Invasion of the enteric nervous system by neurotropic Listeria monocytogenes

单核细胞增生性李斯特菌(Lm)是一种革兰氏阳性兼性胞内细菌，可导致两种类型的大脑 人类感染：弥漫性(脑膜炎/脑膜脑炎)和局灶性脑干(菱形脑炎)。 脑膜炎发生在免疫受损的情况下，可能是由于免疫系统未能限制 巨噬细胞在脾、肝等组织中呈指数级生长。这会导致高滴度菌血症，或者直接 与髓系细胞相关的血脑屏障(BBB)的入侵或LM的“隐形运输” 穿过BBB。相反，菱形脑炎是一种延迟性感染，发生在年轻人，否则 健康的有免疫能力的人，这表明感染依赖于细菌编码 神经毒性因素。这一提议的中心假设是，决定 菱形脑炎期间的神经趋向性在肠道而不是在大脑中调节关键的早期事件。 支持这一假说的是我们的初步数据，数据显示，当注射亲神经的LM时 静脉注射(绕过感染的肠道阶段)，它们不会传播到大脑。此外，其他人 表明菱形脑炎分离株在牛体内的生存和复制能力没有增强 与其他LM菌株相比，体外器官型脑片。直到最近，还可以研究菱形脑炎。 仅在奶牛或绵羊中，由于缺乏一种小型动物模型的LM脑干感染。然而，我们最近 结果表明，部分临床分离株(UKVDL9和SD4000)能优先定植于脑组织。 小鼠在感染过程的后期，血液中没有达到高滴度。这两个嗜神经性菌株WE 已报道属于谱系III，这是最小和最不具特征的LM分离物群。这项提案的目标是 目的是确定在李斯特菌病的肠道阶段，LM、UKVDL9和SD4000促进神经趋向性的因素。 我们预测嗜神经性LM可能在肠道感染的三个不同方面具有优势； 这些构成了该提案的三个具体目标。在目标1中，我们确定用于穿越肠道的路线 黏膜或炎症反应促进嗜神经性LM菌株在神经束中的定位 肠粘膜下层或迷走神经隐窝内围绕肠内淋巴隐窝的末端。在……里面 目的2，我们鉴定了一种新的LM表面蛋白，它介导了肠神经胶质细胞的增强侵袭 围绕肠道神经的类型。在目标3中，我们测试了这样的假设，即在 嗜神经性LM促进一种改变类型的细胞内运动，使细菌能够沿着 轴突的整个长度一直延伸到脑干。这项工作将推动李斯特菌病领域的发展，为 对这种威胁生命的食源性感染期间的神经趋向性的第一次真正的洞察，也可能为 为新的致病机理领域或微生物组相关研究了解细菌如何相互作用奠定基础 肠道神经系统的细胞。

Listeria monocytogenes (Lm) are Gram-positive, facultative intracellular bacteria that cause two types of brain infections in humans: diffuse (meningitis/meningoencephalitis) and focal brainstem (rhombencephalitis). Meningitis occurs in the setting of immune compromise, likely due to the failure of the immune system to limit exponential growth of Lm in tissues such as spleen or liver. This leads to high titer bacteremia and either direct invasion of the blood-brain-barrier (BBB) or “stealth transport” of Lm associated with myeloid-derived cells that cross the BBB. In contrast, rhombencephalitis is an infection of a delayed nature that occurs in young, otherwise healthy immune competent people, which suggests that the infection is dependent on bacterially encoded neurovirulence factors. The central hypothesis of this proposal is that the virulence factors which define neurotropism during rhombencephalitis mediate critical early events in the intestines, rather than in the brain. Support for this hypothesis comes from our preliminary data showing that when the neurotropic Lm are injected intravenously (bypassing the gut phase of the infection), they do not disseminate to the brain. In addition, others showed that rhombencephalitis isolates did not have an increased ability to survive and replicate in bovine organotypic brain slices ex vivo relative to other Lm strains. Until recently, rhombencephalitis could be studied only in cows or sheep due to the lack of a small animal model of Lm brainstem infections. However, we recently showed that some clinical isolates of Lm (UKVDL9 and SD4000) could preferentially colonize the brainstems of mice late in the course of infection, without reaching high titer in the blood. Both of the neurotropic strains we reported belong to lineage III, the smallest and least characterized group of Lm isolates. The goal of this proposal is to define the factors that promote neurotropism by Lm UKVDL9 and SD4000 during the gut phase of listeriosis. We predict that neurotropic Lm could have an advantage in three different aspects of the intestinal infection; these form the three Specific Aims of the proposal. In Aim 1, we determine if the route used to cross the gut mucosa or inflammatory response induced promotes localization of neurotropic Lm strains in neural bundles in the intestinal submucosa or within the vagal crypt endings surrounding lymphoid cryptopatches in the gut. In Aim 2, we identify the novel Lm surface protein that mediates enhanced invasion of enteric glial cells, the cell type that surrounds nerves in the gut. In Aim 3, we test the hypothesis that a truncated actA allele found in neurotropic Lm promotes an altered type of intracellular movement that allows the bacteria to migrate along the entire length of an axon all the way to the brainstem. This work will move the listeriosis field forward by providing the first real insights into neurotropism during this life-threatening foodborne infection and could also lay the groundwork for new areas of pathogenesis or microbiome-related research to understand how bacteria interact with cells of the enteric nervous system.