Non‐replicating vaccinia vector efficiently expresses bacteriophage T7 RNA polymerase

Abstract

Modified vaccinia virus Ankara (MVA), a host range restricted and highly attenuated vaccinia virus strain, is unable to multiply in human and most other mammalian cell lines. Since viral gene expression is unimpaired in non‐permissive cells recombinant MVA viruses are efficient as well as exceptionally safe expression vectors. We constructed a recombinant MVA that expresses the bacteriophage T7 RNA polymerase and tested its usefulness for transient expression of recombinant genes under the control of a T7 promoter. Using the chloramphenicol acetyltransferase (CAT) gene as a reporter gene, infection with MVA‐T7pol allowed efficient synthesis of recombinant enzyme in mammalian cells. Despite the severe host restriction of MVA, enzyme activities induced by infection with MVA‐T7pol were similar to those determined after infection with a replication‐competent vaccinia‐T7pol recombinant virus. Thus, MVA‐T7pol may be used as a novel vaccinia vector to achieve T7 RNA polymerase‐specific recombinant gene expression in the absence of productive vaccinia virus replication.