FIG. 1.
Fusion and infection mediated by functionally divergent env clones within the 89.6PI quasispecies. (A) Cloned env genes were analyzed for CCR5 and CXCR4-mediated fusion in a cell-cell fusion assay, along with the R5 and X4 prototypes JRFL and 3B, respectively. The env gene designated 89.6 is derived from the full-length infectious clone described previously (8, 11). Only data for the five variants with distinct R5 or X4 patterns and one representative R5X4 env variant are shown in this graph. Each envelope-coreceptor combination was tested a minimum of three times. (B) Pseudotype virions generated with one R5 and one X4 env variant were used to confirm coreceptor selectivity in infection. To generate pseudotype virions, env genes were cotransfected with an env-defective HIV-1 plasmid that carries the luciferase reporter gene in place of nef. U87 cells were transfected with CD4 and the indicated chemokine receptor, infected with equal amounts of each pseudotype virus based on p24 antigen content, and lysed 3 days later for measurement of luciferase expression. Pseudotype infections were tested in three independent experiments.