PROMOTER ATTENUATION IN GENE-THERAPY - INTERFERON-GAMMA AND TUMOR-NECROSIS-FACTOR-ALPHA INHIBIT TRANSGENE EXPRESSION

One of the major limitations to current gene therapy is the low-level and transient vector gene expression due to poorly defined mechanisms, possibly including promoter attenuation or extinction. Because the ap plication of gene therapy vectors in vivo induces cytokine production through specific or nonspecific immune responses, we hypothesized that cytokine-mediated signals may alter vector gene expression. Our data indicate that the cytokines interferon-gamma (IFN-gamma) and tumor nec rosis factor-alpha (TNF-alpha) inhibit transgene expression from certa in widely used viral promoters/enhancers (cytomegalovirus, Rous sarcom a virus, simian virus 40, Moloney murine leukemia virus Long terminal repeat) delivered by adenoviral, retroviral or plasmid vectors in vitr o. A constitutive cellular promoter (beta-actin) is less sensitive to these cytokine effects. Inhibition is at the mRNA level and cytokines do not cause vector DNA degradation, inhibit total cellular protein sy nthesis, or kill infected/transfected cells. Administration of neutral izing anti-IFN-gamma monoclonal antibody results in enhanced transgene expression in vivo. Thus, standard gene therapy vectors in current us e may be improved by altering cytokine-responsive regulatory elements. Determination of the mechanisms involved in cytokine-regulated vector gene expression may improve the understanding of the cellular disposi tion of vectors for gene transfer and gene therapy.