FIG 1.

Sensitivity of VACV strains to IFN-β. (A) Resistance of VACV WR to IFN-β. A549 and A549 RNase L and PKR double-knockout (DKO) cells were pretreated with 0, 2, 20, 200, or 2,000 IU/ml of IFN-β for 24 h and then infected with WR at 1 PFU/cell. After 3 h with no IFN or 24 h with no or various amounts of IFN, the virus yields were determined by plaque assay. (B) Mock-infected A549 and A549 DKO cells were treated with 0 to 2,000 IU/ml of IFN-β for 24 h, and lysates were analyzed by Western blotting using antibody to OAS1 and actin. (C) IFN-β sensitivity of attenuated VACV strains. A549 and A549 DKO cells were untreated or treated with 2,000 IU/ml of IFN-β for 24 h and infected with 0.01 PFU/cell of VACV WR, 6/2, ACAM2000, or Dryvax. After 48 h, the lysates were analyzed by Western blotting using antibody to VACV, the L1 late protein, and actin. Short and long exposures for L1 are shown. The positions of protein markers (in kilodaltons) are shown on the right of panels B and C.