Purging effect of reovirus on CLL cells. (A) Cytopathic effect of reovirus on human CLL cells 72 hours after infection (original magnification, × 200). Purified cells were infected with 40 MOI live virus. Photomicrographs were taken at 72 hours after infection. Significant cytopathic effect was evident in reovirus-treated cells. (B) Flow cytometric analysis of CLL following reovirus purging. Apheresis product cells were mixed with CLL cells (10%) and purged for 4 to 5 days with reovirus. CLL was detected using a CD5⁺CD19⁺ region (gate A) combined with 5⁺ dim 20⁺ region (gate B) to detect monoclonal λ B cells (gate A + B). (C) Representative histograms of viable CLL cells for 4 patients following reovirus purging. Arrows indicate that CLL cells for patients 2 and 3 after virus treatment was not detected.