Date on Master's Thesis/Doctoral Dissertation

5-2020

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Microbiology and Immunology

Degree Program

Microbiology and Immunology, PhD

Committee Chair

Shirwan, Haval

Committee Co-Chair (if applicable)

Yolcu, Esma

Committee Member

Egilmez, Nejat

Committee Member

Ratajczak, Mariusz

Committee Member

Li, Bing

Author's Keywords

GVHD; CD47; FasL; IBMIR; Islet transplantation

Abstract

The major premise of this dissertation was to transiently display novel immunological ligands on biological membranes as a localized means of modulating innate and adaptive immune responses with applications to bone marrow and pancreatic islet transplantation. In Chapter two, we engineered donor allogeneic bone marrow cells to transiently display a novel form of FasL, SA-FasL, to efficiently purge out alloreactive donor T cells to prevent acute GVHD. In Chapter three, we engineered pancreatic islets with a novel form of CD47, SA-CD47, to modulate instant blood mediated inflammatory reaction (IBMIR) to prevent immediate islet graft loss following intraportal transplantation. GVHD is initiated and perpetuated by mature T cells in the bone marrow inoculum following transplantation into conditioned recipients. Upon activation, T cells upregulate Fas receptor and become sensitive to FasL-mediated apoptosis. Thus, we hypothesized that the display of SA-FasL on T cells in bone marrow will result in their apoptosis potentially in autocrine fashion following activation in response to recipient alloantigens and engagement of Fas with SA-FasL on the T cells, thereby resulting in the prevention of vi acute GVHD. We demonstrated that SA-FasL engineered T cells underwent apoptosis following response to alloantigens both in vitro and in vivo. Most importantly, in an haploidentical rodent setting where C57BL/6 bone marrow cells containing T cells transplanted into lethally irradiated F1 recipients, engineering cells with SA-FasL resulted in the prevention of lethal acute GVHD in 80% of recipients long term (>100 days). We extended this observation to xenogeneic acute GVHD setting, where mice receiving SA-FasL-engineered human PBMCs were significantly protected. Significant islet mass loss following intraportal transplantation is a major barrier for clinical islet transplantation. IBMIR is initiated and perpetuated by innate immune cells. CD47-SIRPα axis known as innate immune checkpoint delivers “don’t eat me signal” to prevent phagocytosis and activation of myeloid cells. Thus, we hypothesized that engineering islets to transiently display SA-CD47 as an innate immune checkpoint will mitigate IBMIR and enhance engraftment following intraportal transplantation. In a syngeneic marginal mass model of intraportal transplantation, SA-CD47-islets showed better engraftment and function as compared with the control group (87.5 vs 14.3%). Engraftment was associated with low levels of intrahepatic inflammatory cells and mediators of islet destruction, including HMBG-1, tissue factor, and IL-1β. Overall, we show that transient display of immunological ligands on biological membranes is effective in modulating innate and adaptive immune responses with significant translational implication for multiple immune-based disorders.

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