Bacillus Anthracis and Complement

描述(申请人提供)：补体系统是宿主防御微生物的关键组成部分。然而，一些微生物病原体已经进化到与补体级联的特定成分相互作用并操纵，从而打破了对宿主的平衡，有利于病原体。病原体和补体级联成分之间的这种动态相互作用为有效的预防和治疗战略提供了挑战和机会。尽管这很重要，但关于补体系统和炭疽杆菌之间发生的具体相互作用的知识实际上是不存在的。同样，这种相互作用的生物学后果仍不得而知。最近的发现，主要来自我们小组，表明炭疽芽胞已经进化出一种复杂的机制来与补体系统相互作用。我们提出了一个新的模型，在该模型中，孢子表面蛋白BCLA直接与补体成分C1q和补体调节因子H相互作用，与C1q相互作用以补体激活依赖和激活非激活的方式介导孢子进入不同类型的宿主细胞，而与因子H相互作用限制补体激活的程度，促进病原菌的存活和持久性。如果这个模型是正确的，它将在 了解补体在炭疽病发生发展中的作用，并为不同类型宿主细胞对孢子的摄取、由孢子诱导的最小炎症反应和孢子在肺中的滞留提供共同的机制基础，所有这些都是炭疽杆菌致病过程中的重要特征。此外，由于BCLA被证明在实验动物中具有保护作用，了解BCLA-补体相互作用的生物学功能将对未来的疫苗开发具有重要意义。此外，这里提出的研究有望对补体-病原体的相互作用产生广泛的影响。因此，本文提出了两个具体目标。在目标1中，我们将利用一系列重组蛋白以及表达不同蛋白片段的孢子来确定孢子表面蛋白BCLA与C1q和H因子的结合机制。在目标2中，我们将确定孢子与C1q相互作用的生物学功能 以及因子H和重组BCLA片段的疫苗潜力。这将涉及使用C1q结合或因子H结合的特定补体成分和孢子等基因缺陷的小鼠模型。还将用不同的BCLA片段免疫小鼠，以确定它们对急性和持续性感染的保护效果。该项目将与德克萨斯州休斯敦的德克萨斯大学健康科学中心(UTHSC)分子医学研究所免疫学和自身免疫病研究中心教授兼主任Rick Wetsel博士合作进行。

DESCRIPTION (provided by applicant): The complement system is a key component of a host's defense against microorganisms. However, some microbial pathogens have evolved to interact with and manipulate specific components of the complement cascade, tipping the balance against the host and in favor of the pathogen. This dynamic interplay between pathogens and components of the complement cascade presents challenges and opportunities for effective preventive and therapeutic strategies. Despite the importance, knowledge of the specific interactions that occur between the complement system and Bacillus anthracis is virtualy non-existent. Likewise, the biological consequences of such interactions remain unknown. Recent discoveries, primarily from our group, suggest that spores of B. anthracis have evolved a sophisticated mechanism to interact with the complement system. We propose a novel model in which the spore surface protein BclA directly interacts with complement component C1q and complement regulator factor H. Interaction with C1q mediates spore entry into different types of host cells in both a complement activation-dependent and activation-independent manner while interaction with factor H limits the extent of complement activation and promotes pathogen survival and persistence. If this model is correct, it will be significant in understanding the role of complement in the development of anthrax infections as well as providing a common mechanistic basis for; spore uptake by different types of host cells, the minimal inflammatory responses induced by spores and spore persistence in the lung, all of which are important features in the pathogenic process of B. anthracis. In addition, as BclA was shown to be protective in experimental animals, understanding the biological functions of BclA-complement interactions will have significant implications to future vaccine development. Furthermore, the studies proposed here are expected to have broad implications to complement-pathogen interactions in general. Consequently, two specific aims are proposed. In aim 1, we will determine the binding mechanisms of spore surface protein BclA to C1q and factor H, using a series of recombinant proteins as well as spores expressing different segments of the protein. In aim 2, we will determine the biological functions of spore interactions with C1q and factor H and the vaccine potential of recombinant BclA fragments. This will involve using mouse models deficient in specific complement components and spores isogenic for C1q binding or factor H binding. Mice will also be immunized with different fragments of BclA to determine their protective efficacy against both acute and persistent infections. The project will be carried out in collaboration with Dr. Rick Wetsel, Professor and Director, Research Center for Immunology and Autoimmune Diseases, Institute of Molecular Medicine, University of Texas Health Science Center (UTHSC), Houston, Texas.