Effect of SE on HIV infection. (A) Schema describing the experimental procedure. (B) Effect of treatment of virus stocks with 90% (v/v) of SE on R5 HIV-1 infection. TZM-bl cells were infected with the indicated dilutions of SE- or PBS-treated virus stocks. The inoculum was either removed after 2 hours of exposure (wash) or left on the cells. Shown are average β-galactosidase activities (n = 3) measured 2 days after virus exposure. RLU/s: relative light units per second. The numbers above the upper curve give n-fold enhancement of HIV infection by SE relative to that measured for the corresponding PBS control. (C) Metabolic activities of cells analysed in B. (D) Effect of low concentrations of SE on HIV infection. R5 HIV-1 stocks were treated with the indicated concentrations of SE, diluted and used to infect TZM-bl cells. The Y-axis gives average values of triplicate infections, and the X-axis gives the final dilution of the virus stocks. The infection levels were determined as described above. Percentages refer to the SE concentrations during virion treatment. The final concentrations in the cell culture are 15-fold lower.