Recognition of porcine growth hormone by a panel of monoclonal antibodies

A panel of murine monoclonal antibodies (MAbs) against porcine growth hormone (pGH) has been raised from BALB/c mice. MAbs were characterized for binding to growth hormones (GH), prolactins (PRL), and placental lactogen (PL) from different species and to the N-terminal peptides of GH. From their patterns of cross-reactivity MAbs were assigned into nine specificity groups. The sharing of pGH epitopes among hormones of different species was related to the sequence similarity to pGH, i.e., overlap was greatest for equine, ruminant, and rodent GHs and least for human GH, ovine, and porcine PRLs, and human PL. Partial epitope mapping was carried out by relating hormone cross-reactivity patterns with amino acid sequences. Two epitopes were localized to interhelical loops, around valine-73 and glycine-130, respectively. Direct mapping with synthetic peptides localized other epitopes (Groups 7, 8, and 9) to the N-terminal region of the GH molecule. Selected MAbs were studied for the enhancement of the somatogenic activity of pGH in the dwarf mouse bioassay, measuring weight gain and sulphate incorporation into costal cartilage. Only those antibodies with specificities for GHs and not PRL or PL showed significant enhancement in this assay.