Down-regulation of CD40 signal and induction of TGF-β by Phosphatidylinositol mediates reduction in immunogenicity against recombinant human Factor VIII

Factor VIII (FVIII) is an important coagulation cofactor and its deficiency causes Hemophilia A, a bleeding disorder. Replacement therapy using recombinant FVIII is currently the first line of therapy for Hemophilia A, but the development of neutralizing antibody is a major clinical complication for this therapy. Recently, it has been shown that FVIII associated with Phosphatidylinositol (PI) containing lipidic nanoparticles reduced development of neutralizing antibodies in Hemophilia A mice ( 1 ). Here, we investigated the underlying mechanism of this reduction in antibody response in culturing conditions. In vitro , PI interfered with the processing of FVIII by cultured dendritic cells, resulting in a reduction in the up-regulation of phenotypic co-stimulatory signal CD40. Furthermore, PI increased secretion of regulatory cytokines Transforming Growth Factor beta1 (TGF-β1) and Interleukin 10 (IL-10) but reduced the secretion of pro-inflammatory cytokines IL-6 and IL-17. The data suggests that PI reduces the immunogenicity of FVIII by modulating DC maturation and by secretion of regulatory cytokines.