STLV-1 PVL evolution is inversely correlated with the rate of CD8⁺ cell-mediated lysis of STLV-1–infected cells. The lytic efficiency rates (or ϵ) were determined at different times (at 0, 1, and 2 weeks of treatment) for the 4 baboons, whose Tax expression was detectable by flow cytometry in the PBMCs. The variations of the ϵ value over a time period of 1 week were plotted against the corresponding variations of PVL. The plot is overlaid with the line of best. The variations of PVL and ϵ correlate significantly according to a 1-phase exponential decay model (R² = 0.63, or R² = 0.989 if the outlier point is excluded).