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Comparison of T Cell Activities Mediated by Human TCRs and CARs That Use the Same Recognition Domains.

ABSTRACT: Adoptive T cell therapies have achieved significant clinical responses, especially in hematopoietic cancers. Two types of receptor systems have been used to redirect the activity of T cells, normal heterodimeric TCRs or synthetic chimeric Ag receptors (CARs). TCRs recognize peptide-HLA complexes whereas CARs typically use an Ab-derived single-chain fragments variable that recognizes cancer-associated cell-surface Ags. Although both receptors mediate diverse effector functions, a quantitative comparison of the sensitivity and signaling capacity of TCRs and CARs has been limited due to their differences in affinities and ligands. In this study we describe their direct comparison by using TCRs that could be formatted either as conventional ?? heterodimers, or as single-chain fragments variable constructs linked to CD3? and CD28 signaling domains or to CD3? alone. Two high-affinity TCRs (KD values of ?50 and 250 nM) against MART1/HLA-A2 or WT1/HLA-A2 were used, allowing MART1 or WT1 peptide titrations to easily assess the impact of Ag density. Although CARs were expressed at higher surface levels than TCRs, they were 10-100-fold less sensitive, even in the absence of the CD8 coreceptor. Mathematical modeling demonstrated that lower CAR sensitivity could be attributed to less efficient signaling kinetics. Furthermore, reduced cytokine secretion observed at high Ag density for both TCRs and CARs suggested a role for negative regulators in both systems. Interestingly, at high Ag density, CARs also mediated greater maximal release of some cytokines, such as IL-2 and IL-6. These results have implications for the next-generation design of receptors used in adoptive T cell therapies.

SUBMITTER: Harris DT

PROVIDER: S-EPMC5780198 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Comparison of T Cell Activities Mediated by Human TCRs and CARs That Use the Same Recognition Domains.

Harris Daniel T DT Hager Marlies V MV Smith Sheena N SN Cai Qi Q Stone Jennifer D JD Kruger Philipp P Lever Melissa M Dushek Omer O Schmitt Thomas M TM Greenberg Philip D PD Kranz David M DM

Journal of immunology (Baltimore, Md. : 1950) 20171229 3

Adoptive T cell therapies have achieved significant clinical responses, especially in hematopoietic cancers. Two types of receptor systems have been used to redirect the activity of T cells, normal heterodimeric TCRs or synthetic chimeric Ag receptors (CARs). TCRs recognize peptide-HLA complexes whereas CARs typically use an Ab-derived single-chain fragments variable that recognizes cancer-associated cell-surface Ags. Although both receptors mediate diverse effector functions, a quantitative com ...[more]

PMID: 29288199

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Project description:Given the limited set of T cell receptor (TCR) V genes that are used to create TCRs that are reactive to different ligands, such as major histocompatibility complex (MHC) class I, MHC class II, and MHC-like proteins (for example, MIC molecules and CD1 molecules), the V?1 segment can be rearranged with D?-J?-C? or J?-C? segments to form classical ??TCRs or uncommon ??TCRs using a V?1 segment (?/??TCR). Here we have determined two complex structures of the ?/??TCRs (S19-2 and TU55) bound to different locus-disparate MHC class I molecules with HIV peptides (HLA-A*2402-Nef138-10 and HLA-B*3501-Pol448-9). The overall binding modes resemble those of classical ??TCRs but display a strong tilt binding geometry of the V?1 domain toward the HLA ?1 helix, due to a conserved extensive interaction between the CDR1? loop and the N-terminal region of the ?1 helix (mainly in position 62). The aromatic amino acids of the CDR1? loop exploit different conformations ("aromatic ladder" or "aromatic hairpin") to accommodate distinct MHC helical scaffolds. This tolerance helps to explain how a particular TCR V region can similarly dock onto multiple MHC molecules and thus may potentially explain the nature of TCR cross-reactivity. In addition, the length of the CDR3? loop could affect the extent of tilt binding of the V?1 domain, and adaptively, the pairing V? domains adjust their mass centers to generate differential MHC contacts, hence probably ensuring TCR specificity for a certain peptide-MHC class I (pMHC-I). Our data have provided further structural insights into the TCR recognition of classical pMHC-I molecules, unifying cross-reactivity and specificity.IMPORTANCE The specificity of ?? T cell recognition is determined by the CDR loops of the ??TCR, and the general mode of binding of ??TCRs to pMHC has been established over the last decade. Due to the intrinsic genomic structure of the TCR ?/? chain locus, some V? segments can rearrange with the C? segment, forming a hybrid V?C?V?C? TCR, the ?/??TCR. However, the basis for the molecular recognition of such TCRs of their ligands is elusive. Here an ??TCR using the V?1 segment, S19-2, was isolated from an HIV-infected patient in an HLA-A*24:02-restricted manner. We then solved the crystal structures of the S19-2 TCR and another ?/??TCR, TU55, bound to their respective ligands, revealing a conserved V?1 binding feature. Further binding kinetics analysis revealed that the S19-2 and TU55 TCRs bind pHLA very tightly and in a long-lasting manner. Our results illustrate the mode of binding of a TCR using the V?1 segment to its ligand, virus-derived pHLA.

Dataset Information

Comparison of T Cell Activities Mediated by Human TCRs and CARs That Use the Same Recognition Domains.

Publications

Comparison of T Cell Activities Mediated by Human TCRs and CARs That Use the Same Recognition Domains.

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