Composition and formation of the cyst wall

摘要：弓形虫是一种广泛存在于哺乳动物体内的顶复门原虫， 鸟这是不寻常的，因为传播不需要通过其最终宿主，使T。 弓形虫通过其中间宿主进行克隆繁殖。t.弓形虫导致先天性感染， 免疫活性宿主和免疫受损宿主中的机会性感染。好发 这种寄生虫的中枢神经系统引起坏死性脑炎和眼睛引起 脉络膜视网膜炎是其对患者的主要威胁。这些疾病的发展是一个 在组织包囊内发现的缓殖子转变为活跃复制的结果 速殖子据认为，组织囊肿不是静态结构，而是定期破裂， 宿主细胞在慢性弓形虫病（即潜伏感染）中，宿主细胞内的组织囊肿很可能， 有规律地转化为速殖子，然后被免疫系统清除或隔离。 慢性弓形虫病小鼠的大脑中经常可见退化的囊肿。这种动态 包囊和复制形式之间的平衡导致反复的抗原刺激， 在慢性感染宿主中发现的持续抗体滴度。T.弓形虫 人类和其他动物的感染是由于组织囊肿允许这种感染的口腔传播的能力。 孢囊壁是T.刚地。 了解T.弓形虫发育生物学和囊壁的形成将为以下策略提供信息， 作为疫苗开发和治疗剂，以消除潜伏期并防止再激活 弓形虫病一些证据表明缓殖子的分化是应激介导的 囊壁（一种改良的寄生空泡膜）含有许多阶段特异性的 蛋白质和糖蛋白。我们的实验室小组已经确定了几个囊壁特异性蛋白质 其中几种具有O-糖基化的粘蛋白型结构域，并证明， 糖基化对于囊壁稳定性是重要的。CST1是一种囊壁糖蛋白，似乎是一种 我们假设其他的囊壁蛋白 与CST1相互作用形成囊壁。我们的实验室团队已经开发出了技术， 纯化囊壁，使得能够对该结构以及适应的BirA进行蛋白质组学表征 标签技术，使定义的囊肿壁相互作用组。此外，我们有 建立ppGalNAcTs敲除T.能够研究O-糖基化作用的弓形虫菌株 形成囊壁。采用蛋白质组学、免疫学和遗传学的综合方法 技术将被用来充分表征T.弓形虫囊壁蛋白质组及其重要性 识别的囊壁成分的相互作用。更好地理解形成 这些研究提供的囊壁将为新的策略提供基础， 消除潜伏感染，从而防止再激活弓形虫病。

ABSTRACT: Toxoplasma gondii is a ubiquitous Apicomplexan protozoan parasite of mammals and birds. It is unusual in that propagation does not require passage through its definitive host enabling T. gondii to propagate clonally through its intermediate hosts. T. gondii causes congenital infections in immune competent hosts and opportunistic infections in immune compromised hosts. The predilection of this parasite for the central nervous system causing necrotizing encephalitis and for the eye causing chorioretinitis constitutes its major threat to patients. The development of these diseases is a consequence of the transition of bradyzoites, found within tissue cysts into actively replicating tachyzoites. It is believed that tissue cysts are not static structures, but regularly rupture reinvading new host cells. It is likely that in chronic toxoplasmosis, i.e. latent infection, tissue cysts within host cells, regularly transform to tachyzoites which are removed or sequestered by the immune system. Degenerating cysts are often seen in the brains of mice with chronic toxoplasmosis. Such a dynamic equilibrium between encysted and replicating forms leads to recurrent antigenic stimulation and the persistent antibody titers found in chronically infected hosts. The widespread distribution of T. gondii in humans and other animals is due to the ability of tissue cysts to permit oral transmission of this infection. The cyst wall is the critical structure for survival, reactivation and transmission of T. gondii. Understanding T. gondii developmental biology and formation of the cyst wall will inform strategies such as vaccine development and therapeutic agents to eliminate latency and prevent reactivation toxoplasmosis. Several lines of evidence suggest that bradyzoite differentiation is stress mediated and that the cyst wall (a modified parasitophorous vacuole membrane) contains many stage specific proteins and glycoproteins. Our laboratory group has identified several cyst wall specific proteins several of which have mucin type domains that are o-glycosylated and demonstrated that glycosylation is important for cyst wall stability. CST1, a cyst wall glycoprotein, appears to be a scaffolding protein for formation of the cyst wall and we hypothesize that other cyst wall proteins interact with CST1 in establishing the cyst wall. Our laboratory group has developed techniques to purify the cyst wall enabling proteomic characterization of this structure as well as adapted BirA tagging techniques to enable definition of the cyst wall interactome. Furthermore, we have established ppGalNAcTs knockout T. gondii strains that enable studies on the role of o-glycosylation in cyst wall formation. An integrated approach employing proteomic, immunologic and genetic techniques will be used to fully characterize the T. gondii cyst wall proteome and the importance and interactions of the identified cyst wall components. The improved understanding of the formation of the cyst wall provide by these studies will provide the basic underpinnings of new strategies to eliminate latent infection thereby preventing reactivation toxoplasmosis.