Deciphering mechanisms of Listeria placental-fetal invasion

项目摘要 单核细胞增生李斯特菌（Listeria monocytogenes，Lm）是一种革兰氏阳性食源性胞内细菌病原体， 能够导致人类严重的侵入性疾病。作为一种广泛分布的环境生物， Lm是食品加工设施的常见污染物， 美国历史上最大、最昂贵、最致命的食品召回事件。Lm是选定数量的 在怀孕期间从母亲传播给胎儿的病原体。这些感染可能是 毁灭性的，因为通常感染的妇女甚至没有意识到她已经感染了Lm，直到 她流产或产下死胎或全身感染的婴儿。高死亡率和 尽管进行了抗生素治疗，但伴随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Lm的选择分离物具有增强的靶向胎盘的能力 和胎儿基于细菌表面蛋白InlB的表达增加。InlB增加是 足以将通常表现出低频率胎儿定殖的菌株转化为 几乎能造成100%胎儿感染InlB内天然存在的氨基酸变异 可能既增加蛋白质稳定性又增强对宿主生长因子受体c-Met的刺激 由InlB。Met在胎盘组织中大量表达，是胚胎发育和胚胎发育所必需的。 胎盘发育我们假设表达InlB的选择变体的Lm菌株表现出 通过操纵c-Met信号传导途径增强侵袭， 胎儿传播。这些菌株还刺激了强大的免疫应答， 胎盘屏障功能障碍和胎儿死亡。这项建议的具体目标将是： Lm InlB的功能评估，以揭示垂直传播的分子机制， 以及检查母体和胎儿免疫信号对妊娠结局的贡献。目的 1将在功能上定义InlB表面定位和活性的机制。这一目标将 定义有助于InlB在细菌细胞表面稳定性的机制，并将检查 表面定位和分泌之间的功能差异。目标二号将破解 Lm垂直传输的潜在InlB增强。我们将检查和比较Lm的门户网站 进入怀孕的小鼠，并探讨宿主对Lm感染的反应，影响怀孕的结果。 目的3将探讨由高效垂直传播引发的母体和胎儿防御 导致病理的菌株。这些研究将阐明选择的Lm分离株如何获得 对胎盘/胎儿组织的高效率导致毁灭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.