The effect of mCTLA4-Ig on antifactor VIII antibody formation.

Four groups of hemophilia A mice were injected with recombinant human factor VIII on days 0, 23, 44, and 66 (initially 1 μg intravenously and then 0.2 μg for the second, third, and fourth injections). Mice in groups G-3 and G-4 were also injected intraperitoneally with 0.2 μg factor VIII on days 2-12. Blood samples for the antifactor VIII assay were obtained on days 20, 37, 58, and 82. Control groups G-1 and G-3 (○) were injected with only factor VIII. Groups G-2 and G-4 (•) were also injected intraperitoneally with 250 μg mCTLA4-Ig on the day before and the day after the first factor VIII injection. The antifactor VIII antibody concentration was determined by ELISA. Antifactor VIII assay data points indicated as less than 0.16 μg/mL were similar to those for plasma samples obtained from unimmunized hemophilia A mice.