FIG. 6.

N36^Mut(e,g) and C34 peptides inhibit infectivity additively in an HXB2 Env-pseudotyped virus neutralization assay. Dose-response curves for antiviral activity of N36^Mut(e,g) alone (green), C34 alone (red), and C34 plus N36Mut^(e,g) in two combination ratios, 1:100 and 1:200, are shown. The concentrations for the combination curves refer to the concentration of C34. The experimental data (averages of two measurements, with error bars representing standard deviations) are fit by nonlinear least-squares minimization to a simple binding isotherm (see the Fig. 5 legend). For this data set, the IC₅₀s for C34 and N36^Mut(e,g) alone are 27.5 ± 5.2 nM and 6.2 ± 0.8 μM, respectively. The DRIs for C34 and N36^Mut(e,g) in a combination ratio of 1:100 are 1.3 ± 0.3 and 3.0 ± 0.7, respectively, giving a CI of 1.3 ± 0.5. The corresponding values at a combination ratio of 1:200 are 2.2 ± 0.6, 2.5 ± 0.5, and 1.1 ± 0.4, respectively. Thus, in this combination ratio range, the average CI is 1.2 ± 0.4, indicative of additive inhibition.