Reactivation of Chronic Toxoplasmosis

慢性弓形虫病的重新激活

• 批准号: 10239417
• 负责人: L. David Sibley
• 金额: $ 24.82万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-02-01 至 2023-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10239417
• 关键词: Acquired Immunodeficiency Syndrome; Address; Animals; Antibiotics; Antigens; Area; Brain; Calcium; Carbohydrates; Cell Wall; Cells; Chitinase; Chronic; Consumption; Cyst; Daughter; Digestion; Disease; Encephalitis; Enzymes; Feces; Felis catus; Frequencies; Gene Proteins; Genetic; Glycoproteins; Goals; HIV; HIV Infections; High Prevalence; Highly Active Antiretroviral Therapy; Human; Hydrolase; Immune; Immune system; Immunity; Immunocompromised Host; Impairment; In Vitro; Individual; Infection; Ingestion; Lead; Legal patent; Life; Link; Meat; Mucins; Muscle; Oligosaccharides; Oocysts; Opportunistic Infections; Organ; Parasites; Pathway interactions; Patients; Pharmacotherapy; Phenotype; Process; Proliferating; Proteins; Refractory; Risk; Role; Rupture; Side; Signal Transduction; Substrate Specificity; Testing; Tissues; Toxoplasma gondii; Toxoplasmosis; cell motility; chronic infection; contaminated water; effective intervention; glycosylation; in vivo; latent infection; mouse model; mutant; novel; sugar; undercooked

Project Summary/Abstract Toxoplasma gondii is a widespread parasite of animals that cycles between cats, which shed infectious oocysts in their feces, and a variety of animals that harbor long-lived chronic infections. Humans are also commonly infected either by ingestion of oocysts in contaminated water, or by ingestion of tissue cysts in undercooked meat. Following infection, the parasite initially proliferates as fast-growing tachyzoites, which disseminate widely in the body. It then differentiates into semi-dormant bradyzoites that reside within tissue cysts, most commonly in muscle and brain. Although infections in healthy individuals are controlled by the immune system, tissue cysts persist in the face of immunity and are not eliminated by drug treatment. As such, chronic infections with T gondii pose a serious risk to HIV-infected AIDS patients due release of parasites from semi-dormant tissue cysts and re-emergence of the highly proliferative tachyzoite stage, which can lead to life threatening complications. Although once considered latent, newer studies reveal that bradyzoites replicate, albeit asynchronously and infrequently. Moreover, tissue cysts periodically rupture to release bradyzoites that infect new host cells and give rise to daughter tissue cysts. One barrier to egress of bradyzoites is their rigid cyst wall, comprised of proteins and carbohydrates, including the dominant antigen CST1, which is heavily glycosylated by O-linked sugars. Loss of CST1, or deletion of its mucin domain, results in fragile cysts, implying that this glycoprotein provides rigidity to the cell wall. Consistent with the idea that carbohydrates form a critical part of the cyst wall, our studies demonstrate that exogenously added glucanase and chitinase enzymes digest the cyst wall and result in release of bradyzoites. To explore endogenous pathways that control this process, we will examine the roles of two parasite glycosyl hydrolases that are expressed in bradyzoites, secreted from the parasite, and localized to the cyst wall. Genetic disruption of glucanase (GLN1) and chitinase-like protein (CLP1) genes in a cystogenic strain of T. gondii results in reduced formation of daughter cysts, supporting the hypothesis that these enzymes contribute to cyst maturation and turnover. We will examine the substrate specificity of these enzymes in vitro and assess their roles in vivo in formation and turnover of tissue cysts. We will also examine the role of these glycosyl hydrolases in chronic infection of immunocompromised mouse models that closely mimic impaired immunity seen in HIV-infected AIDS patients. The proposed studies will explore the hypothesis that glycosyl hydrolase enzymes contribute to the turnover of tissue cysts resulting in reactivation of toxoplasmosis, which poses a major risk for severe disease in HIV-infected AIDS patients.

项目总结/摘要 弓形虫是一种广泛存在于动物体内的寄生虫，在猫与猫之间循环， 粪便中的卵囊，以及各种长期慢性感染的动物。人类也是 通常通过摄入受污染的水中的卵囊或通过摄入 未煮熟的肉感染后，寄生虫最初增殖为快速生长的速殖子， 在体内广泛传播。然后分化为半休眠的缓殖子， 囊肿，最常见于肌肉和大脑。尽管健康个体的感染受到 在免疫系统中，组织囊肿在免疫力面前持续存在，并且不能通过药物治疗消除。因此，在本发明中， 慢性弓形虫感染对HIV感染的艾滋病患者构成严重风险， 半休眠的组织囊肿和高度增殖的速殖子阶段的重新出现，这可能导致生命 危险的并发症 虽然曾经被认为是潜伏的，但新的研究表明，缓殖子复制，尽管是异步的 而且很少。而且，组织包囊周期性破裂释放出感染新宿主细胞的缓殖子 并产生子组织囊肿。阻碍缓殖子排出的一个障碍是它们坚硬的囊壁， 蛋白质和碳水化合物，包括优势抗原CST 1，其通过O-连接的 糖。CST 1的缺失，或其粘蛋白结构域的缺失，导致脆弱的包囊，这意味着这种糖蛋白 为细胞壁提供刚性。与碳水化合物形成囊壁的关键部分的想法一致， 我们的研究表明，外源加入的葡聚糖酶和几丁质酶消化了孢囊壁， 导致缓殖子的释放。为了探索控制这一过程的内源性途径，我们将研究 两种寄生虫糖基水解酶的作用，其在缓殖子中表达，从寄生虫分泌，和 局限于囊壁一株大肠杆菌中葡聚糖酶（GLN 1）和几丁质酶样蛋白（CLP 1）基因的遗传破坏 T.弓形虫导致子包囊的形成减少，支持以下假设： 这些酶有助于包囊成熟和更新。我们将研究这些底物的特异性， 酶在体外和评估其在体内的作用，在形成和组织囊肿的周转。我们亦会研究 这些糖基水解酶在免疫受损小鼠模型慢性感染中的作用， 与艾滋病患者免疫力受损相似。拟议的研究将探讨这一假设 糖基水解酶有助于组织囊肿的周转，导致 弓形虫病，这是艾滋病毒感染的艾滋病患者严重疾病的主要风险。