FIG. 8.

CD63 is not involved in Env-mediated cell-cell fusion. (A) Cell-cell fusion in QT6 cells. The indicated expression constructs were transfected into QT6 cells and allowed to fuse with QT6 cells expressing ADA Env (striped bars) or HXB Env (black bars). Relative levels of fusion were determined by luciferase production at 6 h, as described in Materials and Methods. Decreasing amounts of transfected CD4 plasmid are shown by decrescendo bars. (B) Macrophage fusion assay. Macrophages were treated with anti-CD63 or control MAb followed by cross-linking (XL) with anti-mouse secondary antibody, and the relative levels of fusion with JRFL or UG021 Env-transfected 293T cells were measured at 6 h, as described in Materials and Methods. RLU, relative light units.