluid from mice injected with two of these hybridomas (8C4.1 and 8C10.5) was negative in immobilization and agglutination methods, however, acrosome positive on methanol fixed sperm and plasma membrane positive on unfixed sperm in indirect immunofluorescence. Insemination of female rabbits with the sperm treated with either of these monoclonal antibodies resulted in significant reduction in fertility as seen by the percentage of 9-day implants/corpora lutea ratio (8C4.1, 25.7%; 8C10.5, 1.9%; and control, 64.7%). Though the antibodies inhibited in vitro binding of the rabbit sperm with zonac pellucidae of rat ova, fertilization in vivo was not affected significantly. The antibodies did not demonstrate antiblastocyst activity by immunofluorescence. Both of these monoclonal antibodies appeared to recognize the same antigen by the SDS-PAGE/Protein Blot enzyme immunobinding procedure. The antigen was of testicular origin and had a molecular weight of approximately 63,000 daltons. It is concluded that these monoclonal antibodies which were organ specific, block post-fertilization fertility by inhibiting some step necessary for viable embryo formation