FIG. 2.

Fusion activity of SIV and SIV-MuLV chimeric Env proteins in cells expressing the coreceptor CCR5. Env proteins were expressed in HeLa cells using the vaccinia virus T7 expression system. HeLa cells were infected by recombinant virus VTF7-3 (a recombinant vaccinia virus expressing the T7 polymerase, provided by B. Moss) for 1 h and then transfected with DNA constructs encoding the Env proteins. At 12 h posttransfection, HeLa cells were overlaid with Ghost cells (obtained from the NIH AIDS Research and Reference Reagent Program) which express CD4 and CCR5. Cell fusion pictures were taken at 8 h after overlay of Ghost CCR5 cells under a Nikon microscope. (a) Mock transfection; (b) full-length SIV Env; (c) S-Menv; (d) S-MenvR-; (e) SIVenv733T+R; (f) SIVenv733T.