Immunological effect of a synthetic growth hormone peptide on the growth performance in swine

Long-lasting rat growth enhancement by an immunoregulating synthetic peptide

We have studied the long-lasting effects on rat weight gain of an active immunization with a peptide construction consisting of the covalent linkage of the 104-113 GH sequence to the 323-339 sequence of ovalbumin and to adjuvant muramyl dipeptide (MDP). The 104-113 GH sequence has already been identified as a potential epitope capable of enhancing growth hormome (GH) activity when complexed with the specific antibodies. Our results show that: a) 104-113 peptide antibodies after reacting with the endogenous GH produced a weight gain up to 7% higher than that observed in unimmunized rats; and b) the position of the adjuvant sequence in the molecule was critical for the immune response. Antibodies elicited in hypophysectomised rats had no effect on weight gain, thus confirming that the increase in hormonal activity is actually linked to the binding of specific peptide antibodies to endogenous GH.

Active immunization of ewes against ovine placental lactogen increases birth weight of lambs and milk production with no adverse effect on conception rate

In two experiments, 16 Booroola-Assaf and 35 Assaf ewe-lambs were actively immunized at 5 months of age against recombinant ovine placental lactogen (oPL). At 9 months of age, the ewe-lambs were mated for the first time and then introduced into a frequent mating-system. Anti-oPL antibody titers, reproductive performance, maternal serum levels of oPL during pregnancy, lamb birth weight and milk production of the ewes were followed in the immunized ewes and in their non-immunized control counterparts. All the immunized ewes developed anti-oPL antibodies, which interfered with oPL bioactivity in an in vitro cell proliferation assay. Conception rates did not differ (P>0.05) between immunized and non-immunized ewes. Abundant antibody-bound non-active oPL detected in sera of immunized ewes by western blotting indicated enhanced oPL production by the placenta following immunization. An increase (P<0.02) in serum oPL bioactivity, but not immunoreactivity, was observed in the immunized ewes in late gestation relative to control ewes. The average litter size was 1.83 and 1.32 lambs born per ewe lambing in the first and second experiments, respectively. Average birth weights of lambs born to the immunized ewes were higher (P<0.01) than for lambs born to control ewes by 10, 17 and 39% for those born as singles, twins and triplets, respectively. Immunized ewes produced 19 and 33% more milk (P<0.02) than the control ewes in the first 3.5 months of the first and second lactations, respectively. These findings do not suggest a role for oPL in maternal recognition of pregnancy, but they strongly suggest important roles for oPL in fetal growth and mammogenesis. Immunization of ewes against oPL may thus represent a novel practical technique for enhancing birth weights of lambs born to prolific sheep, as well as milk production by both dairy and mutton ewes.

Somatotropin delivery to farmed animals

Bovine somatotropin (bST) is marketed worldwide for increased milk production in cows while porcine somatotropin (pST) is approved in one country for increasing growth in swine. Somatotropin physicochemical properties, animal production method limitations and the need for cost effectiveness each contribute to the type of formulation developed. Various somatotropin physicochemical properties made formulation design difficult: heat and enzyme lability, tendency to aggregate, pH dependent solubility and stability, complicated degradation pathways and rapid in vivo clearance. The main problem of improving chemical and physical stability has been partially solved using certain excipients and vehicles. Formulations design to prolong somatotropin release include implants (matrix, osmotic), oleaginous suspensions and microparticles. This article presents the current status of somatotropin delivery in farmed animals, reviews the challenges encountered with formulation development, summarizes formulation approaches and discusses future somatotropin uses.

Augmentation of hormonal activities with antibodies from cattle immunized with a combination of synthetic and recombinant growth hormone peptide

Antibodies generated against a synthetic growth hormone (GH) peptide in a number of animal species were shown to enhance the efficacy of GH. However, the ability to produce the effective antibodies diminished over time and repeated boosters failed to overcome the hurdle. Therefore, this study was designed to address the issue on the failed antibody responses by employing different GH peptide antigen preparations in cattle. Holstein steers were repeatedly immunized with a synthetic peptide corresponding to an amino acid sequence 54-95 of porcine GH (pGH). The peptide was conjugated to ovalbumin (OVA) as a carrier. Animals initially responded to the antigen well and elicited antibodies specific to the peptide. However, the 4th challenge with the same OVA-peptide antigen rendered animals unresponsive, resulting in a decline in antibody production. This unresponsiveness was overcome by switching the antigen at the 5th immunization from OVA-peptide to a recombinant peptide preparation which was composed of maltose binding protein (MBP) as a carrier. Antibodies generated in cattle after the 5th immunization recognized not only the pGH(54-95) peptide, but also bovine GH (bGH) and pGH. These antibodies were not immunoreactive with an unrelated control peptide. Hypophysectomized (hypox) rats were used for functional analysis and bGH was active in promoting the growth of these GH-deficient rats. The growth-promoting effect of bGH was significantly enhanced by mixing it with bovine anti-peptide antibodies prior to administration. Therefore, the present findings suggest that peptide 54-95 induces cattle to elicit antibodies capable of not only recognizing bGH but also augmenting the somatogenic effectiveness of bGH in hypox rats.

Augmentation of hormonal activities with antibodies from cattle immunized with a combination of synthetic and recombinant growth hormone peptide

Antibodies generated against a synthetic growth hormone (GH) peptide in a number of animal species were shown to enhance the efficacy of GH. However, the ability to produce the effective antibodies diminished over the time and repeated boosters failed to overcome the hurdle. Therefore, this study was designed to address the issue on the fallen antibody responses by employing different GH peptide antigen preparations in cattle. Holstein steers were repeatedly immunized with a synthetic peptide corresponding to an amino acid sequence 54-95 of porcine GH (pGH). The peptide was conjugated to ovalbumin (OVA) as a carrier. Animals initially responded to the antigen well and elicited antibodies specific to the peptide. However, the 4th challenge with the same OVA-peptide antigen rendered animals unresponsive, resulting in a decline in antibody production. This unresponsiveness was overcome by switching the antigen at the 5th immunization from OVA-peptide to a recombinant peptide preparation which was composed of maltose binding protein (MBP) as a carrier. Antibodies generated in cattle after the 5th immunization recognized not only the pGH(54-95) peptide, but also bovine GH (bGH) and pGH. These antibodies were not immunoreactive with an unrelated control peptide. Hypophysectomized (hypox) rats were used for functional analysis and bGH was active in promoting the growth of these GH-deficient rats. The growth-promoting effect of bGH was significantly enhanced by mixing with bovine anti-peptide antibodies prior to administration. Therefore, the present findings suggest that peptide 54-95 induces cattle to elicit antibodies capable of not only recognizing bGH but also augmenting the somatogenic effectiveness of bGH in hypox rats.

Molecular interaction of growth hormone with two monoclonal antibodies recognizing distinct epitopes

Two monoclonal antibodies (mAb), designated PS-7.6 and PS-11.2, were generated against recombinant porcine growth hormone (pGH) and shown to enhance the hormonal activity in promoting the growth of animals. The mAb were compared and their functional relationship investigated. It was demonstrated by radioimmunoassay that PS-11.2 did not compete, but rather enhanced binding of 125I-pGH tracer to PS-7.6, suggesting that both mAb recognized distinct epitopes and also were additive in their antigen bindings. Surface plasmon resonance analysis using optical BIAcore technology (Pharmacia Biosensor, Piscataway NJ, USA) provided additional data to support this idea because pGH, after being captured by PS-11.2, remained capable of interacting with PS-7.6. An anti-idiotypic mAb was employed and shown to interact with PS-7.6 but not PS-11.2, implying that the differences in the Fab variable regions of these two mAb might contribute to their epitope specificity. Binding kinetics were determined by the BIAcore and the individual affinities of PS-7.6 and PS-11.2 to pGH were 6.8 x 10(-8) and 1.2 x 10(-9) mol/L, respectively. When these mAb were sequentially subjected to the BIAcore, however, their affinities decreased by approximately 100-fold. Therefore, binding of pGH with one mAb significantly impaired a subsequent interaction with another mAb despite the fact that both mAb targeted different epitopes. Hypophysectomized rats were used for functional analysis and pGH was active in promoting growth of these GH-deficient animals. The hormonal effect was further improved by incubating pGH with either PS-7.6 or PS-11.2 prior to administration. However, enhancement by individual mAb was completely abolished when pGH was treated with both mAb together, indicating their unpredictable biological interference with each other. Therefore, the present findings clearly demonstrate that although PS-7.6 and PS-11.2 recognize separate epitopes, their individual interactions with pGH are closely interrelated both immunologically and biologically.

Enhancement of the insulin antagonistic effect of porcine somatotropin in swine using a monoclonal antibody

A monoclonal antibody (mAb), PS-7.6, to porcine somatotropin (pST) significantly enhanced the growth responses to pST injections in hypophysectomized (hypox) rats but could not be tested in pigs because of the large quantity of antibody required for a growth trial. Because pST inhibits the hypoglycemic effects of insulin, an insulin tolerance test procedure was established to measure pST activity in jugular-catheterized pigs. Doses of 0, 30, 100, and 300 micrograms/kg per day of pST were split and administered subcutaneously (sc) in equal portions twice daily for 2 d. After a 17-hr fast, plasma samples were obtained at 10-min intervals for 30 min before an intravenous injection of insulin (0.08 IU/kg) and then for an additional 50 min. Because pST increased fasting plasma glucose concentrations, preinsulin glucose values were used as a covariate to adjust the postinsulin concentrations. pST caused a dose-dependent increase in resistance to the insulin injection in these pigs. The areas under the curves (AUC), for plasma glucose were 22.1, 29.0, 39.0, and 47.2 mg/dl per min for the 0, 30, 100, and 300 micrograms/kg pST doses, respectively. Because different doses of pST could be detected, the PS-7.6 enhancement of pST treatment was evaluated. In the first experiment, five pigs/group each received sc injections of either vehicle, pST (75 micrograms/kg; approximately 3.0 mg/d), pST (75 micrograms/kg) + PS-7.6 at 3.75 mg/kg, or pST (75 micrograms/kg) + PS-7.6 at 15 mg/kg for 2 d before the insulin test. The pST and PS-7.6 were combined and incubated for at least 1 hr at room temperature before being injected. The injection of pST alone did not significantly change insulin tolerance activity (23.1 vs. 21.1, AUC), but insulin resistance was enhanced when this dose of pST also included PS-7.6 (27.4 and 29.5, AUC, respectively; P < 0.05). In a second experiment, the effects of PS-7.6 and PS-4.2, a mAb that did not potentiate the pST-stimulated growth of hypox rats, were compared. The five pigs/treatment received either vehicle, pST (75 micrograms/kg), pST (75 micrograms/kg) + PS-7.6 (3.75 mg/kg), or pST (75 micrograms/kg) + PS-4.2 (3.75 mg/kg) for 2 d. The administration of pST increased the resistance to insulin (26.7 vs. 18.8, AUC; P < 0.01), which was markedly potentiated by PS-7.6 (54.3, AUC, P < 0.001) but not affected by PS-4.2 (27.6 AUC). The injection of PS-7.6 at 7.5 mg/kg without exogenous pST did not alter the sensitivity to insulin. These results indicate that PS-7.6, but not PS-4.2, enhanced the insulin antagonistic activity of pST in swine, suggesting that an enhancement of pST-stimulated growth would also occur in PS-7.6-treated pigs.