Anti-AAV immunity limits hFIX expression.

C57Bl/6 mice were preimmunized to AAV by administering 5 × 1010 vp of AAV-lacZ by tail vein. Levels of anti-AAV antibodies were tested 1 month following vector administration (top panel). Then, 4 × 1011 vp of AAV-hFIX was administered to AAV-immune mice into the portal vein by way of a cannula or by direct administration into the quadriceps muscle. Sera were harvested from the animals 11 (gray bars), 25 (white bars), and 42 (black bars) days after AAV-hFIX administration and analyzed for the presence of hFIX (middle panels) and anti-hFIX antibodies (bottom panels).