BCG vaccination impacts the epigenetic landscape of progenitor cells in human bone marrow (scRNA-Seq). BCG vaccination impacts the epigenetic landscape of progenitor cells in human bone marrow (scRNA-Seq)

While the Bacille-Calmette-Guérin (BCG) vaccine is used to prevent tuberculosis, it also offers protection against a diverse range of non-mycobacterial infections. However, the underlying protective mechanisms in humans are not yet fully understood. Here, we surveyed at single-cell resolution the gene expression and chromatin landscape of human bone marrow, aspirated before and 90 days after BCG vaccination or placebo administration. We show that BCG vaccination significantly alters both the gene expression and epigenetic profiles of human hematopoietic stem and progenitor cells (HSPCs). Changes in gene expression occur primarily on the most uncommitted stem cells and are reflective of a persistent myeloid bias. In contrast, BCG-induced changes in chromatin accessibility are most prevalent within differentiated progenitor cells at sites influenced by Kruppel-like factor (KLF)/SP and EGR transcription factors (TFs). These TFs are also activated in the most uncommitted stem cells, indicating that activated TFs, which drive persistent changes in HSC gene expression, likely also drive chromatin dynamics appearing within downstream progenitor cells. This perspective contests the prevailing notion that epigenetic modifications linked to innate immune memory transfer directly from stem cells to their differentiated derivatives. Finally, we show that alterations in gene expression and chromatin accessibility in HSPCs due to BCG vaccination were highly correlated (r>0.8) with the IL-1β secretion capacity of paired PBMCs upon secondary immune challenge. Overall, our findings shed light on BCG vaccination's profound and lasting effects on HSPCs and its influence on innate immune responses. Overall design: Multi-plexed RNA expression profiles of HSPCs isolated from the bone marrow of individuals before and 90 days after either BCG vaccination or placebo

尽管卡介苗（Bacille-Calmette-Guérin, BCG）主要用于预防结核病，但其同时可对多种非分枝杆菌感染提供保护。然而，其在人体中的潜在保护机制尚未完全阐明。本研究以单细胞分辨率，对接种BCG疫苗或安慰剂前、后90天采集的人体骨髓样本的基因表达与染色质景观进行了全景分析。研究结果显示，BCG疫苗接种可显著改变人体造血干细胞与祖细胞（hematopoietic stem and progenitor cells, HSPCs）的基因表达与表观遗传谱。基因表达变化主要发生在最未定向的干细胞中，且呈现出持续的髓系偏倚特征。相比之下，BCG诱导的染色质可及性变化则在分化祖细胞中最为显著，其发生位点受Kruppel样因子（Kruppel-like factor, KLF）/SP及EGR转录因子（transcription factors, TFs）的调控。这些转录因子在最未定向的干细胞中也被激活，这表明驱动造血干细胞基因表达持续变化的活化转录因子，同样可能推动下游祖细胞内出现的染色质动态变化。该观点与当前主流认知相悖——后者认为与固有免疫记忆相关的表观遗传修饰可直接从干细胞传递至其分化子代细胞。最后，本研究发现，BCG疫苗接种导致的HSPCs基因表达与染色质可及性变化，与配对外周血单个核细胞（peripheral blood mononuclear cells, PBMCs）在二次免疫攻击后的IL-1β分泌能力高度相关（r>0.8）。综上，本研究结果阐明了BCG疫苗对HSPCs的深远且持久的影响，及其对固有免疫应答的调控作用。总体实验设计：对接种BCG疫苗或安慰剂前、后90天的个体骨髓分离得到的HSPCs进行多重RNA表达谱分析。