Parasite autophagy as a key survival mechanism for the AIDS-associated pathogen Toxoplasma gondii

慢性弓形虫感染的再激活可引起免疫缺陷个体的眼部、心脏、呼吸道和神经系统疾病。目前的治疗方法不能消除缓慢复制的、持续存在的弓形虫缓殖子包囊，这些包囊导致再活化和疾病，最严重的表现为弓形虫脑炎。我们的长期目标是确定破坏弓形虫持久性的关键责任，从而消除高危人群中潜在致命性弓形虫脑炎的风险。为了实现这一目标，我们最近已经证明，培养和感染小鼠中的缓殖子包囊的生存能力严重依赖于寄生虫具有基于TgATG 9的靶向破坏的功能性自噬途径。TgATG9缺陷的缓殖子在培养物和实验感染的小鼠中显示出显著减少的自噬和严重的生存能力丧失。由于自噬是细胞稳态所必需的，我们的研究结果支持了一个新的概念，破坏寄生虫的稳态，以平息感染。然而，对弓形虫中的自噬知之甚少，追求这一概念需要识别途径中新的和不同的组分。为了满足这一需求，我们将发现新的自噬途径的早期组件，定义它们如何协同介导自噬结构的发展，并确定它们在体外和体内对寄生虫持久性的贡献。完成拟议的研究将提供概念验证，即靶向寄生虫体内平衡是破坏持久性的有效策略。

Reactivation of chronic Toxoplasma gondii infection causes ocular, cardiac, respiratory, and neurologic disease in immune-deficient individuals. Current treatments fail to eliminate the slow replicating, persistent Toxoplasma bradyzoite cysts that seed reactivation and disease, which manifests most severely as Toxoplasmic encephalitis. Our long-term goal is to identify critical liabilities for disrupting Toxoplasma persistence, thereby eliminating the risk of potentially fatal Toxoplasmic encephalitis in at-risk individuals. Toward this goal, we have recently demonstrated that the viability of bradyzoite cysts in culture and in infected mice critically relies on the parasite having a functional autophagy pathway based on targeted disruption of TgATG9. TgATG9 deficient bradyzoites show markedly reduced autophagy and severe loss of viability in culture and in experimentally infected mice. Since autophagy is necessary for cellular homeostasis, our findings support a new concept of disrupting parasite homeostasis to quell infection. However, little is known about autophagy in Toxoplasma and pursuing this concept requires identifying new and divergent components in the pathway. To meet this need, we will discover novel early components of the autophagy pathway, define how they cooperatively mediate the development of autophagic structures, and determine their contributions to parasite persistence in vitro and in vivo. Completing the proposed studies will provide proof-of-concept that targeting parasite homeostasis is an effective strategy to disrupt persistence.