Chimeric Antigen Receptor Regulatory T Cells (CAR-Tregs) Provide Significantly Greater Modulation of Alloimmune Responses Than Alternative Alloantigen-Specific Treg Strategies
1King's College London, London, United Kingdom, 2Quell Therapeutics, London, United Kingdom
Meeting: 2022 American Transplant Congress
Abstract number: 379
Keywords: Immunosuppression, Liver transplantation, T cell reactivity, Tolerance
Topic: Basic Science » Basic Science » 10 - Treg/Other Regulatory Cell/Tolerance
Session Information
Session Name: Immunoregulation and Tolerance
Session Type: Rapid Fire Oral Abstract
Date: Monday, June 6, 2022
Session Time: 5:30pm-7:00pm
Presentation Time: 5:40pm-5:50pm
Location: Hynes Room 302
*Purpose: Conferring alloantigen-specificity to ex vivo expanded CD4+CD25+Foxp3+ Tregs increases their capacity to counteract effector alloimmune responses following adoptive transfer into transplant recipients. This has been achieved in humans by: 1) expanding Tregs in the presence of donor B cells (donor-reactive DR-Tregs); 2) culturing Tregs in the presence of donor material and co-stimulation blockade (CSB-Tregs); and 3) transducing Tregs with a HLA-A2-specific chimeric antigen receptor specific (CAR-Tregs). All 3 modalities of manufactured Treg products are currently undergoing clinical development. We lack, however, a clear understanding of the relative potency of each of these strategies. Our goal here was to directly compare the 3 manufacture approaches both in vitro and in vivo.
*Methods: Allogenic material (PBMCs or B cells) was isolated from HLA-A2+ positive and HLA-II mismatched donors. CSB Tregs were generated by culturing HLA-A2 negative PBMCs with irradiated allogenic donor PBMCs in the presence of CD80 (2D10.4) and CD86 (IT2.2) antibodies for 14 days. For DR-Tregs and CAR Tregs, we FACS isolated CD4+CD25+CD127- Tregs and co-cultured them with irradiated CD40L-activated donor B cells on the day of isolation at a ratio of 1 to 4 and transduced them with an anti-HLA-A2 second-generation CAR construct, respectively. In addition, we generated polyclonal (PC) non-antigen specific Tregs by expanding FACS isolated Tregs with CD3/CD28 beads. Antigen-specificity and suppressive function of the cell products were evaluated in vitro by performing activation, proliferation, and T cell suppression assays 14 days post isolation. Therapeutic efficacy was assessed in vivo in a xenogeneic GvHD model in humanized NSG mice.
*Results: As compared to PC Tregs, all 3 strategies increased the proportion of alloantigen-specific Tregs within the manufactured cell product, with the highest level being observed in the CAR-Treg products (6-fold higher than in DR-Tregs). The differences in the precursor frequency of alloreactive Tregs were consistent with the results of the suppression assays, in which on a cell-per-cell basis CAR-Tregs exhibited the strongest effects, followed by DR-Tregs and CSB-Tregs. In vivo, infusion of CAR-Tregs together with HLA-A2+ PBMCs into irradiated NSG mice resulted in most prolongation of recipient survival.
*Conclusions: The CAR technology is both more efficient and more powerful than non-engineered strategies in conferring alloantigen specificity to ex vivo expanded Treg products. This information will be essential to adequately interpret data derived from ongoing clinical trials.
To cite this abstract in AMA style:
Kurt AS, Ruiz P, Kodela E, Lombardi G, Martinez-Llordella M, Sanchez-Fueyo A. Chimeric Antigen Receptor Regulatory T Cells (CAR-Tregs) Provide Significantly Greater Modulation of Alloimmune Responses Than Alternative Alloantigen-Specific Treg Strategies [abstract]. Am J Transplant. 2022; 22 (suppl 3). https://atcmeetingabstracts.com/abstract/chimeric-antigen-receptor-regulatory-t-cells-car-tregs-provide-significantly-greater-modulation-of-alloimmune-responses-than-alternative-alloantigen-specific-treg-strategies/. Accessed September 7, 2024.« Back to 2022 American Transplant Congress