Innate Immune Response Induced by Baculovirus Attenuates Transgene Expression in Mammalian Cells.

The baculovirus Autographa californica nucleopolyhedrovirus (AcNPV) has been widely used to achieve a high level of foreign gene expression in insect cells, as well as for efficient gene transduction into mammalian cells without any replication. In addition to permitting efficient gene delivery, baculovirus has been shown to induce host innate immune responses in various mammalian cells and in mice. In this study, we examined the effects of the innate immune responses on the gene expression by recombinant baculoviruses in cultured cells. The reporter gene expression in IRF3-deficient mouse embryonic fibroblasts (MEFs) by the infection with the recombinant baculovirus was shown to be enhanced in accordance with the suppression of IFN-β production. Furthermore, efficient gene transduction by the recombinant baculovirus was achieved in MEFs deficient for STING, TBK1, IRF3 or IPS-1, but not in those deficient for IRF7, MyD88 or ZBP1/DAI. An enhancement of gene expression by the recombinant baculovirus was also observed in human hepatoma cell lines replicating hepatitis C virus (HCV), in which innate immunity was impaired by the cleavage of IPS-1 by the viral protease. In addition, infection with the recombinant baculovirus expressing the BH3-only protein, BIMS, a potent inducer of apoptosis, resulted in a selective cell death in the HCV replicon cells. These results indicate that innate immune responses induced by infection with baculovirus attenuate transgene expression, and this characteristic might be useful for a selective gene transduction into cells with impaired innate immunity arisen from infection with various viruses. [ABSTRACT FROM AUTHOR]