Figure 1. Assay scheme for HIV-1 Env-mediated cell-cell fusion.
An activator (tTA) is used for inducible expression of the HIV-1 Envs in the effector cells, allowing Env expression to be turned on by the removal of Dox from the medium. When effector and target cells are cocultivated, cell-cell fusion enables the diffusion of tTA to the target cell. This activates the transcription of the F-Luc reporter gene, which is also under the control of a tTA responsive promoter. F-Luc activity can be measured and is quantitatively related to the extent of fusion.
