Date: Tuesday, June 4, 2019
Session Time: 4:30pm-6:00pm
Presentation Time: 5:06pm-5:18pm
Location: Room 310
*Purpose: Adoptive cell transfer of regulatory T cells (TReg) has shown great potential in animal models of auto- and alloimmunity. The translation of TReg therapies to the clinic, however, has been impeded by the short in vivo homeostasis of TRegs. Here, we describe a novel drug-delivery platform which can be engineered on TRegs to secrete interleukin (IL-)2 in response to TCR activation, and thus maintain TRegs in sites of antigen encounter.
*Methods: CD4+CD25+FoxP3+ TRegs were magnetically sorted from C57BL/6 (B6) splenocytes and conjugated with nanogel (NG) prior to adoptive transfer studies. NG particles were synthesized by reversibly crosslinking IL-2/Fc fusion (IL-2) protein with a bis-N-hydroxy succimide crosslinker. Further surface modification with monoclonal anti-CD45 and PEG-PLL ensured long-term surface retention.
*Results: In primary in vitro experiments we proved that IL-2 NG could be backpacked onto >90% of TRegs and spur 4-fold greater expansion compared with unmodified (CT) TRegs in a seven-day culture. Additionally, in a TReg suppression assay, we found the suppressive qualities of NG compared to CT TRegs to be unaltered. To test the TReg homeostasis in vivo, we transplanted BALB/c skin onto B6.RAG1-/- mice and injected an equal ratio of B6 TRegs to CD8 T cells. Comparing CT TRegs, CT TRegs plus systemic IL-2, and NG TRegs 7 days post adoptive transfer we found that only CT+IL-2 treatment improved peripheral TReg homeostasis. These mice, however, showed an unrepressed expansion of graft-resident CD8+CD69+ T cells. NG-treated mice, on the contrary, exhibited gross suppression of CD8 cells in the draining lymph nodes and skin graft. We later confirmed that solely NG TReg therapy could significantly prolong the mean skin graft survival (6 vs.18 days). We hypothesized that the NG platform was selectively benefitting antigen-specific TRegs, and to test this, we performed OVA to B6.RAG1-/- skin transplants and injected an equal ratio of OT-II TRegs to OT-I CD8 T cells. For the NG TReg-treated mice we observed a resounding suppression of OT-I CD8 T cells in the skin graft and a 30-fold increase in the TReg:CD8 ratio. Finally, to assess if this platform could be translated to humans, we transplanted NSG mice with skin grafts from a healthy patient and transferred PBMCs and TRegs from a healthy donor 7 days later. We found that 21 days post adoptive transfer, the human NG TReg treatment had efficiently attenuated CD8 T cell proliferation in the skin grafts, and while 5/6 (83%) of NG grafts remained healthy, only 3/6 (50%) of CT grafts and 1/4 (25%) of CT+IL-2 grafts did.
*Conclusions: Here, we describe a novel method for enhancing TReg transfer therapy through spatiotemporal provision of IL-2 to antigen-specific TRegs. Importantly, our platform can be harnessed to complement CAR-TReg therapies.
To cite this abstract in AMA style:Eskandari SK, Melo MB, Sulkaj I, Li N, Cai S, Allos H, Choi JY, Irvine DJ, Azzi JR. Engineering Regulatory T Cells With TCR-Signaling-Responsive Interleukin 2 Nanoparticles Provides In Situ Suppression Of Alloimmunity [abstract]. Am J Transplant. 2019; 19 (suppl 3). https://atcmeetingabstracts.com/abstract/engineering-regulatory-t-cells-with-tcr-signaling-responsive-interleukin-2-nanoparticles-provides-in-situ-suppression-of-alloimmunity/. Accessed February 19, 2020.
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