Dissecting the role of the Leishmania flagellum in pathogenicity

利什曼原虫是通过白蛉叮咬传播的寄生虫。感染利什曼原虫的人可以出现轻微的症状，局部皮肤病变，或危及生命的全身感染。目前全世界约有1 200万人受到感染;每年约有30 000人死于这种疾病，幸存者往往留下毁容的疤痕。利什曼原虫是一种小的单细胞，在人体内，它们生活在称为巨噬细胞的血细胞中。巨噬细胞最重要的工作之一是发现和破坏致病微生物。简单地说，巨噬细胞吞噬并消化一些入侵的微生物，然后通知免疫系统的其他细胞进行协调攻击并摧毁微生物。当巨噬细胞吞下利什曼原虫时，寄生虫不会死亡。相反，它会改变形状，繁殖，然后扩散感染其他细胞。我们想知道寄生虫如何与巨噬细胞沟通，以阻止其杀伤机制并促进自身的生存。我们认为寄生虫上的一个薄的突起，称为鞭毛，可以作为“细胞天线”或信号装置。我们现在想知道这种鞭毛的构建模块（蛋白质）是什么，以及为什么它似乎是寄生虫在宿主细胞中生存所必需的。我们已经生成了一系列鞭毛蛋白，现在将使用一种名为基因编辑的新技术来产生一组数百种突变寄生虫，其中鞭毛的不同部分被破坏。我们将在实验室中将这些突变体寄生虫与巨噬细胞混合，几天后观察哪些突变体成功进入巨噬细胞，哪些突变体没有成功进入巨噬细胞。我们将详细研究那些没有感染的突变体，以发现感染需要鞭毛的哪些部分，以及鞭毛及其连接如何帮助寄生虫在巨噬细胞的破坏机制中生存。

Leishmania are parasites that are transmitted by the bite of the sand fly. A person infected with Leishmania can develop mild symptoms, with localized skin lesions, or a life-threatening infection of the whole body. About 12 million people across the world are currently infected; about 30,000 people die every year from the disease and those that survive are often left with disfiguring scars. Leishmania parasites are small single cells and in the human body they live inside blood cells called macrophages. One of the most important jobs of the macrophage is the discovery and destruction of microbes that cause disease. Simply put, macrophages swallow and digest some of the invading microbes and then inform other cells of the immune system to mount a coordinated attack and destroy the microbes. When a macrophage swallows a Leishmania parasite, the parasite does not die. Instead it changes its shape, multiplies and then spreads to infect other cells. We want to find out how the parasites communicate with the macrophage to block its killing mechanisms and promote their own survival. We think a thin projection on the parasite, called the flagellum, could function as a 'cellular antennae' or signalling device. We now want to discover what the building blocks (proteins) of this flagellum are and why it appears to be required for parasite survival in the host cell. We have generated a list of flagellar proteins and will now use a new technology called gene editing to produce a set of several hundred mutant parasites, where different parts of the flagellum are disrupted. We will then mix these mutant parasites with macrophages in the laboratory and look a few days later to see which mutants were successful in entering the macrophages and which ones didn't make it. Those that fail to infect will be studied in detail to discover which parts of the flagellum are required for infection and how the flagellum and the connections it makes help the parasite to survive the destruction mechanisms of the macrophage.