In vivo expression of hFIX from AAV serotype vectors. C57Bl/6 mice (n = 5 or 8) were injected with AAV serotype 1 to 6 vectors expressing the hfIX gene at 3 different particle doses—2 × 10¹⁰ (low dose, l), 2 × 10¹¹ (middle dose, m), or 2 × 10¹² (high dose, h) genome-containing particles. Vectors were injected through the portal vein (pv) or the tail vein (tv). Shown are plasma levels (mean ± SD) of FIX protein measured by ELISA between day 3 after particle injection up to day 84. The lines in each graph indicate 1% of normal FIX levels (solid line), 5% (dotted line), or 100% (dashed line). An hFIX plasma level of 5 ng/mL was considered the detection limit of the assay; protein levels below this limit are thus not shown.