Fig 2. Non-linear least squares analysis and subsequent fitness landscape of HSV-1 IE, E and L genes show that IE and E genes are more vulnerable to A3 mutation than L genes.

A) Relative mean, defined as the ratio of means (μ) from each increasing mutation probability versus the mean when the mutation probability is zero (μ₀). For each baseline probability, these values are fit to an exponential curve f(x) = e^-bx using non-linear least squares. The numbers for each stratification in the legend denotes the half-maximal inhibitory probability (IP50) for that stratum. The IP50 is analogous to the half-maximal inhibitory concentration–it measures how high of a mutation probability we need to reduce μ/μ₀ by 50%, calculated by $\frac{\mathit{ln}\left(2\right)}{b}$. Shown here are the strata: IE/E/L = .1/.2/.7 (light green), IE/E/L = 1/0/0 (dark red), IE/E/L = 0/1/0 (yellow), and IE/E/L = 0/0/1 (dark green). B) A heatmap of all strata. The gradient up the x-axis denotes a higher proportion of pressure on IE genes. The gradient up the y-axis denotes a higher proportion of pressure on E genes. Finally, the gradient down both the x-axis and y-axis denotes a higher proportion of pressure on L genes. The intensity of each color reflects the IP50 for that stratification–redder indicates a higher A3 pressure (low IP50), and greener indicates a lesser A3 pressure (high IP50). Note that the line colors in A) correspond to the heatmap intensities of those strata in B).