TSA is a potent enhancer of vaccinia virus spread.

4T1 cells were plated in 96-well plates then pre-treated with a concentration gradient of the indicated drugs. DMSO was used as a control. Following pre-treatment with drugs, cells were challenged with VVdd-GFP at an MOI of 0.1. After 120 h incubation period, fluorescence pictures were taken of each well, spanning the entire well-surface. Green fluorescence, indicating vaccinia spread, was measured using an image analysis software (Image J, NIH) and reported as a fold change in GFP-positive comparison to control (average of triplicate). + indicates increase in spread <2-fold, ++ indicates between 2 and 3-fold increase, +++ indicates >3-fold increase. TSA was the most active compound at the lowest dose tested. 10 cm plates of confluent 4T1 cells were treated with indicated HDI and samples were probed for hyper-acetylated histone H4 by Western Blot and reported as level of acetylated H4 relative to the untreated control.