Figure 6. Effect of replacement R55W in 2C on FMDV cytopathology.

A, BHK-21 cell-killing assay [40] carried out with either FMDV WT (expressing three VPgs) with the standard 2C (abbreviated as WT) or FMDV WT with substitution R55W in 2C (abbreviated as WT R55W). Serial dilutions of either FMDV WT or FMDV R55W were applied to wells containing 10⁴ BHK-21 cells each. The plot depicts the minimum MOI (PFU/cell) required to cause complete cytopathology (detachment of all cells from the monolayer) at the indicated hours post-infection, as previously described [40]. Results are the average of four independent determinations. Note that the presence of R55W in 2C decreases the MOI needed to cause complete cytopathology for a given time. B, Quantification of cytopathology (percentage of cells detached from the monolayer) in cells with RNA from wild type (WT) or mutants V19-4, V15-9 or V3 expressing either wild type 2C or 2C with substitution R55W. At 8 h post-electroporation the total number of cells and the number of detached cells were counted; a correction was introduced to account for the number of cells that were detached due to the electroporation by parallel measurements with mock-electroporated cells (around 50% of cell detachment). Results are the average of three determinations.