Hemophilia B mice deficient in clotting Factor IX (FIX) that underwent IUGT via either intramuscular AAV1 [11] or intraperitoneal (IP) delivery of VSVG-lentivirus vector [12] expressing the FIX transgene demonstrated amelioration of disease and immune tolerance to FIX during postnatal life. Here, F9 is linked to hemophilia.