Table 1.

Cell-to-Cell Fusion Mediated by Feline Immunodeficiency Virus Env Glycoproteins

Env glycoprotein	Relative fusion (%)a
—b	NDc
Wild-type	100
ΔV3	0.5±0.2
HV3	56±7

^aBlue foci were counted in 20 independent fields and the mean number of syncytia per field was multiplied by the total number of fields per well. The resulting values were referred to that obtained with wild-type Env,±standard deviations (three independent experiments).

^b293T cells expressing only HIV-1 Tat.

^cNo blue syncytia were detected.

293T cells expressing the wild-type, the mutant ΔV3, or the chimeric HV3 Env glycoproteins together with the HIV-1 Tat protein were dissociated and equivalent numbers of cells were added at a 1:5 ratio to 4×10⁴ MAGI-CXCR4 cells. Coculture was continued for 48 h. Cells were then stained for β-galactosidase and scored for syncytia formation.