Low-dose transduction efficiency with ss and scAAV vectors in murine models. (A) Transgene expression in C57Bl/6 mice. hFIX-expression profile over 31 weeks after tail-vein administration of 2 × 10⁹ vg/mouse (n = 3) of scAAV2/8-LP1-hFIXco (▵), scAAV2/8-LP1-hFIX (□), ssAAV2/8-LP1-hFIXcoS (○), and ssAAV2/8-HCR-hAAT-FIX (⋄) into C57Bl/6 mice. All hFIX results are depicted as the average together with the standard error of the mean. (B) Correction of clotting times and expression of hFIX:C in 129/sv HB mice. Following tail-vein injection of either 1 × 10¹⁰ (low-dose cohort, n = 6) or 5 × 10¹⁰ (high-dose cohort, n = 4) scAAV2/8-LP1-hFIXco vector particles into 129/sv HB mice, the clotting time (left-hand panel at 4 weeks) and biologically active hFIX:C levels (right-hand panel) over 16 weeks were determined.