Ovaries Remain Functional in Squirrel Monkeys (Saimiri sciureus) Immunized with Porcine Zona Pellucida 55,000 Macromolecule1

Fifty female squirrel monkeys were each immunized with 200 micrograms of a purified preparation of the 55,000 macromolecule (ZP3) from porcine zona pellucida. The fertility status of these immunized monkeys, as well as the effect of ZP3 antibodies on ovarian function, was monitored. High anti-ZP3 titers were achieved (> 75% binding levels as determined by radioimmunoassay) and remained high (~ 67% binding level) for the duration of this study. Hormonal evaluations indicated initial disturbances in normal ovarian steroid secretion and function that were confirmed by laparoscopic observation and oocyte production data. Histological examination of ovaries at 6–7 mo post-injection suggested an interference in folliculogenesis. No pregnancies were observed in the immunized monkeys during this period. By 10–15 mo post-immunization, hormonal and laparoscopic data indicated that ovarian function was recovering in injected monkeys despite the continued presence of high titers to ZP3. Collectively, these results demonstrate that although immunization with ZP3 initially produces disturbances in normal ovarian function that inhibit fertility, these effects are reversible. Such findings encourage the continued intensive investigation of purified porcine zona macromolecules for immunocontraceptive purposes.