FIG. 7.

BLeeRG- and mutant virus-infected MDCK and BM2-expressing cells. MDCK and BM2CK#1-3 cells were infected with 10⁴ TCID₅₀ of wild-type BLeeRG, BLeeBM2stop#4, or BLeeBM2del virus (which had been grown in BM2CK#1-3 cells) and overlaid with 1.0% agarose. The cells were fixed at different times and treated with 0.1% Triton X-100 in 3% formaldehyde solution. The viral proteins were detected by immunostaining with anti-influenza B virus nucleoprotein monoclonal antibody as the primary antibody and biotinylated secondary antibody with the Vectastain ABC kit. The left, middle, and right dishes in each row show cells infected with the wild-type BLeeRG, BLeeBM2stop#4, and BLeeBM2del viruses, respectively.