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9.4.3.3 Effect of the Coreceptor Utilization Phenotype
The evolutionary response of the virus to antibody selection was also investigated
for viral populations initialized with V3 phenotypes other than R5 (Fig. 8). The simu-
lation conditions used were otherwise the same as described in Fig. 5 and with an
antibody stimulation threshold frequency of 0.1. The dynamics of the neutralization
component of fitness were altered very little, given that the dynamics of the functional
component of fitness were substantially different from when the population was ini-
tialized with an optimal R5 sequence. As in previous simulations, the functional com-
ponent of fitness decreased with adaptation to antibody surveillance. For populations
initialized with a near-optimal X4R5 V3 sequence, the final value for the functional
component of fitness, 0.58, is near that observed for a population initialized with an
optimal R5 V3 sequence under otherwise identical simulation conditions.
This is because the population evolved to R5 phenotype within the first 30
Figure 8.
Viral population mean fitness plotted over viral generations for simulations initial-
ized with X4R5 or X4 phenotype V3 sequences. Lines are means of 20 replicate simulations.
The antibody production stimulation threshold is 0.1. Other parameter values are as described
in Fig. 5.
