Role of Toll-like receptors in Coxiella burnetii infection

描述(申请人提供)：尽管自20世纪30年代以来，伯氏梭菌一直被认为是Q热病的病原体，但我们对宿主细胞进入、疾病发病机制或该病原体如何避免免疫清除仍有不完全的了解。Toll样受体(Toll-like Receptor，TLR)通路被认为在细菌的摄取和清除中发挥作用，但我们对Q热中Toll样受体的了解还不完全。虽然已发表了一些关于TLR缺陷动物腹膜感染伯氏梭菌的研究，但迄今为止还没有利用TLR缺陷动物和通过肺的自然感染途径感染的报道。肺TLR的使用是独一无二的，因此需要这些研究来真正相关地了解TLRs在伯氏梭菌感染中的作用。在初步研究中，我们检测到TLR2、TLR4和MyD88(TLR2和4的关键炎症信号分子)缺陷动物在肺攻击后细菌清除的差异，其中一些差异与其他人在腹膜感染后的定义相反。我们建议对这些初步观察结果进行扩展和确认。我们对TLRs在伯氏梭菌感染中作用的另一个认识不足是，TLR功能是否与骨髓来源的巨噬细胞最相关，或者非巨噬细胞甚至非骨髓来源细胞上的TLRs是否显著促进宿主对该细菌的反应。特别令人感兴趣的是肥大细胞对TLR的识别/功能在伯氏梭菌发病机制中的潜在作用。这些问题也将在拟议的研究中加以研究。最后，拟议研究的一个创新部分将涉及使用新型的人类TLR4/MD2转基因小鼠来比较人和小鼠在体内对伯氏梭菌的TLR4反应。在这项建议中要检验的具体假设是：TLR信号在宿主/伯氏梭菌在肺中的相互作用中是重要的。这一假设将在以下具体目标中得到解决。目的1：比较肺攻击后野生型、TLR和MyD88缺陷小鼠的伯氏梭菌感染情况。目的：确定TLRs在肺内感染伯氏梭菌后对造血细胞和非造血细胞反应的重要性，包括肥大细胞的作用。目标3：比较 人TLR4/MD2转基因小鼠和小鼠TLR4感染反应的研究 公共卫生相关性：目前，Q热的唯一治疗方法是使用抗生素，必须在感染后尽早开始使用，并延长使用时间才能有效。因此，有必要开发用于治疗Q热的新疗法。来自这些基础科学研究的信息应有助于开发未来的疫苗和/或佐剂来对抗Q热。

DESCRIPTION (provided by applicant): Even though C. burnetii has been recognized as the Q fever agent since the 1930s, we still have an incomplete understanding of host cell entry, disease pathogenesis or how the agent avoids immune clearance. Toll-like receptor (TLR) pathways have been hypothesized to play a role in bacterial uptake and clearance, but our understanding of TLRs in Q-fever is incomplete. Though a few studies of C. burnetii infection of the peritoneum in TLR deficient animals have been published, to date there have been no reports using TLR deficient animals and the natural route of infection via the lung. Lung TLR usage is unique, thus these studies are required to gain a truly relevant picture of the role of TLRs in C. burnetii infection. In preliminary studies we have detected differences in bacterial clearance in TLR2, TLR4 and MyD88 (Key inflammatory signaling molecule for TLRs 2&4) deficient animals following pulmonary challenge, some of which (differences) are contrary to what others have defined following peritoneal infection. We propose to expand on and confirm these preliminary observations. Another deficiency in our understanding of the role of TLRs in C. burnetii infection is whether TLR function is most relevant to bone-marrow derived macrophages, or whether TLRs on non-macrophages or even non-bone-marrow derived cells significantly contribute to host responses against the bacterium. Of particular interest is the potential role of TLR recogntion/function by mast cells in C. burnetii pathogenesis. These issues will also be examined in the proposed studies. Finally, an innovative component of the proposed studies will involve use of novel, human TLR4/MD2 transgenic mice to compare human and mouse TLR4 responses to C. burnetii in vivo. The specific hypothesis to be tested in this proposal is: TLR signaling is important in the host/C. burnetii interaction in the lung. This hypothesis will be addressed in the following Specific Aims. Aim 1: Compare C. burnetii infection in wild type, and TLR- and MyD88 deficient mice following lung challenge. Aim 2: Determine the importance of TLRs on the responses of hematopoietic and non-hematopoietic cells, including the role of mast cells following C. burnetii infection in the lung. Aim 3: Compare C. burnetii infection response in human TLR4/MD2 transgenic and mouse TLR4 competent mice. PUBLIC HEALTH RELEVANCE: Currently, the only treatment for Q-fever is the use of antibiotics, which must be started as early as possible after infection and used for extended periods of time in order to be effective. As such, there is a need for the development of new therapeutics for use against Q-fever. Information from these basic science studies should facilitate development of future vaccines and/or adjuvants to counter Q-fever.