Date: Saturday, May 30, 2020
Session Time: 3:15pm-4:45pm
Presentation Time: 3:15pm-3:27pm
*Purpose: Adoptive transfer of regulatory T cells (Tregs) has been shown to improve alloengraftment in animal models. However, ex vivo Treg expansion for the purpose of infusing large numbers is technically challenging. An innovative approach is to engineer an orthogonal IL-2 (oIL-2) cytokine-receptor pair that selectively interacts with each other and transmits native IL-2 signals, but does not interact with the natural cytokine or receptor counterparts, thereby enabling selective stimulation of target cells in vivo. Here, we introduced this ortho cytokine-receptor combination into Tregs with the goal of improving donor hematopoietic cell engraftment upon adoptive transfer in a murine mixed chimerism model to induce organ transplantation tolerance.
*Methods: CD4+CD25hiFoxp3GFP+cells were purified from BALB/c Foxp3GFP mice and transduced with oIL-2 receptor β chain (oTregs). oTregs were injected at 1 × 106 /mouse together with 15 × 106 bone marrow cells (BMCs) that were obtained from luciferase-transgenic C57BL/6 donor mice into WT BALB/c recipient mice that received 3.3-Gy total body irradiation and anti-CD40L mAb (0.3 mg, ip on d0) as preconditioning. Recipients were treated with PBS, WT IL-2, or oIL-2 (both 25K IU/day; each n = 10) for 14 days.
*Results: Without oTreg transfer, donor cells were rejected by d10 as measured by bioluminescence. oTreg transfer with PBS slightly improved engraftment though the impact was not statistically significant (P=0.13 compared to BMC + PBS group on d28). WT IL-2 injection increased CD8+T cells and resulted in rapid graft rejection. On the other hand, oIL-2 injection significantly increased %Foxp3GFP+ in CD4+T cells (PBS; 4.3±1.6%, oIL-2; 9.3±4.7%, P=0.007) without increasing CD8+T cells. Consequently, donor cell engraftment was significantly improved in this group (P<0.0001 compared to BMC + PBS group on d28). oIL-2 did not have an impact when Tregs were transferred without oIL-2Rβ transduction, implying exquisite cytokine-receptor selectivity. Those recipients accepted heart allografts that were transplanted from C57BL/6 donor mice after chimerism induction whereas they rejected 3rd party heart graft, indicating the establishment of donor specific tolerance.
*Conclusions: Our data indicate that selective IL-2 stimulation improves Treg potential for facilitation of engraftment and for the induction of transplantation tolerance.
To cite this abstract in AMA style:Hirai T, Simonetta F, Su LL, Picton L, Baker J, Lin J, Li P, Leonard WJ, Garcia KC, Negrin RS. Orthogonal IL-2 Cytokine-Receptor Pair Capable of Selective Expansion of Regulatory T Cells Facilitates Alloengraftment [abstract]. Am J Transplant. 2020; 20 (suppl 3). https://atcmeetingabstracts.com/abstract/orthogonal-il-2-cytokine-receptor-pair-capable-of-selective-expansion-of-regulatory-t-cells-facilitates-alloengraftment/. Accessed September 16, 2021.
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