Role of platelet CD40 in experimental cerebral malaria coagulopathy

描述（由申请人提供）：我们提出疟疾发病机制是由于止血系统、免疫应答和寄生虫隔离之间的复杂相互作用。该提案的总体目标是确定血小板-CD 40促进血小板活化和实验性脑型疟疾（ECM）凝血障碍的机制。ECM发病机制的定义是需要开发旨在保护CM患者免受导致死亡、认知障碍和精神病的宿主反应的连续治疗，而抗寄生虫治疗杀死恶性疟原虫。我们假设CD 40是ECM发病机制和功能的关键血小板分子，通过促进血小板活化，微粒形成，因此ECM凝血病。关于血小板上在ECM发病机制中起作用的分子的信息很少，如果有的话。使用血小板的过继转移模型，我们的初步数据表明，血小板CD 40恢复ECM的发展，ECM耐药的CD 40-KO小鼠。目的1的重点是确认这些数据，并确定血小板CD 40是否恢复CD 40-KO脑中的血管渗漏、出血和白细胞粘附;这些致病过程是ECM的标志。血小板在ECM发病机制中发挥作用的机制存在争议，大多数研究者关注ECM的晚期阶段，其中由于血小板减少症而存在很少的血小板。然而，我们已经报道了血小板在ECM早期（~第1天）被激活，并且在病原性宿主反应的激活早期起作用。我们的研究结果还表明，血小板减少症是不足以形成ECM，因为几个品系的ECM耐药小鼠表现出严重的血小板减少症类似于对照组。血小板生物学中导致凝血系统活化的关键事件包括表面积增加、脱粒、微粒释放和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志物的表达，并形成血小板微粒，这可能在ECM发病机制中起作用。我们的第二个目的是确定血小板CD 40在ECM过程中血小板活化和微粒形成中的作用，以及这是如何导致ECM凝血病的。我们的研究结果代表了第一个血小板分子在ECM发病机制中发挥作用的鉴定，并使我们能够研究血小板对ECM发病机制的作用。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。这些研究是新颖的，重要的，可以在有限的2年时间内以较低的预算进行，使该提案适合RO 3赠款机制。 公共卫生相关性：疟疾是由单一传染因子引起的发病率和死亡率的主要原因，但对于脑型疟疾患者的任何预防性治疗几乎没有共识;这是因为我们不了解发病机制。我们已经报道了血小板和血小板微粒在脑型疟疾中的作用，我们现在研究一种特异性血小板分子CD 40在发病机制中的作用。

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.