INTRODUCTION: T-cell receptor (TCR) recognition of foreign peptides presented by the major histocompatibility complex (MHC) initiates the adaptive immune response against pathogens. While a large number of TCR sequences specific to different antigenic peptides are known to date, the structural data describing the conformation and contacting residues for TCR-peptide-MHC complexes is relatively limited. In the present study we aim to extend and analyze the set of available structures by performing highly accurate template-based modeling of these complexes using TCR sequences with known specificity. METHODS: Identification of CDR3 sequences and their further clustering, based on available spatial structures, V- and J-genes of corresponding T-cell receptors, and epitopes, was performed using the VDJdb database. Modeling of the selected CDR3 loops was conducted using a stepwise introduction of single amino acid substitutions to the template PDB structures, followed by optimization of the TCR-peptide-MHC contacting interface using the Rosetta package applications. Statistical analysis and recursive feature elimination procedures were carried out on computed energy values and properties of contacting amino acid residues between CDR3 loops and peptides, using R. RESULTS: Using the set of 29 complex templates (including a template with SARS-CoV-2 antigen) and 732 specificity records, we built a database of 1585 model structures carrying substitutions in either TCRα or TCRβ chains with some models representing the result of different mutation pathways for the same final structure. This database allowed us to analyze features of amino acid contacts in TCR - peptide interfaces that govern antigen recognition preferences and interpret these interactions in terms of physicochemical properties of interacting residues. CONCLUSION: Our results provide a methodology for creating high-quality TCR-peptide-MHC models for antigens of interest that can be utilized to predict TCR specificity.

• Klíčová slova
• T-cell receptor, TCR-peptide-MHC complex, antigen recognition, database, structural modeling,
• MeSH
• aminokyseliny MeSH
• antigenní specifita receptorů T-buněk MeSH
• COVID-19 * MeSH
• komplement MeSH
• lidé MeSH
• SARS-CoV-2 MeSH
• specificita protilátek MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• aminokyseliny MeSH
• komplement MeSH

BACKGROUND AND AIMS: Intestinal inflammation in inflammatory bowel diseases [IBD] is thought to be T cell mediated and therefore dependent on the interaction between the T cell receptor [TCR] and human leukocyte antigen [HLA] proteins expressed on antigen presenting cells. The collection of all TCRs in one individual, known as the TCR repertoire, is characterised by enormous diversity and inter-individual variability. It was shown that healthy monozygotic [MZ] twins are more similar in their TCR repertoire than unrelated individuals. Therefore MZ twins, concordant or discordant for IBD, may be useful to identify disease-related and non-genetic factors in the TCR repertoire which could potentially be used as disease biomarkers. METHODS: Employing unique molecular barcoding that can distinguish between polymerase chain reaction [PCR] artefacts and true sequence variation, we performed deep TCRα and TCRβ repertoire profiling of the peripheral blood of 28 MZ twin pairs from Denmark and Germany, 24 of whom were discordant and four concordant for IBD. RESULTS: We observed disease- and smoking-associated traits such as sharing, diversity and abundance of specific clonotypes in the TCR repertoire of IBD patients, and particularly in patients with active disease, compared with their healthy twins. CONCLUSIONS: Our findings identified TCR repertoire features specific for smokers and IBD patients, particularly when signs of disease activity were present. These findings are a first step towards the application of TCR repertoire analyses as a valuable tool to characterise inflammatory bowel diseases and to identify potential biomarkers and true disease causes.

• Klíčová slova
• T cell receptor [TCR] repertoire, inflammatory bowel diseases [IBD], monozygotic twins,
• MeSH
• C-reaktivní protein analýza   MeSH
• Crohnova nemoc * diagnóza   imunologie   patofyziologie   MeSH
• dospělí MeSH
• dvojčata monozygotní MeSH
• feces MeSH
• geny TcR alfa * MeSH
• geny TcR beta * MeSH
• kouření imunologie   MeSH
• leukocytární L1-antigenní komplex analýza   MeSH
• lidé MeSH
• posouzení stavu pacienta MeSH
• receptory antigenů T-buněk alfa-beta krev   MeSH
• sekvenční analýza DNA MeSH
• ulcerózní kolitida * diagnóza   imunologie   patofyziologie   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• studie na dvojčatech MeSH
• Geografické názvy
• Dánsko MeSH
• Německo MeSH
• Názvy látek
• C-reaktivní protein MeSH
• leukocytární L1-antigenní komplex MeSH
• receptory antigenů T-buněk alfa-beta MeSH

Hypervariable T cell receptors (TCRs) play a key role in adaptive immunity, recognizing a vast diversity of pathogen-derived antigens. Our ability to extract clinically relevant information from large high-throughput sequencing of TCR repertoires (RepSeq) data is limited, because little is known about TCR-disease associations. We present Antigen-specific Lymphocyte Identification by Clustering of Expanded sequences (ALICE), a statistical approach that identifies TCR sequences actively involved in current immune responses from a single RepSeq sample and apply it to repertoires of patients with a variety of disorders - patients with autoimmune disease (ankylosing spondylitis [AS]), under cancer immunotherapy, or subject to an acute infection (live yellow fever [YF] vaccine). We validate the method with independent assays. ALICE requires no longitudinal data collection nor large cohorts, and it is directly applicable to most RepSeq datasets. Its results facilitate the identification of TCR variants associated with diseases and conditions, which can be used for diagnostics and rational vaccine design.

• MeSH
• adaptivní imunita genetika   MeSH
• antigeny virové MeSH
• antigeny MeSH
• hypervariabilní oblasti genetika   fyziologie   MeSH
• imunoterapie MeSH
• lidé MeSH
• receptory antigenů T-buněk imunologie   metabolismus   fyziologie   MeSH
• sekvenční analýza DNA metody   MeSH
• shluková analýza MeSH
• vysoce účinné nukleotidové sekvenování metody   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antigeny virové MeSH
• antigeny MeSH
• hypervariabilní oblasti MeSH
• receptory antigenů T-buněk MeSH

T cell receptor (TCR) repertoire data contain information about infections that could be used in disease diagnostics and vaccine development, but extracting that information remains a major challenge. Here we developed a statistical framework to detect TCR clone proliferation and contraction from longitudinal repertoire data. We applied this framework to data from three pairs of identical twins immunized with the yellow fever vaccine. We identified 600 to 1,700 responding TCRs in each donor and validated them using three independent assays. While the responding TCRs were mostly private, albeit with higher overlap between twins, they could be well-predicted using a classifier based on sequence similarity. Our method can also be applied to samples obtained postinfection, making it suitable for systematic discovery of new infection-specific TCRs in the clinic.

• Klíčová slova
• RepSeq, T cell receptor, high-throughput sequencing, twins, vaccination,
• MeSH
• antigeny virové imunologie   MeSH
• dárci tkání MeSH
• dvojčata monozygotní MeSH
• imunizace metody   MeSH
• lidé MeSH
• receptory antigenů T-buněk imunologie   MeSH
• T-lymfocyty imunologie   MeSH
• vakcína proti žluté zimnici imunologie   MeSH
• vakcinace metody   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antigeny virové MeSH
• receptory antigenů T-buněk MeSH
• vakcína proti žluté zimnici MeSH

BACKGROUND: Adaptive immune responses to newly encountered pathogens depend on the mobilization of antigen-specific clonotypes from a vastly diverse pool of naive T cells. Using recent advances in immune repertoire sequencing technologies, models of the immune receptor rearrangement process, and a database of annotated T cell receptor (TCR) sequences with known specificities, we explored the baseline frequencies of T cells specific for defined human leukocyte antigen (HLA) class I-restricted epitopes in healthy individuals. METHODS: We used a database of TCR sequences with known antigen specificities and a probabilistic TCR rearrangement model to estimate the baseline frequencies of TCRs specific to distinct antigens epitopespecificT-cells. We verified our estimates using a publicly available collection of TCR repertoires from healthy individuals. We also interrogated a database of immunogenic and non-immunogenic peptides is used to link baseline T-cell frequencies with epitope immunogenicity. RESULTS: Our findings revealed a high degree of variability in the prevalence of T cells specific for different antigens that could be explained by the physicochemical properties of the corresponding HLA class I-bound peptides. The occurrence of certain rearrangements was influenced by ancestry and HLA class I restriction, and umbilical cord blood samples contained higher frequencies of common pathogen-specific TCRs. We also identified a quantitative link between specific T cell frequencies and the immunogenicity of cognate epitopes presented by defined HLA class I molecules. CONCLUSIONS: Our results suggest that the population frequencies of specific T cells are strikingly non-uniform across epitopes that are known to elicit immune responses. This inference leads to a new definition of epitope immunogenicity based on specific TCR frequencies, which can be estimated with a high degree of accuracy in silico, thereby providing a novel framework to integrate computational and experimental genomics with basic and translational research efforts in the field of T cell immunology.

• Klíčová slova
• Antigen, Immune repertoire, Immunogenicity, T cell receptor,
• MeSH
• epitopy imunologie   MeSH
• lidé MeSH
• MHC antigeny I. třídy imunologie   MeSH
• peptidy imunologie   MeSH
• receptory antigenů T-buněk imunologie   MeSH
• statistické modely MeSH
• T-lymfocyty imunologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• epitopy MeSH
• MHC antigeny I. třídy MeSH
• peptidy MeSH
• receptory antigenů T-buněk MeSH

Diverse repertoires of hypervariable immunoglobulin receptors (TCR and BCR) recognize antigens in the adaptive immune system. The development of immunoglobulin receptor repertoire sequencing methods makes it possible to perform repertoire-wide disease association studies of antigen receptor sequences. We developed a statistical framework for associating receptors to disease from only a small cohort of patients, with no need for a control cohort. Our method successfully identifies previously validated Cytomegalovirus and type one diabetes responsive TCR[Formula: see text] sequences .

• Klíčová slova
• computational biology, condition associated receptors, human, immunology, inflammation, repertoire sequencing, statistical analysis, systems biology,
• MeSH
• adaptivní imunita genetika   MeSH
• Cytomegalovirus imunologie   MeSH
• diabetes mellitus genetika   imunologie   MeSH
• genetická variace imunologie   MeSH
• hypervariabilní oblasti genetika   MeSH
• lidé MeSH
• receptory antigenů B-buněk genetika   MeSH
• receptory antigenů T-buněk genetika   imunologie   MeSH
• receptory antigenů genetika   imunologie   MeSH
• receptory imunologické genetika   imunologie   MeSH
• vysoce účinné nukleotidové sekvenování MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• hypervariabilní oblasti MeSH
• receptory antigenů B-buněk MeSH
• receptory antigenů T-buněk MeSH
• receptory antigenů MeSH
• receptory imunologické MeSH

For understanding the rules and laws of adaptive immunity, high-throughput profiling of T-cell receptor (TCR) repertoires becomes a powerful tool. The structure of TCR repertoires is instructive even before the antigen specificity of each particular receptor becomes available. It embodies information about the thymic and peripheral selection of T cells; the readiness of an adaptive immunity to withstand new challenges; the character, magnitude and memory of immune responses; and the aetiological and functional proximity of T-cell subsets. Here, we describe our current analytical approaches for the comparative analysis of murine TCR repertoires, and show several examples of how these approaches can be applied for particular experimental settings. We analyse the efficiency of different metrics used for estimation of repertoire diversity, repertoire overlap, V-gene and J-gene segments usage similarity, and amino acid composition of CDR3. We discuss basic differences of these metrics and their advantages and limitations in different experimental models, and we provide guidelines for choosing an efficient way to lead a comparative analysis of TCR repertoires. Applied to the various known and newly developed mouse models, such analysis should allow us to disentangle multiple sophisticated puzzles in adaptive immunity.

• Klíčová slova
• T cell, T-cell receptor repertoires, aging, diversity, functional T-cell subsets,
• MeSH
• buněčná imunita fyziologie   MeSH
• hypervariabilní oblasti genetika   imunologie   MeSH
• myši MeSH
• T-lymfocyty - podskupiny cytologie   imunologie   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• hypervariabilní oblasti MeSH