Abstract:
An orally-delivered immunocontraceptive vaccine is being developed for thecontrol of fox populations. A number of genes (PH-20,LDH-C<emph type="8">4, ZP3) encoding gamete proteins have been cloned,produced in recombinant expression systems and used in fertility trials totest the efficacy of these antigens. As the immunocontraceptive vaccine willbe delivered in a bait, there is a requirement for a greater understanding ofthe immune responses of the reproductive mucosa in canids, and the assessmentof the best vaccine delivery system that will evoke a mucosal antibodyresponse. Several vaccine delivery systems including microencapsulatedantigens, and both vaccinia virus and bacterial vectors are beinginvestigated. Oral administration ofSalmonella typhimurium recombinants expressing differentfox sperm antigens stimulates both systemic IgG responses to the antigen and amucosal immune response within the female reproductive tract in the fox,indicating that salmonella may have potential with respect to the oraldelivery of antigen. The enhancement of mucosal immune responses toorally-delivered vaccines is also being examined, research focussing on thepossible use of fox-specific cytokines or the β-subunit of cholera toxinin forming part of the vaccine construct.