Immune response limits hFIX expression following IM administration of AAV-hFIX.

Increasing doses, 1.2 × 1010 vp (gray circles), 6 × 1010 vp (stippled circles), and 3 × 1011 vp (solid circles) of AAV-hFIX, were administered to Balb/c (left panel) and NIH-3 (right panel) mice by direct administration into the quadriceps muscle. Sera were harvested from the animals at various time points following vector administration and analyzed for the presence of hFIX.