Detection of Anti-hGH Antibodies in Serum Samples of Children Treated with RhGH

The present study deals with the comparison and establishment of methods for the detection of antibodies against recombinant human growth hormone (rhGH). Therefore, different methods for the detection of hGH-Abs were evaluated and compared in order to establish a test system that can be used for the detection of neutralizing antibodies against hGH, which could be developed under rhGH treatment. This manuscript describes in detail the validation of a newly developed biological assay, the neutralizing hGH-antibody assay (NAb assay). Therefore, a cell line transfected with the growth hormone receptor, that proliferates in the presence of hGH, was used. This proliferation was quantified by an increase of the optical density (OD/ absorbance) after addition of a colorimetric reagent, whereas the presence of hGH-antibodies leads to an inhibition of cell proliferation. To validate the test system for the detection of hGH-antibodies, we tested serum samples of 4 patients suffering from neurosecretory dysfunction (NSD) and samples taken from 6 patients with growth hormone deficiency (GHD) which were treated with rhGH and were highly suspected for a-hGH antibodies. These samples were tested in two different immunological assays, capable to screen sera for anti-hGH immunreactivity in the case of hGH-insensitivity during GH treatment. Using the NAb assay the neutralizing activity of specific hGH-antibodies was proved in serum samples of NSD and GHD type 1A patients. In case of neutralizing hGH-antibody activity, a clinically based decision can be made whether rhGH therapy should be stopped or the rhGH dosis should be increased. By the use of our test system, we offer the measurement of anti-hGH-antibody activity to other laboratories in cases when secondary hGH-insensitivity is assumed or observed