T-bet-regulated myeloid innate defense against Toxoplasma gondii

摘要 弓形虫是弓形虫病的病原体，据估计，它会感染三分之一的人类。 全球人口。弓形虫感染可导致严重并发症，包括先天性弓形虫病 免疫受损个体的胎儿和死亡。不幸的是，目前治疗弓形虫的方案 治疗显示出很高的毒性，并且只能治疗寄生虫感染的急性期。 因此，迫切需要开发针对弓形虫的特效新药。寄主 对弓形虫的免疫是由依赖于MyD88的IL-12反应定义的，它产生一种CD4Th1- 派生的干扰素-γ反应是宿主生存所必需的。转录因子T-bet被认为是 弓形虫感染过程中先天淋巴细胞和Th1细胞的发育和功能。T-Bit是 传统上被认为是淋巴细胞衍生干扰素-γ(γ)产生的主要调节因子。然而， T细胞非依赖性ILC和Th1来源的干扰素-γ对宿主免疫是不够的，这表明单独的干扰素-γ T-bet必须诱导不依赖干扰素-γ的抗寄生虫反应。 例如，尽管干扰素-γ产生强劲，T-bet缺陷小鼠死于感染的速度要快得多 与缺乏淋巴细胞的动物相比，这表明T-bet表达的髓系细胞是宿主生存所必需的。 我们的目标是确定T-bet在调节抗弓形虫髓系细胞依赖性免疫中的作用。我们的 初步发现了一种表达CD11c MHCII-髓系细胞群的独特T-bet 对消灭弓形虫至关重要。根据这些结果，我们推测T-bet在髓系细胞中的表达 在弓形虫感染过程中调节病原体清除和宿主存活。为了检验我们的假设，我们将(I) 确定T-bet调节髓系细胞介导的弓形虫防御的潜在机制(S) (目标1)和(2)定义T-bet表达的髓系细胞在介导宿主抵抗中的分子功能 抗弓形虫(AIM 2)。我们将利用无偏见的T-bet报告小鼠和细胞类型特异性T-bet缺陷小鼠 本实验室建立的小鼠，结合各种分子生物学技术，光谱细胞仪， 免疫荧光和单细胞RNA测序。总之，这些实验将是第一次 确定T-bet在介导髓系细胞依赖的宿主对弓形虫的防御中的作用，从而提供 治疗干预的新的特定靶点。

Abstract Toxoplasma gondii is the causative agent of toxoplasmosis, and it is estimated to infect a third of the human population globally. T. gondii infection can result in serious complications including congenital toxoplasmosis of the fetus and death among immunocompromised individuals. Unfortunately, current regimens for T. gondii treatment show high rates of toxicity, and are only able to treat the acute stage of the parasitic infection. Therefore, there is an urgent need develop new medicines with specific efficacy against T. gondii. Host immunity against T. gondii is defined by a MyD88-dependent IL-12 response, which generates a CD4+ Th1- derived IFN-γ response necessary for host survival. The transcription factor T-bet is considered essential for the development and function of innate lymphoid cells (ILCs) and TH1s during T. gondii infection. T-bet is traditionally considered the master regulator of lymphocyte-derived interferon-gamma (IFN-γ) production. Yet, T-bet-independent ILC- and TH1-derived IFN-γ is insufficient for host immunity, demonstrating that IFN-γ alone is insufficient for host defense and that T-bet must be inducing an IFN-γ-independent anti-parasitic response. For instance, despite robust IFN-γ production, T-bet-deficient mice succumb to infection significantly faster than animals lacking lymphocytes, suggesting T-bet-expressing myeloid cells are required for host survival. Our objective is to define T-bet’s role in regulating myeloid cell-dependent immunity against T. gondii. Our preliminary findings have identified a unique T-bet expressing CD11c+MHCII- myeloid cell population that are critical for eliminating T. gondii. Based on these results, we hypothesize that T-bet expression in myeloid cells regulates pathogen clearance and host survival during T. gondii infection. To test our hypothesis, we will (i) determine the underlying mechanism(s) of T-bet in regulating myeloid cell-mediated defense against T. gondii (AIM 1) and (ii) define the molecular functions of T-bet-expressing myeloid cells in mediating host resistance against T. gondii (AIM 2). We will utilize unbiased T-bet reporter mice and cell-type-specific T-bet-deficient mice established in our lab, in combination with various molecular biology techniques, spectral cytometry, immunofluorescence, and single-cell RNA-sequencing. Together, these experiments will for the first time establish T-bet’s role in mediating myeloid cell-dependent host defense against T. gondii, thereby providing novel specific targets for therapeutic intervention.