DC-mediated HIV-1 transmission is co-receptor dependent. (A) FACS analysis of TN, TCM and TEM cells for CD4 and co-receptors CCR5 and CXCR4. Open histograms represent isotype controls. (B) Transmission inhibition by co-receptor ligands and a fusion inhibitor. A single-cycle transmission assay to TN, TCM and TEM cells was performed with R5 and X4 HIV-1 loaded DC. Prior to co-culture with DC, the T cells were pre-incubated with ligands for CCR5 (RANTES) or CXCR4 (AMD3100) (grey bars) or alternatively, with fusion inhibitor T1249 (black bars). After 2 days, the percentage CA-p24+ T cells was determined by FACS. The percentage inhibition of transmission relative to transmission without inhibitors is indicated on the y-axis. Error bars represent standard deviations.