FIG. 3.

CD4- and CXCR4-pseudotyped MLV vector selectively infects HIV-1-infected cells. HeLa CD4-LTR/β-gal cells (18) were incubated with a supernatant from HIV-1-producing Molt-IIIB cells for 2 days. The cells were then infected with a CD4- and CXCR4-pseudotyped or amphotropic (Ampho) MLV vector containing the GFP gene. At 2 days postinfection, the cells were analyzed for GFP expression by fluorescence microscopy and photographed. The cells were then stained for β-Gal expression (25) with 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside. The same field was photographed under bright-field microscopy; β-Gal expression (blue) indicates HIV-1 infection. Note that the amphotropic vector transduces both HIV-1-infected and uninfected cells (arrow and arrowhead, respectively). The CD4- and CXCR4-pseudotyped vector transduces only HIV-1-infected cells (all cells that are green are also blue).