Protection against
foot-and-mouth disease (FMD) using
DNA technology has been documented for sheep and pigs but not for the highly susceptible species of cattle. Twenty-five Holstein Friesian cross-bred cattle were vaccinated twice, 21 days apart, with
a DNA vaccine containing the capsid coding region (P1) along with the non-structural
proteins 2A, 3C and 3D (pcDNA3.1/P1-2A3C3D) of O(1) Kaufbeuren alone or coated onto PLG (d,l-
lactide-co-glycolide) microparticles. In some pcDNA3.1/P1-2A3C3D was also combined with an adjuvant plasmid expressing bovine
granulocyte macrophage colony stimulating factor (
GM-CSF).
DNA vaccinations were administered intramuscularly with, or without, the use of electroporation and at 42 days post primary vaccination cattle received a
protein boost of 146S FMD virus (FMDV)
antigen and non-structural
protein 3D. For comparison, four cattle were vaccinated with a conventional FMD
vaccine and two more included as unvaccinated controls. Apart from those immunised with PLG microparticles all cattle were challenged with 10(5) TCID(50) cattle adapted O(1) Lausanne FMDV virus at day 93 post primary vaccination. All
DNA vaccinated cattle regardless of regime developed good humoral and cell mediated responses prior to challenge. The best overall virus neutralising antibody, IFN-γ and clinical protection (75%) were seen in the cattle whereby the
DNA was delivered by electroporation. In contrast, only 25% of cattle vaccinated with the
DNA vaccine without electroporation were clinically protected. The addition of
GM-CSF in combination with electroporation further improved the efficacy of the
vaccine, as demonstrated from the reduction of clinical disease and virus excretions in nasal swabs. We thus demonstrate for the first time that cattle can be clinically protected against FMDV challenge following
a DNA prime-
protein boost strategy, and particularly when
DNA vaccine is combined with
GM-CSF and delivered by electroporation.