Investigating the Role of Cellular Signaling in Liver-Stage Malaria Infection

疟疾是一种严重的健康负担，特别是在发展中国家，但目前还没有疫苗。寄生虫通过雌性按蚊的叮咬进入人类宿主，首先感染肝细胞，然后转移到导致所有疾病的血液感染。在肝脏发育阶段，寄生虫通过防止被感染细胞的程序性细胞死亡（凋亡）来保护它们在宿主肝细胞中的家园。基因减毒寄生虫（GAP）在小鼠体内诱导无菌免疫已被开发出来，其中一株被证明不能控制宿主细胞凋亡。然而，野生型寄生虫抑制细胞凋亡的机制尚未阐明。我将首先充分描述肝细胞的凋亡表型感染野生型寄生虫和间隙使用各种表型测定。接下来，我计划监测肝细胞中应对野生型和GAP感染的一些候选信号蛋白。这将使我们能够识别在促凋亡减毒寄生虫和抗凋亡野生型寄生虫反应中差异激活的候选基因。最后，我建议使用细胞培养模型以及小鼠免疫和激发实验进一步研究差异调节的候选基因。这项研究将导致发现对调节野生型寄生虫抑制细胞凋亡至关重要的肝细胞蛋白。由于受感染的凋亡细胞比存活细胞对免疫系统有更好的刺激作用，抑制这些宿主蛋白可能导致野生型寄生虫诱导细胞凋亡，也可能增强减毒活疫苗诱导的免疫力。改变肝细胞对感染的反应可以将一种野生型、促进疾病的寄生虫转化为一种促进保护性免疫的寄生虫，从而可能在疟疾感染的早期阶段为新的干预策略提供信息。

Malaria presents a severe health burden, particularly in the developing world yet no vaccine is currently available. The parasites enter the human host through the bite of the female Anopheles mosquito and first infect liver hepatocytes, before moving to the blood infection that causes all disease. During liver stage development, parasites protect their home in the host hepatocyte by preventing programmed cell death (apoptosis) of the infected cell. Genetically attenuated parasite (GAP) strains that induce sterile immunity in mice have been developed, and it was shown for one of these strains that it cannot control host cell apoptosis. The mechanism of the inhibition of apoptosis by wildtype parasites, however, has not been elucidated. I will first fully delineate the apoptotic phenotype of hepatocytes infected with wildtype parasites and GAPs using a variety of phenotypic assays. Next, I plan to monitor a number of candidate signaling proteins in hepatocytes in response to both wildtype and GAP infections. This will allow us to identify candidate genes that are differentially activated in response to pro-apoptotic attenuated parasites and anti-apoptotic wildtype parasites. Finally, I propose to further investigate candidate genes that are differentially regulated using a cell culture model, as well as immunization and challenge experiments in mice. This study will lead to the discovery of hepatocyte proteins critical to modulating the inhibition of apoptosis by wildtype parasites. Since infected apoptotic cells are a better stimulus for the immune system than surviving cells, inhibiting these host proteins may cause the induction of apoptosis by wildtype parasites and might also enhance immunity induced by live-attenuated vaccines. Altering the hepatocyte response to infection could convert a wildtype, disease promoting parasite into one that promotes protective immunity and might thus inform new intervention strategies at the early stage of malaria infection.