NONREPLICATING VACCINIA VECTOR EFFICIENTLY EXPRESSES BACTERIOPHAGE-T7 RNA-POLYMERASE

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.