Immunity to Pneumonic Tularemia

对肺炎兔热病的免疫力

• 批准号: 7964623
• 负责人: Catharine Bosio
• 金额: $ 103.21万
• 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/7964623
• 关键词: Aerosols; Alveolar Macrophages; Animals; Antibiotics; Antibodies; Attenuated; Attenuated Vaccines; B-Cell Development; B-Lymphocytes; Bacteria; Bacterial Antigens; Binding; Biological; Breathing; CD14 gene; Cells; Coagulation Process; Data; Dendritic Cells; Development; Disease; Enzymes; Francisella; Francisella tularensis; Goals; Human; Immune; Immune response; Immunity; Immunoglobulin G; Immunoglobulins; Immunosuppression; In Vitro; Individual; Infection; Inflammation; Inflammatory; Inflammatory Response; Interferon-beta; Investigation; Laboratories; Licensing; Lung; Modeling; Molecular; Mus; Nature; Organ; Phase; Plasmin; Plasminogen; Play; Refractory; Research; Role; Route; Secondary to; Serine Protease; Symptoms; System; Time; Tissues; Transforming Growth Factor beta; Tularemia; USSR; United States; Urokinase; Vaccinated; Vaccines; Virulent; Wound Healing; cytokine; in vivo; insight; microbial; mortality; nonhuman primate; novel therapeutics; pathogen; prevent; receptor; research study; response; therapeutic vaccine; transmission process; vector; weapons

Summary: Francisella tularensis, the causative agent for tularemia, can infect humans by a number of routes, including vector-borne transmission. However, it is inhalation of the bacterium, and the resulting pneumonic tularemia, that represents the most dangerous form of disease. This is due to the short incubation time (3-5 days), non-specific symptoms, and a high mortality rate (greater than 80%) in untreated individuals. Furthermore, F. tularensis has been weaponized by both the United States and the former Soviet Union making it a viable candidate for use as a biological weapon. Despite over 80 years of research on F. tularensis around the world, very little is understood about the dynamic interaction of this bacterium with the host, especially following aerosol infection. In the last several years my laboratory has provided abundant evidence that one of the primary mechanisms by which F. tularensis successfully infects and replicates in the host is via active suppression of the host immune response in the lungs. We have a developed a reproducible murine model in which mice intranasally infected with 10 CFU to study the dynamic changes and progress of infection. This model has revealed several important points concerning pneumonic tularemia. One of the most important observations is that, unlike more attenuated strains, virulent F. tularensis actively suppresses the host immune response, including pulmonary dendritic cells, during the first few days of infection. Although we have not identified the primary mechanism of suppression there are several host molecules that appear to be involved, including Transforming Growth Factor-beta (TGF-beta) and Interferon-beta (IFN-beta). Furthermore, we have recently shown that CD14 is a critical player in the elicitation of inflammation following exposure of cells to F. tularensis. Cells that lack CD14 are still susceptible to infection, but fail to produce pro-inflammatory cytokines. Furthermore, these cells become refractory to further stimulation by other microbial components. The specific role and the mechanism in which F. tularensis and its components interacts with CD14 is currently under investigation in the laboratory. In addition to CD14, we have made surprising and important observations involving the host plasminogen system (PAS) and its manipulation by virulent F. tularensis. Using both in vitro and in vivo systems we have shown that F. tularensis bind plasminogen and then converts it to the active serine protease plasmin in the presence of the host enzyme urokinase plasminogen activator (uPA). These plasmin coated bacteria readily degrade immunoglobulin in vitro. Importantly, we also observed that mice lacking uPA, and thus would not allow formation of plasmin coated bacteria, readily control F. tularensis infection, have higher numbers of B cells in specific target organs and develop F. tularensis specific IgG. Together these data provide both important insight into the role of the host PAS during Tularemia infections as well as important new understanding of how uPA might control B cell development and proliferation. In addition to understanding the way in which F. tularensis manipulates the host innate immune response we are investigating host components required for development of a protective adaptive response. To date, the only vaccine available (although not licensed in the United States) is an attenuated, Type B strain of F. tularensis known as Live Vaccine Strain or LVS. However, there are a number of problems associated in the use of this vaccine including an unpredictable phase shift in its LPS which renders the bacterium completely ineffective against pneumonic tularemia. Furthermore, the specific mechanism by which this vaccine protects against tularemia is not known. We have initiated experiments to identify host cellular and molecular components required for protection against F. tularensis. Since LVS offers incomplete protection we have developed an additional model of Francisella immune mice. By treating mice that have been infected with virulent F. tularensis for several days with antibiotic we have generated mice that develop an effective immune response against virulent F. tularensis without the concern of additional, potentially non-specific, responses generated in LVS vaccinated animals.

摘要：土拉热弗朗西斯菌是土拉菌病的病原体，可通过多种途径感染人类，包括媒介传播。然而，吸入细菌和由此产生的肺炎土拉菌病是最危险的疾病形式。这是由于潜伏期短（3-5天），非特异性症状，以及未经治疗的个体的高死亡率（大于80%）。此外，F.美国和前苏联都已将土拉热病毒武器化，使其成为一种可行的生物武器。尽管对F.尽管土拉热菌在世界各地流行，但人们对这种细菌与宿主的动态相互作用，特别是在气溶胶感染后的相互作用知之甚少。 在过去的几年里，我的实验室提供了大量的证据，证明F。土拉菌在宿主中成功感染和复制是通过主动抑制宿主在肺部的免疫应答。我们建立了一种可重复的小鼠模型，在该模型中，小鼠鼻内感染10 CFU，以研究感染的动态变化和进展。这个模型揭示了几个重要的点，关于肺炎兔热病。最重要的观察结果之一是，与更弱的菌株不同，强毒F。在感染的最初几天内，土拉菌主动抑制宿主免疫应答，包括肺树突细胞。虽然我们还没有确定抑制的主要机制，但似乎有几种宿主分子参与其中，包括转化生长因子-β（TGF-β）和干扰素-β（IFN-β）。此外，我们最近发现CD 14是细胞暴露于F后引发炎症的关键因素。土拉热。缺乏CD 14的细胞仍然容易受到感染，但不能产生促炎细胞因子。此外，这些细胞变得对其他微生物组分的进一步刺激不敏感。探讨了F.土拉热菌及其组分与CD 14相互作用的研究目前正在实验室进行。 除了CD 14，我们还发现了宿主纤溶酶原系统（PAS）及其被强毒F.土拉热。利用体外和体内系统，我们已经表明，F。土拉热菌结合纤溶酶原，然后在宿主酶尿激酶纤溶酶原激活物（uPA）的存在下将其转化为活性丝氨酸蛋白酶纤溶酶。这些纤溶酶包被的细菌在体外容易降解免疫球蛋白。重要的是，我们还观察到缺乏uPA的小鼠，因此不允许形成纤溶酶包被的细菌，容易控制F。土拉菌感染，在特定靶器官中具有较高数量的B细胞，并发展为F.土拉菌特异性IgG。总之，这些数据提供了重要的洞察宿主PAS在兔热病感染过程中的作用，以及重要的新的理解uPA如何可能控制B细胞的发育和增殖。 除了理解F.土拉菌操纵宿主先天免疫反应我们正在研究保护性适应性反应发展所需的宿主成分。迄今为止，唯一可用的疫苗（尽管在美国尚未获得许可）是一种减毒的B型F。土拉热菌称为活疫苗株或LVS。然而，在使用这种疫苗时存在许多相关的问题，包括其LPS中不可预测的相移，这使得细菌对肺炎土拉菌完全无效。此外，这种疫苗保护兔热病的具体机制尚不清楚。 我们已经开始了实验，以确定宿主细胞和分子组成部分所需的保护对F。土拉热。由于LVS提供不完全的保护，我们开发了另一种弗朗西斯菌免疫小鼠模型。 通过治疗感染了强毒F.用抗生素处理土拉热杆菌数天后，我们已经产生了对强毒F. LVS疫苗接种的动物中产生的额外的、潜在的非特异性应答。