Figure 4

Inhibition of MPV-GFP replication by siA6-a and siE8-d. Cells transfected with various concentrations of scrambled non-targeting siRNA (A), siA6-a (B) or siE8-d (C) were infected with MPV-GFP, and viral replication was followed for 7 days PI by measuring the fluorescence increase in culture. (A) Cells treated with scrambled siRNA did not exhibit any antiviral activity and viral replication was similar to mock-transfected cells. (B) siA6-a maintained its potent antiviral activity up to 7 days PI in concentrations higher than 10 nm. (C) Inhibition by siE8-d was significant only at 40 nm with rapid degrading activity reflecting relative low stability. (D) Randomly picked images from virus infected-transfected cells at day 6 PI. Comparable fluorescence in cells transfected with scrambled siRNA at concentrations of 40 nm or less (upper panel). Cells transfected with siA6-a at concentrations of 10 nm or more did not show significant increase in fluorescence (middle panel), similar to those treated with 100 μM of Cidofovir (not shown) underscoring the potent antiviral function of siA6-a. Cells treated with siE8-d showed significant viral replication at concentrations of 20 nm or less as indicated by fluorescence intensity similarity with cells treated with scrambled non-inhibitory siRNA (last panel). Uninfected-transfected cells remained viable and no signs of cytopathy were detected until the end of the experiment (not shown).