Objective: To investigate the immunogenicity of a domestic recombinant human growth hormone (rhGH) preparation and assess its influence on the growth-promoting effect.
Methods: We developed a specific and sensitive radioimmuno-precipitation assay to determine the anti-hGH-antibody (GH-Ab) in serum of GH-deficient (GHD) children treated with rhGH preparation. The study included 61 GHD children (49 boys and 12 girls) who were treated with daily subcutaneous injections of rhGH (0.1 IU/Kg) before sleep for six months. The patients' height, growth velocity and height standard deviation score were measured prior to and after treatment. The binding ratio with 125I-hGH and titer of GH-Abs were measured by radioimmuno-precipitation assay; the binding capacity and affinity (Ka) were analyzed by competitive RIA and Scatchard plot method.
Results: Three months after rhGH therapy, serum GH-Abs were detected in 29 patients (48%), and their GH-Abs were persistently positive till the end of the trial. Serum GH-Ab was not detectable in the other 32 patients (52%) during treatment. The GH-Abs positive samples, according to the 125I-hGH binding ratio (B/T%), were divided into the weakly positive (B/T < 10%, n = 20) and strong positive (B/T > 15%, n = 9) groups; their binding capacity, affinity (Ka) and titer were (0.1-4.8) pmol/L, (1.7 x 10(7)-6.5 x 10(8))L/mol and 1:4-1:8, respectively. They were weak and not available to give negative effect to rhGH activity. The height and growth velocity as well as height standard deviation score of the GH-Ab positive patients presented no decrease during treatment and were not significantly different from that of negative patients.
Conclusion: The domestic rhGH preparation certainly had growth-promoting effect on the children with GHD. Nearly forty-eight percent patients showed GH-Ab positive in serum, but due to the lower titer and binding capacity, the GH-Ab had no negative effect on the height velocity of GHD children.