Protection of swine from foot-and-mouth disease with one dose of an all-D retro peptide.

Nine pigs were given a single inoculum of 100 microg of the all-D retro peptide corresponding to the immunodominant GH loop encompassing residues 141-159 of capsid protein VP1 of foot-and-mouth disease virus serotype A, sub-type 12. The peptide was conjugated to activated keyhole limpet haemocyanin and oil-adjuvanted before inoculation. The animals were challenged eleven weeks post-vaccination by exposing them to a pig which had been infected with the virus by inoculation. Two naive animals were included in the challenge study as controls. One of the vaccinated animals was completely unprotected and two developed very small lesions. None of the six remaining animals exhibited any clinical signs but two developed antibodies against nonstructural proteins indicating that replication of the virus had occurred. No evidence of replication could be detected in the remaining four animals, either by rise in neutralizing antibody titre or by production of antibodies against non-structural proteins specific for virus replication.