Role of Legionella pneumophila Lvh TIVSS in virulence

抽象的。军团菌属有60多种，其中20种与军团菌有关 疾病，非典型肺炎的一种形式。90%以上的退伍军人病病例是由L。 嗜肺杆菌血清群1.军团菌倾向于定植于管道系统生物膜和阿米巴包囊，这些都是 耐净水处理。军团菌的能力。在阿米巴和阿米巴中持续繁殖 人类和临床疾病的发生依赖于一套毒力基因和基因的协调调控 对抗先天和后天宿主防御的功能。因此，这一行动的主要目标是 建议阐明嗜肺军团菌进化成战胜宿主的分子机制 先天免疫反应，并允许它建立感染。 嗜肺乳杆菌基因组包含编码两种类型的IV型(TIVSS)分泌物的基因簇 系统；LVH和DOT/ICM。虽然DOT/ICM的遗传组织及其在毒力中的作用已经确立， 关于LVH TIVSS的作用的信息有限。缺乏LVH TIVSS的军团菌菌株有 细胞毒性显著降低。此外，LVH TIVSS在L. 嗜肺菌在30°C下生长，并在吞噬小体酸化的有效延迟。嗜肺性乳杆菌左心室肥大基因座 是DOT/ICM突变体在孵育后恢复进入和细胞内增殖所必需的 在水和阿米巴包囊中。我们已经证明了嗜肺军团菌的LVH TIVSS机械 定位于细胞极点，据报道，这种定位对其他病原体的毒力很重要。 我们还证明了当军团菌分离时，LVH TIVSS对于宿主细胞caspase-3/7的激活是重要的 在30°C下生长，根据我们的初步数据和文献中的数据，我们的中心假设是 LVH有助于军团菌在环境感染下的毒力并调节细胞的后期阶段 细菌的感染和进一步传播。我们将测试我们的中心假设，并通过以下方式实现我们的目标 评价LVH TIVSS在调节宿主细胞免疫、基因表达和基因表达中的作用 程序性细胞死亡。 揭示左心室肥厚的功能将发现细菌病原体中可能被利用的潜在弱点 用于治疗干预、开发合理、最有效的疫苗和疾病控制。因此， 这个项目的主要目标是了解宿主细胞免疫系统如何识别微生物的毒力。 感染过程中的因素，产生保护性反应，以及军团菌抑制LVH的机制 这种保护性反应。这项工作的结果将对人类健康产生重要的积极影响 因为它们将提供有关嗜肺乳杆菌LVH改变的通路或网络的重要信息 TIVSS在宿主中的表达，这可能为开发新的靶向治疗奠定基础。

Abstract. The Legionella genus has more than 60 species from which 20 are associated with Legionnaires’ disease, a form of atypical pneumonia. More than 90% of Legionnaires’ disease cases are caused by L. pneumophila serogroup 1. Legionella tends to colonize plumbing system biofilms and amoebae cysts which are resistant to water purification treatment. The ability of Legionella spp. to persist and multiply in amoeba and humans and cause clinical disease depends on a set of virulence genes and on the coordinate regulation of gene functions that combat the effects of innate and acquired host defenses. Therefore, the main objective of this proposal is to elucidate the molecular mechanisms that Legionella pneumophila has evolved to overcome host innate immune responses and allow it to establish an infection. The L. pneumophila genome contains clusters of genes that encode two types of type IV (TIVSS) secretion systems; lvh and dot/icm. While the genetic organization of dot/icm, and its role in virulence is well established, there is limited information about the role of Lvh TIVSS. The Legionella strains that lack Lvh TIVSS have markedly reduced cytotoxicity. Additionally, Lvh TIVSS plays an important role in host-cell infection by L. pneumophila grown at 30°C, and in the effective delay of phagosome acidification. The L. pneumophila lvh locus is required for the restoration of entry and intracellular multiplication in dot/icm mutants following incubation in water and amoeba encystment. We have demonstrated that Legionella pneumophila’s Lvh TIVSS machinery localize at cell poles, and such localization has been reported to be important for virulence in other pathogens. We also demonstrated that Lvh TIVSS is important for host-cell caspase-3/7 activation when Legionella strains are grown under 30°C. Based on our preliminary data and data from the literature, our central hypothesis is that Lvh contributes to Legionella virulence under infection from the environment and regulates late stages of cellular infection and further dissemination of bacteria. We will test our central hypothesis and attain our objective by evaluating the role of Lvh TIVSS in the modulation of host cell immunity, gene expression, and programmed cell death. Revealing Lvh functions will uncover sites of potential weakness in bacterial pathogens that may be exploited for therapeutic intervention, development of rational, optimally efficacious vaccines, and disease control. Thus, the main goal of this project is to understand how the host-cell immune system recognizes microbial virulence factors during infection, produces a protective response, and the mechanism by which Legionella Lvh can inhibit this protective response. The results from this work will have an important positive impact on human health because they will provide important information about pathways or networks altered by L. pneumophila Lvh TIVSS in the host, which may lay the groundwork for the development of a new class of targeted treatments.