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

慢性刚地弓形虫感染的再激活导致免疫缺陷个体的眼部、心脏、呼吸和神经系统疾病。目前的治疗方法不能消除缓慢复制、持续的弓形虫慢殖子囊肿，这种囊肿会导致重新激活和疾病，最严重的表现是弓形虫脑炎。我们的长期目标是确定破坏弓形虫持续性的关键责任，从而消除高危人群中潜在致命的弓形虫脑炎风险。为了实现这一目标，我们最近证明，在培养和感染小鼠中，慢殖子囊的生存能力严重依赖于寄生虫具有基于靶向破坏TgATG9的功能性自噬途径。TgATG9缺陷缓殖子在培养和实验感染小鼠中表现出明显的自噬减少和生存能力严重丧失。由于自噬是细胞内稳态所必需的，我们的研究结果支持了破坏寄生虫内稳态以抑制感染的新概念。然而，人们对弓形虫的自噬知之甚少，要想了解这一概念，就需要在这一途径中发现新的和不同的成分。为了满足这一需求，我们将发现新的自噬途径的早期组成部分，确定它们如何协同介导自噬结构的发展，并确定它们对体外和体内寄生虫持久性的贡献。完成拟议的研究将提供概念证明，以寄生虫的体内平衡为目标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.