Transcriptional signature of MAITs in LTBI. Transcriptional signature of MAITs in LTBI

We applied a cell population transcriptomics strategy to sorted human memory CD8 T cells to define novel immune signatures of latent tuberculosis infection (LTBI) and understand the phenotype of tuberculosis (TB)-specific T cells. We found a 41-gene signature that could discriminate between memory CD8 T cells from healthy LTBI subjects and noninfected controls. The gene signature was dominated by genes known to be associated with mucosal associated invariant T cells (MAITs) and reflected the lower frequency of MAITs observed in individuals with LTBI. There was no evidence for a conventional CD8 T cell specific signature between the two cohorts. We therefore investigated the MAITs in more detail in these cohorts. Phenotyping based on Vα7.2 and CD161 expression and MR1 tetramers revealed 2 distinct populations of CD8+Vα7.2+CD161+ T cells: MR1 tetramer+ and MR1 tetramer−, both of which had a distinct gene expression profile compared to CD8 memory T cells. Transcriptomic analysis of LTBI vs. noninfected individuals did not reveal significant differences for MR1 tetramer+ cells. However, gene expression of MR1 tetramer− cells showed a very different profile with large inter-individual diversity and a TB-specific signature. This was further strengthened by a more diverse TCR-α and -β repertoire of MR1 tetramer− cells as compared to MR1 tetramer+. Thus, cell population transcriptomics revealed a dominant MAIT signature in CD8 memory T cells that upon detailed investigation provided novel insights into the phenotype of different MAIT populations implicated in tuberculosis. Overall design: RNAseq of sorted memory CD8 T cells from cryopreserved PBMC of 31 individuals with latent TB infection and 29 uninfected controls.

本研究采用细胞群体转录组学策略，对分选获取的人记忆性CD8 T细胞开展分析，旨在明确潜伏结核感染（latent tuberculosis infection, LTBI）的新型免疫特征，并解析结核（tuberculosis, TB）特异性T细胞的表型。本研究筛选得到一组包含41个基因的特征集，可有效区分健康潜伏结核感染受试者与未感染对照者的记忆性CD8 T细胞。该基因特征集以与黏膜相关恒定T细胞（mucosal associated invariant T cells, MAITs）相关的基因为主导，且反映出潜伏结核感染个体中MAITs频率降低的特征。两组队列间未检测到常规CD8 T细胞特异性的基因特征集，据此本研究针对该两组队列中的MAITs展开了更为深入的分析。基于Vα7.2与CD161的表达水平及MR1四聚体进行表型分型，结果显示CD8+Vα7.2+CD161+ T细胞存在两个截然不同的亚群：MR1四聚体阳性（MR1 tetramer+）与MR1四聚体阴性（MR1 tetramer−）；与记忆性CD8 T细胞相比，这两个亚群均具备独特的基因表达谱。对潜伏结核感染个体与未感染个体的转录组分析显示，MR1四聚体阳性细胞未出现显著的表达差异。但MR1四聚体阴性细胞的基因表达谱则呈现出显著差异：个体间异质性较高，且携带结核特异性的基因特征集。与MR1四聚体阳性细胞相比，MR1四聚体阴性细胞拥有更为多样的T细胞受体α（TCR-α）与β（TCR-β）库，这一结果进一步佐证了前述发现。综上，细胞群体转录组学分析揭示了记忆性CD8 T细胞中占主导的MAIT特征集；通过深入研究，本研究为解析与结核相关的不同MAIT亚群表型提供了全新视角。实验设计概况：对31名潜伏结核感染受试者与29名未感染对照者的冻存外周血单个核细胞（peripheral blood mononuclear cell, PBMC）中分选获得的记忆性CD8 T细胞进行RNAseq检测。