A HYBRID BACULOVIRUS-T7 RNA-POLYMERASE SYSTEM FOR RECOVERY OF AN INFECTIOUS VIRUS FROM CDNA

We established a hybrid baculovirus-T7 RNA polymerase system for trans ient expression in mammalian cells. Two recombinant baculoviruses carr ying cDNA of bacteriophage T7 RNA polymerase, with or without a nuclea r localization signal, under the control of a mammalian promoter were constructed, High level expression of T7 RNA polymerase was observed i n various mammalian cell lines after infection with the recombinant ba culoviruses. After transfection of plasmids containing the luciferase gene under the control of the T7 promoter, high luciferase activity wa s detected in cells infected with the recombinant baculoviruses. We al so constructed a plasmid containing an entire cDNA clone of type 1 pol iovirus under the T7 promoter. Two days after transfection of the plas mid into the cells infected with the recombinant baculoviruses, a high titer of poliovirus was recovered. The use of the recombinant baculov iruses did not cause any cytopathic effects even at a high multiplicit y of infection. The lack of replication ability and low toxicity are t he advantageous features of the hybrid baculovirus-T7 polymerase syste m in comparison with the widely used vaccinia-T7 polymerase system for gene expression and recovery of infectious viruses from its cDNA. (C) 1997 Academic Press.