Pathogenesis

胃肠感染每年夺去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，儿童死亡中有相当一部分与肠致病性大肠杆菌（EPEC）和志贺氏菌感染有关。在本项目中，我们将研究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，并将在EPEC中发现新的此类因子。我们将测定最近从死于腹泻的儿童中分离出的20株EPEC菌株、从非致死性症状感染儿童中分离出的20株菌株和从无症状对照儿童中分离出的20株菌株的基因组序列。我们将专门寻找与症状性感染和致命结果相关的新基因位点。我们将确定两种蛋白质的宿主细胞靶点和作用机制，NIeB和NIeE是由EPEC分泌并注射到宿主细胞中，并且在先前的研究中与人类毒性增加有关。我们还将确定与上述基因组测序鉴定的毒力相关的新型EPEC遗传位点的发病机制。我们将确定一种名为ShET2的蛋白的靶点和作用机制，这种蛋白由EPEC和志贺氏菌产生和分泌，与人类EPEC感染的毒力增加有关，已经提出但尚未证实可以注射到宿主细胞中。总之，这些实验将在EPEC发病机制的遗传基础上产生前所未有的大量数据，揭示EPEC和志贺氏菌毒力因子的作用机制，特别是确定与致命感染相关的新位点。这些数据将为预防和治疗严重肠道感染的新举措提供极其宝贵的资源。

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.