FIG. 3.

Coreceptor usage of residual viruses. Residual virus-infected indicator Ghost cells were visualized under a UV microscope. (A) GFP-expressing green cells were observed only when Ghost cells expressed CCR5 as an HIV coreceptor (panels on right). (B) Increase in the levels of HIV p24, measured by an HIV-1 p24 antigen capture assay (Advanced BioScience Laboratories, Inc.) in culture supernatants of infected Ghost cells 72 h after infection. Only data for C1P, one of three infectious residual-virus clones, is shown here. Standard laboratory strains JRCSF (R5 tropic) and MCK (X4 tropic) were used as positive controls for infection (data not shown).