The effectiveness in rhesus monkeys of an antifertility vaccine based on neutralization of chorionic gonadotropin

A model system, employing non-human primates, is needed to test the postulate that active immunization to achieve neutralization of the biological activity of chorionic gonadotropin could be used as a basis for fertility regulation in women. Adult female rhesus monkeys were actively immunized with the β-subunit of ovine LH (oLHβ) mixed with Freund's complete adjuvant. All monkeys developed circulating antibodies which bound iodinated oLH and human chorionic gonadotropin (hCG). The bound hCG was displaced by rhesus chorionic gonadotropin (rhCG). Antisera were also able to neutralize the biological activity of rhCG in the immature rat uterine weight assay. Serum progesterone levels and menstrual bleeding patterns indicated that normal ovulatory cycles continued to occur in most cases after immunization. Results of mating the animals reveal that the fertility of the immunized animals was significantly reduced.