Figure 1. A simulation of HIV dynamics for the model (A.1) - (A.3) with T(0) = 600/mm³ and V_s(0) = 10/mm³. The curves correspond to data in (11). The set-point of the virus is in the middle range (15) and corresponds to a typical disease progression of about 9 years. The contribution to the plasma virus from the external lymphoid compartment is more than 90%, as may be computed from equation (A.3). The curves T(t) and V_s(t) are approximately inversely proportional, as may be seen from equation (A.3) (the inverse proportionality is specific to a given set-point). In c,d, a simulation of a combined drug treatment corresponds to data in (9). The treatment begins with the uninfected CD4+ T-cell count at 200/mm³, the infected CD4+ T-cell count at 9.5/mm³, and the virus level at 34/mm³ (these values are obtained from the simulation in a, b at 7.9 years). In d, the heavy line is the total virus population, the thin line is the wild-type virus population, and the dashed line is the drug-resistant virus population. Complete replacement of wild-type virus by resistant virus occurs by week 5. The treatment parameters are c₁=.5, c₂=.025, c₃=.15, and the resistance mutation parameter is q=10^-7.