Dissecting the role of the Leishmania flagellum in pathogenicity

利什曼原虫是通过沙蝇叮咬传播的寄生虫。感染利什曼病的人可能会出现轻微的症状，出现局部皮肤损害，或者全身感染，危及生命。目前，全球约有1200万人受到感染；每年约有3万人死于这种疾病，幸存下来的人往往会留下难看的疤痕。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内。巨噬细胞最重要的工作之一是发现和摧毁导致疾病的微生物。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发动协同攻击，摧毁这些微生物。当巨噬细胞吞噬利什曼原虫时，该寄生虫不会死亡。相反，它会改变形状，繁殖，然后传播，感染其他细胞。我们想要找出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，这种寄生虫上的一个叫做鞭毛的细小突起，可以起到‘细胞天线’或信号装置的作用。我们现在想要发现这种鞭毛的构建块(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。我们已经生成了一份鞭毛蛋白质清单，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。然后，我们将在实验室将这些突变的寄生虫与巨噬细胞混合，并在几天后查看哪些突变成功进入巨噬细胞，哪些没有进入。那些未能感染的寄生虫将被详细研究，以发现感染需要鞭毛的哪些部分，以及鞭毛及其建立的连接如何帮助寄生虫通过巨噬细胞的破坏机制存活下来。

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.