Immunity to Pneumonic Tularemia

对肺炎兔热病的免疫力

• 批准号: 7592364
• 负责人: Catharine Bosio
• 金额: $ 142.25万
• 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/7592364
• 关键词: Acellular Vaccines; Adjuvant; Aerosols; Animals; Antibiotics; Antigens; Attenuated; Attenuated Live Virus Vaccine; Attenuated Vaccines; Bacteria; Binding; Biological; Biological Response Modifier Therapy; Breathing; Cells; Coagulation Process; Collaborations; Colorado; Combined Vaccines; Complex; DNA; Dendritic Cells; Depth; Development; Dinoprostone; Disease; Disease Outbreaks; Dose; Event; Francisella; Francisella tularensis; Goals; Human; Immune response; Immune system; Immunity; Immunosuppression; Immunosuppressive Agents; Individual; Infection; Injection of therapeutic agent; Invaded; Investigation; Laboratories; Licensing; Lipids; Liposomes; Lung; Modeling; Mus; Nature; Nucleic Acids; Numbers; Organ; Phase; Plasmin; Plasminogen; Rate; Reporting; Research; Role; Route; Symptoms; System; Testing; Therapeutic; Therapeutic immunosuppression; Time; Tissues; Transforming Growth Factor beta; Tularemia; USSR; United States; Universities; Vaccinated; Vaccine Adjuvant; Vaccines; Vascular Endothelial Growth Factors; Virulent; Wound Healing; base; day; design; immunoregulation; mortality; novel therapeutics; pathogen; prevent; response; therapeutic vaccine; transmission process; vector

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 are exposed to a low dose, whole body, aerosol (30-50 CFU) in which 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), Prostaglandin E2 (PGE2) and Vascular Endothelial Growth Factor (VEGF). The specific role and the mechanism by which F. tularensis modulates expression of these molecules is currently under investigation in the laboratory. One elusive goal in combatting pneumonic tularemia is the development of effective non-antibiotic based therapeutics that can provide protection shortly before or after infection. Previous reports have suggested that appropriate immunogens may be able to overcome the immunosuppression invoked by Francisella and enable the host to effectively eradicate the bacterium. For example, LPS purified from the attenuated F. tularensis Live Vaccine Strain (LVS) injected 3 days prior to a lethal LVS challenge protects all infected animals. A similar phenomenon has been observed following injections of CpG nucleic acid motifs or cationic-lipid DNA complexes (CLDC). While it has been previously shown that LVS LPS does not protect against infections with fully virulent F. tularensis, it is not known if CpG or CLDC can engender protective immunity against similar strains. In collaboration with Juvaris Biotherapeutics, we are currently examining the protective efficacy of CLDC against aerosol challenge with virulent F. tularensis with the goal of developing an easily administrated therapeutic that could be quickly distributed following a natural outbreak of terror event. 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. In collaboration with Dr. John Belisle (Colorado State University) we are testing acellular vaccines derived from LVS. Using crude sub-cellular fractions we have been able to generate protection against low dose aerosols nearly equivalent as that observed in animals vaccinated with LVS. Furthermore, we are currently identifying correlates of immunity for survival of pneumonic tularemia using these vaccines combined in adjuvants designed to skew the immune response in a polarized fashion. This approach will allow us to identify specific requirements in the host without the complications of using genetically modified mice.

摘要：土拉热弗朗西斯菌是兔热病的病原体，可通过多种途径感染人类，包括媒介传播。 然而，吸入细菌以及由此产生的肺炎兔热病才是最危险的疾病。 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死亡率高（大于80%）。 此外，美国和前苏联都已将土拉杆菌武器化，使其成为用作生物武器的可行候选者。 尽管世界各地对土拉杆菌的研究已有 80 多年的历史，但人们对这种细菌与宿主的动态相互作用知之甚少，尤其是在气溶胶感染后。 在过去的几年中，我的实验室提供了充足的证据，表明土拉弗朗西斯成功感染宿主并在宿主中复制的主要机制之一是通过主动抑制宿主肺部的免疫反应。 我们开发了一种可重复的小鼠模型，将小鼠暴露于低剂量的全身气溶胶（30-50 CFU）中，以研究感染的动态变化和进展。 该模型揭示了有关肺炎兔热病的几个要点。 最重要的观察结果之一是，与减毒菌株不同，强毒土拉弗朗西斯菌在感染的最初几天会主动抑制宿主免疫反应，包括肺树突状细胞。 尽管我们尚未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)、前列腺素 E2 (PGE2) 和血管内皮生长因子 (VEGF)。 F. tularensis 调节这些分子表达的具体作用和机制目前正在实验室中进行研究。 对抗肺炎兔热病的一个难以实现的目标是开发有效的非抗生素疗法，可以在感染前后不久提供保护。 先前的报告表明，适当的免疫原可能能够克服弗朗西斯菌引起的免疫抑制，并使宿主能够有效地根除细菌。 例如，在致死性 LVS 攻击前 3 天注射的减毒土拉弗朗西斯活疫苗株 (LVS) 中纯化的 LPS 可保护所有受感染的动物。 在注射 CpG 核酸基序或阳离子脂质 DNA 复合物 (CLDC) 后观察到类似的现象。 虽然之前已经表明 LVS LPS 不能防止完全毒力土拉弗朗西斯菌的感染，但尚不清楚 CpG 或 CLDC 是否可以产生针对类似菌株的保护性免疫力。 我们目前正在与 Juvaris Biotherapeutics 合作，研究 CLDC 对有毒土拉弗拉菌气溶胶攻击的保护功效，目标是开发一种易于管理的治疗方法，可以在恐怖事件自然爆发后快速分发。 除了了解土拉弗朗西斯操纵宿主先天免疫反应的方式外，我们还在研究发展保护性适应性反应所需的宿主成分。 迄今为止，唯一可用的疫苗（尽管未在美国获得许可）是土拉弗朗西斯杆菌的 B 型减毒株，称为活疫苗株或 LVS。 然而，这种疫苗的使用存在许多相关问题，包括其 LPS 的不可预测的相移，这使得该细菌对肺炎兔热病完全无效。 我们正在与 John Belisle 博士（科罗拉多州立大学）合作测试源自 LVS 的非细胞疫苗。 使用粗亚细胞部分，我们已经能够产生针对低剂量气溶胶的保护，几乎与在接种 LVS 的动物中观察到的效果相同。 此外，我们目前正在使用这些疫苗与佐剂相结合来确定肺炎兔热病生存的免疫相关性，这些佐剂旨在以极化方式扭曲免疫反应。 这种方法将使我们能够确定宿主的具体要求，而不会出现使用转基因小鼠的并发症。