Therapeutic levels of human factor VIII and IX using HIV-1-based lentiviral vectors in mouse liver

Lentiviral Vectors have the potential to play an important role In hemophilia gene therapy. The present study used human immunodeficiency virus (HIV)-based lentiviral vectors containing an EF1 alpha enhancer/promoter driving human factors VIII (hFVIII) or IX (hFIX) complementary DNA expression for portal vein injection Into C57B1/6 mice. Increasing doses of hFIX-expressing lentivirus resulted in a dose-dependent, sustained increase in serum hFIX levels up to approximately 50-60 ng/ml, Partial hepatectomy resulted in a 4- to 6-fold increase (P < 0.005) in serum hFIX of up to 350 ng/mL compared with the nonhepatectomized counterparts. The expression of plasma hFVIII reached 30 ng/mL (15% of normal) but was transient as the plasma levels fell concomitant with the formation of anti-hFVIII antibodies, However, hFVIII levels were persistent in immunodeficient C57BI/6 scid mice, suggesting humoral immunity-limited gene expression in immunocompetent mice. This study demonstrates that lentiviral vectors can produce therapeutic levels of coagulation factors in vivo, which can be enhanced with hepatocellular proliferation. (C) 2000 by The American Society of Hematology.