eIF4B在流感病毒感染引起宿主淋巴器官损伤中的作用及其机制

Eukaryotic translation initiation factor 4B (eIF4B), an integral component of the translation initiation apparatus, is involved in cell survival and proliferation, oncogenic transformation and virus infection. Our previous study showed that eIF4B had a profound effect on influenza virus replication, but its roles in the organic pathology induced by influenza virus infection are not fully understood. Based on our preliminary study, in this project we will investigate the involvement of eIF4B in the lesion of host lymphoid organs induced by avian H9N2 and mouse-adapted WSN influenza virus infection at the molecular, cellular and in vivo level. First, the apoptosis and migration of lymphocytes in H9N2 or WSN influenza virus infected mouse thymus and spleen will be assessed by flow cytometry analysis and Western blotting; Second, whether and how eIF4B is involved in the lymphocytic apoptosis and migration will be determined using eIF4B knockdown and knockout mouse model; Finally, since influenza virus NS1 can affect eIF4B protein stability at a cellular level, we will address whether NS1 also plays a role in the regulation of eIF4B protein level in mouse thymus and spleen. Together, these studies will further elucidate the pathogenesis of influenza virus in host, and provide novel targets for antiviral drug development.

真核翻译起始因子eIF4B是蛋白翻译起始复合物的重要成分，参与细胞增殖与凋亡、细胞癌变及病毒感染等过程。我们前期的研究结果表明eIF4B在流感病毒复制过程中发挥重要作用，但是其在流感病毒感染引起器官损伤中的功能仍不清楚。本项目在前期工作的基础上，从分子、细胞和动物水平上研究eIF4B在H9N2禽流感病毒和鼠适应株WSN流感病毒感染引起宿主淋巴器官损伤中的作用及其机制。首先通过流式细胞术和蛋白免疫印迹技术分析H9N2或WSN流感病毒感染后小鼠胸腺和脾脏淋巴细胞的凋亡和迁移情况；然后通过eIF4B 敲低和敲除小鼠模型研究eIF4B与小鼠胸腺和脾脏中淋巴细胞凋亡和迁移之间的相关性；鉴于流感病毒NS1蛋白能够在细胞水平影响eIF4B蛋白的稳定性，我们将探讨NS1是否影响小鼠胸腺和脾脏中eIF4B的蛋白水平。这些研究将进一步阐明流感病毒的致病机理，也为寻找新型抗流感病毒药物靶标提供依据。

我们前期研究工作发现流感病毒感染后小鼠胸腺和脾脏中eIF4B蛋白表达水平显著降低，本项目通过进一步研究阐明了eIF4B在流感病毒感染引起宿主淋巴器官损伤中的作用及其机制。我们发现，流感病毒感染可以通过刺激糖皮质激素的分泌引起小鼠胸腺细胞发生自噬，自噬作用使eIF4B蛋白降解，进而影响抗凋亡蛋白的翻译过程，最终导致胸腺细胞发生凋亡造成胸腺萎缩。另外，淋巴细胞迁移也在一定程度上影响了胸腺的萎缩，并且是脾脏萎缩的主要原因。我们还发现，流感病毒NS1蛋白可以影响小鼠胸腺中eIF4B的蛋白水平，并且NS1第212和178位氨基酸位点对维持NS1的功能和蛋白稳定性至关重要。最后，我们将H9N2禽流感病毒在小鼠肺脏中进行连续传代获得小鼠适应株，病毒全基因组测序表明小鼠适应株发生了多个氨基酸位点突变，且这些突变可以使鼠适应株引起更严重的胸腺、脾脏萎缩。本项目取得的成果进一步阐明了流感病毒的致病机理，也为寻找新型抗流感病毒药物靶标提供了依据。