Role of TraJ in Neonatal E. coli Sepsis and Meningitis

TraJ 在新生儿大肠杆菌败血症和脑膜炎中的作用

• 批准号: 6717669
• 负责人: JULIE L BADGER
• 金额: $ 26.04万
• 依托单位: CHILDREN'S HOSPITAL OF LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-04-01 至 2005-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6717669
• 关键词: Escherichia coli; bacteria infection mechanism; bacterial disease; bacterial genetics; blood brain barrier; gel electrophoresis; gene expression; genetic transcription; laboratory rat; meningitis; newborn animals; phenotype; plasmids; polymerase chain reaction; secretory protein; septicemia; tissue /cell culture; virulence

DESCRIPTION (provided by applicant): Despite the use of modern therapeutics and diagnostic measures, neonatal bacterial sepsis and meningitis continues to be a disease with unacceptable rates of morbidity and mortality. The fatality rate of this disease is 15-75 percent; furthermore, approximately 50 percent of meningitis survivors have significant neurological and developmental abnormalities. The primary, route of infection for E. coli K1 (the most common causative agent of gram-negative meningitis) is oral. Following intestinal colonization, bacteria translocate through the GI tract to extra-intestinal sites of mesenteric lymph nodes (MLN), liver, spleen, and the blood. E. coli K1 then multiply systemically within the bloodstream reaching a necessary threshold of bacteremia to gain access to the central nervous system (CNS). Recently we identified an E. coli K1 plasmid-encoded blood-brain barrier (BBB) invasion gene, traJ, with homology to traJ of various F-like plasmid tra operons. Our preliminary data indicate that the traJ mutation specifically attenuates dissemination from the MLN to the liver, spleen, blood, and the CNS in the neonatal rat. In addition, although animals orally infected with the traJ mutant demonstrated a decrease or no recoverable bacteria in the liver or spleen, these tissues showed a significant inflammatory response. In vitro studies determined that the traJ mutant is taken-up less by macrophages and shows a loss of a 55 kDa-secreted protein. The central hypothesis of this application is that TraJ controls the expression of a set of genes whose products (i.e., 55 kDa secreted protein) are involved in E. coli K1 dissemination, systemic infection and crossing the BBB, and these events within the disease process occur via TraJ-dependent interactions with professional phagocytes. The following proposed experiments are designed to test and substantiate our hypotheses. We aim to 1) Elucidate the genetic and molecular characteristics of the traJ region and plasmid, evaluate the ability of the endogenous plasmid to self-transfer, and determine the potential role of the traJ-containing plasmid in E. coli K1 neonatal rat virulence, 2) Evaluate the function of the TraJ-regulated proteins (i.e., 55 kDa-secreted protein) in E. coli K1 systemic dissemination and meningitis, and 3) Determine the mechanism of TraJ-dependent host inflammatory response in the neonatal rat. Improved knowledge of molecular mechanisms for early systemic dissemination and the exact interplay of the host inflammatory response during these events will assist in achieving our long-term goal of identifying novel rational approaches to development of new treatments and preventive strategies for E. coli K1 sepsis and meningitis.

描述（由申请人提供）：尽管使用了现代治疗和诊断措施，新生儿细菌性败血症和脑膜炎仍然是一种发病率和死亡率不可接受的疾病。该病的死亡率为15-75%；此外，大约50%的脑膜炎幸存者有明显的神经和发育异常。大肠杆菌 K1（革兰氏阴性脑膜炎最常见的病原体）的主要感染途径是口腔。肠道定植后，细菌通过胃肠道易位至肠系膜淋巴结 (MLN)、肝脏、脾脏和血液等肠外部位。然后，大肠杆菌 K1 在血流中全身繁殖，达到菌血症所需的阈值，从而进入中枢神经系统 (CNS)。最近，我们鉴定了大肠杆菌K1质粒编码的血脑屏障（BBB）入侵基因traJ，与各种F样质粒tra操纵子的traJ具有同源性。我们的初步数据表明，traJ 突变特异性减弱新生大鼠中从 MLN 到肝脏、脾脏、血液和 CNS 的传播。此外，虽然口服感染traJ突变体的动物肝脏或脾脏中的细菌减少或没有可恢复的细菌，但这些组织表现出显着的炎症反应。体外研究确定 traJ 突变体被巨噬细胞摄取较少，并且显示出 55 kDa 分泌蛋白的损失。该应用的中心假设是 TraJ 控制一组基因的表达，这些基因的产物（即 55 kDa 分泌蛋白）参与大肠杆菌 K1 传播、全身感染和穿过 BBB，并且疾病过程中的这些事件通过 TraJ 依赖性与专业吞噬细胞的相互作用发生。以下提出的实验旨在测试和证实我们的假设。我们的目的是：1) 阐明 traJ 区域和质粒的遗传和分子特征，评估内源质粒自我转移的能力，并确定含有 traJ 的质粒在大肠杆菌 K1 新生大鼠毒力中的潜在作用，2) 评估 TraJ 调节蛋白（即 55 kDa 分泌蛋白）在大肠杆菌 K1 系统中的功能 传播和脑膜炎，3) 确定新生大鼠中 TraJ 依赖性宿主炎症反应的机制。提高对早期全身传播的分子机制以及这些事件期间宿主炎症反应的确切相互作用的了解将有助于实现我们的长期目标，即确定新的合理方法来开发大肠杆菌 K1 败血症和脑膜炎的新治疗方法和预防策略。