轻症和重症人感染H7N9禽流感病毒的致病性

Pathogenicity of Avian Influenza A(H7N9) Viruses Isolated from Mild and Severe Cases of Human Infection

【目的】研究来自不同临床类型H7N9感染者病毒分离株的致病性,探索病毒分子特性与致病差异的关系。【方法】建立人PBMC体外培养及病毒感染模型,人肺组织体外培养及病毒感染模型以及小鼠感染H7N9动物模型,分别从以上3个层次研究两株来自轻症和重症H7N9感染者病毒分离株(即GD-6和GD-7)的感染性及病理损伤状况。【结果】两株病毒均能感染人PBMC、人肺组织体外培养模型和Balb/C小鼠的肺组织,并在其中有效复制,且GD-7的增殖能力强于GD-6。病毒主要感染人肺组织的II型肺泡上皮细胞,GD-7引起肺组织的病例变化更加明显。在小鼠肺组织,GD-7的病毒载量高于GD-6,小鼠感染病毒后其肺指数增大,肺组织的病理变化明显,且GD-7对小鼠的致病力强于GD-6。【结论】重症分离株GD-7的复制能力和致病力强于轻症分离株GD-6,结合前期研究结果 ,两株病毒存在关键氨基酸位点的差异,其中PB2蛋白的627位点在GD-7发生了突变E627K,因此推测病毒载量及关键位点突变可能对病毒的致病力起重要作用。

[Objective] To compare the pathogenicity of two HTN9 virus isolates from patients with different clinical outcomes and explore the relationship between molecular properties of viruses and pathogenic differences. [ Methods ] Establish the H7N9 infection models of in vitro human peripheral blood mononuclear cells （PMBCs）, ex vivo human lung tissues, and in vivo Balb/C mice. Analyses the infectivity and pathological damage status of two H7N9 isolates from mild and severe patients （named GD-6 and GD-7） using in vitro, ex vivo, and in vivo studies. [Results] Both GD-6 and GD-7 could infect and replicate in vitro, ex vivo, and in vivo models and GD-7 replicated to higher levels than GD-6. They were detected predominantly in type II pneumocytes in human lung tissue culture, furthermore, GD-7 infection resulted in more severe lung damage than GD-6 infection. The two virus isolates could efficiently replicated in the lung of the mice, and the viral loads of GD-7 were higher than that of GD-6. The lung index of the mice became larger, and the lungs had histopathological change, moreover, GD-7 was more pathogenic than GD-6. [Conclusion] The results suggest that the high viral loads and mutation E627K in PB2 may play an important role in the pathogenesis of avian influenza A （H7N9） virus.