Quantitation of viral copy number in mouse organs after lentivector transduction. Mice were killed at various time points, and the number of integrated viral copies was determined by quantitative PCR analysis. Integrated transgene copy number is represented as copies per cell using the copy number of the murine β-actin sequence as an endogenous reference. (A) The mean viral copy numbers in livers and spleens from the mice 12 to 13 weeks posttemporal vein infusion with Lenti-CMV-cFVIII (n = 5) or Lenti-HCR/hAAT-cFVIII (n = 6). Error bars represent the SEM. (B) Mice treated intravenously with Lenti-HCR/hAAT-cFVIII were killed at 13 (n = 1) or between 30 and 32 (n = 4) weeks after treatment. Organ distribution of the vector was studied in liver, spleen, heart, lung, kidney, and small intestine isolated from 5 mice, as well as testis and white blood cells (WBCs) isolated from a single mouse. Plasma cFVIII:C expression in the mouse that was killed at 13 weeks was 1033 mU/mL, whereas no plasma cFVIII:C could be detected in the mice killed at 30 to 32 weeks (n = 4).