IFN-α6, IFN-α14, IFN-α16, and IFN-α17 inhibit EBV entry and B-cell transformation into LCLs. (A) Raji cells were exposed to EBV and the indicated concentrations of IFN-α subtypes for 48 hours. GFP expression as a measure of EBV entry was determined by using flow cytometry, and the ratios of EBV plus IFN-α to EBV only are shown in the graph. Statistical analysis was done on raw data (percent GFP-positive cells), and paired Student t tests were applied. IFN-α6: n = 3. IFN-α14: 100 ng/mL, n = 6; 10 ng/mL, n = 15; 1 ng/mL, n = 12. IFN-α16: 100 ng/mL, n = 3; 10 ng/mL and 1 ng/mL, n = 5. IFN-α17: 100 ng/mL and 10 ng/mL, n = 4; 1 ng/mL, n = 1. (B) Isolated B cells or total PBMCs were exposed to EBV in the presence or absence of the IFN-α subtypes for 6 days, and proliferation was measured by CellTrace Violet (CTV) dilution. Statistical analysis was performed on raw data (percent proliferating cells), and paired Student t tests were applied. B cells: IFNα6, n = 2; IFN-α14, n = 16; IFN-α16, n = 4; IFN-α17, n = 2. PBMCs: IFN-α6, n = 2; IFN-α14, n = 16; IFN-α16, n = 6; IFN-α17, n = 2. (C) Proliferation of isolated B cells was also measured after 8 days of culture by pulsing the cells with [³H]-thymidine for 16 hours and thereafter measuring [³H]-thymidine incorporation (n = 2). In the lower graph, n = 2 for IFN-α6 and n = 4 for IFN-α14. (D) The proliferation of LCLs in the presence or absence of IFN-α14 was measured after 4 days by thymidine incorporation (n = 3). Paired Student t tests were applied. (E) Resistance of lytic EBV reactivation against IFN-α subtypes was shown by using AKBM cells (n = 5 for PBS, n = 4 for IFN-α6 and IFN-α14, n = 3 for IFN-α16 and IFN-α17).