The role of human pentraxins in the Leishmania-vector lifecycle

利什曼病是一种由原生动物寄生虫利什曼原虫引起的疾病，由白蛉沙蝇媒介传播。利什曼病有一系列不同严重程度的临床形式，其中一些可导致器官衰竭和死亡。世界卫生组织估计，每年有超过60万新病例，超过10亿人生活在流行地区。为了完成其生命周期并传播给新的宿主，利什曼原虫必须通过附着在沙蝇的肠道上来抵抗沙蝇的排便。然而，这种附着的机制因利什曼原虫和沙蝇的种类而异。一些沙蝇物种只允许少数特定利什曼原虫物种（限制性媒介）存活和成熟。其中一种沙蝇的附着机制已经发表，沙蝇的中肠受体与利什曼原虫表面分子LPG上的特定糖相互作用。其他沙蝇物种可以支持一系列利什曼原虫物种（允许载体）的成熟，但这些沙蝇的附着机制尚不清楚，被认为是不依赖于液化石油气的。最近有人提出，一些蠓是利什曼原虫的媒介，其中肠附着机制尚不清楚。该项目以全球传染病健康为主题，将研究人类血清成分戊烷素的作用，看看它们是否将利什曼原虫与沙蝇和蠓的中肠交联。它还将研究利什曼-中肠结合的替代机制和戊烷素在载体中的不同作用，希望最终阻断寄生虫的结合。这个项目的一部分是学习如何进行中肠附着测定。中肠附着试验包括将载体中肠移除并纵向打开，然后将寄生虫放在顶部，以观察在一系列条件下结合的差异。也可以使用感染寄生虫的媒介。利用这种技术，我们可以研究整个生物体的生理学。在过去的几年里，我在这些检测方面积累了很多经验。我也花时间回顾文献，比较使用这种方法的研究。可以使用适当的统计测试比较不同方案和条件的结果，使我们能够量化我们的数据。为了观察抗戊烷素抗体和化合物的效果，研究人员进行了苍蝇感染试验。生物信息学还将用于寻找媒介受体候选物，并查看利什曼原虫或媒介是否具有与人血清中发现的成分相似的成分。通过参加LSHTM的一个模块，我扩展了我在生物信息学方面的知识。Biacore表面等离子体共振、western blots和elisa被用于了解寄生虫和沙蝇与人血清成分的结合相互作用。Western blots和elisa使我们能够看到利什曼原虫或媒介中肠的哪些部分与人类血清成分结合。Biacore表面等离子体共振系统允许我们了解更多关于结合相互作用的信息，例如，我们可以发现结合强度以及结合/解离速率。我在这方面的经验有限，但我的合作导师是专家，这意味着我有机会学到很多东西，并扩展我的跨学科技能。在这项研究中，共聚焦显微镜也被用于观察这些人类血清成分与寄生虫和中肠表面的结合。通过LSHTM的成像单元，我已经学会了如何使用共聚焦显微镜。我参加了LSHTM的四个硕士模块和一系列可转换技能课程。最近，我在哥伦比亚卡塔赫纳举行的WorldLeish7会议上展示了我的作品海报。

Leishmaniasis is a disease caused by the protozoan parasite species Leishmania and is spread by the phlebotomine sand fly vector. Leishmaniasis has an array of clinical forms with varying severity, of which some can lead to organ failure and death. The WHO have estimated there are over 600,000 new cases every year and over one billion people living in endemic areas. In order to complete its lifecycle and be transmitted to a new host, the Leishmania parasite must resist being defecated by the sand fly by attaching to the sand fly gut. However, the mechanism of this attachment differs depending on the species of Leishmania and sand fly. Some sand fly species only allow the survival and maturation of a few particular Leishmania species (restrictive vector). An attachment mechanism for one of these sand fly species has already been published with a sand fly midgut receptor interacting with specific sugars presented on a Leishmania surface molecule called LPG. Other sand fly species can support the maturation of a range of Leishmania species (permissive vector) but the mechanism of attachment for these sand flies is still unclear and it is thought to be LPG-independent. More recently it has been suggested that some midges are vectors of Leishmania, with the midgut attachment mechanism unknown. This project comes under the theme of global infectious health and will look at the role of the human serum components pentraxins, to see if they cross-link the Leishmania parasite to the sand fly and midge midgut. It will also look at alternative Leishmania-midgut binding mechanisms and different roles for pentraxins within the vector, with the hope of eventually blocking parasite binding. One part of this project has been to learn how to carry out midgut attachment assays. Midgut attachment assays involve the vector midgut being removed and opened longitudinally with parasites then being placed on top to see how binding differs under a range of conditions. Vectors infected with parasites can also be used. Using this technique allows us to study whole organism physiology. I have gained a lot of experience with these assays in the past couple of years. I have also spent time reviewing the literature, comparing studies which use this method. Results of different protocols and conditions can be compared using the appropriate statistical tests allowing us to quantify our data. Fly infections have been carried out to look at the effects of anti-pentraxin antibodies and compounds. Bioinformatics will also be used to look for vector receptor candidates and to see if Leishmania or the vectors have a similar component to that found in human serum. I have been able to expand my knowledge in bioinformatics by attending a module ran at LSHTM. Biacore surface plasmon resonance, western blots and ELISAs are being used to learn about the binding interaction of parasites and sand flies with the human serum components. Western blots and ELISAs allow us to see what parts of the Leishmania parasite or vector midgut the human serum components are binding to. The Biacore surface plasmon resonance system allows more information to be learnt about a binding interaction, for example we can find out about binding strength as well as rates of association/dissociation. I have limited experience in this technique, however my co-supervisor is an expert meaning I have the opportunity to learn a great deal and expand my interdisciplinary skill set. Confocal microscopy is also being used in this study to look at the binding of these human serum components to parasite and midgut surfaces. I have been able to learn how to use the confocal microscope through the imaging unit at LSHTM. I have attended four MSc modules at LSHTM and a range of the transferable skills courses. I was recently able to present a poster of my work at the WorldLeish7 conference in Cartagena, Colombia.