Host Responses to E. Coli Urinary Tract Infection

描述（由申请人提供）： 尿路感染（UTI）是美国第二大常见的传染病，也是一个重要的发病原因，具有重大的经济和社会影响。这些感染通常由革兰氏阴性细菌大肠杆菌引起。一旦尿致病性E.大肠杆菌（UPEC）的引入，这些细菌在尿路中的生存和持久性需要一组特定的毒力因子。最近在小鼠膀胱炎模型中的研究揭示了大肠杆菌中的致病性级联反应。大肠杆菌UTI，包括细菌附着和内化，随后在尿路上皮的表面小面细胞内形成细菌的细胞内生物膜样豆荚。宿主反应包括尿路上皮细胞产生炎性细胞因子和中性粒细胞流入膀胱。UPEC菌株在体外急剧减弱上皮细胞因子的产生，表明UPEC可能试图破坏这种免疫反应以在膀胱内获得立足点的机制。此外，尽管存在显著的中性粒细胞浸润，但UPEC在小鼠膀胱内增殖至高水平。我们假设UPEC采用策略来减弱宿主细胞因子信号传导，抵抗吞噬作用，在吞噬细胞内存活，和/或影响中性粒细胞内活性氧的产生。我们进一步假设到达的中性粒细胞对特定的化学信号作出反应，只针对豆荚感染的尿路上皮细胞。该提案融合了体外中性粒细胞和组织培养试验、细菌遗传学、鼠膀胱炎模型、定量基因表达谱和蛋白质组学，以鉴定UPEC与宿主免疫组分（特别是中性粒细胞）之间相互作用的分子决定因素。这些结果将促进我们对膀胱内宿主-病原体相互作用的理解，为UTI的新治疗和预防策略提供目标，并为宿主-病原体串扰的新范例提供基础，这些新范例可以推广到其他革兰氏阴性细菌感染。

DESCRIPTION (provided by applicant): Urinary tract infections (UTIs) represent the second most common infectious disease in the United States and a significant cause of morbidity, with major economic and social impact. These infections commonly are caused by the Gram-negative bacterium Escherichia coli. Once uropathogenic E. coli (UPEC) is introduced, survival and persistence of these bacteria in the urinary tract require a specific set of virulence factors. Recent work in the murine cystitis model has revealed a pathogenic cascade of events in E. coli UTI, including bacterial attachment and internalization, followed by the formation of intracellular biofilm-like pods of bacteria within superficial facet cells of the uroepithelium. Host responses include uroepithelial production of inflammatory cytokines and an influx of neutrophils into the bladder. UPEC strains attenuate epithelial cytokine production sharply in vitro, suggesting a mechanism by which UPEC may attempt to subvert this immune response to gain a foothold within the bladder. In addition, UPEC multiply to high levels within the mouse bladder despite the presence of a significant neutrophil infiltrate. We hypothesize that UPEC employs strategies to attenuate host cytokine signaling, resist phagocytosis, survive within phagocytes, and/or affect the generation of reactive oxygen species within neutrophils. We further hypothesize that arriving neutrophils respond to specific chemical signals to target only pod-infected uroepithelial cells. This proposal blends in vitro neutrophil and tissue culture assays, bacterial genetics, the murine cystitis model, quantitative gene expression profiling, and proteomics to identify the molecular determinants of the interactions between UPEC and components of host immunity, particularly neutrophils. The results will advance our understanding of host-pathogen interactions within the bladder, offer targets for new therapeutic and preventive strategies for UTI, and provide a foundation for new paradigms in host-pathogen crosstalk that can be generalized to other Gram-negative bacterial infections.