title: Infection and activation of bursal macrophages by virulent infectious bursal disease virus.
abstract: 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.
authors.affiliation: Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, 1971 Commonwealth Avenue, St. Paul, MN 55108, USA.
authors.forename: Mahesh
authors.initials: M
authors.lastname: Khatri
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Palmquist
authors.forename: Ra Mi
authors.initials: RM
authors.lastname: Cha
authors.forename: Jagdev M
authors.initials: JM
authors.lastname: Sharma
mesh_terms: 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
chemical_list: D007375:Interleukin-1; D020382:Interleukin-18; D015850:Interleukin-6; D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins