The cell-mediated immune response induced by plasmid encoding bovine herpesvirus 1 glycoprotein B is enhanced by plasmid encoding IL-12 when delivered intramuscularly or by gene gun, but not after intradermal injection

Bovine herpesvirus 1 (BHV-1) causes respiratory and genital infections in cattle. Previously we demonstrated that a DNA vaccine encoding a truncated, secreted form of BHV-1 glycoprotein B (tgB) induces cytotoxic T lymphocyte (CTL) responses in C3H mice. In this study we investigated the potential of interleukin 12 (IL-12) to further enhance the CTL response. C3H mice were immunized with a plasmid encoding tgB or with plasmids encoding tgB and murine IL-12. When the plasmid encoding tgB was delivered intramuscularly or epidermally by a gene gun, co-administration with IL-12 plasmid stimulated the synthesis of more IgG2a, the production of higher levels of IFN-γ, and more effective killing by CTLs. In contrast, after intradermal delivery no effect of co-administration of IL-12 encoding plasmid was observed. Further investigation suggested that antigen and IL-12 need to be expressed in the draining lymph nodes, where IL-12 can have a direct effect on T cells.