Bacterial chitinases as new virulence factors

描述（由申请人提供）：最近，我们发现军团病的病原体嗜肺军团菌分泌的几丁质酶促进了实验感染小鼠肺部细菌的持续存在。体外实验证明，嗜肺乳杆菌几丁质酶（ChiA）促进肺上皮细胞的生长，但对巨噬细胞没有促进作用。综上所述，这些数据首次证明了几丁质酶，这种酶传统上被认为只与含有几丁质的环境生态位有关，就像一个毒力因子。因此，我们假设细菌几丁质酶代表了一类新的毒力因子。为了探索这一假设，我们将进一步研究几丁质酶在嗜肺乳杆菌细胞内感染中的作用，并首次测试几丁质酶在第二种细胞内病原体单核增生李斯特菌的毒力中的重要性。更具体地说，我们将确定受ChiA影响的细胞内位置和运输模式，并开始确定ChiA对肺部炎症反应的影响。对于李斯特菌实验，将构建新的几丁质酶突变体，然后在确认其几丁质酶活性丧失及其体外生长特性后，在李斯特菌病小鼠模型中进行测试。拟议的研究将i)增加我们对Lp发病机制的理解，这是美国乃至全世界重要的公共卫生问题，ii)首次检查几丁质酶在单核增生乳杆菌发病机制中的作用，这也是一个重要的公共卫生问题，iii)扩大我们对细菌细胞内感染的认识以及几丁质酶在其中的新作用。Iv)对许多其他也表达几丁质酶的环境病原体有启示，Iv)为疾病诊断、治疗或预防提供潜在的新靶点。公共卫生相关性：我们最近发现嗜肺军团菌分泌的几丁质酶促进细菌在实验感染小鼠肺部的持久性。根据这一新发现，我们假设微生物几丁质酶，传统上被认为只与环境生态位相关，实际上代表了一类新的毒力因子，因此是抗菌治疗的潜在新靶点。为了探索这一假设，我们将进一步研究几丁质酶在嗜肺乳杆菌细胞内感染中的作用，并首次测试几丁质酶在第二种细胞内病原体单核增生李斯特菌的毒力中的重要性。

DESCRIPTION (provided by applicant): Recently, we discovered that a secreted chitinase of Legionella pneumophila, the agent of Legionnaires' disease, promotes the persistence of the bacterium in the lungs of experimentally infected mice. In vitro experiments then documented that the L. pneumophila chitinase (ChiA) promotes growth in lung epithelial cells but not in macrophages. Taken together, these data are the first demonstration of a chitinase, a type of enzyme that is traditionally viewed as only being relevant in chitin-containing environmental niches, acting like a virulence factor. Thus, we hypothesize that bacterial chitinases represent a new class of virulence factor. To explore this hypothesis, we will further investigate the role of chitinase in L. pneumophila intracellular infection of lung cells as well as test for the first time the importance of a chitinase in the virulence of a second intracellular pathogen, Listeria monocytogenes. More specifically, we will determine the intracellular location of and trafficking patterns influenced by ChiA and begin to ascertain the effects of ChiA on the lung inflammatory response. For the Listeria experiments, new chitinase mutants will be constructed and then, after confirmation of their loss of chitinase activity and their in vitro growth characteristics, tested in murine models of listeriosis. The proposed studies will i) increase our understanding of the pathogenesis of Lp, which is an important public health concern within the US and throughout the world, ii) examine for the first time the role of chitinase in the pathogenesis of L. monocytogenes, an organism that is also an important public health concern, iii) expand our appreciation of bacterial intracellular infection and the novel role that a chitinase can have in it, iv) have implications for numerous other environmental pathogens that also express chitinases, and iv) offer potential new targets for disease diagnosis, treatment, or prevention. PUBLIC HEALTH RELEVANCE: We recently discovered that the secreted chitinase of Legionella pneumophila promotes bacterial persistence in the lungs of experimentally infected mice. From this novel finding, we hypothesize that microbial chitinases, which have traditionally been viewed as being relevant only in environmental niches, actually represent a new class of virulence factor and therefore are potential new targets for antimicrobial therapy. To explore this hypothesis, we will further investigate the role of chitinase in L. pneumophila intracellular infection of lung cells as well as test for the first time the importance of chitinases in the virulence of a second intracellular pathogen, Listeria monocytogenes.