This study was conducted to investigate whether the co-delivery of
DNA encoding porcine
cytokines would enhance a protective immune response in pigs to a Pseudorabies virus (PRV; or Aujeszky's disease virus)
DNA vaccine.
Aujeszky's disease in pigs results in respiratory and nervous symptoms with important economic losses. To evaluate
cytokine effects, eukaryotic expression vectors were constructed for porcine
GM-CSF,
IL-2 and IFN-gamma.
cDNA for each of these
cytokines was inserted under the control of a CMV promoter in the pcDNA3 plasmid and
cytokine expression was confirmed after
DNA transfection in various mammalian cell cultures by bioassays (
GM-CSF and
IL2) and ELISA (IFN-gamma). Pigs were vaccinated by single
intramuscular injection with plasmid
DNA encoding PRV gB and gD along with various combinations of
cytokine plasmid constructs. Pig serum was tested for the production of antibody by isotype specific anti-PRV ELISA. Pigs were then challenged with the highly virulent PRV strain NIA3 on day 21 after vaccination. The survival and growth rate of pigs were monitored for seven days after the viral challenge. The co-administration of
GM-CSF plasmid increased the immune response induced by gB and
gD PRV DNA vaccine. This immune response was characterized by an earlier appearance of anti-PRV
IgG2, a significantly enhanced anti-PRV
IgG1 and
IgG2 antibody response, a significantly decreased and shortened viral excretion in nasal swabs and an improved protection to the viral challenge. In contrast, the co-administration of porcine
IL-2 or IFN-gamma had no adjuvant effects. Our results thus demonstrate for the first time that the application of porcine
GM-CSF gene in
a DNA vaccine formulation can exert immuno-adjuvant and protective effects with single vaccination in the natural host pig against
Aujeszky's disease.