Infection and activation of bursal macrophages by virulent infectious bursal disease virus.
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-1beta 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.
Khatri
Mahesh
M
Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, 1971 Commonwealth Avenue, St. Paul, MN 55108, USA.
Palmquist
Joseph M
JM
Cha
Ra Mi
RM
Sharma
Jagdev M
JM
D000818:Animals; D018175:Birnaviridae Infections / Q000276:immunology / Q000662:veterinary*; D002060:Bursa of Fabricius / Q000276:immunology* / Q000473:pathology / Q000821:virology; D002452:Cell Count; D002478:Cells, Cultured; D002645:Chickens; D020869:Gene Expression Profiling; D007150:Immunohistochemistry; D007243:Infectious bursal disease virus / Q000276:immunology / Q000472:pathogenicity / Q000502:physiology*; D007375:Interleukin-1 / Q000235:genetics; D020382:Interleukin-18 / Q000235:genetics; D015850:Interleukin-6 / Q000235:genetics; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology* / Q000821:virology*; D011201:Poultry Diseases / Q000276:immunology / Q000821:virology*; D012333:RNA, Messenger / Q000032:analysis; D012367:RNA, Viral / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014764:Viral Proteins / Q000032:analysis
D007375:Interleukin-1; D020382:Interleukin-18; D015850:Interleukin-6; D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins