GENETIC DETERMINANT OF PATHOGENICITY IN LEGIONELLA

描述：（改编自申请人摘要）。 嗜肺军团菌， 军团病的病原体，导致两者的很大比例 社区获得性肺炎和医院获得性肺炎。 更 在估计发生的5万至20万例病例中， 虽然目前已经有30多种军团菌被 鉴定 军团病是以典型的 与细菌性肺炎相关的症状和体征，但除此之外， 许多患者经历疾病的肺外表现， 包括肾、肾和中枢神经系统功能障碍。 的 肺部感染的组织病理学显示纤维蛋白脓性过程， 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。 本文讨论了L. 嗜肺军团菌在其他军团菌属中未发现， 毒性较小的是分泌型金属蛋白酶。 现在我们知道， 蛋白酶具有溶血性和细胞毒性， 在一个多肽中编码所有这些功能。 这个基因现在已经 克隆并测序，与假单胞菌 铜绿弹性蛋白酶 在自然界中，军团菌在水中与变形虫有关， 其他原生动物，它们可以在其中生长。 军团菌 复制受温度的影响，并取决于 菌株的内在“毒性”。 在人类感染和 实验动物，L.嗜肺菌通过一种独特的 过程 毒力菌株能够阻止细胞内杀伤， 生长到从细胞中释放出来的程度， 细菌可以感染其他细胞。 虽然军团菌不被认为是 作为一种真正的专性细胞内寄生虫， 细胞内。 汤普金斯博士建议研究军团菌的遗传决定因素 其允许适应这些不同的细胞内环境， 分离、克隆和表征那些可能在 响应环境信号。 她将使用细胞内 寄生，在变形虫和真核细胞，研究的行为， 军团菌突变株及环境因素对细胞内 增长 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，比较同基因突变体与野生型 菌株 这项建议的另一个主要方面是研究 这些基因在动物模型中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中的作用， 在原生动物和真核细胞中的感染和生长期间。

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.