Purging effect of reovirus on Waldenström macroglobulinemia cells. (A) Cytopathic effect of reovirus on human Waldenström macroglobulinemia cells 72 hours after infection. Original magnification, × 200. Purified cells were infected with 40 MOI reovirus. Photomicrographs were taken at 72 hours after infection. Significant cytopathic effect was observed in live virus-treated but not in untreated cells. (B) Flow cytometric analysis of Waldenström macroglobulinemia following reovirus purging. Apheresis product cells were mixed with Waldenström macroglobulinemia cells (10%) and purged for 5 days with reovirus. Samples were analyzed using region C and lineage gate D (CD10^-CD20⁺) to enumerate κ monoclonal CD10^-CD20⁺ malignant cells (region C + D). Flow Count beads were included in the CAL region to calculate absolute counts. (C) Representative histograms of viable Waldenström macroglobulinemia cells before and after purging with reovirus. Arrow indicates that Waldenström macroglobulinemia cells were not detected.