Volume 2 Supplement 2
S81. Proffered paper: A new PD1-CD28 chimeric receptor overcomes PD-1-mediated immunosuppression in adoptive T cell therapy
© Grassmann et al; licensee BioMed Central Ltd. 2014
Published: 12 March 2014
Although tumour-specific cytotoxic T cells are capable of killing tumour cells both in vitro and in vivo, treatment with adoptive T cell transfer does not lead to sufficient tumour regression without adjuvant therapy. Tumour-promoted T cell exhaustion and anergy have been proposed to contribute to this lack of efficacy. We and others have previously shown that programmed death receptor-1 (PD-1) upregulation is a hallmark of tumour infiltrating, adoptively transferred T cells. PD-1 and its ligand (PD-L1) constitute a major immunosuppressive axis driven by tumour cells. Disruption of this axis may hit an Achilles heel of tumour immune escape.
Material and methods
A PD1-CD28 chimeric receptor was cloned into the retroviral vector pMP71 and expressed in primary murine T cells specific for the model antigen ovalbumin (OT-1 cells). Functionality was addressed in vitro using ELISA and flow cytometry. In vivo, ovalbumin and PD-L1 overexpressing Panc02 cells (syngeneic pancreatic cancer cell line) were inoculated subcutaneously in immunocompetent female C57Bl/6 mice. Mice (n = 6 per group) were treated twice i.v. with PD1-CD28 chimeric receptor-transduced T cells or control T cells.
In vitro, PD-1-CD28 chimeric receptor-transduced primary T cells released 130 fold more interleukin-2 (IL-2) and 300 fold more interferon-γ than untransduced or control-transduced T cells when stimulated with CD3 and PD-L1, demonstrating the functionality of the chimeric receptor (p = 0.0014). In co-culture experiments with the Panc02 tumour cells, effective co-stimulation through PD1-CD28 was only seen in the presence of the TCR-recognized antigen ovalbumine and PD-L1. Upon blockade of MHC or PD-1, co-stimulation through the receptor was abrogated. Culture of transduced T cells in the presence of CD3 and PD-L1 increased cell numbers 4 fold and significantly increased viability of cells compared to untransduced or control-transduced T cells (p < 0.0001). In vivo, treatment of mice with an established (OVA and PD-L1 expressing) Panc02 subcutaneous tumour (mean tumour size at treatment onset 26 mm2) with PD1-CD28-transduced OT-1 slowed tumour growth compared to treatment with control-transduced OT-1 cells (p < 0.001). This demonstrates the functionality of the chimeric receptor in an immunocompetent organism.
Adoptive T cells therapy with PD-1-CD28 chimeric receptor-transduced T cells is a promising approach to overcome PD-1-PD-L1-mediated tumour-induced anergy and immunosuppression.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.