Expression And Distribution Of NLRP3 Inflammatory Pathway Relative Genes In The Lung Of BALB/Cmice Response To H7N9 Avian Influenza Virus With Different Pathogenicity

The surface genes of the H7N9 avian influenza virus are from the wild birds H7 and N9subtype virus,and theinternal genesare from poultry H9N2 subtype viruses.Since the emergence of the first case of human infected H7N9 avian influenza virus in 2013,27provinces and cities,autonomous regions and special administrative regions in china have been found that people infected with H7N9 avian influenza virus,and the casesof infection are increasing.Affected by the H7N9 avian influenza,the poultry farming industry suffered heavy losses in most regions of our country.So the popularity of H7N9 avian influenza virus has greatly threatened the human health and the development of breeding industry.When the influenza virus invades the cells,the clear of the influenza virus requires the development of inflammatory responses by the host.The activation of the NLRP3inflammatory complex,its upstream and downstream signaling pathways play an important role in the identification of the virus and the initiation of the endogenous immune response.The activation of NLRP3-related signaling pathway induces the production of proinflammatory cytokines and chemokines such as IL-1?,TNF-?,then the chemokines can induce inflammatory cell infiltration to the infection siteto against virus.But the cytokine storms can lead to serious pathological damage to the host.The mechanism of NLRP3-related inflammatory signaling pathway remains unknown when the organism is infected with H7N9 avian influenza virus.Especially what is the effect of the virus on the regulation of the inflammatory signaling pathway a ssociated with NLRP3 in the host after infected with the influenza virus that only mutate in the residue 627 of PB2 protein.How the body regulates the pathological damage caused by the cytokine storm.These questions urgently need us to explore and answer.In this research,expression pattern and histological distribution ofNLRP3inflammatory pathway related genes,RIP3,NLRP3,IL-1?,TNF-?,SLIT2 and ROBO4 in the lung of BALB/c mice infected with two H7N9 IAV strains with only a PB2 residue 627difference were investigated,as well as the histopathological injury of the lung.The results are as follows.The pathogenicity of H7N9 avian influenza virus V_K627 strain and its PB2residue 627 single mutant r V_K627E strain on BALB/c mice.Observed and recorded the weight changes and mortality of the two groups of mice infected with different viruses at various time points,collected the lungs of BALB/c mice to make sections for histopathological detection.The results showed that mice infected with V_K627 strain began to lose weight on day 2,with serious diffuse venous hyperemia in alveolar wall,slightly interstitial pneumonia and infiltration of inflammatory cells without death.While the virulence of rV_K627E,a single mutant strain of PB2 residue627,was weak,and the body weight of the challenged mice showed an increasing trend.The alveolar wall had only slightly and locally venous hyperemia and there was no death.The effects of H7N9 Avian Influenza Virus and its mutant strain infection on the expression profile and histological distribution of NLRP3 pathway related genes in Lung of BALB/c mice.The expression level of RIP3,NLRP3,IL-1?,TNF-?,SLIT2 and RO BO4 were detected by real-time PCR and the cell-specific distribution of the protein was detected by immunohistochemistry.The results showed that the expression levels of RIP3,NLRP3,IL-1?and TNF-?were significantly up-regulated in mice infected with H7N9 virus comparing with control group,and the gene expression of V_K627 groups was significantly higher than that of r V_K627E.The results showed that two strains of H7N9 avian influenza virus could activate the expression of NLRP3signal pathway related genes in different degree,which may play an important role in promoting the pathological damage to lung.Compared with the mice infected with V_K627,the expression levels of SLIT2 and ROBO4 were significantly up-regulated in r V_K627Egroups,while the expression of V_K627groups was inhibited.This may be one of the factors that the development of interstitial pneumonia and inflammatory infiltration was inhibited in r V_K627E groups.The histological distribution of RIP3,N LRP3,IL-1?,TNF-?,SLIT2 and ROBO4 showed cell-specific in lung tissue induced by avian influenza virus infection,especially expressed in alveolar epithelium cells.To sum up,these results provide the basis data for further study of the mechanism of inflammatory response and the role of the PB2 residue 627 in the H7N9 influenza virus.In addition,the SLIT2-ROBO4 signal pathway regulates the response of the host vascular system to inflammation,which will provide a new therapeutic direction for H7N9 influenza virus infection.