Phosphatidylserine reduces immune response against human recombinant Factor VIII in Hemophilia A mice by regulation of dendritic cell function

Abstract

A major clinical complication in the treatment of Hemophilia A using exogenously administered recombinant Factor VIII (FVIII) is the development of neutralizing antibodies. It has been shown previously that FVIII complexed with phosphatidylserine (PS) reduces the development of total and neutralizing antibody titers in hemophilic mice. The effect of complexation of FVIII with PS upon dendritic cell (DC) uptake, maturation and processing, T-cell proliferation and cytokine secretion profiles was investigated. Flow cytometric studies of DC showed that PS inhibited the up-regulation of cell surface co-stimulatory markers (CD86 and CD40). PS reduced T-cell proliferation and increased significantly levels of TGF-β and IL-10 but reduced secretion of IL-6 and IL-17 compared to controls. The data suggest that PS reduces immunogenicity of FVIII by regulating dendritic cell maturation and subsequent T-lymphocyte activity through modulation of cytokine secretion. A possible mechanism for PS-mediated induction of FVIII tolerance is discussed.

Phosphatidylserine Converts Immunogenic Recombinant Human Acid Alpha-Glucosidase to a Tolerogenic Form in a Mouse Model of Pompe Disease

“…In addition to the study carried out here, more mechanistic studies are needed to confirm that PS- mediated tolerance induction is functioning in an antigen specific manner, which is independent of the antigen that is co-administered, to induce tolerance. To accomplish this, future studies will be carried out for rhGAA as they were for FVII to further demonstrate the roles of TGF-β, regulatory T cells, and memory B cells in vivo, and to compare the results to what was previously observed for FVIII 36 .…”

Exposure to Factor VIII Protein in the Presence of Phosphatidylserine Induces Hypo-responsiveness toward Factor VIII Challenge in Hemophilia A Mice

“…The studies aimed at understanding the mechanism of this reduction showed that FVIII-PS down-regulated the expression of CD40 upon exposure to bone marrow-derived dendritic cells (DC) (4). Further, T-cell activation studies wherein the incubation of FVIII-PS exposed DC with FVIII-primed splenic CD4…”

Engineering antigen-specific immunological tolerance

“…Phosphatidylserine exposure on the outer cell membrane is a hallmark of apoptosis and is recognized by receptors on phagocytes in a manner that hinders immunogenic responses to the cell-derived components. When chemically conjugated to recombinant Factor VIII and administered to hemophilic mice, the incorporated phosphatidylserine effectively reduced DC activation, drove T cell expression of IL-10 and TGF-b, and induced FoxP3 + regulatory T cells (Tregs) [24]. By deceiving APCs into recognizing the therapeutically administered Factor VIII as a product of an apoptotic cell, Gaitonde and colleagues were able to induce tolerance to the therapeutic protein in mice and enabled follow-on treatment with wild-type Factor VIII without the generation of antiFactor VIII antibodies [25].…”