Antibodies against the beta-subunit of ovine luteinizing hormone can decrease the clearance of human chorionic gonadotropin in rhesus monkeys.

Contraceptive vaccines based on active immunization against gonadotropic hormones are being investigated in humans and other primates. Immunization against the beta-subunit of ovine luteinizing hormone (oLH beta) reduces fertility in rhesus monkeys by inducing inadequate luteal phases and preventing corpus luteum rescue by rhesus chorionic gonadotropin (rhCG). These effects result from the cross-reactions of the oLH beta-antibodies with rhCG and rhLH. We used human CG (hCG), which also cross-reacts strongly with anti-oLH beta to examine how the circulating oLH beta-antibodies affect the metabolic clearance rates (MCR) of hCG in rhesus monkeys. 125I-hCG was injected into four nonimmunized and seven immunized monkeys and blood was collected at frequent intervals over 7 days. Total and immunoprecipitable radioactivity did not differ significantly, suggesting that the radioactivity in the plasma consisted almost entirely of 125I-hCG. This was confirmed by column chromatography. The MCR (mean +/- SE) was significantly lower (p less than 0.001) in six immunized monkeys (0.35 +/- 0.06 liters/day) as compared to controls (1.19 +/- 0.09 liters/day). The hCG disappearance curve in control monkeys was best described by a two-compartmental system (slow and fast) while an additional third (intermediate) compartment of distribution was typical for immunized animals. The half-lives of hCG for the two exponentials corresponding to the slow and fast components of distribution were not significantly different between the two groups. One immunized monkey had a MCR (1.44 liters/day) that was much greater than the MCR of the other six.(ABSTRACT TRUNCATED AT 250 WORDS)