Interferons impair early transgene expression by adenovirus-mediated gene transfer in muscle cells

Recombinant adenovirus (AVR) promises to be an efficient vector in gene therapy for neuromuscular diseases, but in preclinical experiments the expression of therapeutic genes is shorter lived in immunocompetent animals than in immunocompromised hosts. Interferons (IFN), which are known to have a role both in early antiviral activity and in late cytotoxic immunoreaction against the virus or transduced cells, may influence the efficiency of gene transfer. In this study we investigated the role of IFNs in determining the efficiency of gene transfer by AVR. AVRs expressing beta-galactosidase (beta-gal) from either a cytomegalovirus (CMV) or a troponin-l promoter were used. Muscle cells were infected by AVR after exposure to various IFNs. The alpha IFN treatment significantly reduced (up to fivefold) the CMV promoter-driven gene expression in muscle cells in vitro and in immature muscles in vivo, while the least effective inhibitor was beta IFN. The decrease in gene expression by IFNs was more pronounced with the CMV-driven transgene than troponin-I promoter-driven one and was due to a decrease in transcript level. Intrinsic IFNs that are triggered by AVR administration can decrease the efficiency of gene transfer in muscle cells. Therefore the use of muscle specific promoters in AVR and/or IFN inhibitory agents will likely improve the prospects of effective gene therapy by AVR.