We have studied the long-lasting effects on rat weight gain of an active im
munization with a peptide construction consisting of the covalent linkage o
f the 104-113 GH sequence to the 323-339 sequence of ovalbumin and to adjuv
ant muramyl dipeptide (MDP). The 104-113 GH sequence has already been ident
ified as a potential epitope capable of enhancing growth hormome (GH) activ
ity 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 effe
ct on weight gain, thus confirming that the increase in hormonal activity i
s actually linked to the binding of specific peptide antibodies to endogeno
us GH. (C) 2001 Editions scientifiques et medicales Elsevier SAS.