Priming vaccinology for livestock trypanosomes: definition and diversity of the cell surface landscape

非洲锥虫是血液中的单细胞寄生虫，在非洲引起毁灭性的牲畜疾病，并已蔓延到南美洲和亚洲的部分地区。这些寄生虫对粮食安全构成重大威胁，并对世界上一些最贫穷地区的肉类和乳制品生产造成重大负担（例如，牲畜疾病Nagana每年杀死约300万头牛，估计造成非洲经济损失约40亿美元）。目前还没有针对这些寄生虫的疫苗，诊断工具有限，并且日益增加的耐药性使得迫切需要新药物或新方法来提供现有药物。了解细胞表面对于上述挑战至关重要：表面是基于抗体的药物递送的结合位点，它包含可以区分不同类型锥虫感染的蛋白质，并且表面生物学的变化是出现耐药性的一种手段。此外，最近的工作已经显示出基于表面分子的针对非洲锥虫的保护性免疫，这强烈表明可以通过筛选不变的表面蛋白来找到针对这些寄生虫的有效疫苗。然而，这些领域的研究由于缺乏关于非洲锥虫物种表面蛋白质的信息而受到极大阻碍，这些蛋白质造成了牲畜疾病的最大负担。此外，我们目前无法比较不同锥虫物种的表面，以了解表面功能如何，或者表面的哪些部分是高度可变的或受功能限制的（因此不能改变）。我们以前已经开发了用于作为人类疾病模型的非洲锥虫实验室菌株的细胞表面组分的稳健分离和验证的方法。在这里，我们将使用这些方法来定义在3种非洲锥虫表面发现的对牲畜疾病最重要的蛋白质。使用从动物疾病模型中提取的寄生虫，我们将比较寄生虫表面的组成（存在哪些蛋白质）和序列（蛋白质的哪些部分发生变化），以确定可能受功能限制且不同物种共有的共享组件。我们将使用这些共享的组件，结合我们和其他人为家畜锥虫物种的遗传修饰开发的工具，以了解物种的表面如何不同，并测试免疫系统的蛋白质可及性。最后，我们将使用一种可以识别蛋白质并准确测量其丰度的方法来测试单个物种表面的变化程度。这些数据将显示这些重要寄生虫的表面变化有多快-无论是在一个物种内还是在更长的时间内。它还将确定表面的共同不变成分，这些成分是疫苗和药物输送的潜在目标，并开始从功能上了解不同寄生虫的表面。

African trypanosomes are single-celled parasites of the blood that cause devastating diseases of livestock in Africa, and have also spread to parts of South America and Asia. These parasites are a substantial threat to food security and impose a major burden on meat and dairy production in some of the poorest areas of the world (for example, the livestock disease nagana kills ~3 million cattle per year and creates an estimated loss of ~$4 billion from African economies). There is currently no vaccine against these parasites, diagnostic tools are limited, and increasing drug resistance makes the need for new drugs or new methods to deliver existing drugs urgent. Understanding the cell surface is critical to the challenges above: the surface is the site of binding for antibody-based drug delivery, it contains proteins that could distinguish between different types of trypanosome infection, and changes to surface biology are a means for the emergence of drug resistance. Moreover, recent work has shown protective immunity against African trypanosomes based on surface molecules, strongly suggesting that an effective vaccine against these parasites could be found by screening invariant surface proteins. However, research in these areas is greatly hindered by lack of information on the proteins that make up the surface in the African trypanosome species that cause the greatest burden of livestock disease. In addition, we are currently unable to compare the surfaces for different trypanosome species to understand how the surface functions, or what parts of the surface are highly variable or constrained by function (and hence cannot change). We have previously developed methods for robust isolation and validation of cell surface components for a laboratory strain of African trypanosomes used as a model for human disease. Here, we will use these methods to define the proteins found at the surface of the 3 species of African trypanosomes that are most important for livestock disease. Using parasites taken from animal disease models, we will compare the parasite surfaces in terms of composition (which proteins are present) and also sequence (which parts of the proteins change) in order to identify shared components that are likely constrained by function and common to the different species. We will use these shared components, in combination with tools we and others have developed for genetic modification of livestock trypanosome species, to understand how the surfaces of the species differ and test for protein accessibility to the immune system. Finally, we will use a method that can identify proteins and also accurately measure their abundance to test for the degree of variation in the surface that occurs in an individual species. These data will show how quickly the surface of these important parasites changes - both within a species and over longer periods. It will also identify shared invariant components of the surface that are potential targets for vaccines and drug delivery, and begin to functionally understand the surfaces of the different parasites.