About 70-80% confluent CEF cells in 96-well plates were infected with REV-A HLJ07I at a MOI of 0.2. At 5 days postinfection, the infected cells were fixed with icy cold ethanol absolute for 15 min at 4uC, and air dried. The fixed cells were incubated with mAb A9E8, REV-A-positive chicken serum, antiporcine IFN-c mAb (Sigma, St Louis, MO, USA), or REV-Anegative chicken serum for 1 h at 37uC. After washing three times with PBS, 50 mL/well of FITC-conjugated goat anti-mouse IgG or FITC-conjugated rabbit anti-chicken IgG (Sigma, St Louis, MO, USA) at 1:100 dilutions were added and incubated for 1 h at 37uC. The cells were rinsed three times with PBS and once with deionized water, and mounted in 50 mL of 90% glycerol in PBS, and then observed under the Nikon Eclipse Ti-E microscope equipped with NIS-Elements AR software.