Infection and activation of bursal macrophages by virulent infectious bursal disease virus

• Published in: Virus research 2005-10, Vol.113 (1), p.44-50
• Main Authors: Khatri, Mahesh, Palmquist, Joseph M., Cha, Ra Mi, Sharma, Jagdev M.
• Format: Article
• Language: English
• Subjects: Animals; Birnaviridae Infections - immunology; Birnaviridae Infections - veterinary; Bursa of Fabricius - immunology; Bursa of Fabricius - pathology; Bursa of Fabricius - virology; Bursal macrophages; Cell Count; Cells, Cultured; Chickens; Gene Expression Profiling; IBDV; Immunohistochemistry; Infectious bursal disease virus; Infectious bursal disease virus - immunology; Infectious bursal disease virus - pathogenicity; Infectious bursal disease virus - physiology; Interleukin-1 - genetics; Interleukin-18 - genetics; Interleukin-6 - genetics; Macrophage Activation; Macrophages - immunology; Macrophages - virology; Poultry Diseases - immunology; Poultry Diseases - virology; Proinflammatory cytokines; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - analysis; RNA, Viral - analysis; Viral Proteins - analysis
• ISSN: 0168-1702; 1872-7492
• DOI: 10.1016/j.virusres.2005.04.014

In this study the effect of infectious bursal disease virus (IBDV) on bursal macrophages during the acute phase of the infection was examined. Specific-pathogen-free (SPF) chickens were exposed to virulent IBDV and bursal adherent cells were examined by immunohistochemisrty and RT-PCR for virus infection and by real-time quantitative RT-PCR (qRT-PCR) for mRNA transcripts of proinflammatory cytokines and iNOS. Viral genome was detected in bursal macrophages at 3, 5 and 7 days post-infection (dpi). Immuno-histochemical staining revealed double positive cells for KUL01 (macrophage marker) and intracellular viral proteins, showing viral replication in bursal macrophages of infected chickens. We noted a significant decrease in the total number of bursal macrophages in infected chickens, probably due to the lysis of infected cells. However, likely due to extensive necrosis of B cells, the relative proportion of bursal macrophages was significantly higher ( P < 0.05) in infected birds at 3 and 5 dpi than in controls. Among the cytokines examined, IL-6 showed the greatest upregulation (100-fold increase) at 3 dpi. Expression of IL-1β was maximum at 3 dpi whereas IL-18 expression was highest at 1 dpi. Enhanced expression of iNOS mRNA was observed at 5 dpi. Increased expression of the proinflammatory cytokines and iNOS correlated well with the presence of the inflammatory response in the infected bursa. These data suggested that B cells may not be the sole targets for the virus; macrophages and possibly other cells may serve as host for IBDV.