Characterization of the Coxiella Dot/lcm homologues

描述(由申请人提供)： 伯氏柯克斯体是一种革兰氏阴性细菌，可引起人畜共患疾病Q热(问诊热)。这种疾病可能危及生命，范围从急性、流感样疾病到慢性形式，通常表现为心内膜炎。由于其高度的传染性(单个微生物可能导致疾病)，其雾化时具有传染性，以及对恶劣环境条件的极端抵抗力，伯氏梭菌显示出潜在的生物防御剂所需的特性。更好地了解这种微生物是如何引起疾病的，应该为如何防范其滥用提供信息。伯氏梭菌是一种专性的细胞内病原体，它在溶酶体的恶劣环境中奇怪地复制，溶酶体是一个通常具有极强杀菌作用的隔室。允许这种微生物在溶酶体内存活、在宿主细胞内复制并导致疾病的因素尚未确定。缺乏进展的主要原因是，伯氏梭菌在没有真核宿主细胞的情况下无法培养，从而限制了传统的遗传分析。最近完成的伯氏梭菌基因组计划提供了另一种方法。通过检查伯氏梭菌基因组中可能的毒力因子，发现它包含与相关病原体嗜肺军团菌使用的分泌系统同源的物质。与伯氏梭菌相似，嗜肺乳杆菌在宿主细胞内复制，但在与溶酶体融合之前，它在修改过的液泡中开始复制周期。嗜肺性乳杆菌利用其特殊的分泌系统，由DOT/ICM基因编码，将一些毒力因子输出到巨噬细胞中，以改变内吞途径。值得注意的是，伯氏梭菌含有已知的26个嗜肺乳杆菌Dot/ICM蛋白中的23个的同源物。我们建议确定这种病原体是否需要Dot/ICM同源物在宿主细胞内复制，并鉴定该系统分泌的蛋白质。

DESCRIPTION (provided by applicant): Coxiella burnetii is a Gram negative bacterium that causes the zoonotic illness Q fever (for query fever). This disease can be life-threatening and ranges from an acute, flu-like illness to a chronic form of that frequently presents as endocarditis. Due to its high level of infectivity (a single organism may cause disease), its ability to be infectious when it is aerosolized, and its extreme resistance to harsh environmental conditions, C. burnetii displays the properties necessary for a potential biowarfare agent. A better understanding of how this organism causes disease should provide information on how to defend against its misuse. C. burnetii is an obligate intracellular pathogen that curiously replicates inside the hostile environment of a lysosome, a compartment that is normally exceedingly bactericidal. The factors that allow this organism to survive inside lysosomes, replicate inside host cells, and cause disease have not been identified. The major reason for this lack of progress is due to the fact that C. burnetii cannot be cultured in the absence of eukaryotic host cells, thereby limiting traditional genetic analysis. An alternative approach has been provided by the recent completion of the C. burnetii genome project. By examining the C. burnetii genome for possible virulence factors, it was discovered that it contains homologues to a secretion system used by the related pathogen Legionella pneumophila. Similar to C. burnetii, L. pneumophila replicates inside host cells although it begins its replicative cycle in a modified vacuole prior to fusing with lysosomes. L. pneumophila uses its specialized secretion system, encoded by the dot/icm genes, to export a number of virulence factors into macrophages in order to alter the endocytic pathway. Remarkably C. burnetii contains homologues to 23 of the 26 known L. pneumophila Dot/Icm proteins. We propose to determine if the C. burnetii Dot/Icm homologues are needed for this pathogen to replicate inside host cells and to identify proteins secreted by this system.