Toxoplasma gondii GRA protein function

描述（由申请方提供）：致病性真核细胞弓形虫在免疫抑制的情况下引起特别严重的机会性感染。这些感染是由慢性/潜伏性组织囊肿的再激活引起的，通常存在于大脑或CNS中。复发性感染常常是致命的，因为现有的药物治疗急性T。弓形虫感染是次优的。流行病学研究也将慢性/潜伏性T。弓形虫感染与神经系统疾病，如精神分裂症，在其他健康的免疫功能正常的成年人。因此，根除慢性/潜伏T.弓形虫感染为预防免疫抑制引起的复发性感染以及降低免疫能力强的个体的疾病负担提供了一种创新方法。不幸的是，目前可用的针对急性感染的治疗方法对定义慢性/潜伏感染的寄生虫组织囊肿阶段几乎没有影响。确定新的药物靶点，使创新的疗法，以消除慢性/潜伏性组织囊肿将在该领域产生重大影响。我们对寄生虫生物学的认识存在一个重大空白， 并维持组织囊肿。在对口腔感染所需的组织囊肿的生物学特征的理解方面也存在重大差距。GRA蛋白是与寄生虫液泡和组织包囊相关的重要蛋白。GRA蛋白是在包囊形成的顶复虫（弓形虫、新孢子虫、肉孢子虫）中唯一发现的，并且代表了可以选择性靶向的潜在的新型药物靶标。我们假设GRA蛋白与寄生虫空泡的液泡内膜网络（IVN）提供了囊肿发育和口腔感染所需的关键生物学功能。我支持这一假设，我们最近报道，两个主要的致密颗粒（GRA）蛋白的IVN，GRA 4和GRA 6，需要在体内正常的囊肿负担的发展。IVN相关蛋白在口腔感染和传播中的作用被假设。具体目标1将检查IVN相关GRA蛋白（GRA 2、GRA 3、GRA 4、GRA 6、GRA 7和GRA 9）是体内分化、囊肿发育和/或囊肿维持所需的假设。GRA 2蛋白的IVN组织两亲性α螺旋的作用将通过检查GRA 2的突变形式来确定。具体目标2将检查IVN相关GRA蛋白是口腔感染和传播所需的假设。总的来说，这些探索性的高影响目标将在功能上确定IVN相关的GRA蛋白在组织囊肿的发展和口腔传播中发挥的重要作用。这些目标将确定和验证创新干预措施的新药靶点，以根除已感染个体的慢性/潜伏感染。因此，这个探索性的R21项目将通过提供重要的遗传工具和试剂，以及通过提供有关药物靶点发现的高影响力生物信息，指导未来研究的方向，在该领域产生持久的影响。

DESCRIPTION (provided by applicant): The pathogenic eukaryote Toxoplasma gondii causes particularly severe opportunistic infections in the context of immune suppression. These infections arise by the reactivation of chronic/latent tissue cysts, typically residing in the brai or CNS. Recrudescent infections are frequently fatal because the available drug treatments for acute T. gondii infection are suboptimal. Epidemiological studies have also linked chronic/latent T. gondii infections with neurological conditions such as schizophrenia in otherwise healthy immune competent adults. Thus, eradicating chronic/latent T. gondii infection provides an innovative approach to prevent recrudescent infections caused by immune suppression, as well as to reduce the potential of disease burden in immune competent individuals. Unfortunately, currently available treatments that target acute infection have little impact on the parasite tissu cyst stages that define chronic/latent infection. The identification of new drug targets that enabl innovative therapies to eliminate chronic/latent tissue cysts would have a major impact in the field. A major gap exists in our knowledge of parasite biology that is responsible for establishing and maintaining tissue cysts. There is also a major gap in understanding of the biological features of tissues cysts that are required for oral infectivity. GRA proteins are prominent proteins associated with the parasitophorous vacuole and the tissue cyst. GRA proteins are found uniquely in cyst-forming apicomplexans (Toxoplasma, Neospora, Sarcocystis) and represent potential novel drug targets that can be selectively targeted. We hypothesize GRA proteins that associate with the intravacuolar membranous network (IVN) of the parasitophorous vacuole provide critical biological functions required for cyst development and oral infectivity. I support of this hypothesis, we recently reported that two major dense granule (GRA) proteins of the IVN, GRA4 and GRA6, were required for development of normal cyst burdens in vivo. A role for IVN associated proteins in oral infectivity and transmission is hypothesized. Specific aim 1 will examine the hypothesis that IVN associated GRA proteins (GRA2, GRA3, GRA4, GRA6, GRA7, and GRA9) are required for differentiation, cyst development, and/or cyst maintenance in vivo. The role(s) of the IVN organizing amphipathic alpha helices of the GRA2 protein will be established by examining mutant versions of GRA2. Specific aim 2 will examine the hypotheses that IVN associated GRA proteins are required for oral infectivity and transmission. Collectively, these exploratory high impact aims will functionally identify essential roles that IVN associated GRA proteins play in the development of tissue cysts and in oral transmission. These aims will identify and validate new drug targets for innovative interventions to eradicate chronic/latent infection in already infected individuals. Consequently, this exploratory R21 project will have a lasting impact in the field by providing significant genetic tools and reagents, as well as by providing high impact biological information regarding drug target discovery that will guide the direction of future studies.