HCV-LP binding to DCs and C-type lectins. (A) Expression of mannose receptor, DC-SIGN, DEC-205, and Langerin on monocyte-derived DCs. C-type lectin expression on imDCs and mDCs was analyzed by FACS using cell surface protein-specific antibodies (NC indicates negative control corresponding to cells incubated with the respective isotype control antibody). (B, left) Inhibition of FITC-dextran binding and uptake into imDCs by mannan. FITC-dextran binding and uptake at 37°C was measured by FACS in the absence or presence of mannan (3 mg/mL). (B, right) Mannan does not inhibit cellular HCV-LP binding to imDCs. HCV-LPs in subsaturating concentrations (1 μg HCV-LP E2/mL) were added to imDCs in the absence or presence of mannan (3 mg/mL) and HCV-LP binding was analyzed as described in Figure 1. (C) Quantitative analysis of cellular HCV-LP binding in the presence of anti–DC-SIGN, anti–DC-SIGN/L-SIGN, anti–DEC-205, anti-Langerin antibodies, or control IgG. DCs were preincubated with mannan (3 mg/mL) or antibody (50 μg/mL) for 1 hour at 25°C. HCV-LPs (1 μg HCV-LP E2/mL) were added to the cells and HCV-LP binding was analyzed by flow cytometry as described in Figure 3A. To study whether trypsin pretreatment of DCs modifies HCV-LP binding, imDCs were exposed to 0.5% trypsin prior to the addition of HCV-LPs as described recently.²⁷  Mean ± SD of 3 experiments is shown (HCV-LP binding in the absence of antibody = 100%).