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Epitope-specific T cell responses after SARS-CoV-2 vaccination [scRNA_dextramer_mixed_time]

ABSTRACT: Clonal expansion is a hallmark of adaptive immunity, and appears to be driven by high antigen-specific receptor avidity as shown by research using murine in vivo models. In humans, however, the functionality of antigen-specific T cell clonotypes that are recruited into primary and recall immune responses remains surprisingly elusive. In this regard, the vaccination program during the SARS-CoV-2 pandemic represented a unique research opportunity by provision of highly standardized cohorts of healthy human individuals receiving immunizations against a previously unseen antigen. Here, we analyzed 30 HLA-typed individuals before, short-term and long-term after three mRNA vaccinations against SARS-CoV-2. We performed an in-depth characterization of the magnitude, phenotype, clonal composition and functionality of antigen-specific CD8 T cell responses by ELISPOT, flow cytometry and single-cell RNA sequencing, including CITE seq of 130 surface antigens and 16 T cell epitope specificities. 89 T cell receptors (TCRs) covering three complete epitope-specific repertoires were re-expressed by CRISPR/Cas9-mediated orthotopic TCR replacement and tested for their avidity. TCR repertoires underwent continuous tailoring, with high TCR avidity being linked to both clonal persistence and expansion. However, epitope-specific repertoires also maintained diversity by concomitant contraction and new emergence of functional T cell clones over time. These data on the phenotype and clonal selection within human antigen-specific T cell responses instruct our understanding of human T cell biology and may guide the development of enhanced or novel vaccines.

ORGANISM(S): Homo sapiens

PROVIDER: GSE261967 | GEO | 2024/10/31

REPOSITORIES: GEO

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Project description: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. Here, we quantified monomeric TCR-pMHC dissociation rates on CMV- and EBV-specific individual TCR-alpha-beta clonotypes and polyclonal CD8 T cell populations in healthy donors over a follow-up time of 15-18 years. 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. Together, these 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 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.

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Epitope-specific T cell responses after SARS-CoV-2 vaccination [scRNA_dextramer_mixed_time]

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