The enhancing effect of SE is independent of the viral coreceptor tropism. (A) Analysis of CEMx-M7 cells infected with untreated or SE-treated (10% v/v) X4 and R5 HIV-1 by fluorescence microscopy 2 dpi. (B) Treatment with SE enhances HIV-1 infection of primary PBMCs. Stimulated PBMCs were infected with the same dose of the indicated HIV-1 NL4-3 V3 recombinants that were either not treated or treated with 10% (v/v) SE. Three days later, 100 μl of the cell-free PBMC culture supernatant was used to infect TZM-bl indicator cells. Shown are average infection rates of TZM-bl cell ± SD (n = 3) measured 2 days after virus exposure. X4 virus is color-coded red; R5 virus, green; and X4R5 HIV-1, black.