Replication kinetics of influenza A viruses in BxPC-3, HPDE6, and MDCK cells. Cells were infected at an MOI of 0.001 PFU/cell, and virus titers in infected supernatants were determined via the TCID50 assay at 24 (black bars), 48 (light-gray bars), and 72 (dark-gray bars) hours postinfection. Results represent means plus standard deviations of results from three independent experiments of three replicate samples each.