Autophagic Defense Against Intracellular Parasites

描述(申请人提供)：弓形虫和疟原虫是人类最流行和最重要的两种寄生虫病。这类寄生虫的成功在于它们能够形成寄生虫空泡(PV)，避免与宿主细胞溶酶体融合并被其破坏。我们最近发现了一种新的途径，通过破坏PV膜并随后在暴露的病原体周围形成自噬空泡来破坏这些寄生虫的免疫。利用一种新开发的体外细胞内预置巨噬细胞杀灭弓形虫寄生虫的方法，我们将首先确定干扰素-γ受体信号和IGTP与CD40和肿瘤坏死因子受体信号在介导弓形虫自噬消除中的单独和联合作用。我们还将确定病原体的毒力菌株是否已经开发和产生了阻断启动的巨噬细胞消除侵袭性寄生虫的能力的因子(S)。抗CD40治疗克服这种宿主防御反应的阻断的能力将被评估，这种阻断是由寄生虫的强毒株或干扰素-伽马反应途径中的遗传缺陷造成的。这项拟议的研究将促进对免疫宿主-寄生虫关系的基本理解，并准确地指出通过诱导自噬来增强宿主对细胞内病原体的防御的具体策略。公共卫生相关性：由顶丝复合体寄生虫、弓形虫病和疟疾引起的感染是人类最重要的两种寄生虫病。我们最近描述了一种通过破坏病原体空泡和消除自噬来清除这种寄生虫的新机制。在NIH的这项探索性建议中，我们的研究将产生重要的信息，即免疫反应是如何调节的，并可以被操纵以促进这种类型的抗寄生虫宿主防御。

DESCRIPTION (provided by applicant): Apicomplexan parasites, Toxoplasmaand Plasmodiumare two of the most prevalent and important parasitic diseases of mankind. The success of this class of parasite lies in their ability to form parasite vacuoles (PVs) that avert fusion with and destruction by host cell lysosomes. We have recently discovered a novel pathway for immune destruction of these parasites by disruption of the PV membrane and subsequent formation of an autophagic vacuole around the exposed pathogen. Using a newly developed ex vivo assay for intracellular killing of Toxoplasma gondii parasites by primed macrophages, we will first define the individual and combined roles of IFN-gamma receptor signaling and IGTP versus CD40 and TNF-receptor signaling in mediating autophagic elimination of the parasite. We will also determine whether virulent strains of the pathogen have developed and produce factor(s) that block the ability of the primed macrophages to eliminate invasive parasites. The ability of anti-CD40 treatment to surmount a blockade of this host defense response by virulent strains of the parasite or by genetic deficiencies in the IFN-gamma response pathway will be evaluated. The proposed research will advance basic understanding of the immune host-parasite relationship and pinpoint specific strategies for boosting host defenses to intracellular pathogens via induction of autophagy. PUBLIC HEALTH RELEVANCE: Infections caused by apicomplexan parasites, toxoplasmosis and malaria are two of the most important parasite diseases of mankind. We have recently described a new mechanism for immune clearance of this type of parasite by pathogen vacuole disruption and autophagic elimination. In this NIH exploratory proposal, our studies will yield important information how the immune response is regulated and can be manipulated to promote this type of anti-parasite host defense.