Sustained platelet-FIX expression in sequential transplantation recipients. To ascertain that long-term repopulating hematopoietic stem cells were transduced by 2bF9 LV, BM mononuclear cells isolated from some primary (1°) recipients (n = 3 in the 1,100 cGy group and n = 4 in the 660 cGy group) were transplanted into secondary (2°) recipients preconditioned with 1,100 cGy (n = 4) or 660 cGy (n = 5). Animals were analyzed for 2bF9 transgene expression 4 weeks after transplantation. Bars represent mean ± SD. (a) Average copy numbers of 2bF9 proviral DNA per cell determined by qPCR. For individual mice analyzed more than once over the study, the average copy number was calculated. (b) The expression levels of platelet-FIX:Ag in 2bF9 LV-transduced recipients determined by ELISA assay. For individual mice analyzed more than once over the study, the average platelet-FIX:Ag was calculated. (c) The expression levels of platelet-FIX:C in 2bF9 LV-transduced recipients determined by chromogenic assay. For individual mice analyzed more than once over the study, the average platelet-FIX:C was calculated.