Structural Bases for the Affinity-Driven Selection of a Public TCR against a Dominant Human Cytomegalovirus Epitope

Gras, Stéphanie; Saulquin, Xavier; Reiser, Jean‐Baptiste; Debeaupuis, E.; Echasserieau, Klára; Kissenpfennig, Adrien; Legoux, François; Chouquet, Anne; Gorrec, M. Le; Machillot, Paul; Neveu, B.; Thielens, Nicole M.; Malissen, Bernard; Bonneville, Marc; Housset, D.

doi:10.4049/jimmunol.0900556

Cited by 90 publications

(105 citation statements)

References 42 publications

(43 reference statements)

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“…Therefore, the high frequency of T cells specific for these p-MHC observed in the various thymic compartments may originate from a structural predisposition of the TRAV12-2 TCR segment to interact with MelA-A2 and PGT-A2. In an opposite manner, the productive recognition of pp65-A2 complexes requires joint contributions of CDR1, 2 and 3 loops from both alpha and beta chains of the TCR [23,24], suggesting that such TCRs might be expressed by only a low frequency of thymic precursors. Therefore, the respective contribution of germline-versus nongermline-encoded TCR residues in the recognition of p-MHC complexes probably affects the hierarchy of Ag-specific cell repertoires in the various thymic compartments.…”

Section: Quantitative Impact Of the Expression Of The Mhc Class I-resmentioning

confidence: 99%

Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

et al. 2015

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In the thymus, a T-cell repertoire able to confer protection against infectious and noninfectious agents in a peptide-dependent, self-MHC-restricted manner is selected. Direct detection of Ag-specific thymocytes, and analysis of the impact of the expression of the MHCrestricting allele on their frequency or function has never been studied in humans because of the extremely low precursor frequency. Here, we used a tetramer-based enrichment protocol to analyze the ex vivo frequency and activation-phenotype of human thymocytes specific for self, viral and tumor-antigens presented by HLA-A*0201 (A2) in individuals expressing or not this allele. Ag-specific thymocytes were quantified within both CD4CD8 double or single-positive compartments in every donor. Our data indicate that the maturation efficiency of Ag-specific thymocytes is poorly affected by HLA-A2 expression, in terms of frequencies. Nevertheless, A2-restricted T-cell lines from A2 + donors reacted to A2 + cell lines in a highly peptide-specific fashion, whereas their alloreactive counterparts showed off-target activity. This first ex vivo analysis of human antigen-specific thymocytes at different stages of human T-cell development should open new perspectives in the understanding of the human thymic selection process. Keywords: Antigen r Human T cells r MHC r Tetramers r Thymocytes See accompanying Commentary by Ciucci and BosselutAdditional supporting information may be found in the online version of this article at the publisher's web-site IntroductionThe thymus generates a highly diverse T-cell repertoire able to recognize virtually any antigen that could be encountered by a given individual along his/her life. This diversity is achieved through two main mechanisms. First by the acquisition by CD4 + CD8 + double-positive (DP) thymocytes of a clonally distributed T cell receptor (TCR) that is generated after somatic recombination of TCR V(D)J gene segments and nontemplated nucleotide Correspondence: Dr. Xavier Saulquin e-mail: xavier.saulquin@univ-nantes.fradditions. This quasi-random mechanism allows for the generation of up to 10 15 different receptors [1]. Second, by the shaping of this initial T-cell repertoire by positive and negative thymic selection processes that will favor emergence of a self major histocompatibility molecules (MHC)-restricted, yet self-tolerant, TCR repertoire carried by mature naïve single-positive (SP) T cells. As a consequence of this maturation process, the diversity of SP αβ T cells in a given individual falls in the range of 10 6 to 10 8 [2]. * LH and FL equally contributed to this work. The respective contributions of positive and negative thymic selection processes to the generation of a mature T-cell repertoire possibly biased towards recognition of peptides restricted by host MHC alleles are still debated. Indeed, this phenomenon referred to as "host or Self-MHC-restriction" is a consequence of a balance between (i) the need for a thymocyte to get survival signals from TCR upon interactions of weak/intermediate avidi...

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Section: Quantitative Impact Of the Expression Of The Mhc Class I-resmentioning

confidence: 99%

Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

et al. 2015

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“…The GG and GL starting complexes were created, deleting appropriate atoms from this structure. The ILKEPVGHV crystal structure [PDB ID code 3GSO (29)] represents the starting structure for the A2 bound to the full length peptide, whereas its modification defines the A2 GG complex. The A2 GL complex was modeled based on the SLFNTIAVL crystal structure [PDB ID code 2C7U (30)].…”

Section: Tdtf Measurement Andmentioning

confidence: 99%

Dipeptides promote folding and peptide binding of MHC class I molecules

Saini

Ostermeir

Ramnarayan

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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MHC class I molecules bind only those peptides with high affinity that conform to stringent length and sequence requirements. We have now investigated which peptides can aid the in vitro folding of class I molecules, and we find that the dipeptide glycyl-leucine efficiently supports the folding of HLA-A*02:01 and H-2K b into a peptide-receptive conformation that rapidly binds high-affinity peptides. Treatment of cells with glycyl-leucine induces accumulation of peptide-receptive H-2K b and HLA-A*02:01 at the surface of cells. Other dipeptides with a hydrophobic second amino acid show similar enhancement effects. Our data suggest that the dipeptides bind into the F pocket like the C-terminal amino acids of a highaffinity peptide.antigen presentation | ligand exchange | chemical chaperones | endoplasmic reticulum | quality control M HC class I molecules are transmembrane proteins that are vital to the mammalian antiviral and antitumor immune response. They bind intracellular peptides in the lumen of the endoplasmic reticulum (ER) to transport them to the cell surface for inspection by cytotoxic T lymphocytes. To elicit a sustained immune response, peptides need to form stable complexes with class I molecules (1, 2), which means that they must conform to specific length and sequence requirements that were first identified by elution and sequencing, and then structurally understood by X-ray crystallography. Depending on the class I allotype, high-affinity peptides must be 8 to 10 aa long (such that the termini can form hydrogen bonding networks) and have defined side chains at particular positions that bind into specificity pockets at the bottom of the binding groove (3-5). This knowledge has been used to predict the binding affinity of any peptide sequence to a given class I allotype (6), and, together with theoretical simulations of the conformational movements of class I-peptide complexes, it has allowed the design of altered peptide ligands with higher binding affinities (7). The high-affinity peptides thus identified can be used to fold many bacterially expressed denatured class I molecules into their native state (8). Consequently, high-affinity peptides have been called the "essential third subunit of MHC class I" (9).In living cells, class I molecules bind high-affinity peptides with the help of several chaperone proteins, collectively called the peptide loading complex (PLC). Importantly, experiments in vivo and in vitro have shown that, in the presence of the PLC, peptide loading is iterative, i.e., class I molecules first bind suboptimal peptides (peptides that are too long, too short, or do not have the requisite anchor residues) and gradually exchange them for higher-affinity ones (10, 11). The idea that class I molecules can initially fold with such suboptimal peptides is indeed supported by the crystal structures of several class I molecules with octamer or pentamer peptides (12, 13).In our effort to determine the minimum peptide requirements for the folding of class I, we have analyzed even smaller p...

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“…Other studies have established that biased TCR use may also reflect the selection of TCRs with optimal structural characteristics that impart exquisite specificity for a given pMHC molecular topography (18)(19)(20)(21)(22)(23)(24)(25). Such antigen-driven selection will, of course, be shaped by other factors, such as the availability of naive T-cell precursors and the level and duration of antigenpresentation during infection.…”

mentioning

confidence: 99%

Structural basis for enabling T-cell receptor diversity within biased virus-specific CD8 ⁺ T-cell responses

Day¹,

Guillonneau²,

Gras

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Pathogen-specific responses are characterized by preferred profiles of peptide+class I MHC (pMHCI) glycoprotein-specific T-cell receptor (TCR) Variable (V)-region use. How TCRV-region bias impacts TCRαβ heterodimer selection and resultant diversity is unclear. The D b PA 224 -specific TCR repertoire in influenza A virusinfected C57BL/6J (B6) mice exhibits a preferred TCRV-region bias toward the TRBV29 gene segment and an optimal complementarity determining region (CDR3) β-length of 6 aa. Despite these restrictions, D b PA 224 -specific BV29 + T cells use a wide array of unique CDR3β sequences. Structural characterization of a single, TRBV29 + D b P A224 -specific TCRαβ-pMHCI complex demonstrated that CDR3α amino acid side chains made specific peptide interactions, but the CDR3β main chain exclusively contacted peptides. Thus, length but not amino acid sequence was key for recognition and flexibility in Vβ-region use. In support of this hypothesis, retrovirus expression of the D b PA 224 -specific TCRVα-chain was used to constrain pairing within a naive/immune epitope-specific repertoire. The retrogenic TCRVα paired with a diversity of CDR3βs in the context of a preferred TCRVβ spectrum. Overall, these data provide an explanation for the combination of TCRV region bias and diversity within selected repertoires, even as they maintain exquisite pMHCI specificity.T cell repertoire | T-cell receptor bias | crystal structure T he adaptive T-cell response to viruses is mediated via T-cell receptor (TCR)-αβ glycoprotein heterodimer recognition of pathogen-derived peptides (p) complexed to cell-surface MHC glycoproteins. During T-cell development, somatic recombination of variable (V) and joining (J) or V, diversity (D), and J gene segments (1) leads to the emergence of a diverse spectrum of TCRα-and TCRβ-chains. Segments of hypervariability within the Vα and Vβ domains, termed complementarity determining regions (CDRs), form the TCRαβ binding site and mediate contact with a given pMHC complex. Although the CDR1 and -2 regions are determined by germ-line sequences of V-genes, the CDR3 region is encoded at the junction of spliced VJ (TCRα) and VDJ (TCRβ) gene segments. The murine TCRβ (TRB) locus consists of 35 V, 2 D, and 12 J gene segments and the TCRα (TRA) locus has 71 V and 60 J gene segments (2). Beyond the random splicing of different TCRα and TCRβ genes, the overall spectrum of TCR diversity largely reflects the inefficient splicing of DNA encoding the CDR3α and CDR3β loops (3) plus the addition of nontemplated encoded nucleotides at the V(D)J junctions (4). Finally, different pairings of rearranged TCRα-and TCRβ-chains are selected during thymic differentiation to give the naive TCRαβ repertoire.

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Structural Bases for the Affinity-Driven Selection of a Public TCR against a Dominant Human Cytomegalovirus Epitope

Cited by 90 publications

References 42 publications

Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

Dipeptides promote folding and peptide binding of MHC class I molecules

Structural basis for enabling T-cell receptor diversity within biased virus-specific CD8 ⁺ T-cell responses

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Structural Bases for the Affinity-Driven Selection of a Public TCR against a Dominant Human Cytomegalovirus Epitope

Cited by 90 publications

References 42 publications

Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

Role of the MHC restriction during maturation of antigen‐specific human T cells in the thymus

Dipeptides promote folding and peptide binding of MHC class I molecules

Structural basis for enabling T-cell receptor diversity within biased virus-specific CD8 + T-cell responses

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Structural basis for enabling T-cell receptor diversity within biased virus-specific CD8 ⁺ T-cell responses