Production and biological activity of murine monoclonal antibodies against GnRH
1997
Carson, A.F. | McCaughey, W.J. | Mackie, D.P. | Higgins, H.C. | Steen, R.W.J.
Immunization against GnRH represents a nonsurgical means of castrating domestic species. However, clear target antibody titres for bioactivity have not been established. The aims of this study were to produce characterized anti-GnRH monoclonal antibodies and to determine a threshold titre. Three murine monoclonals were developed which produced IgG2a class immunoglobulins and bound 50% I125-GnRH at a 106 to 107 dilution. The antibodies were specific to GnRH, showed a strong affinity (Ka values from 1.99 to 2.60 x 1010 litres/mole), and were directed towards the amino terminus. In female mice all 3 antibody clones interrupted ovarian cyclicity, causing an extension in diestrus followed by prolonged estrus/metestrus (12 to 30 d) Throughout this period circulating titres were greater than 15% I125-GnRH binding at a 5x 104 dilution. In male mice, immunization with 0.2 ml of ascites significantly reduced testes (P less than 0.05), epididymides (P less than 0.001) and seminal vesicle (P less than 0.01) weights. A 0.1 ml dose (61.4 plus or minus 18.6% binding at a 106 dilution) was ineffective. A serial dilution study indicated that a titre of 50% binding at 2 x 106 dilution (antigen binding capacity of 268 plus or minus 35 ng/ml) was required to completely block GnRH activity. This is a higher tire than threshold levels determined previously Identification of factors determining the titre required for bioactivity is needed.
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