CD4+CCR6+ T cells dominate the BCG-induced transcriptional signature. CD4+CCR6+ T cells dominate the BCG-induced transcriptional signature

The century-old Mycobacterium bovis Bacillus Calmette-Guerin (BCG) remains the only licensed vaccine against tuberculosis (TB). Despite this, there is still a lot to learn about the immune response induced by BCG, both in terms of phenotype and specificity. Here, we investigated immune responses in adult individuals pre and 8 months post BCG vaccination. We specifically determined changes in gene expression, cell subset composition, DNA methylome, and the TCR repertoire induced in PBMCs and CD4 memory T cells associated with antigen stimulation by either BCG or a Mycobacterium tuberculosis (Mtb)-derived peptide pool. Following BCG vaccination, we observed increased frequencies of CCR6+ CD4 T cells, which includes both Th1* and Th17 subsets, and mucosal associated invariant T cells (MAITs). A large number of immune response genes and pathways were upregulated post BCG vaccination with similar patterns observed in both PBMCs and memory CD4 T cells, thus suggesting a substantial role for CD4 T cells in the cellular response to BCG. These upregulated genes and associated pathways were also reflected in the DNA methylome. We described both qualitative and quantitative changes in the BCG-specific TCR repertoire post vaccination, and importantly found evidence for similar TCR repertoires across different subjects. The immune signatures defined herein can be used to track and further characterize immune responses induced by BCG, and can serve as reference for benchmarking novel vaccination strategies. Overall design: 8 sample DNAs were isolated from the PBMC cells using AllPrep DNA/RNA Mini Kit (Qiagen, Germany). DNA concentration was measured by Qubit fluorometer. DNA samples were bisulphite converted, amplified, fragmented and hybridized to an Illumina Infinium Human Methylation EPIC Bead Chip and scanned.

百年历史的牛分枝杆菌卡介苗（Mycobacterium bovis Bacillus Calmette-Guerin，BCG）仍是目前唯一获批的结核病（Tuberculosis，TB）疫苗。尽管已应用百年，学界对卡介苗诱导的免疫应答在表型与特异性层面仍存在诸多认知空白。
本研究针对成年个体在卡介苗接种前及接种后8个月的免疫应答展开系统探究，重点分析外周血单个核细胞（Peripheral Blood Mononuclear Cells，PBMCs）与CD4记忆性T细胞中，经卡介苗或结核分枝杆菌（Mycobacterium tuberculosis，Mtb）来源肽库抗原刺激后，诱导产生的基因表达、细胞亚群组成、DNA甲基化组以及T细胞受体（TCR）库的变化。
研究结果显示，卡介苗接种后，CCR6+ CD4 T细胞（涵盖Th1*与Th17亚群）以及黏膜相关恒定T细胞（Mucosal Associated Invariant T cells，MAITs）的细胞频率显著升高。接种后，大量免疫应答相关基因与通路出现上调，在外周血单个核细胞与记忆性CD4 T细胞中均观察到相似的表达模式，提示CD4 T细胞在卡介苗诱导的细胞免疫应答中发挥核心作用。上述上调基因及其关联通路同样在DNA甲基化组中得到印证。
本研究还揭示了接种后卡介苗特异性TCR库的定性与定量变化，并关键发现不同受试者间存在高度相似的TCR库特征。本研究定义的免疫特征可用于追踪并进一步解析卡介苗诱导的免疫应答，同时可作为新型疫苗策略基准测试的参考依据。
整体实验设计：采用德国Qiagen公司的AllPrep DNA/RNA Mini Kit从外周血单个核细胞中提取8份样本DNA。通过Qubit荧光计测定DNA浓度。将DNA样本进行亚硫酸氢盐转化、扩增、片段化后，与Illumina Infinium Human Methylation EPIC Bead Chip进行杂交并扫描。