CONTRACEPTIVE EFFECT OF SPERM-AGGLUTINATING MONOCLONAL-ANTIBODIES IN RABBITS

Immune infertility in humans correlates clinically with the presence o f anti-sperm antibodies that trap (agglutinate) sperm tn semen and cer vical mucus. To test whether sperm-agglutinating antibodies can be eff ective contraceptive agents, several mouse anti-rabbit sperm (MARS) sp erm-agglutinating monoclonal antibodies (mAbs) were developed that rap idly and completely agglutinate sperm: MARS-M3 (IgM), MARS-G16 (IgG(3) ), and MARS-G17 (IgG(3)). Contraceptive efficacy of these mAbs was tes ted by mixing the mAb with 0.1 ml semen (similar to 1/5 of a whole eja culate) immediately before artificially inseminating rabbits paracervi cally. This paracervical dose of semen provided a rigorous test since it delivered several thousand times more fertilizing doses than does a human ejaculate. All of the mAbs were contraceptively effective, and MARS-G16 reduced the number of fetuses per animal by 88% and 95% with doses of 150 mu g and 2 mg, respectively. The contraceptive efficacy o f the MARS mAbs in the rabbit suggests that human sperm-agglutinating mAbs may be effective agents for vaginal contraception in humans.