食品伙伴网服务号
 
 
当前位置: 首页 » 专业英语 » 专业知识 » 正文

科学:埃博拉病毒(Ebola)对人体的具体作用

放大字体  缩小字体 发布日期:2014-08-18  来源:食品翻译中心
核心提示:埃博拉病毒在西非国家的空前爆发,依赖于突袭到宿主身上的一个可怕的病毒种属,扎伊尔埃博拉病毒(Zaire ebolavirus),丝状病毒家族成员。其致病机制是首先使免疫应答失去防御,然后使血管系统瓦解。这种病毒发展如此之迅速,所以研究者们必须努力梳理出事故发生的前因后果,尤其是正当爆发的时候。关于此病毒很多方面还属未知,包括病毒的RNA通过劫持宿主细胞的工作机制获得的7个蛋白中的部分蛋白的作用,以及病毒扩散到机体前就将其击退所必需的免疫应答的类型。但是研究者们可以通过病毒培养实验分析出活病毒是如何攻击不同

Behind the unprecedented Ebola outbreak in West Africa lies a species with an incredible power to overtake its host. Zaire ebolavirus and the family of filoviruses to which it belongs owe their virulence to mechanisms that first disarm the immune response and then dismantle the vascular system. The virus progresses so quickly that researchers have struggled to tease out the precise sequence of events, particularly in the midst of an outbreak. Much is still unknown, including the role of some of the seven proteins that the virus’s RNA makes by hijacking the machinery of host cells and the type of immune response necessary to defeat the virus before it spreads throughout the body. But researchers can test how the live virus attacks different cells in culture and can observe the disease’s progression in nonhuman primates—a nearly identical model to humans.

Here are some of the basic things we understand about how Ebola and humans interact.

What does Ebola do to the immune system?

Once the virus enters the body, it targets several types of immune cells that represent the first line of defense against invasion. It infects dendritic cells, which normally display signals of an infection on their surfaces to activate T lymphocytes—the white blood cells that could destroy other infected cells before the virus replicates further. With defective dendritic cells failing to give the right signal, the T cells don’t respond to infection, and neither do the antibodies that depend on them for activation. The virus can start replicating immediately and very quickly.

Ebola, like many viruses, works in part by inhibiting interferon—a type of molecule that cells use to hinder further viral reproduction. In a new study published today in Cell Host & Microbe, researchers found that one of Ebola’s proteins, called VP24, binds to and blocks a transport protein on the surface of immune cells that plays an important role in the interferon pathway.

Curiously, lymphocytes themselves don’t become infected with the virus, but a series of other factors—a lack of stimulation from some cells and toxic signals from others—prevent these primary immune cells from putting up a fight.

How does Ebola cause hemorrhaging?

As the virus travels in the blood to new sites, other immune cells called macrophages eat it up. Once infected, they release proteins that trigger coagulation, forming small clots throughout the blood vessels and reducing blood supply to organs. They also produce other inflammatory signaling proteins and nitric oxide, which damage the lining of blood vessels, causing them to leak. Although this damage is one of the main symptoms of infection, not all patients exhibit external hemorrhaging—bleeding from the eyes, nose, or other orifices.

Does the virus target certain organs?

Ebola triggers a system-wide inflammation and fever and can also damage many types of tissues in the body, either by prompting immune cells such as macrophages to release inflammatory molecules or by direct damage: invading the cells and consuming them from within. But the consequences are especially profound in the liver, where Ebola wipes out cells required to produce coagulation proteins and other important components of plasma. Damaged cells in the gastrointestinal tract lead to diarrhea that often puts patients at risk of dehydration. And in the adrenal gland, the virus cripples the cells that make steroids to regulate blood pressure and causes circulatory failure that can starve organs of oxygen.

What ultimately kills Ebola patients?

Damage to blood vessels leads to a drop in blood pressure, and patients die from shock and multiple organ failure.

Why do some people survive infection?

Patients fare better with supportive care, including oral or intravenous rehydration that can buy time for the body to fight off infection. But studies on blood samples from patients during the 2000 outbreak of a different Ebola strain in Uganda have also identified genes and other markers that seem to be predictive of survival. Patients who recovered had higher levels of activated T cells in their blood and had certain variants of a gene that codes for surface proteins that white blood cells use to communicate. Earlier this year, researchers found a new association between survival and levels of sCD40L, a protein produced by platelets that could be part of the body’s attempt to repair damaged blood vessels. The authors note that markers like sCD40L could suggest new therapies that augment the repair mechanisms most important for survival.

*Correction, 15 August, 1:51 p.m.: This article has been corrected to note that nitric oxide, not nitrous oxide, damages blood vessels.

*The Ebola Files: Given the current Ebola outbreak, unprecedented in terms of number of people killed and rapid geographic spread, Science and Science Translational Medicine have made a collection of research and news articles on the viral disease freely available to researchers and the general public.

 

Posted in Health Ebola

参考译文:

   埃博拉病毒在西非国家的空前爆发,依赖于突袭到宿主身上的一个可怕的病毒种属,扎伊尔埃博拉病毒(Zaire ebolavirus),丝状病毒家族成员。其致病机制是首先使免疫应答失去防御,然后使血管系统瓦解。这种病毒发展如此之迅速,所以研究者们必须努力梳理出事故发生的前因后果,尤其是正当爆发的时候。关于此病毒很多方面还属未知,包括病毒的RNA通过劫持宿主细胞的工作机制获得的7个蛋白中的部分蛋白的作用,以及病毒扩散到机体前就将其击退所必需的免疫应答的类型。但是研究者们可以通过病毒培养实验分析出活病毒是如何攻击不同的细胞,并能观察这种疾病在非人类灵长类动物——和人类几乎完全相同的模型——体内的进展。

下面是我们所知的一些关于埃博拉病毒和人体如何相互作用的基本情况。

埃博拉病毒对免疫系统有什么影响?

一旦病毒侵入人体,它就会以几类免疫细胞作为目标,这些免疫细胞通常作为人体第一道防线抵御外界入侵。病毒会感染树突细胞,正常情况下,树突细胞会在细胞表面显示出被感染的信号,从而激活T淋巴细胞——白细胞的一种。这种白细胞能够在病毒进行下一步复制前消灭掉其他已被感染的细胞。有缺陷的树突细胞不能发出正确的信号,T细胞就无法对感染作出应答,那样,依赖于它们的抗体也就不能被激活发生作用,病毒立刻开始迅速地复制。

和很多病毒一样,埃博拉病毒需要通过抑制干扰素的部分作用才能正常工作,干扰素是细胞用来阻止病毒进一步复制的一类分子。在《细胞宿主与微生物》(Cell Host & Microbe)杂志今天发表的一项新的研究中,研究者们发现,埃博拉病毒中的一个叫作VP24的蛋白,能结合免疫细胞表面上的一个运输蛋白以阻止它的运输,这个运输蛋白在干扰素通路上起着重要的作用。

奇怪的是,淋巴细胞自己并不会被病毒感染,但是一系列其他的因素——如缺乏某些细胞的刺激和来自其他细胞的有害信号——阻止了这些初级免疫细胞发起反抗。

埃博拉病毒是怎样导致出血热的?

当这种病毒在血液中被运输到新的据点,另一种叫作巨噬细胞的免疫细胞会把它吞噬掉。一旦发生感染,它们就会释放能触发凝血作用的蛋白,在血管中形成许多小的凝结块,使供应给各个器官的血液减少。它们还会产生造成其他炎症反应的信号蛋白和一氧化氮,一氧化氮会破坏血管内膜,导致血液渗漏。这种损伤是感染的主要症状之一,但并不是所有的患者都会表现出外在的出血现象——如眼睛、鼻孔或其他孔隙出血等症状。

病毒会以某些特定器官作为目标吗?

埃博拉病毒会引发系统全面性的炎症反应和发热现象,还会损伤体内的各种组织,要么通过促使免疫细胞如巨噬细胞释放炎症分子,要么通过入侵细胞并使它们从内部被吞噬而造成直接的破坏。但是在肝脏中造成的后果尤为严重,埃博拉病毒会清除掉肝脏中那些产生凝血蛋白所必需的细胞和其他重要的血浆成分。胃肠道中损伤的细胞会导致腹泻,这通常会给病人带来脱水的危险。而在肾上腺里,病毒会通过削弱细胞利用类固醇调节血压的作用,导致循环系统紊乱,从而使器官因缺氧而衰竭。

是什么最终导致埃博拉病毒患者死亡?

血管的损伤导致血压下降,患者最终会死于休克和多发性器官衰竭。

为什么有些人能够在感染中幸存下来?

通过口服液或静脉输液等辅助治疗手段能够使患者得以好转,这些治疗手段能给机体击败感染赢得更多的时间。2000年,一种埃博拉病毒异种菌株引发的感染在乌干达爆发。通过对其病患进行血液取样研究,证实基因和其他标记物似乎也对幸存者有一定的预防作用。在那些恢复健康的患者血液里,发现有较高活性水平的T细胞和一个基因的某些变异。这个基因是编码白细胞用于通信的表面蛋白的。今年年初,研究者们发现幸存者与sCD40L水平之间有一种新的联系。sCD40L是由血小板产生的一种蛋白,它可能参与机体血管损伤的修复机制。作者指出,像sCD40L这样的标记物表明可能有新的治疗方案,即增强这种可能对幸存者来说最重要的修复机制。

*埃博拉病毒文件:针对当前埃博拉病毒的爆发及其空前的死亡人数与地理传播速度,《科学》和《科学与转化医学》已经联合发布关于这种病毒性疾病的研究和相关新闻报道的专题以供研究者和普通大众自由查阅。
更多翻译详细信息请点击:http://www.trans1.cn
编辑:foodtrans

 
关键词: 埃博拉病毒 Ebola
[ 网刊订阅 ]  [ 专业英语搜索 ]  [ ]  [ 告诉好友 ]  [ 打印本文 ]  [ 关闭窗口 ] [ 返回顶部 ]
分享:

 

 
推荐图文
推荐专业英语
点击排行
 
 
Processed in 0.162 second(s), 16 queries, Memory 0.92 M