Abstract: BACKGROUND ＆ AIM： Sperm_egg fusion is a vital step in the process of fertilization .Izumo protein, only found on the inner acrosomal membrane, is a testis (sperm) _specific protein and belongs to the immunoglobulin superfamily. It is the key molecule which impacts on the sperm_egg fusion in the process of fertilization. In this study, we investigated the expression of pCXN2_mIZUMO in the muscle and its effect on the fertility of C57BL/6 mouse by means of gene immunization. The results could provide useful experimental data for the immunocontraceptive research. MATERIALS AND METHODS： Female and male C57BL/6 mice were inoculated with pCXN2_mIZUMO respectively. Sera titers of antibodies against Izumo were measured using ELISA assay and fertilization in vitro test was exerted to confirm the effect of antiserum. All the animals were introduced to mate with normal mice at a female/male ratio of 2:1. The litter size were analyzed after delivery. RESULTS： The immune system was induced specific response to Izumo antigen. The rate of the fertilization in vitro was decreased in the presence of antiserum values. The numbers of newborns were as follows: experiment female 2.9±0.66; control female 5.4±0.82; experiment male 5.1±0.99; control male 6.0±1.34. The fertility of female mice inoculated with pCXN2_mIZUMO plasmid was impaired. CONCLUSION：compared with the control female groups, low fertility was induced after vaccination with the recombinant plasmid of pCXN2_mIZUMO.

Key words: Izumo, immunocontraception, gene immunization