Abstract
BackgroundCytokines are important mediators and regulators of host responses against foreign antigen, with their main function to orchestrate the functional activities of the cells of the immune system. However little is known about the role of cytokines in pathogenesis and immune responses caused by infectious bursa disease virus (IBDV). The aim of this study was to examine the transcripts of cell-mediated immune response-related cytokine genes in the bursal tissues of chickens infected with IBDVs of varying virulence to gain an understanding of pathological changes and mechanisms of immunosuppression caused by IBDV infection and the immune responses evoked.ResultsReal-time quantitative PCR analysis revealed that the expression levels of both Th1 [interferon (IFN)-γ, interleukins (IL)-2 and IL-12p40] and Th2 (IL-4, IL-5, IL-13 and IL-10) cytokines were significantly up-regulated following challenge with the H strain (vvIBDV) and up to 2- and 30-fold, respectively (P < 0.05). Following infection with the Ts strain (cell-adapted virus) these cytokine transcripts were up-regulated at 5 days post-infection (dpi), 2- and 13-fold respectively (P < 0.05), while the expression levels of IL-2 and IL-4 were not significantly different (P > 0.05). A higher degree of cytokine expression was induced by the H strain compared with the Ts strain.ConclusionThe results indicate that the expression of cell-mediated immune-related cytokine genes is strongly induced by IBDV, especially by the vvIBDV, H strain and reveal that these cytokines could play a crucial role in driving cellular immune responses during the acute phase of IBDV infection, and the cellular immune responses caused by IBDV of varying virulence are through different signaling pathways.
Highlights
Cytokines are important mediators and regulators of host responses against foreign antigen, with their main function to orchestrate the functional activities of the cells of the immune system
Generation of standard curves for real-time PCR analysis Standard curves for the genes encoding IFN-g, IL-2, IL12p40, IL-4, IL-5, IL-13, IL-10, infectious bursa disease virus (IBDV) (H strain and Ts strain) and GAPDH were generated to determine relative quantification of cytokine expression and viral load in the bursa, with GAPDH used as the reference gene
Of the seven genes examined in this study, the levels of expression of IFN-g, IL-2 and IL12P40 genes in the bursa tissues following H strain infection were increased compared with the IL-4, IL-5, IL-13 and IL-10 genes; the expression levels of IL-4, IL5, IL-13 and IL-10 genes in Ts-infected chicken bursa had a higher fold-change than the IFN-g, IL-2 and IL12p40 genes
Summary
Cytokines are important mediators and regulators of host responses against foreign antigen, with their main function to orchestrate the functional activities of the cells of the immune system. Little is known about the role of cytokines in pathogenesis and immune responses caused by infectious bursa disease virus (IBDV). The aim of this study was to examine the transcripts of cell-mediated immune response-related cytokine genes in the bursal tissues of chickens infected with IBDVs of varying virulence to gain an understanding of pathological changes and mechanisms of immunosuppression caused by IBDV infection and the immune responses evoked. Viral infection results in lymphoid depletion of B cells and the destruction of bursal tissues [10], leading to an increased susceptibility to other infectious diseases and poor immune response to vaccines [5]
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