FIG. 6.

Importance of 239-ST1.2-32 mutations for coreceptor use by infectious viruses. (A) Infectivities of the indicated Envs are shown, using a single-cycle luciferase reporter virus on transfected Cf2Th target cells. Percent infection was calculated by using luciferase activity normalized to SIVmac239 fusion with CD4⁺ CCR5⁺ Cf2Th cells or to HIV-1_R3A fusion with CD4⁺ CXCR4⁺ Cf2Th cells. Background infection levels with Cf2Th cells expressing only CD4 were subtracted prior to normalization. The data shown are means of three experiments plus SEM. (B) Growth curves obtained with SupT1 cells for replication-competent SIVmac239 containing the indicated Env mutations or the 239-ST1.2-32 Long CT Env. RT activity in culture supernatants was measured at the indicated time points. Results from a representative experiment are shown.