2013年出现的H7N9低致病力禽流感病毒（LP-H7N9）严重危害人类健康。随着病毒的进化，2017年出现了H7N9高致病力禽流感病毒（HP-H7N9）。基于报道病例，HP-H7N9感染病死率达50%，远高于LP-H7N9的39%。对HP-H7N9和LP-H7N9感染患者比较研究发现：二者在呼吸道的复制能力相当，但HP-H7N9感染患者的细胞因子分泌程度更高；在细胞和小鼠感染实验中也发现，二者复制水平没有差异，但HP-H7N9诱导人肺A549细胞分泌细胞因子的能力、对小鼠的致病力都显著强于LP-H7N9。综上提示：宿主对细胞因子的分泌调控影响了HP-H7N9对哺乳动物/人的致病性。本项目将针对HP-H7N9和LP-H7N9感染宿主细胞差异表达的长链非编码和环状RNA，研究其对宿主因子的表达调控及对病毒感染致病的影响，进而揭示非编码RNA调控H7N9病毒感染致病的分子机制。

A novel H7N9 influenza virus emerged in China during 2013. This virus was found to replicate in chickens but without obvious symptoms, and thus was classified as low pathogenic H7N9 (LP-H7N9). However, LP-H7N9 can still cause severe disease in humans, posing a public health risk. In 2017, a novel highly pathogenic H7N9 variant (HP-H7N9) emerged and caused severe outbreaks of disease in chickens even humans. Importantly, the case fatality rate for HP-H7N9 is ~50%, which is considerably higher than ~39% for LP-H7N9. A comparison study by our group showed that HP-H7N9 and LP-H7N9 replicated well in the respiratory system of infected patients, and HP-H7N9 induced the release of a higher level of cytokines. Further studies showed that HP-H7N9 and LP-H7N9 possessed similar replication rates in mammalian cells, but HP-H7N9 induced significantly higher cytokines than LP-H7N9; in addition, HP-H7N9 was more virulent to mice. Furthermore, HP-H7N9 and LP-H7N9 infected human line A549 cells were found to have differences in expression of non-coding RNA (ncRNA). These results suggest that ncRNA plays an important role in mediating the immune response to H7N9 infection. In this proposal, we will focus on differently-expressed ncRNA (including long non-coding RNA and circular RNA) between HP-H7N9 and LP-H7N9 infections, study the regulation network of host factors induced by the ncRNAs, and link these results to the pathogenicity of H7N9 in mammals or humans. This study will help characterize ncRNA-regulated host responses to H7N9 infections and provide a foundation for the prevention and treatment of H7N9.