Effect of IPTG on yields of infectious vG7Li. (A) BS-C-1 cells were infected with VV WR (♦), vG7L/G7Li (▪), or vG7Li (•) at a multiplicity of infection of 5 and incubated in the presence of 0 to 100 μM IPTG for 24 h. Virus titers were determined by plaque assay in the presence of 50 μM IPTG. (B) BS-C-1 cells were infected with VV WR (⋄), vG7L/G7Li (□, ▪), or vG7Li (○, •) in the absence (open symbols) or presence (filled symbols) of 50 μM IPTG. Cells were harvested at the indicated times after infection, and virus titers were determined as described for panel A.