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

慢性弓形虫感染的重新激活会导致免疫缺陷个体的眼部、心脏、呼吸系统和神经系统疾病。目前的治疗方法未能消除复制缓慢、持续的弓形虫包囊，这些包囊导致重新激活和疾病，最严重的表现为弓形体脑炎。我们的长期目标是确定扰乱弓形虫持久性的关键责任，从而消除高危个体潜在致命弓形体脑炎的风险。为了实现这一目标，我们最近证明了慢殖子包囊在培养和感染小鼠中的生存能力严重依赖于具有基于TgATG9靶向干扰的功能自噬途径的寄生虫。缺乏TgATG9的缓殖体在培养和实验感染的小鼠中显示出显著的自噬减少和严重的生存能力丧失。由于自噬对于细胞内稳态是必要的，我们的发现支持了一个新的概念，即破坏寄生虫的内稳态以平息感染。然而，人们对弓形虫的自噬知之甚少，追寻这一概念需要确定该途径中新的和不同的成分。为了满足这一需求，我们将发现自噬途径的新的早期成分，确定它们如何协同调节自噬结构的发展，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证明，以寄生虫为目标的动态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.