CD4-Specific Designed Ankyrin Repeat Proteins Are Novel Potent HIV Entry Inhibitors with Unique Characteristics
Figure 3
CD4-specific DARPins efficiently inhibit entry of both subtype B and C viruses.
(A) Graphical representation of the IC50 values of a 1st series DARPin, D3.1, and a 2nd series DARPin, D55.2, tested using env-pseudotyped viruses of subtype B (n = 9) and subtype C (n = 4) on TZM-bl cells. The following median IC50 values were determined: 45.4 nM for DARPin 3.1 (67.1 nM and 28.2 nM for clade B and C viruses, respectively) and 1.3 nM for DARPin 55.2 (1.3 nM and 0.7 nM for clade B and C viruses, respectively). (B) Inhibition curves of JR-FL pseudovirus used to assess synergy by analyzing combination indices (CI) in Figure 3C. Equipotent stocks of inhibitors were used to obtain comparable inhibition curves. Inhibitory effects of DARPin 25.2 (gray square) and the 2F5 mAb (gray triangle) alone are shown aside by side with the calculated (light gray, open triangle) and the actual observed inhibitory effect (black circles) of a 1∶1 mixture of the two inhibitor stocks. (C) DARPin 25.2 shows potent synergy in JR-FL pseudovirus inhibition in combination with neutralizing mAbs or entry inhibitors. CI for the inhibitory concentrations 70% and 90% (CI70, CI90) are represented for DARPin 25.2 in combination with mAbs IgG-b12, 2F5, 2G12, 4E10, the fusion inhibitor T-20, the anti-CCR5 mAb Pro140 and CD4-IgG2. Means from three independent experiments are shown. Error bars indicate the standard error of the mean.