Exposure of FVIII in the Presence of Phosphatidyl Serine Reduces Generation of Memory B-Cells and Induces Regulatory T-Cell-Mediated Hyporesponsiveness in Hemophilia A Mice

Self Cite

Development of unwanted immune responses against therapeutic proteins is a major clinical complication. Recently, we have shown that exposure of Factor VIII (FVIII) in the presence of phosphatidylserine (PS) induces antigen-specific hypo-responsiveness to FVIII re-challenge, suggesting that PS is not immune suppressive, but rather immune regulatory in that PS converts an immunogen to a tolerogen. Since PS is exposed in the outer leaflet during apoptosis, we hypothesize that PS imparts tolerogenic activity to this natural process. Thus, immunization with PS containing liposomes would mimic this natural process. Here, we investigate the immune regulatory effects of PS in inducing tolerance towards recombinant human acid alpha-glucosidase (rhGAA). rhGAA was found to complex with PS liposomes through hydrophobic interactions and incubation PS-rhGAA with dendritic cells resulted in the increased secretion of TGF-β. Immunization with PS-rhGAA or OPLS-rhGAA led to a reduction in anti-rhGAA antibody response which persisted despite re-challenge with free rhGAA. Importantly, the titer levels in a majority of these animals remained unchanged after rechallenge and can be considered non-responders. These data provide evidence that PS liposomes can be utilized to induce tolerance towards therapeutic proteins, in general.

Section: Discussionsupporting

confidence: 85%

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

Schneider

Balu‐Iyer

2016

Self Cite

“…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.…”

Section: Discussionmentioning

confidence: 99%

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

Glassman

Schneider

Ramakrishnan

et al. 2018

Self Cite

Phosphatidylserine (PS) exposure during apoptosis leads to silent clearance of cells without adverse immune reactions to self-proteins. Given the biological functions of PS in cellular cleanup and global immunosuppression, we hypothesized that administration of PS-protein complexes would reduce immunogenicity. Here, we report that exposing Pompe disease mice to acid alpha glucosidase (rhGAA) with PS or immunosuppressant dexamethasone resulted in lower anti-rhGAA antibodies than in animals receiving rhGAA alone. However, upon rechallenge with rhGAA, only PS-rhGAA pre-exposed mice displayed a durable hyporesponsiveness even after PS administration was ceased. Thus, pre-exposure of antigens administered together with PS were not silently cleared, but the immune system acquired memory about the antigen that averted mounting of a response during rechallenge. In hemophilia A mice, PS hyporesponsiveness toward Factor VIII was reversed by administration of function-blocking antibody against the PS receptor T-cell immunoglobulin and mucin 4, implicating this receptor in PS's effect. Moreover, pre-exposure of myelin oligodendrocyte glycoprotein peptide with PS delayed the onset and reduced the severity of experimental autoimmune encephalomyelitis. These observations suggest that PS's function in apoptosis is not limited to silent antigen clearance without immune responses toward self-proteins but shows that PS reduces immune response during rechallenge to several antigens that also involves initiation of antigen tolerance.

“…PS either directly or indirectly through Tregs are capable of inhibiting memory B cell development. These properties of PS together are capable of converting an immunogen to a tolerogen 2–4 .…”

Section: Discussionmentioning

confidence: 99%

“…Bone marrow derived dendritic cells (BMDCs) upon exposure of FVIII in the presence of PS showed a downregulation of the costimulatory marker CD40 as well as an increase in the regulatory cytokine TGF-β 3 . Further mechanistic studies showed that PS acts by increasing the regulatory T cells (Tregs) production as well as reducing the memory B cell development in vivo 4 . These results put together indicate that PS converts an immunogen to a tolerogen.…”

Section: Introductionmentioning

confidence: 99%

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

Ramakrishnan

Balu‐Iyer²

2016

Self Cite

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.