Figure 3. Estimating the half-life of SIV DNA in resting CD4+ T cells.

The proportion of WT virus in plasma (green circles), the fraction of WT virus estimated from the area under the curve (AUC) of viral load (blue circles) and the experimentally observed fraction of WT virus SIV DNA in resting CD4+ T cells (red squares) are shown for each animal in the top part of each panel. The black line illustrates the best-fit SIV DNA half-life to the observed fraction of WT virus in resting CD4+ T cells for each animal. Animals are arranged in order of increasing half-life of SIV DNA. The bottom part of each panel (black triangles) represents total plasma viral load. Viral loads are all on the same log₁₀ scale, from 10–10⁹. The bottom right two panels (B0517 and B0547) illustrate two animals in which EM appeared only transiently in plasma. In this case, the fraction WT virus is nearly 100% in both plasma and AUC estimates at the time points where DNA was measured, so the ‘escape clock’ fits equally well with a half-life of 1 day or 100,000 days.