DHV主要侵害1周龄内雏鸭，其分子机制还不清楚。前期用I型DHV感染不同日龄鸭发现，MDA5、IL-6、IFN等先天性免疫相关基因水平均上调，同时病毒含量也有提高，随即下降。MDA5识别小RNA 病毒，在先天性免疫中起重要作用。我们推测DHV的复制有可能激活MDA5通路，通过级联反应诱导I型干扰素及促炎症细胞因子的产生，在感染早期清除或阻断病毒复制和传播。本课题以MDA5为研究对象，通过Real-time PCR和WB技术检测MDA5及接头蛋白MAVS，分析病毒感染对MDA5下游信号分子的转录活性；以iRNA沉默DEF中MDA5和体外转染过表达MDA5系列蛋白，确定MDA5对DHV感染后的免疫调控作用；利用IFN-β抗体阻断JAK-STAT通路，通过WB、构建病毒蛋白基因的真核质粒，反向遗传技术，研究病毒蛋白与MDA5互作，明确MDA5对病毒复制转录的具体机制，对鸭肝炎的防治有重要意义。

Duck hepatitis virus (DHV) can cause an acute, contagious, rapidly spreading, and highly lethal infection characterized by liver necrosis and hemorrhage in young ducklings within 3 weeks old. DHV-1 can cause up to 95% mortality in 1-week-old duckling.The scholars have done a lot of research in the pathogenesis, genome sequencing and immune mechanisms, but the exact molecular mechanism is unclear. . At the initial stage of virus infection, host pattern recognition receptors (PRR) are responsible for sensing viral RNA and initiates innate antiviral responses. PRR contains Toll-like receptor (TLRs) and RIG-I-like receptors (RLRs) including RIG-I and MDA5. RIG-I can recognize Newcastle disease virus, influenza virus, vesicular stomatitis virus, while MDA5 only recognize picornavirus. Early studies have found that innate immune response played an important role in duck hepatitis. In the organs examined of the ducks, the levels of MDA5, IFN-a, IL-6 mRNA were significantly up-regulated, meanwhile, the viral RNA expression was also induced, which prompt that the virus replication may active MDA5 passage, and induce IFN-a, proinflammatory cytokines IL-6 by cascade reaction to limit virus replication and spread in the early stage of the disease. . In order to reveal the role of MDA5 during IFN response induced by duck hepatitis virus infection, duck fibroblasts cells was chosen to observe the IFN response to DHV infection. The levels of MDA5 and the adaptor protein MAVS expression were detected by using Real-time PCR and Western blotting. CAT reporter plasmids that were under the control of IRF3 and IFN-kB promoter were used to analyze the effects of DHV infection. Meanwhile, different isolates of duck hepatitis viruses that differed in serotypes and virulence were used to infect DEF cells, and IFN-βlevels were compared and assayed. What's more, full-length MDA5 and its dominant negative mutant, MDA5N, MDA5C, were transiently expressed in DEF cells followed by DHV infection. Furthermore, siRNAs were used to knockdown the endogenous expression of MDA5 in DEF cells. And the antiviral effects and mechanism of MDA5 against DHV was determined by RNAi and over-expression assay. . In order to study the interaction of MDA5 and duck hepatitis viral protein, the protein level of early infection was detected by Western blotting, while using the reverse genetics technology to construct recombinant viruses and measure cytokine expression to certificate the results, which could provide insights for the understanding of virus-host interaction and development of intervention strategy for DHV infection.