Immune Regulation In Toxoplasmosis And Other Opportunistic Infections

弓形虫病和其他机会性感染的免疫调节

• 批准号: 8156861
• 负责人: Alan Sher
• 金额: $ 108.1万
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8156861
• 关键词: Immune; Opportunistic Infections; Regulation; Toxoplasmosis

The cytokine IFN-gamma is essential for host defense against intracellular pathogens and the development of IFN-gamma producing Th1 lymphocytes plays a critical role in control of these infectious agents. If left unregulated, however, the Th1 immune response can cause serious damage to host tissues and lead to mortality. In the case of Toxoplsma gondii infection, we have previously demonstrated that the induction of mediators that can regulate IFN-gamma effector functions are as important for host survival as the expression of IFN-gamma itself. Thus, mice deficient in IL-10 succumb during the acute phase of infection, despite enhanced parasite control. Subsequently we have demonstrated that this host-protective IL-10 derives in autocrine fashion from conventional IFN-gamma producing T-bet+ Foxp3neg Th1 cells, which simultaneously display both effector and regulatory functions. Our current research in this area focuses on the molecular mechanisms that regulate IL-10 expression in Th1 cells. We have confirmed that expression of IL-10 in Th1 lymphocytes from T. gondii-infected mice is regulated at the level of transcription, and by microarray compared the expression of other genes in IL-10- and IL-10+ Th1 cells as well as the status of chromatin modification in the IL-10 gene locus. Several transcription factors (e.g. TCF-1) and signaling pathways (e.g. STAT) have so far been identified as associated with the differential expression of IL-10. At present we are testing their relevance by employing either knock-out mouse strains for the corresponding genes or by using bone-marrow chimeras. Our results indicate that, while development of IL-10+ Th1 cells is both IL-21- and Stat-3-independent, it is partially dependent on intact signaling through IL-27R or Stat-1 in CD4+ T lymphocytes. We are also comparing the life span of IL-10+ and IL-10neg Th1 cells in order to determine if IL-10 production is a property of terminally differentiated Th1 cells, and whether IL-10+ Th1 cells can establish long-term memory. IL-10+IFN-gamma+ CD4 T cells can be readily detected in the blood of healthy individuals and thus, as an extension of the murine studies described above, we have started to analyze this Th population in human blood samples. In particular, since IL-10 is known to contribute to suppression of HIV immune response, we will analyze blood specimens from HIV+, T. gondii and co-infected individuals for the presence of IL-10+ Th1 cells. We will also test whether their frequency is altered following anti-retroviral therapy. During the report period we have made the new observation that glucocorticoid receptor (GR) expression in T lymphocytes also plays a critical regulatory role in preventing immunopathology during T. gondii infection. Induction of glucorticoids is responsible for the selective loss of double CD4+ CD8+ thymocytes and contributes to the dramatic thymic atrophy ( 90%) observed on day 8 after i.p. injection of either type I or type II strains of the parasite. However, neither soluble extract nor irradiated parasites trigger involution of thymus, indicating a requirement for active infection. The GR knock-out animals which are deficient in GR expression in CD4+ and CD8+ T cells display acute mortality after T. gondii infection and this is associated with an exacerbated systemic IFN-gamma; response, despite no overt changes in parasite load or the responsiveness of innate immune cells as evaluated by serum IL-12 and IL-27 production. Our preliminary results indicate that enhanced IFN-gamma responsiveness by both CD4 and CD8 contributes to the decreased survival of the infected mice. The glucocorticoid-dependent negative feed-back loop may selectively target CD8 T lymphocytes since depletion of CD4 T cells that abrogates systemic IL-10 production and has no significant effect on the survival of infected WT mice, fails to rescue the acute mortality of infected GR KO animals and results in even higher serum IFN-gamma levels than in control or anti-CD8 mAb treated T. gondii-infected GR knock-out mice.

细胞因子IFN-GAMMA对于宿主防御细胞内病原体至关重要，而产生Th1淋巴细胞的IFN-GAMMA的发展对于控制这些感染剂至关重要。但是，如果不受管制，则Th1免疫反应会对宿主组织造成严重损害并导致死亡率。在弓形虫Gondii感染的情况下，我们先前已经证明，可以调节IFN-Gamma效应函数的介导子的诱导对于宿主存活与IFN-GAMMA本身的表达一样重要。因此，尽管寄生虫的控制增强了，但在感染的急性阶段，IL-10缺乏IL-10的小鼠。随后，我们证明了这种宿主保护性IL-10以自分泌方式源自常规的IFN-gamma产生T-bet+ Foxp3neg Th1细胞，它们同时显示效应子和调节函数。 我们目前在该领域的研究集中于调节Th1细胞中IL-10表达的分子机制。我们已经证实，在转录水平上调节了来自T. gondII的小鼠的Th1淋巴细胞中IL-10的表达，并且通过微阵列比较了IL-10和IL-10+ TH1细胞中其他基因的表达，以及IL-10基因基因的Chromatigion在IL-10+ TH1细胞中的表达。到目前为止，已经确定了几种转录因子（例如TCF-1）和信号通路（例如STAT）与IL-10的差异表达相关。目前，我们正在通过使用对应基因的敲除小鼠菌株或使用骨髓嵌合体来测试它们的相关性。我们的结果表明，虽然IL-10+ Th1细胞的发育既是IL-21-和Stat-3独立依赖性的，但它部分取决于CD4+ T淋巴细胞中通过IL-27R或STAT-1的完整信号传导。我们还比较了IL-10+和IL-10NEG TH1细胞的寿命，以确定IL-10产生是否是末端分化的Th1细胞的特性，以及IL-10+ TH1细胞是否可以建立长期记忆。 IL-10+ IFN-gamma+ CD4 T细胞可以在健康个体的血液中很容易检测到，因此，作为上述鼠研究的扩展，我们已经开始在人类血液样本中分析该人群。 特别是，由于已知IL-10有助于抑制HIV免疫反应，因此我们将分析来自HIV+，T。Gondii和共感染个体的血液标本，以便存在IL-10+ TH1细胞。我们还将测试抗返回病毒疗法后的频率是否改变。 在报告期间，我们提出了新的观察结果，即T淋巴细胞中的糖皮质激素受体（GR）表达在防止T. gondii感染期间预防免疫病理学方面也起着关键的调节作用。糖脂的诱导是导致双CD4+ CD8+胸腺细胞的选择性损失，并有助于在I.P.后第8天观察到的戏剧性胸腺萎缩（90％）。注射寄生虫的I型或II型菌株。但是，尚未触发胸腺的可溶性提取物和辐照寄生虫的伴侣，这表明需要进行主动感染。在T. gondii感染后，CD4+和CD8+ T细胞中GR表达不足的GR敲除动物表现出急性死亡率，这与恶化的全身IFN-GAMMA有关。反应，尽管没有明显的寄生虫负载或通过血清IL-12和IL-27产生评估的先天免疫细胞的反应性。我们的初步结果表明，CD4和CD8的IFN-GAMMA反应增强有助于感染小鼠的存活率降低。糖皮质激素依赖性负馈回循环可以选择性地靶向CD8 T淋巴细胞，因为CD4 T细胞的耗竭消除了全身IL-10的产生，并且对感染的WT小鼠的存活没有显着影响，因此无法挽救感染的GR KO动物和更高的静电剂级别的急性对CORM AT的急性死亡率，而MAB静止的IFN-ifn-ifn con and and con and and con and conty conty conty则在ifn-ifn-ifn-ifn-con中均无法挽救。 Gondii感染的GR敲除小鼠。