Persistently JEV-infected cell clones show apoptosis resistance even with active virus replication. (A) BHK-21 cells either mock-infected or infected with JEV at an MOI of 1 and harvested 72 hr later. PI cell clones were harvested at 72 hr after freshly seeding. Prepared cells were stained with annexin V/propidium iodide, and individual flow cytometric dot plots were displayed. (B) The extra- and intracellular virus samples were collected at the indicated p.i. time and counted by plaque-forming assay.