Fig. 2

Antigenic characterization of mIBV and rIBV-wt. a Immunofluorescence analyses of IBV Beaudette, MHV A59 and mIBV #1B3-IIA infected cells. LR7 cells infected with mIBV were fixed and double-immunolabeled with a polyclonal against IBV (green) and a polyclonal antibody against MHV (red). IBV Beaudette-infected BHK-21 cells and MHV-infected LR7 cells were taken along for comparison. Nuclei are visualized with DAPI (blue). Overlay pictures (Merge) are shown on the right. b Similar to (a), except that a monoclonal antibody against IBV S2 was used instead of a polyclonal against IBV, indicating the absence of IBV S2 protein in mIBV infected cells. c Immunohistochemistry of IBV H52 BI and rIBV-wt infected CAM tissues. Ten-day-old embryonated chicken eggs were inoculated with IBV H52 BI (positive control), mIBV-infected and p-IBV transcript electroporated LR7 cells (resulting in generation of rIBV-wt), mIBV infected and p-IBV transcript, but not electroporated, LR7 cells (mIBV + p-IBV mock) or PBS (mock). Formalin-fixed and paraffin-embedded CAM tissues were immunohistochemically stained using a monoclonal antibody against IBV S2. Replication of (r)IBV in the epithelial cells of the CAM is indicated by red cytoplasmic staining, which is absent in eggs inoculated with mIBV-infected non-transfected LR7 cells