Pathogenesis

胃肠道感染每年夺去200万至300万儿童的生命。一项全球肠道多中心研究的中期数据表明，儿童死亡人数与肠致病性大肠杆菌感染有关。大肠杆菌（EPEC）和志贺菌属（Shigella spp.）在这个项目中，我们将调查由EPEC和志贺氏菌产生的与严重疾病相关的特定因子对发病机制的贡献，我们将在EPEC中发现新的此类因子。我们将确定最近从死于腹泻的儿童中分离出的20株EPEC菌株的基因组序列，20株来自非致死性梅毒感染儿童的菌株和20株来自无症状对照儿童的菌株。我们将特别寻找与症状性感染和致命结果相关的新的遗传位点。我们将确定宿主细胞的目标和两种蛋白质，NieB和NieE，这是由EPEC分泌和注射到宿主细胞中，并已在以前的研究中与人类的毒力增加的作用机制。我们还将确定与上述基因组测序鉴定的毒力相关的新EPEC遗传位点对致病的贡献。我们将确定一种被称为ShET 2的蛋白质的作用靶点和机制，该蛋白质由EPEC和志贺氏菌产生和分泌，与人类EPEC感染中的毒力增加有关，并且已被提出但未被证明可注射到宿主细胞中。总之，这些实验将产生一个unprecidented量的数据的遗传基础上的EPEC发病机制，发现机制的毒力因子从EPEC和志贺氏菌，特别是确定新的基因座与致命的感染。这些数据将成为预防和治疗严重肠道感染的新举措的极其宝贵的资源。

Gastrointestinal infections claim the lives of 2-3 million children annually. Interim data from a Global Enteric Multicenter Study indicate that a disporportionate number of deaths among children is associated with infections due to enteropathogenic E. coli (EPEC) and Shigella spp. In this project we will investigate the contribution to pathogenesis of specific factors produced by EPEC and Shigella that are associated with severe disease and we will discover new such factors in EPEC. We will determine the genome sequence of 20 EPEC strains recently isolated from children who succumbed to diarrhea, 20 strains from children with non-lethal sypmptomatic infection and 20 strains from asymptomatic control children. We will specifically seek new genetic loci that are associated with symptomatic infection and with lethal outcome. We will determine the host cell targets and mechanisms of action of two proteins, NIeB and NIeE, that are secreted by EPEC and injected into host cells and that have been associated in previous studies with increased virulence in humans. We will also determine the contributions to pathgenesis of novel EPEC genetic loci associated with virulence identified by the above genomic sequencing. And we will determine the target and mechanism of action of a protein known as ShET2 that is produced and secreted by both EPEC and Shigella, associated with increased virulence in human EPEC infection, and has been proposed but not proven to be injected into host cells. Together, these experiments will yield an unprecidented amount of data on the genetic basis of EPEC pathogenesis, uncover mechanisms of action of virulence factors from EPEC and Shigella, and in particular identify novel loci associated with deadly infections. These data will serve as an extremely valuable resource for new initiatives to prevent and treat severe enteric infections.