Propagation and titration of infectious bursal disease virus, including non-cell-culture-adapted strains, using ex vivo stimulated chicken bursal cells

Infectious bursal disease virus (IBDV) is a Birnaviridae family member of economic importance for poultry. This virus infects and destroys developing B lymphocytes in the cloacal bursa, resulting in a potentially fatal or immunosuppressive disease in chickens. Naturally-occurring viruses and many vaccine strains are not able to grow in in vitro systems without prior adaptation, which process often affects viral properties such as virulence. Primary bursal cells, which are the main target cells of lymphotropic IBDV in vivo, may represent an attractive system for the study of IBDV. Unfortunately, bursal cells isolated from bursal follicles undergo apoptosis within hours following their isolation. Here we demonstrate that ex vivo stimulation of bursal cells with phorbol 12-myristate 13-acetate (PMA) maintains their viability long enough to allow IBDV replication to high titers. A wide range of field-derived or vaccine serotype 1 IBDV strains could be titrated in these PMA-stimulated bursal cells and furthermore were permissive for replication of non-cell-culture-adapted viruses. These cells also supported multistep replication experiments and flow-cytometry analysis of infection. Ex vivo stimulated bursal cells therefore offer a promising tool in the study of IBDV.