Induction of Porcine Cytokine mRNA Expression After DNA Immunization and Pseudorabies Virus Infection

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Abstract
Injection of plasmid DNA encoding pseudorabies virus (PRV) glycoprotein into pig muscle has been shown to result in protective immunity against lethal infection. Here, pigs were vaccinated by a single coinjection of three plasmids encoding PRV glycoproteins gB, gC, and gD, with plasmid expressing porcine granulocytemacrophage colony-stimulating factor (GM-CSF) or porcine interferon-α (IFN-α). DNA immunization induced a primary T cell-mediated response characterized by low rates of IFN-γ, interleukin-2 (IL-2), and IL4 mRNA in peripheral blood mononuclear cells (PBMC). Very low rates of PRV-specific IgG1 and the absence of IgG2 were obtained. Codelivery of plasmid expressing GM-CSF or IFN-α had no effect on cytokine mRNA expression or on B cell response. After a high virulent challenge, high levels of cytokine mRNA, mainly IFN-γ, and high secondary antibody (Ab) response were induced in all DNA-vaccinated pigs. Codelivery of GMCSF gene significantly increased both Th immune response (i.e., IFN-γ and IL-4 mRNA expression) and clinical protection but had no effect on secondary B immune response. Codelivery of IFN-α gene had no beneficial effect on secondary T and B cell immune responses.