FIG 2.

TK is essential for BA71 growing in porcine alveolar macrophages (PAMs) in vitro, while CD2v is not. PAMs were infected at a multiplicity of infection (MOI) of 1 with the following virus stocks: BA71 (BA71 grown in macrophages), BA71-Cos (BA71 grown in COS-1 cells), BA71ΔCD2 (BA71Cos deficient in the CD2v gene grown in COS-1 cells), and BA71ΔTK (BA71-Cos lacking the thymidine kinase gene and grown in COS-1 cells), and the kinetics of virus production was moniotored by harvesting of the cell supernatants at different times. All samples were directly titrated by plaque assay in COS-1 cells, and the results were plotted in the logarithmic scale as PFU per milliliter of cell supernatant.