Fig. 4.

Anti-SIV activity of different C-terminal cystatin C fragments. (A and B) Inhibition of SIVmac239 by (A) full-length cystatin C- and N-terminally truncated or (B) extended CysC peptides. Numbers refer to amino acid positions in the full-length cystatin C sequence. GHOST-GPR15 cells were treated with the indicated concentrations of the cystatin peptides for 2 h at 37 °C before infection with a SIVmac239 Firefly luciferase reporter virus. Three days postinfection, Firefly luciferase activities were analyzed. Experiments shown in all panels were performed at least in triplicates and curves show mean values (±SEM). (C) Overview of the amino acid sequences and antiviral activity of chemically synthesized CysC peptides analyzed. IC₅₀ values were determined by infection of GHOST-GPR15 cells with a SIVmac239 luciferase reporter construct in the presence of increasing quantities of the indicated peptides.