Evaluation of induction of tolerance to cFVIII in mice treated with Lenti-HCR/hAAT-cFVIII. (A) BALB/c neonatal mice (n = 18) were infused with 2 × 107 IU of Lenti-HCR/hAAT-cFVIII via the temporal vein, and levels of plasma cFVIII activity were assayed over the 58-week duration of the experiment. (B) Levels of anti-FVIII inhibitory antibodies were assayed. (C) Hemophilia A mice infused as neonates with Lenti-HCR/hAAT-cFVIII via temporal vein injection were challenged with 4 weekly intravenous infusions of recombinant cFVIII. These mice no longer expressed cFVIII at the time of challenge. Levels of anti-FVIII inhibitory antibodies were assayed. Hemophilia mice that received gene transfer as neonates are referred to as HAAT TV/Tolerized, and mice that did not receive gene transfer, but were challenged in a similar manner, are labeled naive. Hemophilia A mice treated via temporal vein injection with Lenti-CMV-cFVIII as neonates were challenged with the same intravenous cFVIII protocol and are labeled inhibitor. Inhibitor levels were measured at 0, 1, 3, 5, and 7 weeks after the first cFVIII injection.
