Unveiling the protein landscape of the African trypanosome cell surface and chasing down potential targets for therapeutic intervention

被忽视的热带病是一种多种多样的疾病，主要在世界上最贫穷的人口中流行。世界卫生组织最重要的10种被忽视的热带疾病中有3种--非洲锥虫病(又称昏睡病)、利什曼病和恰加斯病--是由密切相关的单细胞寄生虫引起的。人类感染非洲锥虫是在受感染的采采蝇吃血的时候引起的。如果不治疗，这种疾病会通过一般的健康状况恶化，直到昏迷和死亡。目前使用的对抗锥虫的药物陈旧、有毒，而且由于出现耐药性而失败。迫切需要新的研究来确定潜在的新治疗选择。非洲锥虫的一个不同寻常的方面是，它们在人体血液中繁殖，完全可以看到人体的防御系统。它们通过定期改变细胞表面以逃避宿主的识别来做到这一点。然而，寄生虫表面的许多分子发挥着基本的功能，不能改变。锥虫将这些细胞置于细胞表面一个特殊的、受保护的区域。识别暴露在表面的不变分子并了解这种保护性分离是如何维持的，这对揭示锥虫可能对新疗法敏感的方式具有重大的科学意义和实用价值。使用由MRC资助的组合方法，我先前已经确定了非洲锥虫细胞表面的组成。我现在的目标是利用这一知识来挑选出那些对寄生虫在感染期间的生存至关重要的不变表面分子。为此，我建议利用现代DNA测序技术的一些力量来测试哪些细胞表面基因在沉默时会导致寄生虫在宿主体内死亡。一种类似的方法将被用来不仅识别细胞表面基因，而且识别寄生虫用来维持细胞表面组织的任何基因，这对于逃避宿主的免疫攻击是如此关键。最后，我建议测试这些暴露在表面的分子作为疫苗的潜力。我的初步实验表明，我可以使用转基因寄生虫来筛选寄生虫表面可被免疫系统访问的分子。我建议开发这项测试，并在人类疾病的动物模型中测试最有希望的候选对象。拟议的工作将增加我们对一种重要人类寄生虫的基本生物学的理解，并通过揭示必要的表面分子，为开发新的治疗方法提供第一步。

Neglected tropical diseases are a diverse group of diseases that thrive mainly among the poorest of the world's populations. Three of the World Health Organisation's 10 most significant neglected tropical diseases - African trypanosomiasis (also known as sleeping sickness), leishmaniasis, and Chagas' disease - are caused by closely-related single-celled parasites. Human infection with African trypanosomes is brought about when an infected tsetse fly takes a blood meal. Without treatment the disease progresses through general ill health to coma and death. Current drugs in use against trypanosomes are old, toxic and failing due to emergence of resistance. Urgent new research is needed to identify potential new therapeutic options.An unusual aspect of African trypanosomes is that they multiply in the human blood in full view of the body's defence systems. They do this by periodically changing their cell surface to escape recognition by the host. However, many molecules on the parasite surface perform essential functions and cannot be changed. Trypanosomes place these in a special, protected domain on the cell surface. Identifying surface-exposed invariant molecules and understanding how this protective segregation is maintained are of major scientific interest, as well as of practical utility in uncovering ways in which trypanosomes may be vulnerable to new therapies.Using a combinatorial approach funded by the MRC, I have previously identified the composition of the African trypanosome cell surface. I now aim to exploit this knowledge to single out those invariant surface molecules that are essential to the survival of the parasite during infection. For this, I propose to harness some of the power of modern DNA sequencing technologies to test which cell surface genes, when silenced, cause the parasite to die inside the host. A similar method will be used to identify not only cell surface genes, but any genes that the parasite uses to maintain the cell surface organisation, which is so critical to escaping the host immune attack. Finally, I propose to test those surface-exposed molecules for their potential as vaccines. My pilot experiments show that I can use genetically-modified parasite to screen for molecules on the parasite surface that are accessible to the immune system. I propose to develop this assay and test the most promising candidates in an animal model of human disease.The proposed work will increase our understanding of the fundamental biology of a significant human parasite, and also, by exposing essential surface molecules, provide the first steps in developing new treatments.