Anti–HIV-1 activity of SLPI muteins. Adherent monocytes were infected 1 hour with HIV-1_Ba-L in the presence of SLPI muteins, PI, or SLPI single domains. Free virus and inhibitor were washed away, and the infection was monitored by RT or p24 assay. Cells were infected in the absence of virus (Con), with virus only (DMEM), or in the presence of inhibitor. Values shown are at day 21 postinfection. *Significantly different from DMEM. (A) Cells were infected in the presence of PI 5 μg/mL or SLPI mutein Gly⁷² 5 μg/mL. (B) Cells were infected in the presence of SLPI mutein Phe⁷² 5 μg/mL. (C) Cells were infected in the presence of SLPI single domain 1 at concentrations of 10 or 20 μg/mL. (D) Cells were infected in the presence of SLPI single domain 2 at concentrations of 10, 20, or 50 μg/mL.