Role of platelet CD40 in experimental cerebral malaria coagulopathy

描述（由申请人提供）：我们提出疟疾的发病机制是由于止血系统、免疫反应和寄生虫隔离之间的复杂相互作用。本提案的总体目标是确定血小板cd40促进血小板活化和实验性脑疟疾（ECM）凝血病的机制。在抗寄生虫治疗杀死恶性疟原虫的同时，需要明确ECM的发病机制，以开发辅助治疗，以保护CM患者免受宿主反应导致的死亡、认知障碍和精神病。我们假设CD40是一种血小板分子，对ECM的发病机制和功能至关重要，有助于血小板活化，微粒形成，从而导致ECM凝血病。关于血小板上在ECM发病机制中起作用的分子知之甚少。通过血小板过继转移模型，我们的初步数据表明，血小板CD40可恢复ECM抗性CD40- ko小鼠的ECM发育。目的1的重点是确认这些数据，并确定血小板CD40是否能恢复CD40- ko患者大脑中的血管泄漏、出血和白细胞粘附；这些致病过程是ECM的标志。血小板在ECM发病机制中的作用机制存在争议，大多数研究人员关注的是ECM晚期，由于血小板减少，血小板很少。然而，我们已经报道了血小板在ECM过程中被激活较早（~ 1天），并且在病原宿主反应的激活中起作用较早。我们的研究结果还表明，血小板减少并不足以导致ECM的发生，因为几种ECM抗性小鼠表现出与对照组相似的严重的血小板减少。血小板生物学中导致凝血系统激活的关键事件包括表面积的增加、脱颗粒、微粒的释放以及关键表面受体亲和力的变化。我们的数据表明，血小板在ECM早期改变其大小和表面标记物的表达，并形成血小板微粒，这可能在ECM发病过程中起作用。我们的第二个目标是确定血小板CD40在ECM期间血小板活化和微粒形成中的作用，以及这如何导致ECM凝血病。我们的结果代表了第一个血小板分子在ECM发病机制中的功能鉴定，并使我们能够研究血小板促进ECM发病的机制。我们的团队是ECM发病机制的领导小组，在研究血小板生物学及其对ECM的贡献方面有着良好的记录。这些研究新颖、重要，可以在有限的2年时间内以较低的预算进行，因此建议适合RO3拨款机制。

DESCRIPTION (provided by applicant): We have proposed that malaria pathogenesis is due to a complex interaction between the hemostasis system, the immune response, and parasite sequestration. The overall goal of this proposal is to identify the mechanisms whereby platelet-CD40 contributes to the activation of the platelets and experimental cerebral malaria (ECM) coagulopathy. Definition of ECM pathogenesis is required to develop adjunctive therapy aimed at protecting CM patients from the host response leading to death, cognitive impairment, and psychoses while the anti-parasite treatment kills P. falciparum. We hypothesize that CD40 is a platelet molecule critical for ECM pathogenesis and functions by contributing to platelet activation, microparticle formation, and hence ECM coagulopathy. Little if any information is known about the molecules on platelets that function in ECM pathogenesis. Using an adoptive transfer model of platelets, our preliminary data indicate that platelet CD40 restores the development of ECM to ECM-resistant CD40-KO mice. Aim 1 is focused on confirming these data and determining whether platelet CD40 restores vascular leak, hemorrhage, and leukocyte adhesion in the brains of CD40-KO; these pathogenic processes are hallmarks of ECM. The mechanisms whereby platelets function in ECM pathogenesis are controversial with most investigators focusing on the late stages of ECM where few platelets are present due to thrombocytopenia. However, we have reported that platelets are activated early (~day 1) during ECM and function early in the activation of the pathogenic host response. Our results also document that thrombocytopenia is not sufficient for the genesis of ECM because several strains of ECM-resistant mice exhibit profound thrombocytopenia similar to controls. Key events in platelet biology leading to the activation of the coagulation system include the increase in surface area, degranulation, release of microparticles, and the change in affinity of key surface receptors. Our data indicate that platelets alter their size and expression of surface markers early during ECM and form platelet microparticles, which likely function in ECM pathogenesis. Our second aim is to determine the role of platelet CD40 in platelet activation and microparticle formation during ECM and how this leads to ECM coagulopathy. Our results represent identification of the first platelet molecule functioning in ECM pathogenesis and allow us to investigate the mechanisms whereby platelets contribute to ECM pathogenesis. Our team is the leading group in ECM pathogenesis with a strong track record in investigating platelet biology and its contributions to ECM. These studies are novel, important and can be performed in the limited 2 year time frame with a low budget, making the proposal suitable for the RO3 grant mechanism. PUBLIC HEALTH RELEVANCE: Malaria is a leading cause of morbidity and mortality due to a single infectious agent but there is little consensus regarding any adjunctive treatment of patients presenting with cerebral malaria; this is because we do not understand pathogenesis. We have reported that platelets and platelet microparticles function in cerebral malaria and we now investigate the role of a specific platelet molecule CD40 in pathogenesis.