GENETIC DETERMINANT OF PATHOGENICITY IN LEGIONELLA

描述：(改编自申请人的摘要)。嗜肺军团菌， 军团病的病原体导致了这两种疾病的很大比例 美国每年都有社区获得性肺炎和医院获得性肺炎。更多 在估计发生的50,000-200,000起病例中，超过90%是由 这个物种，尽管现在已经有30多个军团菌物种 已确认身份。军团病是以典型的S综合征为特征 与细菌性肺炎有关的体征和症状，但除此之外， 许多患者经历了疾病的肺外表现， 包括肾、肾和中枢神经系统功能障碍。这个 肺部感染的组织病理学表现为纤维蛋白脓化过程和 组织坏死。细菌与巨噬细胞密切相关。 死亡率仍然相对较高(15%-20%)，尽管 适当的诊断和治疗。关于L.的独特性质。 嗜肺性肺炎在其他军团菌中没有发现，这些军团菌本身就是 毒性较小的是一种分泌型金属蛋白酶。现在已经知道， 蛋白水解酶具有溶血和细胞毒性的特性，单个基因 将所有这些功能编码在一个多肽中。这种基因现在已经被 克隆并测序，与假单胞菌有惊人的相似性 铜绿假单胞菌弹性蛋白酶。 自然界中军团菌属(Legionella sp.)在水中发现与阿米巴和阿米巴有关的 其他能够生长的原生动物。军团菌的能力 复制受温度的影响，并取决于 该菌株固有的“毒力”。在人类感染和在 实验动物嗜肺性乳杆菌通过一种独特的方式进入巨噬细胞 进程。毒力强的菌株能够防止细胞内死亡和 生长到一定程度，即它们从细胞中释放出来，从而产生后代 细菌可能会感染其他细胞。虽然军团菌不被认为是 作为一种真正专属的细胞内寄生虫，生长只能发生 在细胞内。 汤普金斯博士建议研究军团菌的遗传决定因素 允许通过以下方式适应这些不同的细胞内环境 分离、克隆和鉴定可能在细胞中表达的基因 对环境信号的反应。她将使用细胞内模型 寄生，在阿米巴和真核细胞中，研究 军团菌突变株及环境因素对胞内的影响 成长。在致病性的假定决定因素中，她将重点关注 包括金属蛋白酶、鞭毛和表型毒力。 将通过基因交换和转座子介导的方法选择同基因突变体 诱变。他们将研究基因的表达和调控。 编码这些特征，以及环境因素的影响，在体内 阿米巴和真核细胞，比较同基因突变体和野生型 菌株。这项建议的另一个主要方面是研究 在一种动物模型中这些基因对感染和疾病的贡献 为了比较和对比这些基因产物在动物体内的作用 在原生动物和真核细胞中感染和生长期间。

DESCRIPTION: (Adapted from applicant's abstract). Legionella pneumophila, the agent of Legionnaire's disease, causes a significant proportion of both community-acquired and nosocomial pneumonia in the U.S. each year. More than 90 percent of the 50,000-200,000 cases estimated to occur are caused by this species, although more than 30 Legionella species have now been identified. Legionnaire's disease is s syndrome characterized by typical signs and symptoms associated with bacterial pneumonia, but in addition, many patients experience extra-pulmonary manifestations of disease, including renal, kidney and central nervous system dysfunction. The histopathology of lung infection shows an fibrinopurulent process and tissue necrosis. Bacteria are seen in close association with macrophages. The mortality rate remains relatively high (15-20 percent) in spite of appropriate diagnosis and therapy. On e of the unique properties of L. pneumophila not found in other Legionella species which are intrinsically less virulent is a secreted metalloprotease. It is now known that the protease has hemolytic and cytotoxic properties and that a single gene encodes all these functions in one polypeptide. This gene has now been cloned and sequenced and bears a striking resemblance to Pseudomonas aeruginosa elastase. In nature Legionella sp. are found in water in association with amoeba and other protozoans in which they are able to grow. The ability of Legionella to replicate is affected by temperature and depends upon the degree of intrinsic "virulence" of the strain. In human infections and in experimental animals, L. pneumophila enters macrophages by a unique process. Virulent strains are able to prevent intracellular killing and grow to the extent that they are released from the cell whereupon progeny bacteria may infect other cells. Although Legionella is not considered to be a true obligate intracellular parasite, growth can only occur intracellularly. Dr. Tompkins proposes to examine the genetic determinants of Legionella which permit adaptation to these diverse intracellular environments by isolating, cloning and characterizing those genes that may be expressed in response to environmental signals. She will use models of intracellular parasitism, in amoeba and eukaryotic cells, to study the behavior of Legionella mutants and the effect of environmental factors on intracellular growth. Among the putative determinants of pathogenicity she will focus upon include the metalloprotease, flagella, and phenotypic virulence. Isogeneic mutants will be selected by gene exchange and transposon-mediated mutagenesis. They will study the expression and regulation of genes encoding these traits, and the effect of environmental factors, in vivo in amoeba and eukaryotic cells, comparing isogeneic mutants with wild-type strains. The other major aspect of this proposal is to examine the contribution of these genes to infection and disease in an animal model in order to compare and contrast the effect of these gene products in animal infection and during growth in protozoans and eukaryotic cells.