Publication Date:
2020-11-05
Description:
Introduction: Immunomonitoring of chimeric antigen receptor (CAR) T cells relies primarily on their quantification in the peripheral blood, which inadequately quantifies their biodistribution and activation status in the tissues. Non-invasive molecular imaging of CAR T cell therapy by positron emission tomography (PET) is a promising approach providing spatial, temporal and functional information. Reported strategies for PET-based monitoring of CAR T cells rely on additional manipulation of the cell product such as the incorporation of reporter transgenes or ex vivo biolabeling, which significantly limits the wider application of CAR T cell molecular imaging. In the present study, we assessed the ability of antibody-based PET (immunoPET) to non-invasively visualize CAR T cells in vivo. Methods: For analysis of human CAR T cell activation, we analyzed publicly available RNA sequencing data (GSE136891) obtained at serial time points during in vitro culture of CD19.CD28z CAR T cells. We analyzed by mass cytometry (CyTOF) the ex vivo ICOS expression on human CD19-28z CAR T cells obtained from 31 patients receiving axicabtagene ciloleucel (Axi-cel) for relapsed/refractory diffuse large B-cell lymphoma (DLBCL). For in vivo murine experiments, CD19-expressing B-cell lymphoma A20 cells (2.5×10e5 cells) were injected by tail vein intravenously (i.v.) into sub-lethally (4.4 Gy) irradiated Thy1.2+ BALB/c mice. Seven days later, murine CD19.CD28z Luc+ Thy1.1+ CAR T cells (1×10e6) were i.v. injected. ICOS expression was analyzed by flow cytometry on CAR T cells recovered from spleen and bone marrow 5 days after injection. For imaging studies, anti-ICOS monoclonal antibody (mAb) specific for murine ICOS (clone:7E.17G9, BioXcell) was modified with the bifunctional chelator deferoxamine (DFO/p-SCN-Bn-Deferoxamine). The DFO-ICOS mAb conjugate was radiolabeled with 37 MBq (~1 mCi) of 89Zr-oxalate (final specific activity 6 µCi/µg/ml and radiochemical purity of 99%). 89Zr-DFO-ICOSmAb (45 μCi ± 3.6, 7.5 μg± 0.6) was injected i.v. 5 days post-CAR T cell administration and PET-CT imaging performed 48 hours later. Following PET-CT, mice were euthanized and radioactivity measured in dissected weighed tissues using a gamma-counter. Results: Analysis of RNA-sequencing data from human CAR T cells identified ICOS as an activation marker whose transcription was up-regulated and sustained during in vitro culture. ICOS was preferentially expressed on CAR+ T cells recovered at day 7 from axi-cel treated patients compared with CAR- cells (p
Print ISSN:
0006-4971
Electronic ISSN:
1528-0020
Topics:
Biology
,
Medicine
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