Proteasome inhibitors increase hFIX expression in vivo following transduction by AAV2 but not AAV8. C57Bl/6 mice (n = 4) were administered 25 µg of bortezomib at different time points (d0, d7) and transduced with (a) AAV2 (2.5 ×1010 vg) or (b) AAV8 (2.5 × 109 vg) expressing the hFIX gene under control of the hAAT promoter (hFIX16) on d0. hFIX levels were assayed by ELISA at time-points indicated. SEM is indicated. AAV, adeno-associated virus; ELISA, enzyme-linked immunosorbent assay; hAAT, human α1-antitrypsin; hFIX, human Factor IX; vg, vector genomes.