Monoclonal antibodies against LHRH: development and immunoactivity in vivo and in vitro.

Mouse myeloma NS1-Ag4 cells were fused with spleen cells from a BALB/c mouse previously immunized with luteinizing hormone releasing hormone (LHRH) conjugated to serum bovine albumin (BSA). Fused cells were grown in HAT restrictive medium which was screened for LHRH binding ability via a primary binding assay employing [125I]LHRH and cold ethanol precipitation. One clone (hy-USASK/DSIL-LHRH-A1) was selected for further study. Cell culture fluid and ascites fluid bound 30% of [125I]LHRH at 1:4000 and 1:400,000 dilution respectively. A competitive inhibition assay using ascites fluid at 1:2,000,000 dilution and LHRH standards at 0.125-32.0 ng/ml was established. Initial studies using rabbit anti-mouse allotype sera in a horseradish peroxidase (HRP)-ELISA system indicate the antibody is IgG1. A dose of 0.5 ml ascites fluid containing LHRH antibody given intravenously (i.v.) on day 9 of gestation was effective in terminating pregnancy in rats. A 1 cm progesterone implant made of elastomer polymer and placed interperitoneally blocked this effect. Ascites fluid (4.5 ml) containing LHRH antibody, when infused i.v. into mature spayed female dogs induced a precipitous decline in mean luteinizing hormone (LH) levels and reduced LH pulsatility over 4 days. It was concluded that the mouse monoclonal antibody is specific for LHRH, and can interrupt reproductive events in vivo.