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Plasticity in the contribution of T cell receptor variable region residues to binding of peptide-HLA-A2 complexes.

ABSTRACT: One hypothesis accounting for major histocompatibility complex (MHC) restriction by T cell receptors (TCRs) holds that there are several evolutionary conserved residues in TCR variable regions that contact MHC. While this "germline codon" hypothesis is supported by various lines of evidence, it has been difficult to test. The difficulty stems in part from the fact that TCRs exhibit low affinities for pep/MHC, thus limiting the range of binding energies that can be assigned to these key interactions using mutational analyses. To measure the magnitude of binding energies involved, here we used high-affinity TCRs engineered by mutagenesis of CDR3. The TCRs included a high-affinity, MART-1/HLA-A2-specific single-chain TCR and two other high-affinity TCRs that all contain the same V? region and recognize the same MHC allele (HLA-A2), with different peptides and V? regions. Mutational analysis of residues in CDR1 and CDR2 of the three V?2 regions showed the importance of the key germline codon residue Y51. However, two other proposed key residues showed significant differences among the TCRs in their relative contributions to binding. With the use of single-position, yeast-display libraries in two of the key residues, MART-1/HLA-A2 selections also revealed strong preferences for wild-type germline codon residues, but several alternative residues could also accommodate binding and, hence, MHC restriction. Thus, although a single residue (Y51) could account for a proportion of the energy associated with positive selection (i.e., MHC restriction), there is significant plasticity in requirements for particular side chains in CDR1 and CDR2 and in their relative binding contributions among different TCRs.

SUBMITTER: Smith SN

PROVIDER: S-EPMC3844621 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Plasticity in the contribution of T cell receptor variable region residues to binding of peptide-HLA-A2 complexes.

Smith Sheena N SN Sommermeyer Daniel D Piepenbrink Kurt H KH Blevins Sydney J SJ Bernhard Helga H Uckert Wolfgang W Baker Brian M BM Kranz David M DM

Journal of molecular biology 20130814 22

One hypothesis accounting for major histocompatibility complex (MHC) restriction by T cell receptors (TCRs) holds that there are several evolutionary conserved residues in TCR variable regions that contact MHC. While this "germline codon" hypothesis is supported by various lines of evidence, it has been difficult to test. The difficulty stems in part from the fact that TCRs exhibit low affinities for pep/MHC, thus limiting the range of binding energies that can be assigned to these key interacti ...[more]

PMID: 23954306

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Project description:HLA-C locus mismatches (MMs) are the most frequent class I disparities in unrelated hematopoietic stem cell transplantation (HSCT) and have a detrimental impact on clinical outcome. Recently, a few retrospective clinical studies have reported some variability in the immunogenicity of HLA-C incompatibilities. To get better insight into presumably permissive HLA-C MMs, we have developed a one-way in vitro mixed lymphocyte reaction (MLR) assay allowing to quantify activated CD56-CD137+CD8+ lymphocytes in HLA-C incompatible combinations. T cell-mediated alloresponses were correlated with genetic markers such as HLA-C mRNA expression and the number of amino acid (aa) MMs in the α1/α2 domains (peptide-binding region). Because of the high rate of HLA-DPB1 incompatibilities in HLA-A-, B-, C-, DRB1-, and DQB1-matched unrelated HSCT patient/donor pairs, the impact of HLA-DPB1 mismatching, a potential bystander of CD4+ T cell activation, was also considered. Heterogeneous alloresponses were measured in 63 HLA-C-mismatched pairs with a positive assay in 52% of the combinations (2.3-18.6% activated CTLs), representing 24 different HLA-A~B~DRB1~DQB1 haplotypes. There was no correlation between measured alloresponses and mRNA expression of the mismatched HLA-C alleles. The HLA-C*03:03/03:04 MM did not induce any positive alloresponse in five MLRs. We also identified HLA-C*02:02 and HLA-C*06:02 as mismatched alleles with lower immunogenicity, and HLA-C*14:02 as a more immunogenic MM. A difference of at least 10 aa residues known to impact peptide/T cell receptor (TCR) binding and a bystander HLA-DPB1 incompatibility had a significant impact on CTL alloreactivity (p = 0.021). The same HLA-C MM, when recognized by two different responders with the same HLA haplotypes, was recognized differently, emphasizing the role of the T-cell repertoire of responding cells. In conclusion, mismatched HLA-C alleles differing by 10 or more aas in the peptide/TCR-binding region, when occurring together with HLA-DPB1 incompatibilities, should be considered as high-risk MMs in unrelated HSCT.

Project description:NY-ESO-1 is a tumor-specific, highly immunogenic, human germ cell antigen of the MAGE-1 family that is a promising vaccine and cell therapy candidate in clinical trial development. The mouse genome does not encode an NY-ESO-1 homolog thereby not subjecting transgenic T-cells to thymic tolerance mechanisms that might impair in-vivo studies. We hypothesized that an NY-ESO-1 T cell receptor (TCR) transgenic mouse would provide the unique opportunity to study avidity of TCR response against NY-ESO-1 for tumor vaccine and cellular therapy development against this clinically relevant and physiological human antigen. To study in vitro and in vivo the requirements for shaping an effective T cell response against the clinically relevant NY-ESO-1, we generated a C57BL/6 HLA-A*0201 background TCR transgenic mouse encoding the 1G4 TCR specific for the human HLA-A2 restricted, NY-ESO-1157-165 SLLMWITQC (9C), initially identified in an NY-ESO-1 positive melanoma patient. The HLA-A*0201 restricted TCR was positively selected on both CD4+ and CD8+ cells. Mouse 1G4 T cells were not activated by endogenous autoimmune targets or a large library of non-cognate viral antigens. In contrast, their activation by HLA-A2 NY-ESO-1157-165 complexes was evident by proliferation, CD69 upregulation, interferon-γ production, and interleukin-2 production, and could be tuned using a twofold higher affinity altered peptide ligand, NY-ESO-1157-165V. NY-ESO-1157-165V recombinant vaccination of syngeneic mice adoptively transferred with m1G4 CD8+ T cells controlled tumor growth in vivo. 1G4 transgenic mice suppressed growth of syngeneic methylcholanthrene (MCA) induced HHD tumor cells expressing the full-length human NY-ESO-1 protein but not MCA HHD tumor cells lacking NY-ESO-1. The 1G4 TCR mouse model for the physiological human TCR against the clinically relevant antigen, NY-ESO-1, is a valuable tool with the potential to accelerate clinical development of NY-ESO-1-targeted T-cell and vaccine therapies.

Dataset Information

Plasticity in the contribution of T cell receptor variable region residues to binding of peptide-HLA-A2 complexes.

Publications

Plasticity in the contribution of T cell receptor variable region residues to binding of peptide-HLA-A2 complexes.

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