| Infectious bursal disease(IBD)is an acute,highly contagious disease caused by infectious bursal disease virus(IBDV),which causes a large number of lymphocytes in the lymphoid organs to be destroyed.IBDV mainly attack the bursa of 3-6 weeks chicken which was the body immune immune organ,leading to vaccine failure,affecting the immune response of various vaccines,and ultimately cause the body's immune dysfunction.In this study,we investigated the expression of cytokines in the bursa of chickens infected with IBDV to determine the transcriptional regulation of pro-inflammatory,anti-inflammatory cytokines and antiviral genes.Cytokines including interferon,interleukin,tumor necrosis factor,transforming growth factor,Mx,Viperin and interferon induced transmembrane proteins were detected.19-day-old chickens were infected with IBDV through eye and intranasal routes.Chickens infected with IBDV exhibited somnolence,anorexia,and some chickens defecated white dung.Histopathological analysis showed that bursa was congestive and atrophy.By immunohistochemistry,we found that IBDV VP2 positive particles were increased firstly and then decreased after infected with IBDV.The results showed that the model of IBD is successful.The mRNA expression of cytokines in bursa of chickens during IBDV infection was detected by real-time quantitative PCR(qRT-PCR).The results showed that the expression of interferon gene in the process of IBDV infection was increased firstly and then decreased,and it was obvious that the expression of IFN-? and IFN-? were higher than that of IFN-? and IFN-?.The transcription of interferon was activated at24 h after IBDV infection.The transcription of IFN-? and IFN-? were highest at 96 h,which was coincident with the level of virus load in bursa.The transcription of IFN-?was suppressed at 72 h,while the transcription of IFN-? stayed in a high level throughout the infecting period.The different expression patterns of different interferon genes might associate with the expression of pro-inflammatory cytokines.Interleukins are important factors in response to viral infection,however some interleukins can promote the development of inflammation,which is harmful to the body recovery.The results showed that the cytokine expression was less than interferon.Cmpared with the control group,the expression of cytokine was increased significantly 24-120 h after infected by IBDV;the expression of proinflammatory cytokins,IL-1?,IL-6 and IL-8 were significantly higher than the other infecting points.At the late stage of infection,the expression had returned to pre-infection level,while the expressions of IL-7 and IL-10 were still higher than the pre-infection level.The expression of TNF-? and TGF-? were also effected by IBDV.The transcription of TNF-? was activated at 12 h after IBDV infection,the expression of TNF-? was higher than control group throughout the infection,while the expression of TGF-?was up-regulated at the late stage of infection,which might be related to the function of TNF-? and TGF-?.The transcription of interferon-induced antiviral genes,except for Viperin,was found to be up-regulated at 48 h after infected by IBDV.The high expression can persist to the late stage of infection.The expression of Mx gene reached maximum at72 h,while the expression of Viperin gene reached maximum at 48 h after infection.The expression of IFITM1,IFITM3 and IFITM5 were the highest at 72 h after IBDV infection.Expression of Mx and IFITM3 showed the same pattern after infected by IBDV.The up-regulation of interferon-induced antiviral genes might relate to the function of antivirus.Is there any relation between the disappearance of IBDV from body and the high expression of antiviral genes needs further study.Analysis of the expression of interferon-induced antiviral genes and related inflammatory factors will help to reveal the effect of IBDV on the immune function of bursa,providing theoretical support for the pathogenesis,immunosuppression and prevention of IBD. |
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