Contraceptive Effect of a Recombinant GnRH Vaccine in Adult Female Pigs

GonaCon is a gonadotropin releasing hormone (GnRH) contraceptive vaccine developed at the USDA National Wildlife Research Center (NWRC) that contains keyhole limpet hemocyanin (KLH) coupled to GnRH. The vaccine is administered intramuscularly in an emulsion with the NWRC adjuvant, AdjuVac. This first-generation vaccine, developed in 1998, has been very effective in contracepting every species tested. However, because of the high cost of KLH, NWRC has developed a second generation GnRH vaccine, replacing KLH with a less expensive mollusk protein. This second generation GnRH vaccine, called GonaCon-Blue, is currently being tested in several species and has proven to be as, or more effective than the original GonaCon. Scientists with the Reproductive Control Methods Project at the NWRC are also testing a recombinant GnRH antigen developed by Dr. Talwar of the Talwar Research Institute, India. The recombinant antigen was produced from plasmid gene expression grown in and extracted from E. coli. The antigen is combined with the NWRC AdjuVac to form an emulsion similar to the GonaCon preparation. The recombinant vaccine has been shown to be effective as a single or duel injection for contraception of adult female pigs in a short-term study at the Swine Research Facility at Penn State University. Although the long term effectiveness of the recombinant vaccine remains to be established, this small molecule of approximately 14,000 MW is of considerable interest because it may be effective in oral or transcutaneous applications. It could also be scaled-up for large field