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.

项目摘要/摘要 弓形虫Gondii是一种循环的动物的广泛寄生虫 粪便中的卵囊和各种具有长期慢性感染的动物。人也是 通常是通过在被污染的水中摄入卵囊或通过摄入组织囊肿而感染的 煮熟的肉。感染后，寄生虫最初以快速增长的速二鼠增殖，这是 在体内广泛传播。然后，它区分为居住在组织内的半休眠曲二核 囊肿，最常见于肌肉和大脑。尽管健康个体的感染受到 免疫系统，面对免疫力，组织囊肿持续存在，并未通过药物治疗消除。像这样， T Gondii的慢性感染对感染HIV感染的AIDS患者构成严重风险 高度增殖的tachyzoite阶段的半休眠组织囊肿和重新出现，可以导致生命 威胁并发症。 尽管曾经考虑过潜在的研究，但较新的研究表明，Bradyzoites会复制，尽管异步 而且很少。此外，组织囊肿会定期破裂，以释放出感染新宿主细胞的胸肌 并引起女儿组织囊肿。 Bradyzoites出口的一个障碍是它们的刚性囊肿墙 蛋白质和碳水化合物，包括主要的抗原CST1，该抗原CST1被O连接大量糖基化 糖。 CST1的丢失或其粘蛋白结构域的缺失会导致脆弱的囊肿，这意味着该糖蛋白 为细胞壁提供刚性。与碳水化合物形成囊肿壁的关键部分的想法一致， 我们的研究表明，外源添加葡萄糖酶和几丁质酶消化了囊肿壁和 导致释放Bradyzoites。为了探索控制这一过程的内源性途径，我们将检查 在寄生虫分泌的两个寄生虫糖基水解酶的作用， 位于囊墙上。葡萄糖酶（GLN1）和几丁质酶样蛋白（CLP1）基因的遗传破坏 T. gondii的囊肿性菌株导致女儿囊肿的形成减少，支持以下假设。 这些酶有助于囊肿的成熟和周转。我们将检查这些的底物特异性 体外酶并评估其在组织囊肿形成和周转中的作用。我们还将检查 这些糖基水解酶在慢性感染的免疫功能低下小鼠模型中的作用，该模型紧密 在HIV感染的AIDS患者中，模仿免疫力受损。拟议的研究将探讨假设 该糖基水解酶有助于组织囊肿的营业额，从而重新激活 弓形虫病在艾滋病毒感染的艾滋病患者中构成严重疾病的主要风险。