Composition and formation of the cyst wall

摘要：弓形虫是一种普遍存在的哺乳动物原生动物寄生虫。 鸟。它的不同寻常之处在于，繁殖不需要通过其最终宿主使T。 通过中间寄主进行克隆繁殖。弓形虫在中国引起先天性感染 免疫能力强的宿主和免疫受损宿主中的机会性感染。偏爱 引起坏死性脑炎的中枢神经系统和引起眼睛的这种寄生虫 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种 组织包囊内发现的缓殖子转变为活跃复制的后果 速殖子。人们认为组织囊肿不是静态的结构，而是规律性的破裂重新侵袭新的 宿主细胞。在慢性弓形虫病，即潜伏感染中，宿主细胞内的组织包囊， 有规律地转化为速殖子，被免疫系统移走或隔离。 慢性弓形虫病小鼠的大脑中常可见退行性包囊。这样一种动态 包膜和复制形式之间的平衡导致反复的抗原刺激和 在慢性感染宿主中发现的持久性抗体滴度。弓形虫在中国的广泛分布 人类和其他动物是由于组织包囊的能力，允许这种感染的口腔传播。 囊壁是弓形虫存活、复活和传播的关键结构。 了解弓形虫的发育生物学和囊壁的形成将有助于采取以下策略 作为疫苗开发和治疗剂，以消除潜伏期和防止再次激活 弓形虫病。有几条证据表明，缓殖子分化是由压力介导的。 囊壁(一种改良的寄生液泡膜)含有许多阶段特有的 蛋白质和糖蛋白。我们的实验室小组已经鉴定了几种囊壁特异性蛋白质 其中几个具有o-糖基化的粘蛋白类型结构域，并证明了 糖基化对囊壁的稳定性很重要。CST1是一种囊壁糖蛋白，似乎是一种 囊壁形成的支架蛋白，我们推测其他囊壁蛋白 在建立囊壁时与CST1相互作用。我们的实验室小组已经开发出技术来 纯化囊壁，能够对该结构和适应的Bira进行蛋白质组学表征 能够定义囊壁相互作用体的标记技术。此外，我们还拥有 建立ppGalNActs基因敲除弓形虫菌株，使o-糖基化作用的研究成为可能 在囊壁形成中。利用蛋白质组、免疫学和遗传学的综合方法 技术将被用来充分表征弓形虫囊壁蛋白质组和重要性和 已鉴定的囊壁成分之间的相互作用。对新陈代谢的形成有了新的认识 这些研究提供的囊壁将为以下新策略提供基本基础 消除潜伏感染，从而防止弓形虫病复发。

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.