Totally synthetic peptide-based immunocontraceptive vaccines show activity in dogs of different breeds

In this study we examine the immunogenicity of totally synthetic peptide-based immunocontraceptive vaccines in dogs. Seven individual epitope-based vaccines were assembled in which a different T helper (T(H)) cell epitope derived from the sequence of F protein of canine distemper virus was synthesized in tandem with a peptide representing luteinising hormone releasing hormone (LHRH). Each of the individual T(H)-LHRH peptide vaccines was inoculated subcutaneously into dogs. The results demonstrate that five of the seven peptide vaccines were able to elicit strong anti-LHRH antibody responses in beagle foxhounds accompanied by a concomitant suppression in the levels of the hormones testosterone and progesterone in the majority of the animals. A pool of these five peptides was then used to inoculate five different breeds of dogs. All animals responded with high levels of anti-LHRH antibody. An investigation of the proliferative responses of peripheral blood mononuclear cells (PBMC) obtained from inoculated dogs showed that the majority of breeds responded to each of the individual T helper cell epitope tested. The results provide a strategy for development of an immunocontraceptive vaccine for use in multiple breeds of dogs.