PRODUCTION AND BIOLOGICAL-ACTIVITY OF MURINE MONOCLONAL-ANTIBODIES AGAINST GNRH

Immunization against GnRH represents a nonsurgical means of castrating domestic species. However, clear target antibody titres for bioactivi ty have not been established. The aims of this study were to produce c haracterized anti-GnRH monoclonal antibodies and to determine a thresh old titre. Three murine monoclonals were developed which produced IgG2 a class immunoglobulins and bound 50% I-125-GnRH at a 10(6) to 10(7) d ilution. The antibodies were specific to GnRH, showed a strong affinit y (Ka values from 1.99 to 2.60 x 10(10) litres/mole), and were directe d towards the amino terminus. In female mice all 3 antibody clones int errupted ovarian cyclicity, causing an extension in diestrus followed by prolonged estrus/metestrus (12 to 30 d). Throughout this period cir culating titres were greater than 15% I-125-GnRH binding at a 5 x 10(4 ) dilution. In male mice, immunization with 0.2 ml of ascites signifrc antly reduced testes (P<0.05), epididymides (P<0.001) and seminal vesi cle (P<0.01) weights. A 0.1 ml dose (61.4 +/- 18.6% binding at a 10(6) dilution) was ineffective. A serial dilution study indicated that a t itre of 50% binding at 2 x 10(6) dilution (antigen binding capacity of 268 +/- 35 ng/ml) was required to completely block GnRH activity. Thi s is a higher the than threshold levels determined previously. Identif ication of factors determining the titre required for bioactivity is n eeded. (C) 1997 by Elsevier Science Inc.