Expression of target genes by coinfection with replication-deficient viral vectors.

An in vivo transcription system was developed by coinfection of cells with replication-deficient viral vectors. Recombinant baculovirus (AcT7HCVLuc) and fowlpox virus (FPVT7HCVLuc) carrying a cDNA of the hepatitis C virus (HCV) minigene encoding the HCV 5' untranslated region (UTR), a luciferase gene and the 3' UTR, including the 98 nt extra sequence, under the control of the T7 promoter were constructed. The HCV minigene was synthesized in various cells by coinfection with one of these two viruses and recombinant baculovirus (AcCAT7) or adenovirus (AdexCAT7) expressing T7 RNA polymerase under the control of a mammalian promoter. Only a low level of luciferase expression was obtained in cells coinfected with AcT7HCVLuc and either AcCAT7 or AdexCAT7. In contrast, high-level luciferase expression was detected when the same cells were coinfected with FPVT7HCVLuc and either AcCAT7 or AdexCAT7. We further constructed a recombinant fowlpox virus with its HCV minigene extended to contain the whole HCV core protein region. Significantly high levels of expression of HCV core protein were detected in MT-2, COS7 and Vero cells by coinfection with the recombinant fowlpox virus and AdexCAT7. A coinfection system consisting of recombinant fowlpox virus and AdexCAT7 was established for high level of expression of a target gene in various cells.