Regulation of transgene expression in genetic immunization

The use of mammalian gene expression vectors has become increasingly import ant for genetic immunization and gene therapy as well as basic research. Es sential for the success of these vectors in genetic immunization is the pro per choice of a promoter linked to the antigen of interest. Many genetic im munization vectors use promoter elements from pathogenic viruses including SV40 and CMV, Lymphokines produced by the immune response to proteins expre ssed by these vectors could inhibit further transcription initiation by vir al promoters. Our objective was to determine the effect of IFN-gamma on tra nsgene expression driven by viral SV40 or CMV promoter/enhancer and the mam malian promoter/enhancer for the major histocompatibility complex class I ( MHC I) gene. We transfected the luciferase gene driven by these three promo ters into 14 cell lines of many tissues and several species. Luciferase ass ays of transfected cells untreated or treated with IFN-gamma indicated that although the viral promoters could drive luciferase production in all cell lines tested to higher or lower levels than the MHC I promoter, treatment with IFN-gamma inhibited transgene expression in most of the cell lines and amplification of the MHC I promoter-driven transgene expression in all cel l lines. These data indicate that the SV40 and CMV promoter/enhancers may n ot be a suitable choice for gene delivery especially for genetic immunizati on or cancer cytokine gene therapy. The MHC I promoter/enhancer, on the oth er hand, may be an ideal transgene promoter for applications involving the immune system.