肝期约氏疟原虫ΔCSP下调自噬相关蛋白在其抑制IFN-γ杀伤EEF中的作用和机制

探讨肝期疟原虫的免疫逃避机制是设计有效预防疟疾感染手段的前提。研究发现，疟原虫子孢子蛋白CSP被水解生成ΔCSP后，可进入肝细胞胞浆并促进疟原虫EEF的发育，但其机制并不清楚。课题组研究发现，转染ΔCSP重组质粒并不能直接促进EEF的发育，却能够显著抑制IFN-γ对EEF的杀伤作用；转录组测序、Western和ATG回补实验提示ΔCSP可能通过下调自噬相关蛋白抑制IFN-γ的杀伤；而Pull-down实验发现ΔCSP可能通过HSPA8下调自噬相关蛋白，但其中的机制尚不清楚。鉴此，本项目拟在此基础上，首先利用CSP突变子孢子和肝细胞ATG5 条件敲除小鼠，进一步证实ΔCSP可通过下调自噬相关蛋白抑制IFN-γ的杀伤；然后采用分子截短、pull-down，探讨HSPA8在ΔCSP下调自噬相关蛋白中的分子机制。这不但有助于揭示肝期疟原虫免疫逃避新机制，为寻找新的疟疾防治干预靶点提供重要理论依据。

Understanding the underlying mechanism of malaria parasite to escape or suppress the host innate immune responses will shed us with new light on the designation of prophylactic strategy against pre-erythrocytic stage. It is well known that the main sporozoites surface protein CSP(circumsporozoites protein), which is translocated into cytoplasma of hepatocyte after it is cleaved into ΔCSP, is essential for the development of liver stage. However, the underlying mechanism is still unclear. Our preliminary data showed that transfection of ΔCSP couldn’t promote the development of EEF in vitro, but could resist to the IFN-γ-induced killing of EEFs. RNA-seqencing and Western blotting results indicated that transfection of ΔCSP could resist to the IFN-γ-induced killing of EEFs through down-regulation of autophagy-related proteins, and pull-down assay showed ΔCSP downregulates the autophagy-related proteins possibly through binding to the HSPA8, but the underlying mechanism is still unknown. In this study, we would like to confirm the abovementioned hypothesis by using CSP-mutant sporozoites and mice with ATG5 conditional knockout in hepatocyte; and test whether ΔCSP down regulates the autophagy-related proteins through binding to the HSPA8. This study could not only shed new light on the escape strategy of exo-erythrocytic stage, but also provide novel clues to design prophylactic strategies against the liver-stage.