Fig. 4.

Plaque sizes and replication kinetics of recombinant viruses expressing mutated M2 proteins. (A and C) Plaque diameters of MDCK cells infected with the indicated recombinant viruses at 3 days postinfection (dpi). The cells were fixed and stained with a Naphthol Blue Black solution, and individual plaque diameters were measured from scanned images by using ImageJ. Representative data from triplicate experiments are shown. The Student t test was performed to determine significant differences compared to wild-type virus. (B and D) MDCK cells were infected with the indicated recombinant viruses at an MOI of 0.001. At the indicated hpi, cell supernatants were collected and the numbers of infectious virus particles were determined by TCID₅₀ assay on M2-expressing cells. The means and standard errors of the means for triplicate samples from a representative experiment are shown. The limit of detection is marked by a horizontal dotted line.