FIG. 4.

PI susceptibilities of proteases containing primary resistance substitutions with and without I50L. PI susceptibilities (IC₅₀ of mutant/IC₅₀ of wild type) were measured using Western blotting of total cell lysates after transfection of gag-pol expression vectors (n = 3) and plotted for primary resistance substitutions + A71V (double mutants, white bars) and for primary resistance substitutions + I50L/A71V (triple mutants, shaded bars). Parallel dose-response experiments using infectious virus mutants with V82A, I84V, and L90M substitutions (+A71V) with and without I50L were conducted. The I50L fold change for each virus (EC₅₀ of triple mutant/EC₅₀ of double mutant) was calculated. These values are shown on the line below the plots for the corresponding proteases (virus I50L change).