Development of a DNA vaccine for population control: A zona pellucida based nucleic acid vaccine (ZP-NAV)

This study introduces the use of a ZP-NAV for contraception purposes as an alternative to traditional zona pellucida vaccines. Using the mouse and dog models, plasmids encoding homologous, heterologous zona pellucida and irrelevant genes were prepared. Experiments were performed using 7-8 week-old female Balb/c mice and 3-18 month-old mix-bred dogs. Mice were bred from 2 to 40-45 weeks post vaccination and dogs during estrus. ELISA, Western Blot, passive transfer of immunoglobulins and ELISA isotyping assays measured immune responses. Ovarian integrity and estrous cycles were assessed by histopathology and vaginal cytology. Bacterial, mammalian and plasmid DNA and synthetic oligodeoxynucleotides were evaluated for their contraceptive effect in mice.; All DNA and oligonucleotides tested prevented pregnancies or reduced litter sizes. In mice, infertility was prolonged or temporary. Plasmid encoding zona genes induced a prolonged infertility of at least 40 weeks. A transient period of infertility lasting 17 weeks was observed in mice injected with irrelevant genes. Antibody titers do not correlate with fertility. Passive transfer of immunoglobulins from vaccinated animals did not prevent pregnancies. Heterologous and irrelevant plasmid injected mice showed an early increased ovarian atresia and a decrease in the number of follicles without inflammation. Afterwards, these features were undetectable and the estrous cycle was uninterrupted. In contrast, animals vaccinated with the homologous vaccine had a persistent decrease in follicle number for at least 44 weeks and altered estrous cycles were observed. Temporary contraception resulted when dogs were vaccinated with homologous, heterologous zona and irrelevant genes. Antibody titers do not correlate with infertility and estrous cycles were uninterrupted.; We conclude that DNA itself induces infertility. In mice, vaccinations resulted in long-lasting infertility using zona genes and a transient infertility using unrelated genes; while in dogs, the transient infertility is induced by both. The mechanism by which DNA produces infertility is unknown and needs further investigation.