Transcriptionome Analysis Of Lung Of Quails Infected With H9N2 Subtype Avian Influenza Virus

H9N2 subtype avian influenza virus?AIV?was a low pathogenic AIV,which can cause infection in poultry,wild birds,human and other animals.Birds infected with H9N2subtype AIV mostly showed recessive infection or mild clinical symptoms,but the different degrees of damage were observed in their digestive tract and respiratory tract.Quails can cause infection and transmit the virus to other birds,mammals and humans as a host of H9N2 subtype AIV.Quails was more susceptible to H9N2 subtype AIV infection and their lungs showed more severe pathological damage than chickens from previous studies.At present,the pathogenic mechanism of chickens infected with H9N2 subtype AIV had tended to be perfect,but the molecular pathogenic mechanism of quails infected with H9N2subtype AIV was still unclear.In this study,a H9N2 subtype AIV?A/chicken/Jinmen/JM0305/2017?isolated from live poultry market in Jingmen City,Hubei Province was used to infecte 28-day-old quails at the dose of 10^7.0 EID₅₀/100ul by nose-drop.The molecular pathogenesis and immune response mechanism of quails infected with H9N2 subtype AIV were comprehensively analyzed by histopathology,immunology and transcriptome.The results are as follows:1.Histopathological analysis of quails infected with H9N2 subtype AIVThree days post infection,all quails were dissected and histopathology and immunohistochemistry were used to analyze.The results showed that the pulmonary hemorrhage,congestion,interstitial pneumonia in the lung,edema,necrosis and exfoliation of mucosal epithelial cells in the trachea,necrosis and exfoliation of renal tubular epithelial cells in the kidney,slight ulcer in the laryngeal,and enhancement of hepatocyte eosinophilia in the liver were observed.The virus mainly distributed in and around the site of injury,including alveolar epithelial cells,bronchial epithelial cells,tracheal mucosal epithelial cells,cilia and chondrocytes,renal tubular epithelial cells.2.Transcriptionomic analysis of the lung of quails infected with H9N2 subtype AIVThe transcriptome analysis showed that there were 288 differentially expressed genes?DEGs?in the infected group compared with the control group,including 212 up-regulated genes and 76 down-regulated genes,containing 32 immune-related DEGs.There were 23up-regulated genes and 9 down-regulated genes in immune-related genes.In up-regulated genes,OASL?16.80 times?,CMPK2?11.79 times?and MX1?10.85 times?were up-regulated by more than 10 times,down-regulation of ADCY8 were the highest?-4.89 times?in down-regulated genes.The up-regulated genes in immune-related DEGs were mainly related to the regulation of type I IFN and inhibition of viral replication.MX1 gene can induce inflammation to inhibit viral entry into host cells,which may be related to inflammation in infected quail lungs.The immune response was initiated through activation of Jak-STAT,RIG-like receptor,Toll-like receptor and other signaling pathways for infected quails.At the same time,down-regulation of ADCY8 and up-regulation of C1S and CMPK2 can inhibit cell energy metabolism to affect virus proliferation.In conclusion,no-clinical symptoms was although showed in quails infected with H9N2 subtype AIV,but mild respiratory tract injury was observed,up-regulation of MX1may be involved in the occurrence of pneumonia in infected quails.The infection of virus was resisted by initiating innate immune response and inhibiting energy metabolism of host cells in infected quails.This study was the first to conduct a transcriptome analysis of lung of quail infected with H9N2 subtype AIV,which would increase our understanding of the molecular pathogenesis and immune response mechanism of quail infected with H9N2subtype AIV,and provide new targets for future research and development of vaccines and anti-AIV drugs.