Data_Sheet_1_Single-cell transcriptomes and T cell receptors of vaccine-expanded apolipoprotein B-specific T cells.PDF

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.

动脉粥样硬化性心血管疾病（Atherosclerotic cardiovascular diseases）是全球范围内的首要致死病因。针对多数脂蛋白核心蛋白载脂蛋白B（Apolipoprotein B, ApoB）产生应答的CD4阳性T细胞（CD4 T cells），已被证实为关键的疾病调控因子。在健康个体中，识别ApoB的ApoB反应性CD4 T细胞（ApoB+ CD4 T cells）大多为调节性T细胞（regulatory T cells, Tregs），可发挥抗炎作用；但这类细胞也可获得促炎表型，进而转变为促动脉粥样硬化表型。动物研究证据显示，针对特定主要组织相容性复合体（major histocompatibility complex, MHC）II类分子结合的ApoB表位肽进行疫苗接种，可促进ApoB+ Tregs的扩增，从而发挥抗动脉粥样硬化的保护作用。截至目前，尚未对疫苗扩增的ApoB+ T细胞开展深入的表型分型研究。为此，我们使用ApoB表位肽P6（ApoB978–993 TGAYSNASSTESASY）对C57BL/6J小鼠进行疫苗接种，并对四聚体分选得到的P6+ T细胞开展单细胞RNA测序（single-cell RNA sequencing）。结果显示，P6+细胞发生了克隆扩增（包含1个主要克隆与2个次要克隆），并形成了一个独特的转录簇，该转录簇与主要包含未扩增P6+及P6-细胞的转录簇存在显著差异。转录组分析表明，多数扩增的P6+细胞具有典型的Treg特征，并高表达介导抑制功能的基因；但部分扩增的P6+细胞仅残留微弱的Treg特征，且高表达与辅助性T细胞1（T helper 1, TH1）相关的基因，而TH1细胞属于促动脉粥样硬化表型的细胞群。对T细胞受体（T cell receptor, TCR）与P6:MHC-II复合物的相互作用进行建模后发现，TCR的α链与β链上仅存在3个氨基酸残基，可在MHC-II分子的肽结合槽中与P6肽结合，进而决定该TCR对P6的特异性。本研究的数据首次揭示了疫苗诱导的针对ApoB表位的免疫应答特征。