HIV-1-Env-Mediated Cell-to-Cell Fusion Assay. A β-galactosidase
cell fusion assay was performed as previously described.19,20
Briefly, HeLa ADA cells were mixed with HeLa-P5 cells, in 96-well
plates, in a 1:1 ratio (20 000 total cells), in the absence or presence of
5 μM of the different molecules assayed. These cocultures were kept at
fusion for 16 h at 37 °C. The fused cells were washed with Hanks’
balanced salt solution and lysed, and the enzymatic activity was
evaluated by chemiluminescence (β-galactosidase reporter gene assay;
Roche Diagnostics, Germany). Anti-CD4 neutralizing mAb (5 μg/mL
was preincubated in HeLa-P5 cells for 30 min at 37 °C before
coculture with Env+ HeLa cells) was used as a control for the blockage
of cell fusion.