FIG. 2.

Chimeric virus infection of U87-CD4-coreceptor-expressing cells. Each cell-free transfection supernatant (200 μl, containing comparable levels of p24 antigen) was used to infect U87-CD4-coreceptor cells at ∼20% confluency in 1-cm² wells. Virus was left for 3 days to infect. The cells were then stained for intracellular p24 antigen. (A) Representative fields of view shown for selected viruses. (B) Infection of all chimeras was measured by scoring the number of blue foci (both single blue cells and syncytia) per well: — ≡ 0 blue foci; ± ≡ <5 foci; + ≡ 5 to 10 foci; ++ ≡ 11 to 30 foci; +++ ≡ 31 to 100 foci; ++++ ≡ >100 foci.