The vaccinia virus/bacteriophage T7 hybrid transient expression system
employs a recombinant vaccinia virus that encodes the T7 RNA polymera
se gene, a plasmid vector with a gene of interest regulated by a T7 pr
omoter, and any cell line suitable for infection and transfection. Alt
hough high expression in a majority of cells is achieved, the severe c
ytopathic effects of vaccinia virus and the safety precautions require
d for use of infectious agents are undesirable features of the system.
Here, we report the construction of a highly attenuated and avian hos
t-restricted vaccinia virus recombinant that encodes the T7 RNA polyme
rase gene (MVA/T7 pol) and demonstrate the use of the virus for transi
ent expression in mammalian cells. MVA/T7 pol has reduced cytopathic e
ffects compared to the previously used replication-competent vaccinia
virus, while providing a high level of gene expression in multiple mam
malian cell lines. (C) 1995 Academic Press, Inc.