Apoptosis and efferocytosis: regulators of immunity to tuberculosis

描述（由申请人提供）：持续的HIV/AIDS流行和耐多药结核分枝杆菌（Mtb）的传播使结核病在世界各地的人群中持续流行。虽然卡介苗被普遍用作疫苗，但它对预防肺结核并不有效。为了与这一持续的世界性祸害作斗争，开发结核病疫苗是一个优先事项。细胞凋亡是一种固有的Mφ防御机制，它限制了细菌的复制和Mtb的扩散。细胞凋亡还与先天免疫和克隆免疫有关。DC将包装在凋亡囊泡中的细菌抗原呈递给T细胞，导致更好的体内T细胞引发和保护。细胞凋亡是如何调节的， 限制结核杆菌复制，以及是否可以操纵它来加强疫苗接种是这项建议的重点。创新：类花生酸在对分枝杆菌的免疫中的作用在鱼类、小鼠和人类中是保守的，突出了它们的根本重要性。我们发表的关于体外感染的人Mφ和体内感染的小鼠的工作建立了Mtb感染的Mφ的凋亡作为抗结核的至关重要的宿主防御机制。Mtb感染的Mφ中死亡途径的复杂性直到最近才被认识到。毒力Mtb诱导脂氧素A4（LXA 4），抑制前列腺素E2（PGE 2）合成，阻断细胞凋亡，并促进坏死性Mφ死亡。相反，PGE 2防止坏死并增加细胞凋亡。为什么细胞凋亡作为宿主防御机制尚不清楚。在此我们提出了一个新的假说，即不是凋亡本身导致了控制，而是Mtb感染的凋亡Mφ的吞噬作用是关键事件。我们预测：（1）Mφ的吞噬作用将包含感染;（2）DC的吞噬作用将导致幼稚T细胞的启动。除了类花生酸途径，IL-1 β和I型IFN（IFN β）之间的平衡正在成为影响先天性和克隆免疫的第二个轴。我们提出了一个新的模型，其中LXA 4和IFN γ，都由结核分枝杆菌诱导，相互作用，以抑制先天免疫，而PGE 2，IL-1 β和TNF促进抗菌免疫。目的：在目标1中，我们将确定类花生酸如何调节感染的巨噬细胞的活化并诱导细胞内细菌复制的控制。特别是，我们将确定类花生酸如何影响IL-1 β和I型IFN（IFN β）之间的平衡，这是新兴的第二个轴，影响先天性和克隆免疫。在第二个目标中，我们将检验这样的假设，即杀死Mtb的不是凋亡本身，而是被感染的凋亡Mφ的吞噬作用限制了细胞内Mtb的生长。凋亡细胞的吞噬作用，称为巨噬细胞，是一个主要的组成性Mφ功能，但很少有人知道它在感染过程中的作用。最后，在第三个目标中，我们将确定类花生酸凋亡与克隆免疫之间的关系。我们推测类花生酸的生物合成和细胞信号转导途径可以被调控以增强感染的Mφ的凋亡。通过促进细胞凋亡，我们希望增加减毒细菌疫苗的安全性和有效性。我们相信，对促凋亡疫苗如何诱导更好的免疫力的机制理解将导致开发针对结核病和其他使用分枝杆菌载体的疾病的更好的免疫策略。总结：更好地了解细胞凋亡和胞浆细胞增多症如何影响对结核分枝杆菌的先天免疫，最终控制细菌复制和刺激T细胞免疫，将提高我们对结核病发病机制的理解，并将导致研究新的治疗方法。

DESCRIPTION (provided by applicant): The continuing HIV/AIDS epidemic and the spread of multi-drug resistant Mycobacterium tuberculosis (Mtb) has perpetuated an epidemic of tuberculosis in human populations around the world. While BCG is used universally as a vaccine, it is not effective in preventing pulmonary tuberculosis. To combat this ongoing worldwide scourge, vaccine development for tuberculosis is a priority. Apoptosis is an innate Mφ defense mechanism that limits bacterial replication and restricts dispersal of Mtb. Apoptosis also links innate and clonal immunity. DC present bacterial antigens packaged in apoptotic vesicles to T cells, leading to better T cell priming and protection in vivo. How apoptosis is regulated and restricts Mtb replication and whether it can be manipulated to enhance vaccination is the focus of this proposal. Innovation: The role of eicosanoids in immunity to mycobacteria is conserved in fish, mice and humans, highlighting their fundamental importance. Our published work on in vitro infected human Mφ and on in vivo infected mice establish apoptosis of Mtb infected Mφ as a critically important host defense mechanism against tuberculosis. The complexity of death pathways in Mtb infected Mφ has only recently been appreciated. Virulent Mtb induces lipoxin A4 (LXA4), inhibits prostaglandin E2 (PGE2) synthesis, blocks apoptosis, and promotes necrotic Mφ death. In contrast, PGE2 protects against necrosis and increases apoptosis. Why apoptosis acts as a host defense mechanism is not understood. Here we put forward a new hypothesis that it is not apoptosis per se that leads to control, but instead phagocytosis of Mtb infected apoptotic Mφ that is the crucial event. We predict: (1) phagocytosis by Mφ will contain the infection; and (2) phagocytosis by DC will lead to priming of naïve T cells. In addition to the eicosanoid pathways, the balance between IL-1ß and type I IFN (IFNß) is emerging as a second axis that affects innate and clonal immunity. We propose a new model in which LXA4 and IFNß, both induced by Mtb, interact to inhibit innate immunity, while PGE2, IL-1ß and TNF promote antibacterial immunity. Aims: In Aim 1, we will determine how eicosanoids regulate activation of infected macrophages and induce control of intracellular bacterial replication. In particular, we will determine how eicosanoids affect the balance between IL-1ß and type I IFN (IFNß), which is emerging as a second axis that affects innate and clonal immunity. In the second aim, we will test the hypothesis that it is not apoptosis per se that kills Mtb - rather it is the phagocytosis f infected apoptotic Mφ that restricts intracellular Mtb growth. Phagocytosis of apoptotic cells, termed efferocytosis, is a major constitutive Mφ function; however, little is known about its role during infection. Finally, in the third aim, we will determine the relationship between eicosanoids apoptosis and clonal immunity. We hypothesize that the eicosanoid biosynthetic and cell signaling pathways can be pharmacologically manipulated to enhance apoptosis of infected Mφ. By promoting apoptotic death, we hope to increase the safety and the efficacy of attenuated bacterial vaccines. We believe that a mechanistic understanding of how pro-apoptotic vaccines induce better immunity will lead to the development of better immunization strategies against tuberculosis and other diseases that are using mycobacterial vectors. Summary: A better understanding of how apoptosis and efferocytosis affect innate immunity to Mtb culminating in control of the bacterial replication and stimulation of T cell immunity will improve our understanding of TB pathogenesis and will lead to research into novel therapies.