Potent inhibition of HIV-1 replication by 2nd generation shRNA. Stable cell lines (SupT1) expressing the shRNA inhibiters (wt, G8A, G15A or combined) were infected with wt HIV-1 (1 ng CA-p24), the escape viruses (G8A and G15A) or the double mutant (G8A/G15A). Virus replication was monitored over time. SupT1 cells with the empty lentiviral vector JS1 served as positive control. Results were obtained in three independent infection experiments.