Wang and Martin et al. generated Jurkat and primary human T cells expressing one of 14 CARs, each specific for one of five different peptide–HLA-A*02 complexes, but differing by their ligand binding and/or signaling domains (ICD), or one of five TCRs specific for the same peptide–HLA-A*02 complexes. In short- and long-term antigen stimulation in vitro assays of CAR- and TCR-mediated activation, proliferation, and cytolysis, no consistent difference was observed for cells expressing TCRs and CARs with scFvs derived from two cycles of optimization, nor were there differences in their relative sensitivity to PD-L1, CD80/86 or IL-2. A CAR’s ICD had only a small impact.
Contributed by Paula Hochman
ABSTRACT: Though TCRs have been subject to limited engineering in the context of therapeutic design and optimization, they are used largely as found in nature. On the other hand, CARs are artificial, composed of different segments of proteins that function in the immune system. This characteristic raises the possibility of altered response to immune regulatory stimuli. Here we describe a large-scale, systematic comparison of CARs and TCRs across 5 different pMHC targets, with a total of 19 constructs examined in vitro. These functional measurements include CAR- and TCR-mediated activation, proliferation, and cytotoxicity in both acute and chronic settings. Surprisingly, we find no consistent difference between CARs and TCRs as receptor classes with respect to their relative sensitivity to major regulators of T cell activation: PD-L1, CD80/86 and IL-2. Though TCRs often emerge from human blood directly as potent, selective receptors, CARs must be heavily optimized to attain these properties for pMHC targets. Nonetheless, when iteratively improved and compared head to head in functional tests, CARs appear remarkably similar to TCRs with respect to immune modulation.