Targeting T Cell Bioenergetics by Modulating P-Glycoprotein Selectively Depletes Alloreactive T Cells To Prevent Graft-versus-Host Disease

Abstract

T lymphocytes play a central role in many human immunologic disorders including autoimmune and alloimmune diseases. In hematopoietic stem cell transplant, acute graft-versus-host-disease (GVHD) is caused by an attack on the recipient’s tissues from donor allogeneic T cells. Selectively depleting GVHD-causing cells prior to transplant may prevent GVHD. In this report we have evaluated 24 chalcogenorhodamine photosensitizers for their ability to selectively deplete reactive T lymphocytes, and identified the photosensitizer 2-Se-Cl that accumulates in stimulated T cells in proportion to oxidative phosphorylation (OXPHOS). The photosensitizer is also a potent stimulator of P-glycoprotein (P-pg). Enhanced P-gp activity promotes the efficient removal of photosensitizer not sequestered in mitochondria, and protects resting lymphocytes essential for antipathogen and antitumor responses. To evaluate the selective depletion of alloimmune responses, donor C57BL/6 splenocytes were cocultured for 5 days with irradiated Balb/c splenocytes, and then photodepleted (PD). PD-treated splenocytes were then infused into lethally irradiated BALB/c (same-party) or C3H/HeJ (third-party) mice. Same-party mice that received PD-treated splenocytes at the time of transplant lived 100 days without evidence of GVHD. In contrast, all mice that received untreated primed splenocytes and third-party mice that received PD-treated splenocytes died of lethal GVHD. To evaluate the preservation of antiviral immune responses, acute lymphocytic choriomeningitis virus (LCMV) infection was employed. After PD, expansion of antigen-specific naïve CD8+ T cells and viral clearance remained fully intact. The high selectivity of this novel photosensitizer may have broad applications and provide alternative treatment options for patients with T lymphocyte mediated diseases.

Photodepletion with 2-Se-Cl prevents lethal graft-versus-host disease while preserving antitumor immunity

“…The photosensitizer 2-Se-Cl targets the unique metabolic profile and exploits the inherent weakness of alloreactive T cells by inhibiting oxidative phosphorylation and increasing oxidative stress. We have previously shown that after priming, alloreactive T cells are highly oxidative, and that 2-Se-Cl can be employed ex-vivo to prevent GVHD while maintaining primary antiviral immunity [5]. In this report, we demonstrate PD with 2-Se-Cl also preserves curative antitumor immunity.…”

“…We designed a novel photosensitizer 2-Se-Cl that targets the unique metabolic profile and exploits the inherent weakness of pathogenic T cells by inhibiting OXPHOS and increasing oxidative stress. In 2016 we showed that ex-vivo application of 2-Se-Cl selectively eliminates highly alloreactive lymphocytes from the graft prior to HCT to prevent GVHD while maintaining primary antipathogen immunity in the complete MHC-mismatched setting [5] In this report we furthered our investigations to determine whether 2-Se-Cl promotes a curative graft-versus-leukemia (GVL) response essential for a successful transplantation.…”

“…On the day of HCT, recipient Balb/c mice were irradiated (8.5 Gy), and then received 10 7 T cell-depleted (TCD) donor-derived bone marrow cells (<0.1% mature CD3 + T cells) together with 10 5 recipient specific (A20, Balb/c-derived) leukemia cells engineered to express firefly luciferase, and 5 x10 6 PD-treated cells (treatment group) or untreated (control group 1) primed splenocytes via tail vein injection. To evaluate for the retention of 3rd party responses, C3H/HeJ (H2 k ) mice were irradiated (9.5 Gy) and received a combination of 10 7 TCD donor-derived bone marrow cells accompanied by 5 x10 6 PD-treated cells [5,7]. To compare the efficacy of our approach to post-transplant cyclophosphamide (PTCy) administered for GVHD prophylaxis, a group of mice received 10 7 TCD bone marrow cells accompanied by 5 x 10 6 primed splenocytes on day of HCT, followed by 50 mg/kg cyclophosphamide i. p. on days + 3 and + 4 after transplant (control group 2) [8,9].…”

“…We have previously shown that ex-vivo application of 2-Se-Cl selectively eliminates activated highly alloreactive lymphocytes from the graft prior to HCT to prevent GVHD while maintaining antipathogen immunity [5]. The elimination of unwanted immune responses provides us with the opportunity to investigate the changes in cell composition that mediate clinical outcomes.…”