Induction of porcine cytokine mRNA expression after DNA immunization and pseudorabies virus infection

Injection of plasmid DNA encoding pseudorabies virus (PRV) glycoprotein int o pig muscle has been shown to result in protective immunity against lethal infection. Here, pigs were vaccinated by a single coinjection of three pla smids encoding PRV glycoproteins gB, gC, and gD, with plasmid expressing po rcine granulocyte-macrophage colony-stimulating factor (GM-CSF) or porcine interferon-alpha (IFN-alpha). DNA immunization induced a primary T cell-med iated response characterized by low rates of IFN-gamma, interleukin-2 (IL-2 ), and IL-4 mRNA in peripheral blood mononuclear cells (PBMC). Very low rat es of PRV-specific IgG1 and the absence of IgG2 were obtained. Codelivery o f plasmid expressing GM-CSF or IFN-alpha had no effect on cytokine mRNA exp ression or on B cell response. After a high virulent challenge, high levels of cytokine mRNA, mainly IFN-gamma, and high secondary antibody (Ab) respo nse were induced in all DNA-vaccinated pigs. Codelivery of GM-CSF gene sign ificantly increased both Th immune response (i.e., IFN-gamma and IL-4 mRNA expression) and clinical protection but had no effect on secondary B immune response. Codelivery of IFN-alpha gene had no beneficial effect on seconda ry T and B cell immune responses.