Role of DC-SIGN and CD4 molecules in primary DCs. (A) Effects of anti-DC-SIGN and anti-CD4 mAbs on MHC-II-restricted HIV antigen presentation by B-cell lines. Stimulators (BRE and B-BRE-DCS cells) were exposed to HIV_MN-AT2 (1 nM p24) for 2 hours at 37°C. Anti-DC-SIGN (1B10), anti-CD4 (Q4120), and IgG isotype control mAbs (20 μg/mL) were added 30 minutes prior to and maintained during viral exposure. Cells were then cocultivated with HS cells (clone IV9) for about 8 hours, and activation of IV9 cells was assessed in an IFNγ ELISPOT assay. (B) Role of DC-SIGN and CD4 molecules in primary imDCs. Stimulators (primary DCs) were treated with mAbs as described in panel A, and were then exposed to HIV_MN-AT2 (1 nM p24) or to gag1 peptide (22 nM) and cocultivated with IV9 cells. Activity of IV9 cells was tested as in panel A. (C) Effects of anti-DC-SIGN mAbs on various HIV strains in primary imDCs. ImDCs (from a different donor than in B) were treated with mAbs as described in panel A, and were exposed to the indicated viruses: HIV_Yu2b, HIV_MN-AT2 (produced in 293T and T1 cells, respectively, at 4 nM p24), and HIV_Bru (produced in activated PBMCs, 0.5 nM p24). Cells were then cocultivated with IV9 cells. Activity of IV9 cells was tested as in panel A. All experiments were performed in the presence of AZT. For each panel, data are mean ± SD of triplicates and are representative of 3 independent experiments.