Production of antibodies specific to human chorionic gonadotropin in mice immunized against its chemical analogs

Mice immunized against DS5-hCG-Β and DS6-hCG-Β, chemical analogs of Β-subunit of human choriogonadotropin (hCG-Β) in which 5 and 6 disulphide bonds respectively were reduced and alkylated, were found to produce antibodies specific to hCG without significant crossreactivity with human lutropin (hLH) as tested in a radioimmunoassay. In contrast, mice immunized against the native hCG-Β subunit produced hLH crossreacting antibodies. While the anti-DS5, DS6-hCG-Β serum was capable of selectively blocking the binding of [125I]-hCG to rat testicular LH/hCG receptors, it failed to inhibit the binding of [125I]-hLH to the same receptors. The radioimmunoassay for hCG using the mouse anti-DS5, DS6-hCG-Β serum was not as sensitive as that employing rabbit anti-DS5, DS6-hCG-Β serum. The minimal detection limit was 5 ng/ml for the mouse antibody as compared to 1 ng/ml for the rabbit antibody.