Evaluation of two GnRH-I based vaccine formulations on the testes function of entire Suffolk cross ram lambs.

A modified GnRH peptide (CHWSYGLRPG-NH(2)) was conjugated to tetanus toxoid (TT) or diphtheria toxoid (DT) and formulated with Quil A saponin or a sustained release injectible PLGA (poly(lactide-co-glycolide)/triacetin). For the Quil A formulations, two administrations of TT conjugate at 3-weekly intervals were followed by two booster injections with the DT conjugate in entire ram lambs. With the PLGA formulations, only two injections were administered; the first containing TT and the second DT at 6-weekly intervals. Evaluation was carried out by comparing the specific antibody levels produced in relationship to hormone profiles and testicular changes. The Quil A formulation was considered the most effective, as it caused significant reduction in testosterone and follicle stimulating hormone levels, resulting in marked suppression of spermatogenesis.

Immune responses to a GnRH-based anti-fertility immunogen, induced by different adjuvants and subsequent effect on vaccine efficacy.

A modified GnRH peptide (CHWSYGLRPG-NH2) was conjugated to tetanus toxoid and formulated with different adjuvants (non-ionic surfactant vesicles, aluminium hydroxide, Quil A, PLGA (poly(lactide-co-glycolide)/triacetin), and Quil A/PLGA). A comparison of the anti-fertility efficacy of the formulations was made by examining specific antibody levels, antibody subclasses, endocrine ablation and gonadal atrophy. The production of IgG2b antibody provided the best correlation for castration. PLGA was considered the most effective adjuvant as it produced a consistent anti-fertility response in all the treated animals.

Sustained-release injectables formed in situ and their potential use for veterinary products.

The controlled drug delivery of hydrophilic and lipophilic drug substances via the parenteral route has gained increasing importance in the development of pharmaceutical dosage forms. In particular, the animal health industry has generated strong interest in long-term drug delivery for both companion and farm animals during the past few years. At present sustained-release injectables formed in situ for s.c./i.m. administration have become an attractive alternative to common slow release technologies such as microspheres or standard implants. In this context, technologies based on PLA/PLGA, sucrose acetate isobutyrate (SAIB) and the amphipathic molecules Poloxamer, glycerol monooleate or PEG-PLA-PEG copolymers, are discussed. Release periods from hours to months can be obtained by choosing one of these drug delivery technologies. The release times are strongly dependent on the biodegradation of the polymers and the physico-chemical properties of the drug substance used. Furthermore, the use of different solvents for the matrix-forming agents and the individual loading capacity are critically assessed. Additionally acceptance of the excipients for parenteral use by the regulatory authorities is closely considered. Scientific articles as well as patent publications are reviewed to give a wide overview of the existing approaches and their future potential for animal health products.