Analysis of platelet FVIII expression in 2bF8LV-transduced xenotransplanted recipients. Platelets were lysed in 0.5% 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). The levels of platelet-derived FVIII expression were determined by chromogenic FVIII activity (FVIII:C) assay of platelet lysates from recipients at least 3 weeks after transplantation. Bars represent mean ± SD. The average FVIII level was calculated for individual mice analyzed more than once over the course of study. Platelets from NSG mice, C57BL/6 mice, and normal human individuals were used as controls. (A) Quantitative evaluation of FVIII activity levels in platelet lysates from 2bF8LV-transduced hCBT NSG or NSGF8KO recipients. (B) Quantitative evaluation of FVIII activity levels in hCB-derived human platelets based on human platelet numbers as determined by flow cytometry. Data are summarized from 10 trials of xenotransplants. NA, not applicable.