Elucidating the mechanisms and consequences of MDSC-regulated immunity in TB

项目总结： 髓系抑制细胞(MDSCs)是一种未成熟的髓系细胞，具有很强的抑制作用。 巨噬细胞和T细胞。骨髓间充质干细胞与结核之间的联系，结核是一种由分枝杆菌引起的疾病 结核病(Mtb)是由小鼠的研究支持的，在小鼠的研究中，MDSC重新聚集到肺部与疾病相关 在人类中，外周血MDSC的丰度与结核病的进展呈正相关。 在小鼠身上的研究还表明，骨髓间充质干细胞被招募到卡介苗接种部位，在那里它们吞噬细胞。 细菌和抑制局部T细胞激活，表明MDSCs可能会降低抗结核的效果 疫苗接种和促进结核病作为全球公共卫生问题的地位。多药耐药干细胞之间的关系 结核病已经引起了人们对以宿主为导向的疗法来改善结核病治疗的兴趣。近期 在豚鼠和小鼠身上使用FDA批准的小分子MDSC抑制剂tasquiimod(TSQ)的研究发现 靶向骨髓间充质干细胞可以减少肉芽肿的形成，降低细菌载量，提高治疗效果。 抗结核药物的疗效。这些结果令人鼓舞，但关键问题需要在 MDSCs可以安全地作为人类结核病的靶点。知识差距包括不完全理解如何 如果MDSCs抑制或促进病理性炎症，则MDSCs与病变组织中的巨噬细胞相互作用 结核分枝杆菌，MDSC活性与肉芽肿细菌负荷的关系，以及MDSC是否允许或限制结核分枝杆菌复制。 这些缺口在人类结核病中尤其严重，因为无法接触肉芽肿而进展受阻。 目的：研究MDSCs在小鼠和人结核病病理生理学中的原位和基本差异。我们的 一项提案通过使用来自人脐带血和非人类的MDSCs的创新研究来解决这些差距 准确反映人类结核病病理生理学的灵长类动物(NHP)模型。我们假设MDSCs 抑制巨噬细胞介导的抗结核分枝杆菌活性，是结核分枝杆菌的允许宿主并抑制其功能 将提高免疫力，限制细菌持久性，并改善结核病的结局。在目标1中，我们建议 研究MDSCs、巨噬细胞和结核分枝杆菌之间影响免疫的关系的机制研究。 我们将确定无细胞DNA释放是否是一种新的抑制巨噬细胞功能的MDSC效应。我们 还要确定MDSCs是否支持结核分枝杆菌作为允许宿主细胞，并确定吞噬小体的分子特征 有助于提高Mtb主办能力的级别。在目标2中，我们用表达mCherry的结核分枝杆菌和 使用TSQ介导的MDSC抑制作为干预措施来评估MDSC如何调节肺部炎症， 豁免权，如果他们主办结核分枝杆菌。在这里，我们使用PET/CT和荧光成像，定量微生物学，和 用流式细胞术确定肉芽肿中MDSC调节的免疫相关因素。我们还定义了MDSC 并使用CosMx空间分子成像来鉴定MDSCs是如何调控的 生理和空间背景下的肉芽肿级别免疫。这些研究解决了以下重大问题 MDSCs调节结核病中的免疫，并为未来针对MDSCs的结核病试验提供有价值的数据。

PROJECT SUMMARY: Myeloid derived suppressor cells (MDSCs) are immature myeloid cells with potent inhibitory properties for macrophages and T cells. The link between MDSCs and tuberculosis (TB), a disease caused by Mycobacterium tuberculosis (Mtb), is supported by work in mice where MDSC recruitment to the lungs correlates with disease severity, and in humans, where peripheral blood MDSC abundance positively correlates with TB progression. Work in mice also demonstrates that MDSCs are recruited to sites of BCG vaccination where they phagocytose bacteria and suppress local T cell activation, suggesting that MDSCs may reduce the effectiveness of anti-TB vaccination and contribute to TB’s status as a global public health concern. The relationship between MDSCs and TB has generated interest in targeting them with host-directed therapies to improve TB treatment. Recent work using tasquinimod (TSQ), an FDA-approved small molecule MDSC inhibitor, in guinea pigs and mice finds that targeting MDSCs lowers reduces granuloma formation, lowers bacteria loads, and improves the treatment efficacy of anti-TB drugs. These results are encouraging but critical questions need to be answered before MDSCs can be safely targeted in human TB. Knowledge gaps include an incomplete understanding of how MDSCs interact with macrophages in diseased tissue, if MDSCs restrain or promote pathologic inflammation in TB, how MDSC activity relates to bacterial burden in granulomas, and if MDSCs permit or restrict Mtb replication. These gaps are particularly acute in human TB where progress is inhibited by the inability to access granulomas to study MDSCs in situ and fundamental differences between mouse and human TB pathophysiology. Our proposal addresses these gaps with innovative studies using MDSCs from human cord blood and a nonhuman primates (NHPs) model that accurately reflects human TB pathophysiology. We hypothesize that MDSCs suppress macrophage-mediated anti-Mtb activity and are permissive hosts for Mtb and inhibiting their functions will improve immunity, restrict bacterial persistence, and improve outcomes in TB. In Aim 1, we propose mechanistic studies investigating relationships between MDSCs, macrophages, and Mtb that influence immunity. We will determine if cell-free DNA release is a novel MDSC effector that suppresses macrophage function. We also determine if MDSCs support Mtb as a permissive host cell and define molecular features at the phagosomal level that contribute to competency for hosting Mtb. In Aim 2, we infect NHPs with mCherry-expressing Mtb and use TSQ-mediated MDSC inhibition as an intervention to assess how MDSCs regulate lung inflammation, immunity, and if they host Mtb. Here, we use PET/CT and fluorescence imaging, quantitative microbiology, and flow cytometry to identify MDSC-regulated correlates of immunity in granulomas. We also define MDSC transcriptional profiles in scRNAseq and use CosMx spatial molecular imaging to identify how MDSCs regulate granuloma-level immunity in physiologic and spatial context. These studies address significant questions on MDSCs-regulated immunity in TB and provide valuable data for future trials targeting MDSCs in TB.