| Objective:In order to explore the the correlation between levels of the pro-inflammatory cytokines, IFN-y, IL-4, IL-12, IL-10 and the degree of damage pathological changes of chickens infected with nephropathogenic IBV.Methods:1-day-old chickens were experimentally infected with nephropathogenic IBV strain isolated by our laboratory. Experimental group was inoculated with 0.2 mL of allantoic fluid containing 1×105 median embryo infectious doses (EID 50) of the IBV strain by intraocular instillation. The control group was inoculated with sterile allantoic fluid. Chickens of two groups were housed in independent environment and other breeding conditions were the same. The chickens were examined daily for signs of infected chickens up to 21 days postinoculation. Blood samples were collected from chicken heart randomly at days 2,3,4,5,6,7,14 and 21 postinoculation; Lymphocytes were separated from a blood samples and then extracted total RNA from the lymphocytes for RT-PCR. Necropsy was also examined and the kidney of chicken was collected for histopathology and virus detection by Immunochemical staining techniques.Results:Chickens were in good mental state from 1 to 3 days postchallenge. Chickens in treated group exhibited obviously clinical signs from 4 to 5 days and more severe until 6 to7 day post-inoculation. And some chickens were dead. The clinical signs of challenged chickens began to disappear gradually after 8 to 21 days of inoculation. Autopsy pathological:The infected chickens had no obvious pathological changes after challenged from 1 to 3 days. Ureters experienced obvious swelling at 4 day and loss of blood to the kidneys at 5 day postchallenge. Gross lesions were mainly in the kidneys of diseased chickens postchallenge from 4 to 7 days. The kidney parenchyma was pale, swollen, and mottled; tubules and urethras were distended with uric acid crystals. Histopathology examination:The infected chickens had no obvious histopathological changes after challenged from 1 to 2 days. Glomerular capsule had no clear boundary at 3 day postchallenge. Kidney tissue was full of blood cells and epithelial cell of kidney tubule fall off from 4 to 5 days postchallenge. Histopathological changes became more severious from 6 to7 days post-inoculation. Histopathological changes of kidney tended to disappear after 8 days of inoculation. IBV could be located in epithelial cell of kidney tubule by Immunochemical staining techniques. However, chickens in the control group did not show any clinical sign of gross lesions gross or histolgical lesions as observed in the challenged group.The relative mRNA expression level of IFN-?, IL-4, IL-12 in lymphocytes appeared to a significant up-regulation from 5 to 7 day and reached maximum at 7 day postchallenge, respectively. Expression of IFN-?, IL-4, IL-12 in lymphocytes mRNA were also seen to have a significant down-regulation at 8 day postchallenge, respectively. For IL-10 mRNA expression, a significant up-regulation was observed from 5 to 7 day and reached maximum at 7 day postchallenge. The relative mRNA expression level of IL-10 mRNA expression was lower than that of FN-?, IL-4, IL-12. Conclusion:The results study suggest that IBV infection induces an innate immune response with increased mRNA expression of pro-inflammatory cytokines such as IL-4, IL-12, IL-10 and anti-viral IFN-y,while severe kidney damage was observed. |
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