Influence of CD44 expression on RANTES-induced HIV infectivity enhancement. HeLa-CD4 cells were transfected with CD44e3 dsRNA and invCD44e3 dsRNA or mock transfected. Three days after transfection, CD44 protein expression was monitored by FACS and MFI levels are indicated above the respective panel. Cells were then treated with 640 nM RANTES for 24 hours (gray bars) or were mock treated (no chemokine; open bars). After 24 hours, chemokine was removed and cells infected with HIV-1_MuLV-luc (1 ng p24 antigen/mL). Data shown are means of 2 independent experiments. The extent of viral infection was measured by luciferase readout (RLU) on day 3 after infection and the results are presented as percentages of control (no chemokine added = 100%) for each cell set. Absolute infection rates observed in the individual cell sets in absence of RANTES were 73, 69, and 70 RLU for mock-transfected, CD44e3 dsRNA, and invCD44e3 dsRNA cells, respectively.