Comparison of Anthrax Edema and Lethal Toxins in a Rat M

大鼠 M 炭疽水肿和致死毒素的比较

• 批准号: 7332575
• 负责人: Peter Q Eichacker
• 金额: --
• 依托单位: CLINICAL CENTER
• 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/7332575
• 关键词: Comparison; Anthrax; Edema; Lethal; Toxins

The threat of inhaled Bacillus anthracis (B. anthracis) as an agent of bioterrorism is an important problem in the United States today. Systemic B. anthracis following pulmonary inhalation results in shock and pulmonary edema and is fatal in almost 50% of cases despite effective antibiotic and other support. B. anthracis produces 2 toxins; lethal toxin (LeTx) comprised of lethal factor (LF) and protective antigen (PA), and edema toxin (ETx) comprised of edema factor (EF) and PA. Much data supports a central role of LeTx in the pathogenesis of B. anthracis. Lethal factor is a zinc protease that could inactivate members of the mitogen-activated protein kinases (MAPKKs or MEKs) family and subsequently inhibits phosphorylation and activation of downstream mitogen-activated protein kinases (MAP kinases) such as extracellular signal regulated kinase (ERK), c-Jun NH2-terminal kinase/stress-activated protein kinase (JNK/SAPK) and p38. Mutant strains lacking LeTx are much less virulent and the direct administration of LeTx is lethal in many animal models. Work with LeTx has been facilitated by the availability of recombinant forms of the protein. Despite its likely importance in the pathogenesis of B. anthracis however, administration of LeTx in animal models, while producing shock and lethality, does not result in the characteristic hemorrhagic tissue injury found in patients dying with this infection. This has suggested that virulence factors in addition to LeTx, such as ETx, may contribute to the pathogenesis of this microbe. Although B. anthracis mutants lacking ETx have been reported to retain virulence, studies support a role for this protein in the pathogenesis of the disease. ETx is an adenyl cyclase that transforms ATP to cAMP and can alter immune and other responses by the host. Past studies in some animal models with early preparations of this toxin had suggested that ETx would add to the effects of LeTx. However, studies with ETx were hampered by lack of recombinant preparations. Such preparations are now becoming available. A critical question at this time, both for better defining the pathogenesis of B. anthracis as well as its treatment is to understand how ETx functions alone and in combination with LeTx. In the present experiments, recently available preparations of recombinant ETx and LeTx were investigated. We first compared the effects of increasing concentrations of LeTx and ETx alone. In these experiments, ETx in doses less than a log less than LeTx resulted in hypotension and lethality similar to LeTx. Thus, ETx alone appears to have potentially lethal effects at concentration comparable to lethal doses of LeTx. We then tested the effects of ETx and LeTx in combination and found that their effects are additive but not synergistic. In recent experiments now completed, we described the effects of similarly lethal doses of ETx and LeTx either alone or in combination on cardiopulmonary and histology changes and the host inflammatory and defense responses. We also showed that protective antigen directed antibody was protective against the combination of ETx and LeTx. These studies have recently been accepted for publication. In one final set of experiments from this protocol we are specifically looking at the effects of ETx and LeTx alone and in combination on myocardial function and myocardial cellular structure as assessed by electrom microscopy.

吸入炭疽杆菌（B.炭疽菌）作为生物恐怖主义的媒介是当今美国的一个重要问题。全身性B。肺吸入炭疽菌后会导致休克和肺水肿，尽管有有效的抗生素和其他支持，但几乎50%的病例是致命的。B。炭疽病产生2种毒素;致死毒素（LeTx）由致死因子（LF）和保护性抗原（PA）组成;水肿毒素（ETx）由水肿因子（EF）和PA组成。大量数据支持LeTx在B发病机制中的核心作用。炭疽病致死因子是一种锌蛋白酶，其可以抑制丝裂原活化蛋白激酶（MAPK或MEK）家族的成员，并随后抑制下游丝裂原活化蛋白激酶（MAP激酶）的磷酸化和活化，所述下游丝裂原活化蛋白激酶例如细胞外信号调节激酶（ERK）、c-Jun NH 2-末端激酶/应激活化蛋白激酶（JNK/SAPK）和p38。缺乏LeTx的突变菌株毒性小得多，并且直接施用LeTx在许多动物模型中是致命的。蛋白质重组形式的可用性促进了LeTx的工作。 尽管它在B的发病机制中可能很重要。然而，在动物模型中施用LeTx，虽然产生休克和致死性，但不会导致在死于这种感染的患者中发现的特征性出血性组织损伤。这表明除了LeTx之外的毒力因子，如ETx，可能有助于这种微生物的发病机制。虽然B.据报道，缺乏ETx的炭疽突变体保留了毒力，研究支持这种蛋白质在疾病发病机制中的作用。ETx是一种腺苷酸环化酶，可将ATP转化为cAMP，并可改变宿主的免疫和其他反应。过去在一些早期制备这种毒素的动物模型中进行的研究表明，ETx会增加LeTx的作用。然而，由于缺乏重组制剂，ETx的研究受到阻碍。这种准备工作现在已经开始。一个关键的问题，在这个时候，既为更好地定义发病机制的B。炭疽病及其治疗的关键是了解ETx如何单独发挥作用以及与LeTx联合发挥作用。 在本实验中，最近可用的重组ETx和LeTx的制剂进行了研究。我们首先比较了单独增加LeTx和ETx浓度的效果。在这些实验中，ETx的剂量小于LeTx的对数，导致与LeTx相似的低血压和致死率。因此，单独的ETx似乎在与致死剂量的LeTx相当的浓度下具有潜在的致死作用。然后，我们测试了ETx和LeTx组合的效果，发现它们的效果是相加的，但不是协同的。在最近完成的实验中，我们描述了类似致死剂量的ETx和LeTx单独或组合对心肺和组织学变化以及宿主炎症和防御反应的影响。我们还表明，保护性抗原导向抗体对ETx和LeTx的组合具有保护性。这些研究最近已被接受出版。 在本方案的最后一组实验中，我们专门研究了ETx和LeTx单独使用和联合使用对心肌功能和心肌细胞结构的影响，如通过电子显微镜评估的。