title: A novel retro-inverso gonadotropin-releasing hormone (GnRH) immunogen elicits antibodies that neutralize the activity of native GnRH.
abstract: GnRH vaccines have been successfully used for the inhibition of gonadotropin secretion and gonadal function. As an alternative to native GnRH, retro-inverso (RI) GnRH might be an improved immunogen. The RI peptides are composed of D-amino acids assembled in the reverse order (C to N terminus) in relation to the parent L peptide. These peptides are immunogenic and can produce high titers of antibodies that bind the parent peptide with high affinity and specificity. We show that RI-GnRH peptides conjugated to ovalbumin as well as unconjugated RI-GnRH elicit high titers of anti-GnRH antibodies in rabbits and mice. Antibodies were affinity purified and shown by ELISA to be selective for mammalian GnRH compared with GnRH II and [Gln(8)]GnRH. The binding kinetics of antibody-peptide interactions was determined using biosensor technology (BIACORE). The purified anti-GnRH antibodies inhibited GnRH-stimulated signal transduction in COS-1 cells expressing the human GnRH receptor. Immunization of mice with unconjugated and conjugated RI-GnRH peptide, in the absence of complete Freund's adjuvant, produced antisera that cross-reacted with mammalian GnRH. As RI peptides are resistant to cleavage by proteolytic enzymes, they are potentially orally active. The ability of RI-GnRH peptides to produce antibodies to GnRH without conjugation and without Freund's complete adjuvant constitutes a novel vaccine with improved properties of potential application in animal management and sex hormone-dependent cancers.
authors.affiliation: Division of Medical Biochemistry, University of Cape Town Faculty of Health Sciences, 7925 Observatory, South Africa.
authors.forename: B
authors.initials: B
authors.lastname: Fromme
authors.forename: P
authors.initials: P
authors.lastname: Eftekhari
authors.forename: M
authors.initials: M
authors.lastname: Van Regenmortel
authors.forename: J
authors.initials: J
authors.lastname: Hoebeke
authors.forename: A
authors.initials: A
authors.lastname: Katz
authors.forename: R
authors.initials: R
authors.lastname: Millar
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D003270:Contraceptive Agents / Q000276:immunology; D005260:Female; D005620:Freund's Adjuvant / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000276:immunology* / Q000378:metabolism; D007114:Immunization; D007295:Inositol Phosphates / Q000378:metabolism; D008297:Male; D051379:Mice; D009369:Neoplasms / Q000276:immunology / Q000628:therapy; D011817:Rabbits; D014612:Vaccines / Q000494:pharmacology*
chemical_list: D001323:Autoantibodies; D003270:Contraceptive Agents; D007295:Inositol Phosphates; D014612:Vaccines; D007987:Gonadotropin-Releasing Hormone; D005620:Freund's Adjuvant