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：图拉氏方济氏菌是图拉热病的病原体，可通过多种途径感染人类，包括通过媒介传播。然而，吸入细菌和由此导致的肺炎图拉热症是最危险的疾病形式。这是由于未经治疗的患者的潜伏期短(3-5天)、非特异性症状以及高死亡率(大于80%)。此外，美国和前苏联都已将其武器化，使其成为用作生物武器的可行候选者。尽管世界各地对图拉氏杆菌进行了80多年的研究，但人们对这种细菌与宿主的动态相互作用知之甚少，特别是在气溶胶感染之后。 在过去的几年里，我的实验室提供了大量的证据，证明图拉氏杆菌成功感染宿主并在宿主体内复制的主要机制之一是通过主动抑制宿主在肺部的免疫反应。我们建立了一种可重复性的小鼠模型，用小鼠鼻内感染10CFU来研究感染的动态变化和进展。该模型揭示了有关肺炎性图拉热症的几个重要问题。最重要的观察之一是，与更弱的菌株不同，毒力图拉氏杆菌在感染的头几天积极抑制宿主免疫反应，包括肺树突状细胞。虽然我们还没有确定抑制的主要机制，但似乎有几个宿主分子参与其中，包括转化生长因子-β(TGF-β)和干扰素-β(干扰素-β)。此外，我们最近表明，CD14在细胞暴露于图拉氏杆菌后引发炎症的过程中发挥了关键作用。缺乏CD14的细胞仍然容易感染，但不能产生促炎细胞因子。此外，这些细胞对其他微生物成分的进一步刺激变得难以接受。图拉氏丝虫及其组分与CD14相互作用的具体作用和机制目前正在实验室进行研究。 除了CD14，我们还对宿主纤溶酶原系统(PAS)及其被毒力图拉氏杆菌的调控进行了令人惊讶和重要的观察。利用体外和体内系统，我们已经证明了图拉氏F菌与纤溶酶原结合，然后在宿主酶尿激酶型纤溶酶原激活剂(UPA)的存在下将其转化为具有活性的丝氨酸蛋白酶纤溶酶。这些纤溶酶包被的细菌在体外很容易降解免疫球蛋白。重要的是，我们还观察到，缺乏uPA的小鼠不允许形成纤溶酶包被的细菌，很容易控制图拉氏丝虫的感染，在特定的靶器官中有更多的B细胞，并产生图拉氏丝虫特异的免疫球蛋白。总之，这些数据为了解宿主PAS在兔热病感染中的作用提供了重要的见解，也为uPA如何控制B细胞的发育和增殖提供了重要的新理解。 除了了解图拉氏丝虫操纵宿主先天免疫反应的方式外，我们还在研究保护性适应反应发展所需的宿主成分。到目前为止，唯一可用的疫苗(尽管没有在美国获得许可)是一种被称为活疫苗株或LVS的图拉氏F菌B型减毒株。然而，这种疫苗的使用存在一些问题，包括其内毒素的不可预测的相变，使该细菌对肺炎图拉热症完全无效。此外，这种疫苗预防图拉热症的具体机制尚不清楚。我们已经开始了实验，以确定对图拉氏丝虫病的保护所需的宿主细胞和分子成分。由于LVS提供了不完全的保护，我们开发了另一种弗朗西斯氏菌免疫小鼠模型。通过用抗生素治疗感染了几天的图拉氏杆菌强毒株的小鼠，我们产生了对强毒力图拉氏杆菌产生有效免疫反应的小鼠，而不必担心在LVS疫苗接种的动物中产生的额外的、潜在的非特异性反应。