DAP12 and the host response to cryptococcosis

项目摘要 新生隐球菌是一种机会性真菌病原体，可吸入肺部并可 传播到大脑，在免疫功能低下的患者中导致高度致命的脑膜脑炎， 尤其是那些患有艾滋病毒/艾滋病、实体器官移植和癌症的人。即使是当代的组合 在抗真菌治疗方面，隐球菌病的死亡率接近25%，高危人群为 随着针对自身免疫和癌症的新免疫抑制疗法的开发而扩大。我们的能力 开发治疗隐球菌病的新疗法仍然有限，因为我们还不完全了解 真菌逃避宿主免疫。我们最近发现，新生隐孢子菌能够抑制 炎性单核细胞，产生巨噬细胞和树突状细胞的先天免疫细胞，通常 帮助宿主识别和清除真菌。新生芽孢杆菌引导炎性单核细胞 分化为交替激活的(M2)巨噬细胞，允许真菌增殖和 传播，导致感染死亡率增加。我们已经确定了一个信号转接器DNAX- 12 kDa激活蛋白(DAP12)可能在抑制炎性单核细胞中起关键作用 对新生葡萄球菌的反应。DAP12基因的缺失改善了小鼠模型中真菌的清除和存活率 DAP12缺乏的单核细胞来源的巨噬细胞对隐球菌病有更好的摄取和杀伤作用 真菌。此外，Dap12-/-小鼠的肺中CD8+T细胞数量增加，细胞毒适应 免疫细胞可以被巨噬细胞招募和激活，对清除C. 新形态主义者。因此，DAP12可能是逆转新生葡萄球菌抑制作用的重要靶点。 炎性单核细胞杀菌活性及其活化CD8+T细胞的能力。我们的预赛 数据表明，这种抑制性的DAP12活性可能受到新生葡萄球菌与细胞结合的调节 单核细胞表面受体触发的髓系细胞表面受体2(TREM2)表达 巨噬细胞。这项提议的目的是进一步定义这一新的DAP12信号通路。我们 假设新生芽孢杆菌诱导形成一个TREM2-DAP12信号复合体 抑制炎性单核细胞和CD8+T细胞的抗隐球菌防御的效应分子， 从而颠覆宿主对感染的反应。具体目标是1)通过以下方式确定机制 哪些DAP12信号是由新生芽孢杆菌启动的，2)定义了介导DAP12信号转导的信号级联 DAP12在感染过程中的抑制作用，以及3)确定炎性单核细胞固有的作用 DAP12在调节CD8+T细胞对新生葡萄球菌反应中的作用定义这些机制将深化 我们对宿主对机会性真菌免疫的了解，并为免疫调节提供了新的机会 对脆弱宿主中新生葡萄球菌的干预。

Project Summary Cryptococcus neoformans is an opportunistic fungal pathogen that is inhaled into the lungs and can disseminate to the brain, causing a highly fatal meningoencephalitis in immunocompromised patients, particularly those with HIV/AIDS, solid organ transplantation, and cancer. Even with contemporary combination antifungal therapy, the mortality rate for cryptococcosis approximates 25%, and the at-risk population is expanding with the development of new immunosuppressive regimens for autoimmunity and cancer. Our ability to develop new treatments for cryptococcosis remains limited because we do not yet fully understand how the fungus evades host immunity. We recently discovered that C. neoformans is able to suppress the response of inflammatory monocytes, innate immune cells that give rise to macrophages and dendritic cells and typically aid in fungal recognition and clearance by the host. C. neoformans directs inflammatory monocytes to differentiate into alternatively activated (M2) macrophages that are permissive for fungal proliferation and dissemination, leading to increased mortality from the infection. We have identified a signaling adapter DNAX- activating protein of 12 kDa (DAP12) that may play a crucial role in suppressing the inflammatory monocyte response to C. neoformans. The deletion of DAP12 improves fungal clearance and survival in a murine model of cryptococcosis, and DAP12-deficient monocyte-derived macrophages have better uptake and killing of the fungus. Additionally, the lungs of Dap12-/- mice have increased numbers of CD8+ T cells, cytotoxic adaptive immune cells that can be recruited and activated by macrophages and are important for the clearance of C. neoformans. Thus, DAP12 may be an important target for reversing the suppressive effects of C. neoformans on the fungicidal activity of inflammatory monocytes and their ability to prime CD8+ T cells. Our preliminary data indicate that this repressive DAP12 activity may be regulated by the binding of C. neoformans to the cell surface receptor triggering receptor expressed on myeloid cells 2 (TREM2) on monocyte-derived macrophages. The goal of this proposal is to further define this novel DAP12 signaling pathway. We hypothesize that C. neoformans induces formation of a TREM2-DAP12 signaling complex that coordinates effector molecules to inhibit the anti-cryptococcal defenses of inflammatory monocytes and CD8+ T cells, thereby subverting the host response to infection. The specific aims are to 1) determine the mechanism by which DAP12 signaling is initiated by C. neoformans, 2) define the signaling cascade that mediates the suppressive effects of DAP12 during infection, and 3) ascertain the role of inflammatory monocyte-intrinsic DAP12 in the regulation of CD8+ T cell responses to C. neoformans. Defining these mechanisms will deepen our understanding of host immunity to opportunistic fungi and inform new opportunities for immunomodulatory interventions against C. neoformans in vulnerable hosts.