Effect of Biophysical Properties of Phosphatidylserine Particle on Immune Tolerance Induction Toward Factor VIII in a Hemophilia A Mouse Model

Abstract

A major complication in the replacement therapy of Factor FVIII (FVIII) for Hemophilia A (HA) is the development of unwanted immune responses. Previous studies from our lab have shown that pretreatment of FVIII in the presence of Phosphatidylserine (PS) resulted in hyporesponsiveness to subsequent administration of FVIII alone, due to the ability of PS to convert an immunogen to a tolerogen. We investigated the importance of biophysical properties of PS liposomes on its ability to convert an immunogen to a tolerogen. PS particles were prepared differing in size, protein-lipid topology, lamellarity and % association to FVIII keeping the composition of the particle same. PS particles were prepared in two different sizes with differing biophysical properties, smaller particles in the nanometer range (200 nm) and larger size particles in the micron range (2um). HA animals treated with both the nanometer and micron size PS particle showed a significant reduction in anti-FVIII antibody titers when compared to animals receiving free FVIII alone. Upon rechallenge with free FVIII animals that received FVIII along with the nanometer size particle continued to show reduced antibody responses. Animals receiving the micron size particle showed a slight increase in titers although they remained significantly lower than the free FVIII treated group. Upon culture with bone marrow dendritic cells (BMDCs), the nanometer size particle showed a reduction in CD40 expression and an increase in TGF-β cytokine production; which was not observed with the micron size particle. These results show that biophysical properties of PS play an important role in tolerance.

Phosphatidylserine Is Not Just a Cleanup Crew but Also a Well-Meaning Teacher

“…Further, it was determined that the animals that were pre-treated with protein in the presence of PS responded normally when re-challenged with an unrelated antigen ovalbumin (Ova), indicating that the persistent hypo-responsiveness to the original PS associated protein was antigen specific 21 . Thus, the biological function of PS is not simply limited to its cleanup and immunosuppressive activity as previously thought, but it includes a very important functional and durable immune modulation or teaching/tolerance possibly by the ability of PS to convert an immunogen to a tolerogen 15,16,21,22 . The molecular and cellular level studies indicate that the teaching and tolerizing function of PS is mediated by multiple mechanisms including phenotypic changes in antigen presenting cells and also likely direct effect on B and T-cells.…”

Nanoparticles for the Induction of Antigen-Specific Immunological Tolerance

“…Unlike liposomes, PLA/PLGA nanoparticles are solid particles in which the payload is embedded within the matrix. Hydrophobic molecules, such as rapamycin, dexamethasone, and vitamin D3, can be dissolved together with the polymer in a solvent and then emulsified with an aqueous phase-containing surfactants such as polyvinyl alcohol and pluronic ( 57 , 59 ). Proteins and hydrophilic molecules can be incorporated through a double emulsion process ( 78 ).…”

“…Macrophages express various PS-specific scavenger receptors, such as Tyro3, Axl, and Mertk (collectively referred to as TAM receptors), TIM-3 and SCARF-1 that trigger the phagocytosis of dying cells and promote induction of a tolerogenic phenotype, such as the increase in IL-10 and TGFβ secretion, and a decrease in NF-κB signaling and TNFα, IL-1β, and IL-12 secretion ( 97 ). Encapsulating coagulation FVIII in PS-bearing liposomes was effective to prevent the formation of inhibitory anti-FVIII antibodies in hemophilia A animals even when animals were challenged with FVIII alone ( 53 , 57 , 98 , 99 ). A similar approach was demonstrated with alpha-glucosidase (GAA) in a mouse model of Pompe disease.…”

Leveraging the Modularity of Biomaterial Carriers to Tune Immune Responses

“…For example, phosphatidylserine liposomes have been reported to induce hyporesponsiveness to an otherwise immunogenic antigen. [140] Investigation of the biophysical properties governing this result revealed that smaller liposomes reduced DC activation and increased secretion of anti-inflammatory TGF-β, polarizing DCs toward a more tolerogenic phenotype and reducing antibody production against the antigen. In other studies, peptides were conjugated onto a HA polymer backbone to form different size antigen arrays.…”