Structural requirements for the induction of "immunological castration" by linear monomeric LHRH-lys-MDP administered in saline

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.

Immunization against GnRH in male species (comparative aspects)

Active immunization against gonadotropin-releasing hormone (GnRH) was recognized in the 1970s as a potential means by which the reproductive system of mammals might be shut down for various practical and clinical reasons. Numerous studies in males have been performed since that time to determine the applicability of the technique as an alternative to surgical removal of the testes. Reasons for such immunocastration include improvement of meat and carcass characteristics for cattle, sheep, goats, and swine; improvement in feed efficiency relative to castrates in those same species; reduction in male aggressive behavior; reduction in male-associated odors in goats and swine; and fertility neutralization in pet species. Although application as a fertility control agent in men is unlikely, there is renewed interest in active immunization against GnRH as a means of treating prostate cancers and related steroid-dependent pathologies.

Muramyl-peptide/gastrin conjugates as potential immunogens

For a selective covalent linkage of muramyl-peptides with human-little-gastrin the maleimide-thiol reaction principle was adopted. For this purpose thiol-functionalized muramyl-peptide derivatives, i.e. N-acetyl-muramyl-alanyl-D-isoglutaminyl-cysteamine and N-acetyl-muramyl-alanyl-D-isoglutaminyl-N epsilon-palmitoyl-lysyl-cysteamine, were reacted with N alpha-maleoyl-beta-alanyl-[15-methoxinine]-human-little-g ast rin-I-[2-17]. The resulting gastrin conjugates were used in immunization experiments on rabbits and mice. Unexpectedly, these gastrin derivatives proved to be poorly immunogenic despite the built-in immunoadjuvanticity. The titers of the antipeptide antibodies as well as of the unspecific immunoglobulins were in the range of those of the control group.