Mutants of replication competent vaccinia virus

A recombinant vaccinia virus comprising:

• a first nucleic acid comprising a vaccinia virus early/late promoter and a tetR gene, wherein the vaccinia virus early/late promoter is operably linked to the tetR gene;
• and
• a second nucleic acid comprising a recombinant A14 gene and a tet response element, wherein the tet response element is operably positioned between the A14 transcriptional start site and the A14 translational start site,
• wherein the first nucleic acid is in a non-essential region of the vaccinia virus genome.

A recombinant vaccinia virus comprising:

• a first nucleic acid comprising a vaccinia virus late promoter and a tetR gene, wherein the vaccinia virus late promoter is operably linked to the tetR gene;
• and
• a second nucleic acid comprising an expression control sequence comprising a tet response element and the PKR gene, wherein the tet response element is operably linked to the PKR gene,
• wherein the first and second nucleic acids are in non-essential regions of the vaccinia virus genome.

A recombinant vaccinia virus comprising:

• a first nucleic acid comprising a vaccinia virus early/late promoter and a reverse tetR gene, wherein the vaccinia virus early/late promoter is operably linked to the reverse tetR gene;
• and
• a second nucleic acid comprising an expression control sequence comprising a tet response element and the PI<R gene, wherein the tet response element is operably linked to the PKR gene,
• wherein the first and second nucleic acids are in non-essential regions of the vaccinia virus genome.