Figure 3.

Strict dox control of the evolved HIV-rtTA 2Δ tetO. (A) Absence of replication without dox. After infection of SupT1 cells with HIV-rtTA 2Δ tetO (5 ng CA-p24), the culture was split in two and maintained in the absence or presence of 1 μg/ml dox. Virus replication was monitored throughout the experiment by measuring CA-p24 production. (B) Repeated virus activation. After infection of SupT1 cells, dox was added and removed repeatedly (+dox: days 0, 8, and 17; −dox: day 5 and 13) from the culture medium. The experiment was stopped at day 18 because of massive syncytia formation. Virus replication is measured by means of CA-p24 production and by scoring the extent of syncytia formation. (C) Microphotographs of infected SupT1 corresponding to the experiment in B. (D) Sensitivity of HIV-rtTA 2Δ tetO to antiretroviral agents. Infected cells were grown in the presence of dox and either with or without Saquinavir (SQV, 200 nM).