Dose-dependence and kinetics of hFIX expression from AAV serotype vectors. (A) hFIX expression as a function of vector dose and time after injection. hFIX-expressing AAV vectors of type 1, 2, or 6 were injected into the portal veins of C57Bl/6 mice (n = 4 or 5) at 9 different doses, in 2-fold increments ranging from 1.56 × 10⁹ to 4 × 10¹¹ genome-containing particles. hFIX levels in the plasma were measured using ELISA, from day 3 after injection until day 42, and were plotted as mean ± SD against the vector dose. The lines in each graph indicate 1% (solid line), 5% (dotted line), or 100% (dashed line) of normal hFIX levels. (B) Kinetics of hFIX expression. As an example to highlight the different kinetics of AAV-1, -2, and -6 vectors, the graph shows hFIX levels obtained between 3 and 42 days after portal vein injection of 1 × 10¹¹ particles. (C) Ratio of hFIX expression from AAV vector types 1 or 2, respectively, to the AAV-6 vector. For each vector dose and point in time after injection, plasma hFIX levels from the AAV-1 (left) or -2 (right) vectors were plotted as a percentage of expression from the AAV-6 vector, which was always set at 100%.