To evaluate the contraceptive effects of the canine zona pellucida 3 (CZP3) DNA vaccine, initial evaluation of the contraceptive efficacy was made in mouse model in this study. Twelve female mice were divided into 2 groups which were intramuscularly immunized with 50 μg of pcDNA3-CZP3 (experiment group) and pcDNA3 plasmids (negative control group), respectively, and 6 electric pulses (30 V) were delivered subsequently. After the first immunization, blood was collected weekly; the antibody levels of CZP3 and antibody titers of CZP3 at the 6th week after the first immunization were detected by ELISA. The mice were mated with male mice at the 6th week after the first immunization, the litter size of each mouse was calculated and the data were analyzed statistically. Ovaries were collected at the 24th week after the first immunization and conducted for HE staining. Finally, the indirect immunofluorescence of mouse and dog zona pellucida were detected by mouse serum. The results indicated that compared with the negative control group: 1) The levels of antibodies against CZP3 were significantly increased at the 2nd week after the first immunization in the experiment group, and lasted for up to 24 weeks. 2) The antibody titer of CZP3 at 1∶4 000 dilution was significantly different. 3) The fertility rate of mice in the experiment group fell from 100% to 50%, and the litter size fell from 6.667±0.422 to 2.500±1.455. However, the correlation between the litter size and antibody levels in the experiment group was negative. 4) HE staining of ovarian sections showed that the immunization with CZP3 DNA vaccine would not influence the development of mouse ovaries. 5) The results of indirect immunofluorescence assay showed that the serum of mouse immunized with CZP3 could react with mouse and dog zona pellucida. Therefore, these results suggested that CZP3 DNA vaccine could reduce the fertility rate and litter size significantly in mouse model without influencing the development of ovaries.
