CD4-Specific Designed Ankyrin Repeat Proteins Are Novel Potent HIV Entry Inhibitors with Unique Characteristics
Figure 4
Characterization of the binding domain of CD4 specific DARPins.
(A) Competition between the fluorescently labeled DARPins D29.2HLX and D57.2HLX with unlabeled DARPins was analyzed by flow cytometry using CD4+ A3.01 cells. Compared to the control with no competitor (shaded in gray) competitive binding was observed for all CD4-specific DARPins (E3_5: blue; D23.2: light blue; D25.2 red; D27.2: orange; D29.2: brown; D55.2: green; D57.2: purple). The autofluorescence control is shown as dotted line (B) Binding of the same DARPins to human CD4 (hCD), murine CD4 (mCD4) and chimeric human CD4 containing murine D1 domain in the human CD4 context (hCD4mD1), indicating that all tested DARPins bind to the D1 domain of human CD4. The same coloring scheme for DARPins as in Figure 4A was used. MAb OKT4, specific for human CD4-D3, is shown as black dotted line.