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T and B Cell Receptor Immune Repertoire Analysis using Next-generation Sequencing
Published on: January 12, 2021
Single-cell transcriptomes and T cell receptors of vaccine-expanded apolipoprotein B-specific T cells
Felix Sebastian Nettersheim1,2, Yanal Ghosheh1, Holger Winkels1,2
1La Jolla Institute for Immunology, La Jolla, CA, United States.
Insights
Vaccinating mice against Apolipoprotein B (ApoB) peptides expanded regulatory T cells (Tregs) that protect against atherosclerosis. However, some expanded T cells showed pro-inflammatory T helper 1 (TH1) features, revealing complex immune responses to ApoB vaccination.
Area of Science:
- Immunology
- Cardiovascular Research
- Molecular Biology
Background:
- Atherosclerotic cardiovascular diseases are a leading global cause of mortality.
- CD4 T cells targeting Apolipoprotein B (ApoB) are key in atherosclerosis, acting as regulatory T cells (Tregs) or pro-inflammatory T helper 1 (TH1) cells.
- Vaccination strategies targeting ApoB peptides have shown potential for atheroprotection by expanding ApoB-reactive Tregs.
Purpose of the Study:
- To investigate the detailed cellular and molecular characteristics of vaccine-expanded ApoB-reactive CD4 T cells.
- To understand the phenotypic and transcriptomic changes in T cells responding to ApoB peptide vaccination.
- To elucidate the T cell receptor (TCR) interactions with ApoB peptides presented by Major Histocompatibility Complex (MHC) class II molecules.
Main Methods:
- Single-cell RNA sequencing (scRNA-seq) of tetramer-sorted T cells from C57BL/6J mice vaccinated with the ApoB peptide P6.
- Clonal expansion analysis of P6-specific T cells.
- Transcriptomic profiling to identify gene expression signatures associated with T cell function.
- Molecular modeling of TCR-peptide-MHC-II interactions.
Main Results:
- Vaccination with ApoB peptide P6 induced clonal expansion of P6-specific CD4 T cells.
- Transcriptomic analysis revealed distinct clusters, with expanded P6+ T cells predominantly exhibiting a Treg signature and expressing suppressive genes.
- A subset of expanded P6+ T cells displayed a reduced Treg signature and expressed genes characteristic of proatherogenic TH1 cells.
- Structural modeling indicated that specific amino acid residues in the TCR and peptide-MHC-II interaction govern P6 specificity.
Conclusions:
- Vaccine-induced expansion of ApoB-reactive T cells is clonally restricted and results in a heterogeneous population.
- While primarily promoting a regulatory T cell phenotype, ApoB peptide vaccination can also generate pro-inflammatory TH1 cells.
- Understanding these complex T cell responses is crucial for developing effective anti-atherosclerotic vaccination strategies.
- The TCR-peptide-MHC-II interaction interface is a key determinant of the immune response to ApoB epitopes.
Abstract:
Atherosclerotic cardiovascular diseases are the major cause of death worldwide. CD4 T cells responding to Apolipoprotein B (ApoB), the core protein of most lipoproteins, have been identified as critical disease modulators. In healthy individuals, ApoB-reactive (ApoB+) CD4 T cells are mostly regulatory T cells (Tregs), which exert anti-inflammatory effects. Yet, they may obtain pro-inflammatory features and thus become proatherogenic. Evidence from animal studies suggests that vaccination against certain major histocompatibility complex (MHC) II-binding ApoB peptides induces an expansion of ApoB+ Tregs and thus confers atheroprotection. To date, in-depth phenotyping of vaccine-expanded ApoB+ T cells has not yet been performed. To this end, we vaccinated C57BL/6J mice with the ApoB-peptide P6 (ApoB978-993 TGAYSNASSTESASY) and performed single-cell RNA sequencing of tetramer-sorted P6+ T cells. P6+ cells were clonally expanded (one major, two minor clones) and formed a transcriptional cluster distinct from clusters mainly containing non-expanded P6+ and P6- cells. Transcriptomic profiling revealed that most expanded P6+ cells had a strong Treg signature and highly expressed genes mediating suppressive functions. Yet, some expanded P6+ cells only had a residual Treg signature and expressed genes related to T helper 1 (TH1) cells, which are proatherogenic. Modeling the T cell receptor (TCR) and P6:MHC-II interaction showed that only three amino acid residues in the α and β chain contact the P6 peptide in the MHC-II groove and thus determine the specificity of this TCR to P6. Our data begin to reveal the vaccination-induced response to an ApoB epitope.
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