Fig. 5: Application of the tetracycline inducible system as a safety switch to generate a conditionally replicating vaccinia virus.
From: Synthetic virology approaches to improve the safety and efficacy of oncolytic virus therapies
a Schematic illustration of the tetracycline inducible system controlling the expression of the D13L vaccinia virus gene which leads to the conditional growth of the vaccinia virus in the presence of Dox. b Representative images of U2OS cells 48 h after infection with VV-TetR-iD13 (MOI 0.01) in the presence or absence of 100 ng/ml Dox. c, d A549, Hela, HT-29, and SKOV3 cells were infected with control vaccinia virus or VV-TetR-iD13 at MOI 0.01 in the absence or presence of Dox at 100 ng/ml. After 48 h, cells were stained with crystal violet, and cell viability assessed by measuring absorbance at 570 nm using resazurin. e, f Multistep growth curves of VV-TetR-iD13 compared to control vaccinia virus at different time points from U2OS and Hela cells when infected at MOI 0.01 in the presence or absence of 100 ng/ml Dox. g, h IVIS imaging of HT-29 tumors in CD-1 nude mice following injection with VV-TetR-iD13 (1E7 PFU/tumor) when tumors reached 150 mm3. Mice were given a Dox diet either 2 days post viral infection (Group 1, blue bars) or immediately following viral infection (Group 2, brown bars). For Group 2, Dox was removed from the diet after 2 days. Luciferase signal was measured at 12 h, 1, 2, 4 and 6 days after virus and drug administration. Bar graphs show the average total luciferase signal emitted in the tumor area. Scale bars = 200 μm in (b). Data indicate means ± SD of three (c, e, f) or four (h) biological replicates. ns P > 0.05, *P < 0.05 **P < 0.003841, ***P < 0.000125, ****P < 0.001 in unpaired two-samples t-test. Source data are provided as a Source Data file.
