BACH2基因在HIV-1感染者中央记忆性CD4+T细胞稳态维持中的作用及分子机制研究

Homeostasis of CD4+ Central Memory T cells (CD4+ TCM) is considered a key factor sustaining the asymptomatic stage of HIV infection, while progression to acquired immunodeficiency syndrome is attributed to homeostatic failure of CD4+TCM. Activated CD4+TCM from HIV-1 infected patients showed decreased proliferative, differentiation and survival capacities. However, it is still unclear how this homeostatic equilibrium is lost during chronic infection. Several studies have shown that BACH2 plays a role in regulating T cell development and homeostasis. Accumulating data demonstrate specific roles for Bach2 in favoring regulatory T cell generation, restraining effector T cell differentiation, and potentiating memory T cell development. And Bach2 regulates cell death, which is inconsistent in different cell types. In addition, Bach2 also regulates cytokines secretion of T cells by repressing other key transcriptional regulators. In addition, our previous study showed that BACH2 expression was reduced in PBMCs from HIV-1 infected patients and we also identified BACH2 as a regulator involved in HIV-1 infection induced cell death. However, the role of BACH2 on the homeostasis of CD4+ TCM is unknown. Therefore, in this proposal, we will investigate the effect of BACH2 gene on the differentiation, cell death programs and function of the C4+ TCM and the molecular mechanisms in HIV-1 infected subjects. A better understanding of theses mechanisms and the development approaches for the therapeutic manipulation will be critical for the development of cure strategies for HIV patients.

CD4+中央记性T细胞（CD4+Central Memory T cells, CD4+ TCM）稳态的维持是影响HIV-1感染者无症状生存期的重要因素，与艾滋病疾病进展有关。HIV-1感染可能影响了CD4+ TCM细胞的增殖存活、分化及功能，其相关的机制仍不清楚。近年来研究显示BACH2在T细胞稳态维持中具有重要的作用：参与T细胞的分化，影响记忆性T细胞的形成；对不同细胞存活的影响存在差异；作为转录抑制因子调控T细胞因子的分泌等。本课题前期研究结果显示HIV-1感染者BACH2基因下调，且BACH2可能参与HIV-1感染诱导的T细胞凋亡的调控。然而BACH2基因对CD4+TCM细胞稳态的影响尚未见报道。本研究将创新性的探索HIV-1感染者BACH2对CD4+ TCM细胞的分化、存活及功能的影响及其相关的分子机制，针对上述靶点制定的治疗策略对于实现艾滋病治愈具有重要的指导意义。

进行性CD4+T细胞耗竭是HIV-1病毒致病机理的主要特征，是艾滋病研究领域的关键问题。我们应用RNA-seq方法分析了HIV-1急性期感染者和健康对照PBMC样本基因表达的差异，发现Bach2基因显著下调，且被富集在转录因子活性、序列特异性DNA结合的GO分析通路中，表明Bach2作为转录抑制因子可能与HIV-1病毒早期感染的致病机制有关。本研究发现Bach2能够显著抑制HIV-1病毒LTR的转录活性，且上清中P24的含量显著降低，推测Bach2能够影响HIV病毒复制，可能与病毒储存库的建立有关。同时发现Bach2基因不影响依托泊苷（etoposide）、PKC抑制剂(staurosorine)及Fas-FasL诱导的CD4+T细胞凋亡，表明Bach2基因对CD4+T细胞存活无影响。此外，我们应用miRNA-seq方法分析了HIV-1 急性期感染者和健康对照者miRNA表达的差异，发现HIV-1感染者中miR-31-5p显著下调，与缓慢疾病进展有关；进一步研究发现miR-31-5p和miR-144-3p可能调控Bach2基因的表达；CD4+T和CD8+T细胞活化6小时后，miR-31-5p和miR-144-3p表达上调，Bach2基因表达下调，CD4+T细胞中IL-2及CD8+T中IFN-γ的mRNA水平上调，推测在CD4+T和CD8+T 细胞中，miR-31-5p和miR-144-3p可能通过调控Bach2基因影响IL-2和IFN-γ的分泌。最后，我们发现在JurkatT细胞中Bach2基因过表达显著抑制了IFN-γ的分泌，表明Bach2能够通过抑制细胞因子分泌影响细胞功能。综上，明确Bach2对HIV-1病毒LTR转录活性及对CD4+T 和CD8+T功能的影响对于探索病毒储存库的清除实现艾滋病的功能性治愈有重要的意义。