Host-parasite interactions in chronic infection

弓形虫是一种高度流行的寄生虫，感染约1/3的人类和各种动物。在人类和动物中，弓形虫主要在大脑和肌肉中建立慢性感染。弓形虫是导致绵羊流产的主要原因之一，因此对养殖业产生经济影响。动物感染还为人类通过摄入受感染牲畜未煮熟的肉而传播病毒创造了一个宿主。尽管慢性包囊对于这种人畜共患病原体的传播至关重要，但我们对包囊如何形成、持续和影响其宿主知之甚少。弓形虫是破坏宿主细胞过程以获得自身利益的大师，并在感染早期分泌一系列促进其存活的蛋白质。分泌蛋白在慢性感染阶段的作用仍然研究不足，我们假设分泌因子对长期感染也是至关重要的。中枢神经系统和骨骼肌是慢性弓形虫感染的主要部位，寄生虫在细胞内形成包囊。至关重要的是，寄生虫转化为慢性阶段自发发生在神经元和肌肉（肌管）细胞中的高水平。该项目将应用高通量CRISPR筛选来识别建立慢性感染所需的分泌型寄生虫因子。筛选将在成纤维细胞（一种广泛使用的模型）和慢性感染特异性细胞类型（例如，神经元和肌管）。这将确定跨细胞类型保守的机制以及生态位特异性适应。慢性感染所必需的蛋白质将通过确定蛋白质定位，验证它们在寄生虫生存中的作用并确定相互作用伙伴来进一步研究。该项目将确定发展这种不可药用的寄生虫阶段的要求，并进一步了解宿主-寄生虫相互作用。它将寄生虫学，分子生物学，显微镜和下一代测序的培训与生物信息学培训的机会相结合。

Toxoplasma gondii is a highly prevalent parasite that infects ~1/3 of the human population and a wide range of animals. In both humans and animals, Toxoplasma establishes chronic infections, predominantly in the brain and muscles. Toxoplasma is one of the leading causes of abortion in sheep and so has an economic impact on the farming industry. Animal infections also create a reservoir for transmission to humans through ingestion of undercooked meat from infected livestock. Despite the chronic cyst being critical for transmission of this zoonotic pathogen, we understand little of how the cyst forms, persists and impacts its host.Toxoplasma is a master at subverting host cell processes for its own benefit, and secretes an array of proteins that promote its survival early in infection. The role of secreted proteins during the chronic stage of infection remains understudied, and we hypothesise that secreted factors are also crucial for long-term infection. The central nervous system and skeletal muscle are the predominant sites of chronic Toxoplasma infection where the parasite forms cysts within cells. Crucially, parasite conversion to the chronic stage occurs spontaneously at high levels in neuronal and muscle (myotube) cells. This project will apply high-throughput CRISPR screening to identify secreted parasite factors required for establishing chronic infection. Screening will be done in both fibroblasts, a widely used model, and chronic infection specific cell types (eg. neurons and myotubes). This will identify mechanisms that are conserved across cell-types as well as niche-specific adaptations. Proteins essential for chronic infection will be investigated further by determining protein localisations, verifying their role in parasite survival and identifying interaction partners. The project will identify requirements for the development of this undruggable parasite stage and further our understanding of host-parasite interactions. It combines training in parasitology, molecular biology, microscopy, and next-generation sequencing with the opportunity for training in bioinformatics.