Viable double vaccinia virus recombinants with the non-inducible phage T7 expression system.

Double vaccinia virus recombinants expressing both the T7 RNA polymerase gene, controlled by a weak early poxvirus PF promoter, and the Escherichia coli beta-galactosidase gene, controlled by the phage T7 promoter, have been obtained. The viability of the double recombinants depended on the T7 RNA polymerase expression level. If the T7 RNA polymerase gene was inserted into a recombinant already containing the beta-galactosidase gene, the efficiency of formation of the double recombinants was significantly higher compared to that for the reverse insertion order. The negative effect of the phage T7 terminator on beta-galactosidase expression in cells infected with the recombinant viruses has been shown. The dynamics and levels of beta-galactosidase formation by different vaccinia virus recombinants have been studied.