FIGURE 6.

Effects of growth-enhancing mutations in gp120 on viral entry. (A) Entry efficiency into HSC-F cells of 562 and 562 carrying indicated single substitutions. Virus samples were prepared as in Figure 5, and entry assays were performed as described in section “Materials and Methods.” Values obtained for ΔEnv construct (NL-Kp) were subtracted from those for test samples. Entry efficiency of each virus relative to that of 562 is presented. (B) Co-receptor usage of various viruses. Infection of HSC-F cells with viruses was performed as described above, and infected cells were cultured in the absence or presence (1 μM) of antagonists (CXCR4 antagonist AMD3100 or CCR5 antagonist TAK-779). Virus replication was monitored by RT activity released into the culture supernatants. Viral yields in test cultures relative to those on the peak day in cultures without antagonists were determined. 5R and 562 served as controls. (C) Sensitivity of 562 and its mutants to TAK-779. Virus samples prepared as above were inoculated into HSC-F cells pretreated with the indicated concentration of TAK-779. Virus replication was monitored by RT activity released into the culture supernatants. Viral yields in test cultures relative to those on the peak day in cultures without TAK-779 were determined and presented as % inhibition. Representative results from three independent experiments are shown.