Mapping of assembled epitopic regions of human chorionic gonadotropin reveals proximity of CTPα to the determinant loop ß93-100.

Three overlapping assembled epitopes of ßhCG have been mapped using MAb probes and a single step solid phase radioimmunoassay. These epitopes have been shown to be at receptor binding region comprising of the loop region ß Cys93-Cys100. Importance of disulphide bonds in maintaining integrity of these epitopes is assessed. Two MAbs (INN 58 and INN 22) interact with the ß region as well as the α C-terminal peptide, while the other MAb INN 24 interacts with only the ß region. Cross-reactivity pattern with ßhCG and hLH as well as the reported crystal structure of hCG substantiates the epitope identification. The results demonstrate utility of MAbs as probes in investigations on three-dimensional structure of gonadotropins.

Ability of deglycosylated human chorionic gonadotropin (dghCG) to block luteal function and establishment of pregnancy in bonnet monkeys (Macaca radiata).

The ability of deglycosylated hCG (dghCG) prepared by deglycosylation of a clinical hCG (3000 IU/mg) preparation, to block luteal function during regular cycles as well as luteal rescue in simulated and mated cycles of female bonnet monkeys (M. radiata) has been evaluated. The cycle length (C:28 vs E:24 days) and the total progesterone produced during the luteal phase was significantly reduced (by 45%, P < .05) by injecting 450 micrograms of dghCG/day (in split doses) on days 18, 19, and 20 of cycle. At the doses tested the dghCG used did not exhibit any agonistic activity in the female monkey. In a second experiment injection of 200 micrograms of dghCG/day on days 18-20 of cycle blocked the normal response of the luteal tissue to exogenous hCG (10 micrograms of a 12,000 IU/mg preparation) injected on day 23 of cycle. In a third experiment no pregnancies occurred when a group of 5 animals were injected dghCG (450 micrograms dghCG/day) on days 18-21 of their mated cycle. Animals chosen for this study were proven fertile regularly cycling monkeys and these were cohabited with males between days 9 and 14 of cycle. Each of the monkeys was exposed to 3 consecutive treatment cycles. During post-treatment phase 2 out of 3 monkeys exposed to males became pregnant. The study clearly demonstrates that it is possible to block normal luteal function as well as luteal rescue of the female monkey by using dghCG in the right dose and mode.