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

疟疾造成严重的健康负担，特别是在发展中国家，但目前没有疫苗。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，然后转移到血液感染，导致所有疾病。在肝脏发育阶段，寄生虫通过防止受感染细胞的程序性细胞死亡（凋亡）来保护其在宿主肝细胞中的家园。已经开发了在小鼠中诱导无菌免疫的遗传减毒寄生虫（GAP）菌株，并且对于这些菌株中的一种，显示其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。我将首先使用各种表型分析充分描绘野生型寄生虫和GAP感染的肝细胞的凋亡表型。接下来，我计划监测肝细胞中响应野生型和GAP感染的一些候选信号蛋白。这将使我们能够识别候选基因，这些基因在响应促凋亡减毒寄生虫和抗凋亡野生型寄生虫时被差异激活。最后，我建议进一步研究候选基因的差异调节使用细胞培养模型，以及免疫和小鼠的挑战实验。这项研究将导致肝细胞蛋白质的发现，调节野生型寄生虫的细胞凋亡抑制的关键。由于受感染的凋亡细胞比存活细胞更能刺激免疫系统，因此抑制这些宿主蛋白质可能导致野生型寄生虫诱导凋亡，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促进疾病的野生型寄生虫转化为促进保护性免疫的寄生虫，从而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.