Deciphering mechanisms of Listeria placental-fetal invasion

项目摘要 单核细胞增多性李斯特菌(Lm)是一种革兰氏阳性的食源性胞内致病菌。 能够在人类中引起严重的侵袭性疾病。作为一种广泛存在的环境有机体， LM是食品加工设施的常见污染物，并对一些 美国历史上最大、最昂贵、最致命的食品召回事件。Lm是精选的多个 在怀孕期间从母亲传给胎儿的病原体。这些感染可能是 毁灭性的，因为通常一个受感染的妇女甚至不知道她已经感染了LM，直到 她流产或生下死胎或全身感染的婴儿。高死亡率和 尽管接受抗生素治疗，但伴随着LM侵袭性疾病的毁灭性后遗症是 迫切需要新的治疗策略来安全有效地管理LM侵袭性感染。 我们最近发现，精选的LM分离株具有更强的靶向胎盘的能力 而胎儿则基于细菌表面蛋白In1B表达的增加。增加的In1B是 足以将正常情况下胎儿定植频率较低的菌株转变为 这几乎可以避免100%的胎儿感染。InlB中自然发生的氨基酸变异 可能既增加了蛋白质的稳定性，又增强了对宿主生长因子受体c-Met的刺激 受InlB约束。MET在胎盘组织中大量表达，是胚胎和胚胎发育所必需的 胎盘发育。我们推测，表达InlB特定变异体的LM菌株表现出 通过操纵c-Met信号通路增强侵袭力，导致发病率增加 胎儿传播的可能性。这些菌株还刺激了一种强大的免疫反应，导致 胎盘屏障功能障碍与胎儿死亡。这项提案的具体目标将承担 Lm InlB功能评估揭示AS垂直传播的分子机制 以及研究母体和胎儿免疫信号对妊娠结局的影响。目标 1将从功能上定义InlB表面局部化和活性的潜在机制。这一目标将 确定有助于细菌细胞表面InlB稳定性的机制，并将检查 表面定位和分泌之间的功能差异。目标2将破译这些机制 Lm垂直传输的潜在In1B增强。我们将检查和比较LM的门户 进入怀孕小鼠，并探索宿主对LM感染影响妊娠结局的反应。 目标3将探索由高效率垂直传播引发的母婴防御 导致病理改变的菌株。这些研究将阐明精选的LM分离物如何获得 对胎盘/胎儿组织的高效率会导致破坏性的新生儿疾病和死亡。

Project Summary Listeria monocytogenes (Lm) is a gram-positive food-borne intracellular bacterial pathogen that is capable of causing serious invasive disease in humans. As a widespread environmental organism, Lm is a frequent contaminant of food processing facilities and has been responsible for some of the largest, most expensive, and most deadly food recalls in US history. Lm is one of a select number of pathogens that is transmitted during pregnancy from mother to fetus. These infections can be devastating, as often an infected woman does not even realize she has been infected with Lm until she miscarries or gives birth to a stillborn or systemically infected infant. The high mortality rate and devastating sequelae that accompany Lm invasive disease despite antibiotic treatment underlie the critical need for new therapeutic strategies to safely and effectively manage Lm invasive infections. We have recently discovered that select isolates of Lm have an enhanced ability to target the placenta and fetus based on increased expression of the bacterial surface protein InlB. Increased InlB is sufficient to transform a strain that normally exhibits a low frequency of fetal colonization to a strain that is capable off nearly 100% fetal infection. Naturally occurring amino acid variations within InlB may both increase protein stability and enhance stimulation of c-Met, the host growth factor receptor bound by InlB. Met is abundantly expressed by placental tissue and is required for embryonic and placental development. We hypothesize that Lm strains expressing select variants of InlB exhibit enhanced invasion through the manipulation of c-Met signaling pathways, leading to increased rates of fetal transmission. These strains additionally stimulate a robust immune response that leads to placental barrier dysfunction and fetal death. The specific aims of this proposal will undertake a functional assessment of Lm InlB to reveal molecular mechanisms underlying vertical transmission as well as examine the contributions of maternal and fetal immune signaling to pregnancy outcome. Aim 1 will functionally define the mechanisms underlying InlB surface localization and activity. This aim will define mechanisms that contribute to InlB stability at the bacterial cell surface and will examine functional differences between surface localization and secretion. Aim 2 will decipher the mechanisms underlying InlB enhancement of Lm vertical transmission. We will examine and compare portals of Lm entry in pregnant mice, and explore host responses to Lm infection that influence pregnancy outcome. Aim 3 will explore maternal and fetal defenses triggered by high efficiency vertically transmitted strains that contribute to pathology. These studies will clarify how select Lm isolates gain access with high efficiency to placental/fetal tissues to cause devastating forms of neonatal disease and death.