Department of Neuroscience Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
Department of Neurosciences, Karolinska Institutet, Stockholm, Sweden.
Front Immunol. 2018 Dec 11;9:2877. doi: 10.3389/fimmu.2018.02877. eCollection 2018.
Circumventricular organs (CVOs), neural structures located around the third and fourth ventricles, harbor, similarly to the choroid plexus, vessels devoid of a blood-brain barrier (BBB). This enables them to sense immune-stimulatory molecules in the blood circulation, but may also increase chances of exposure to microbes. In spite of this, attacks to CVOs by microbes are rarely described. It is here highlighted that CVOs and choroid plexus can be infected by pathogens circulating in the bloodstream, providing a route for brain penetration, as shown by infections with the parasites . Immune responses elicited by pathogens or systemic infections in the choroid plexus and CVOs are briefly outlined. From the choroid plexus trypanosomes can seed into the ventricles and initiate accelerated infiltration of T cells and parasites in periventricular areas. The highly motile trypanosomes may also enter the brain parenchyma from the median eminence, a CVO located at the base of the third ventricle, by crossing the border into the BBB-protected hypothalamic arcuate nuclei. A gate may, thus, be provided for trypanosomes to move into brain areas connected to networks of regulation of circadian rhythms and sleep-wakefulness, to which other CVOs are also connected. Functional imbalances in these networks characterize human African trypanosomiasis, also called sleeping sickness. They are distinct from the sickness response to bacterial infections, but can occur in common neuropsychiatric diseases. Altogether the findings lead to the question: does the neglect in reporting microbe attacks to CVOs reflect lack of awareness in investigations or of gate-opening capability by microbes?
室周器官（CVOs）位于第三和第四脑室周围，与脉络丛类似，其中的血管没有血脑屏障（BBB）。这使它们能够感知血液循环中的免疫刺激性分子，但也增加了暴露于微生物的机会。尽管如此，微生物对 CVOs 的攻击很少被描述。这里强调的是，CVOs 和脉络丛可以被循环血液中的病原体感染，为病原体穿透大脑提供了途径，如寄生虫感染所示。简要概述了病原体或脉络丛和 CVOs 中的全身感染引起的免疫反应。从脉络丛，锥虫可以进入脑室，并启动脑室周围区域 T 细胞和寄生虫的加速浸润。高度运动的锥虫也可以从中脑导水管周围灰质（位于第三脑室底部的 CVO）穿过边界进入 BBB 保护的下丘脑弓状核，从而进入大脑实质。因此，对于锥虫来说，可能会提供一个进入与昼夜节律和睡眠觉醒调节网络连接的大脑区域的门，其他 CVOs 也与这些网络连接。这些网络中的功能失衡是人类非洲锥虫病（也称为昏睡病）的特征。它们与细菌感染的疾病反应不同，但也可能发生在常见的神经精神疾病中。总的来说，这些发现提出了一个问题：对 CVOs 中微生物攻击的忽视是否反映了对调查的缺乏认识或微生物开放门的能力？
