Suppression of the Immune Response to Human FVIII with FVIII Transgene Modified Tolerogenic Dendritic Cells in Hemophilia A Mice (89.42)

Abstract

Abstract The development of inhibitory antibodies to factor VIII (FVIII) is the most serious complication in hemophilia A patients. In this study we evaluated the ability of tDCs transduced with a human FVIII transgene foamy virus (FV) vector to modulate the immune response to FVIII in hemophilia A mice. The tDCs were generated by culturing bone marrow cells in RPMI1640/10%FBS supplemented with IL-10 and the neural peptides VIP and PACAP38. Na ?ve hemophilia A mice were treated with 2 weekly infusions of tDC-F8, control tDCs (tDCs-Ctrl), or with no cells (Neg-Ctrl) prior to challenge with four weekly intravenous doses of 0.2 µg rhFVIII. Following immunization the inhibitor titers in tDC-F8 mice were 60-61% lower than the controls. The regulatory T cell related markers such as FOXP3 were up-regulated on splenic CD4+ T cells from tDC-F8 mice and the CD4+ T cell proliferation response to FVIII was suppressed by 80 - 90%. In pre-immunized mice, treatment with 4 weekly infusions of FVIII vector transduced tDCs lowered inhibitor titers by 54%. In contrast, treatment with untransduced tDCs had no significant effect. Adoptive transfer of CD4+ T cells from tDC-F8 mice suppressed the immune response to FVIII in subsequently immunized naïve secondary recipients, but not to OVA, an unrelated antigen. We also observed that infusion of tDCs transduced with FV vectors co-expressing FVIII and IL-10 into naïve mice resulted in a 83 - 85% reduction in inhibitor titers after subsequent immunization. The CD4+ T cell proliferation response to FVIII was suppressed over 90%. In summary, these data indicate that FVIII vector transduced tDCs are useful in suppressing the immune response to FVIII in hemophilia A mice and that co- expression of IL-10 by the vector modified tDCs further enhances their effectiveness.