Novel Chemokine-Based Immunotoxins for Potent and Selective Targeting of Cytomegalovirus Infected Cells

Figure 3

Design, binding, and cell killing of FTPs containing parts of the mucin-like stalk of CX₃CL1. (a) FTPs with an extended linker consisting of parts of the mucin-like stalk of CX₃CL1. (b) Binding of F49A-FTP and FTPs from this group on HEK-293 cells induced to express US28 (black circles) and CX₃CR1 (white squares). The IC₅₀ value for F49A-FTP-3 is >10⁻⁶ M (no binding detectable on CX₃CR1 expressing cells; marked with a star) and the binding selectivity was therefore not analyzed in (c). (c) Binding selectivity determined as fold improved affinity for US28 relative to CX₃CR1. (d) Cell killing of F49A-FTP and FTPs from this group on tetracycline induced HEK-293 cells expressing US28 (black circles) and CX₃CR1 (white squares). (e) Selectivity of F49A-FTP and FTPs from this group determined as fold improved potency in killing US28- relative to CX₃CR1-expressing cells. Values present IC₅₀ values from 3–5 independent biological replicates (b) and (d).

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