Long-term FVIII expression in hemophilia A mice after FVIII plasmid-mediated gene therapy and immunomodulation with anti-CD3. Hemophilia A mice were treated with 50 μg of FVIII plasmid by hydrodynamic injection (n = 4) or with 50 μg of FVIII plasmid at day 0 and 40 μg of anti-CD3 by daily intravenous injection at days 0 to 4 (n = 13). FVIII activities were assessed by a modified activated partial thromboplastin time assay and the anti-FVIII antibody titers by Bethesda assay over time. For plasmid only–treated mice: (A) FVIII activity and (B) anti-FVIII antibody titers. For FVIII plasmid + anti-CD3–treated mice: (C) FVIII activity and (D) anti-FVIII antibody titers. Each symbol represents data obtained from an individual mouse.