Role of intrabursal T cells in infectious bursal disease virus (IBDV) infection: T cells promote viral clearance but delay follicular recovery.
Infectious bursal disease virus (IBDV) induces an acute, highly contagious immunosuppressive disease in young chickens. We examined the role of T cells in IBDV-induced immunopathogenesis and tissue recovery. T cell-intact chickens and birds compromised in their T cell function by a combination of surgical thymectomy and Cyclosporin A treatment (Tx-CsA) were infected with an intermediate vaccine strain of IBDV (Bursine 2, Fort Dodge). Our data revealed that functional T cells were needed to control the IBDV-antigen load in the acute phase of infection at 5 days post infection. The target organ of IBDV, the bursa of Fabricius, of Tx-CsA-birds had a significantly higher antigen load than the one of T cell-intact birds (P < 0.05). Tx-CsA-treatment abrogated the IBDV-induced inflammatory response and significantly (P < 0.05) reduced the incidence of apoptotic bursa cells and the expression of cytokines such as interleukin 2 (IL-2) and interferon-gamma (IFN-gamma) in comparison to T cell-intact birds. T cell-released IL-2 and IFN-gamma may have mediated the induction of inflammation and cell death in T cell-intact birds. The IBDV-induced upregulation of tumor necrosis like-factor (TNF) expression was comparable between T cell-intact and Tx-CsA-birds. Tx-CsA-birds showed a significantly faster resolution of IBDV-induced bursa lesions than T cell-intact birds (P < 0.05). This study suggests that T cells modulate IBDV pathogenesis in two ways: a) they limit viral replication in the bursa in the early phase of the disease at 5 days post infection, and b) intrabursal T cells promote bursal tissue damage and delay tissue recovery possibly through the release of cytokines and cytotoxic effects.
Rautenschlein
S
S
Department of Veterinary PathoBiology, University of Minnesota, St. Paul, Minnesota, USA. Silke.Rautenschlein@tiho-hannover.de
Yeh
H Y
HY
Njenga
M K
MK
Sharma
J M
JM
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D018175:Birnaviridae Infections / Q000276:immunology* / Q000503:physiopathology* / Q000821:virology; D002060:Bursa of Fabricius / Q000276:immunology* / Q000821:virology; D002642:Chick Embryo; D002645:Chickens; D016572:Cyclosporine / Q000494:pharmacology; D007243:Infectious bursal disease virus / Q000472:pathogenicity*; D008213:Lymphocyte Activation; D023421:Models, Animal; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D013934:Thymectomy
D016572:Cyclosporine