Inhibition of mouse fertilization in vivo by intra-oviductal injection of an anti-equatorin monoclonal antibody

The monoclonal antibody mMN9 recognizes an antigenic molecule, equatorin, w hich is localized at the equatorial segment of the mammalian sperm acrosome . Our previous results using an IVF system indicated that mMN9 blocked sper m-oocyte fusion. Antibody-containing and control solutions were injected di rectly into the right and left oviductal ampullae, respectively, of anaesth etized female mice to assess the effect of mMN9 on fertilization in vivo. A fter hCG treatment, the females were mated, and their oviductal eggs and im planted embryos were examined. mMN9 was retained in the oviductal lumen at 20 h after injection. The rates of fertilization and concomitant pregnancy were significantly lower than in the control side (P < 0.05). In addition, histological studies showed no evidence of pathological changes in the fema le reproductive tract after the injections. These results indicate that mMN 9 inhibits mouse fertilization significantly under in vivo conditions and t hat this injection method should be useful for studying the effects of anti bodies and agents on fertilization in vivo.