AUGMENTATION OF THE EFFECTIVENESS OF PORCINE GH WITH SWINE ANTIBODIESINDUCED BY A SYNTHETIC GH PEPTIDE

An effort was made to evaluate the potential usefulness of a peptide v accine in improving the growth performance of farm animals. It was pre viously reported that a murine PS-7.6 monoclonal antibody (mAb) which was specific to porcine GH (pGH) enhanced the growth-promoting activit y of pGH in an experimental hypophysectomized rat model. Additional da ta from a epitope mapping study suggested that PS-7.6 mAb recognized a pGH fragment corresponding to an amino acid sequence 54-95. In this r eport, therefore, a peptide pGH(54-95) was synthesized in an attempt t o induce PS-7.6-like antibodies in swine. It was demonstrated that the peptide pGH(54-95) competed with PS-7.6 mAb for the binding to radioa ctive pGH in a competition radioimmunoassay and also caused pigs to el icit polyclonal antibodies immunoreactive to pGH protein. The associat ion and dissociation rate constants of the swine antibody to pGH were 1.9 x 10(2) M(-1) s(-1) and 32 x 10(-4) s(-1) respectively, thus produ cing an overall binding affinity of K-d=1.6 x 10(-6) M. The swine anti body partially competed with murine PS-7.6 mAb for the binding to pGH, suggesting that the pGH-recognizing sites for both antibodies might b e closely related. The biological effect of the swine antibody was exa mined in hypophysectomized rats and shown to significantly augment pGH activity in promoting the growth of these GH-deficient animals. The p resent findings suggest that a synthetic peptide may be developed as a potential growth vaccine for swine to generate antibodies capable of enhancing the effectiveness of endogenous pGH.