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Introduction: The avidity of the T-cell receptor (TCR) for antigenic peptides presented by the MHC (pMHC) on cells is an essential parameter for efficient T cell-mediated immunity. Yet, whether the TCR-ligand avidity can drive the clonal evolution of virus antigen-specific CD8 T cells, and how this process is determined in latent Cytomegalovirus (CMV)- against Epstein-Barr virus (EBV)-mediated infection remains largely unknown. Methods: To address these issues, we quantified monomeric TCR-pMHC dissociation rates on CMV- and EBV-specific individual TCRαβ clonotypes and polyclonal CD8 T cell populations in healthy donors over a follow-up time of 15-18 years. The parameters involved during the long-term persistence of virusspecific T cell clonotypes were further evaluated by gene expression profiling, phenotype and functional analyses. Results: Within CMV/pp65-specific T cell repertoires, a progressive contraction of clonotypes with high TCR-pMHC avidity and low CD8 binding dependency was observed, leading to an overall avidity decline during long-term antigen exposure. We identified a unique transcriptional signature preferentially expressed by high-avidity CMV/pp65-specific T cell clonotypes, including the inhibitory receptor LILRB1. Interestingly, T cell clonotypes of high-avidity showed higher LILRB1 expression than the low-avidity ones and LILRB1 blockade moderately increased T cell proliferation. Similar findings were made for CD8 T cell repertoires specific for the CMV/IE-1 epitope. There was a gradual in vivo loss of high-avidity T cells with time for both CMV specificities, corresponding to virus-specific CD8 T cells expressing enhanced LILRB1 levels. In sharp contrast, the EBV/BMFL1-specific T cell clonal composition and distribution, once established, displayed an exceptional stability, unrelated to TCR-pMHC binding avidity or LILRB1 expression. Conclusions: These findings reveal an overall long-term avidity decline of CMVbut not EBV-specific T cell clonal repertoires, highlighting the differing role played by TCR-ligand avidity over the course of these two latent herpesvirus infections. Our data further suggest that the inhibitor receptor LILRB1 potentially restricts the clonal expansion of high-avidity CMV-specific T cell clonotypes during latent infection. We propose that the mechanisms regulating the longterm outcome of CMV- and EBV-specific memory CD8 T cell clonotypes in humans are distinct. [ABSTRACT FROM AUTHOR]

IntroductionThe avidity of the T-cell receptor (TCR) for antigenic peptides presented by the MHC (pMHC) on cells is an essential parameter for efficient T cell-mediated immunity. Yet, whether the TCR-ligand avidity can drive the clonal evolution of virus antigen-specific CD8 T cells, and how this process is determined in latent Cytomegalovirus (CMV)- against Epstein-Barr virus (EBV)-mediated infection remains largely unknown.MethodsTo address these issues, we quantified monomeric TCR-pMHC dissociation rates on CMV- and EBV-specific individual TCRαβ clonotypes and polyclonal CD8 T cell populations in healthy donors over a follow-up time of 15-18 years. The parameters involved during the long-term persistence of virus-specific T cell clonotypes were further evaluated by gene expression profiling, phenotype and functional analyses.ResultsWithin CMV/pp65-specific T cell repertoires, a progressive contraction of clonotypes with high TCR-pMHC avidity and low CD8 binding dependency was observed, leading to an overall avidity decline during long-term antigen exposure. We identified a unique transcriptional signature preferentially expressed by high-avidity CMV/pp65-specific T cell clonotypes, including the inhibitory receptor LILRB1. Interestingly, T cell clonotypes of high-avidity showed higher LILRB1 expression than the low-avidity ones and LILRB1 blockade moderately increased T cell proliferation. Similar findings were made for CD8 T cell repertoires specific for the CMV/IE-1 epitope. There was a gradual in vivo loss of high-avidity T cells with time for both CMV specificities, corresponding to virus-specific CD8 T cells expressing enhanced LILRB1 levels. In sharp contrast, the EBV/BMFL1-specific T cell clonal composition and distribution, once established, displayed an exceptional stability, unrelated to TCR-pMHC binding avidity or LILRB1 expression.ConclusionsThese findings reveal an overall long-term avidity decline of CMV- but not EBV-specific T cell clonal repertoires, highlighting the differing role played by TCR-ligand avidity over the course of these two latent herpesvirus infections. Our data further suggest that the inhibitor receptor LILRB1 potentially restricts the clonal expansion of high-avidity CMV-specific T cell clonotypes during latent infection. We propose that the mechanisms regulating the long-term outcome of CMV- and EBV-specific memory CD8 T cell clonotypes in humans are distinct.

Immune escape is a prerequisite for tumor growth. We previously described a decline in intratumor activated cytotoxic T cells and T cell receptor (TCR) clonotype diversity in invasive breast carcinomas compared to ductal carcinoma in situ (DCIS), implying a central role of decreasing T cell responses in tumor progression. To determine potential associations between peripheral immunity and breast tumor progression, here, we assessed the peripheral blood TCR clonotype of 485 breast cancer patients diagnosed with either DCIS or de novo stage IV disease at younger (<45) or older (≥45) age. TCR clonotype diversity was significantly lower in older compared to younger breast cancer patients regardless of tumor stage at diagnosis. In the younger age group, TCR-α clonotype diversity was lower in patients diagnosed with de novo stage IV breast cancer compared to those diagnosed with DCIS. In the older age group, DCIS patients with higher TCR-α clonotype diversity were more likely to have a recurrence compared to those with lower diversity. Whole blood transcriptome profiles were distinct depending on the TCR-α Chao1 diversity score. There were more CD8 + T cells and a more active immune environment in DCIS tumors of young patients with higher peripheral blood TCR-α Chao1 diversity than in those with lower diversity. These results provide insights into the role that host immunity plays in breast cancer development across different age groups., Competing Interests: Competing interests statement:K.P. serves on the Scientific Advisory Boards of Novartis, Ideaya Biosciences, and Scorpion Therapeutics, holds equity options in Scorpion Therapeutics and Ideaya Biosciences, and receives sponsored research funding through Dana-Farber from Novartis. F.M. is a cofounder of and has equity in Harbinger Health, has equity in Zephyr AI, and serves as a consultant for Harbinger Health, and Zephyr AI. She is also on the board of directors of Exscientia Plc. F.M. declares that none of these relationships are directly or indirectly related to the content of this manuscript. D.D. receives research funding from Canon, Inc. J.P. is currently an employee of Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA. J.P. contributed to this work prior to their employment at Merck Sharp & Dohme LLC. The opinions or perspectives expressed herein do not represent the opinions or perspectives of Merck Sharp & Dohme LLC.

To find out if the T cell repertoire is efficiently and specifically provoked in patients with breast cancer, we have investigated the clonotypes of main T cell subsets (based on V β -Chain) in tumor draining lymph nodes. CD4+ helper, CD8+ cytotoxic and (CD4+CD127 dim CD25+) regulatory T cells, were negatively selected, and isolated, from lymph node mononuclear cells of 14 untreated patients with breast cancer. Four non-malignant patients, who underwent surgical operation, were also recruited as the control group. Based on sequences and new nomenclature of the T cell Receptor β Variables (TRBVs) available in the international ImMunoGeneTics (IMGT) database, 28 TRBV specific forward primers and two TRB Constant region (TRBC) specific reverse primers were developed to amplify all functional alleles. Fluorescent-labeled PCR products were then run on an ABI PRISM 310 Genetic-Analyzer. The data was analyzed by GeneMapper software version 3.1. Clonotype analysis suggested that activated T cells are present in breast cancer. More TRBV usage were detected among CD4+ helper and regulatory subsets, with Gaussian-like pattern in the majority of functional TRBV families; whereas CD8+ cytotoxic T cells showed oligoclonality in almost all TRBV families with one or two dominant peaks in each family. Similar pattern in some of these TRBVs were also observed among controls. Having no expression or polyclonality in the controls, the oligoclonal pattern observed in the TRBV18, however, appears to be specific to breast cancer patients. This phenomenon may reflect the existence of new antigenic stimulation(s) in BC patients, preferentially activating those clones of T cells that express TRBV18. [ABSTRACT FROM AUTHOR]

In order to clarify the role of B cells in the development of insulitis and diabetes, B cell-deficient (B–) mice treated with streptozocin (STZ) were studied. The extent of insulitis and the cumulative incidence of diabetes were significantly suppressed in B– mice (P < 0.0001), indicating that B cells are crucial for the progression of insulitis and diabetes. Accumulation of both CD4+ T cells and B cells was observed in islets of B+ mice, while CD4+ T cells but not B cells were found in B– mice. A few CD8+ T cells and macrophages were detectable in both types of mice. The immunohistochemical study did not reveal any change in the subpopulations of infiltrating lymphocytes except for the absence of B cells in the B– mice. TCR Vβ gene repertoire usage of islet-infiltrating T cells was restricted to some extent in the B+ or B– mice, but there was no significant difference between the B+ and B– mice, suggesting that the initial islet-reactive T cell response can occur in the absence of B cells. In contrast, TCR clonotype spreading of islet-infiltrating T cells was significantly suppressed in B– mice compared with B+ mice (P < 0.0001). These data suggest that initial priming of T cells is not impaired and TCR Vβ repertoire usage is not limited by the lack of B cells, while B cells are important essentially for the spreading of islet-infiltrating clonal T cells in autoimmune diabetic mice induced with STZ. [ABSTRACT FROM PUBLISHER]

A parietal cell-specific Th1 clone, II-6, which was established from a BALB/c mouse bearing postthymectomy autoimmune gastritis (AIG), recognizes a peptide of the α subunit (α891–905) of HF/KFATPase and induces gastritis in nu/nu BALB/c mice by adoptive cell transfer. In the present study, the primary structure of the TCR of II-6 was determined as Vα10–Jαc5a–Cα and Vβ14–Jβ2.3–Cβ2 by cDNA cloning. Using PCR with specific primers, we defined the use of this II-6 TCR in nu/nu mice with transferred II-6 cells and in mice that spontaneously developed AIG by thymectomy on day 3 after birth (d3-Tx). II-6 TCR mRNAs were detected in the gastric mucosa of all of the nu/nu mice, suggesting that II-6 cells indeed home to the gastric mucosa and thereby were directly involved in the destruction of target parietal cells. TCR β chain mRNAs encoding CDR3 region sequences almost identical with that of II-6 were also found in the gastric mucosa in 43% (six of 14 mice tested) of the d3-Tx AIG mice at 4–12 weeks old by nested RT-PCR. Such a frequent appearance of similar clonotypes in independent individuals suggests that T cells bearing II-6-like TCR including the II-6 itself might be directly involved in, although not essential for, the pathogenesis of AIG in 3d-Tx mice. [ABSTRACT FROM AUTHOR]

The T cells are key players of the response to checkpoint blockade immunotherapy (CBI) and monitoring the strength and specificity of antitumor T-cell reactivity remains a crucial but elusive component of precision immunotherapy. The entire assembly of T-cell receptor (TCR) sequences accounts for antigen specificity and strength of the T-cell immune response. The TCR repertoire hence represents a "footprint" of the conditions faced by T cells that dynamically evolves according to the challenges that arise for the immune system, such as tumor neo-antigenic load. Hence, TCR repertoire analysis is becoming increasingly important to comprehensively understand the nature of a successful antitumor T-cell response, and to improve the success and safety of current CBI. [ABSTRACT FROM AUTHOR]