FIG 7.

Effect of IFITM expression on the late stages of IAV and PIV-3 replication. Control A549 cells or A549 cells with inducible expression of IFITM1, IFITM2, or IFITM3 were cultured and infected with IAV (MOI, 1) (i) or PIV-3 (MOI, 0.5) (ii) in various experimental conditions, namely, in DOX-free media before and after virus infection (no DOX; group a), pretreated with DOX and with DOX retained in the media throughout the experiment (pre- and post-DOX; group b), or in DOX-free media during incubation with virus before the addition of DOX after washing at 1 hpi (post-DOX, group c). (A) Experimental design. (B) Cell-free supernatants (SNs) were harvested at 2 and 24 hpi for IAV or at 2 and 48 hpi for PIV-3. Titers of infectious virus were determined by plaque assay (IAV) or virospot assay (PIV-3) and expressed as PFU/ml or virospots/ml, respectively. In undiluted supernatant, a minimum of 10 plaques per well (133.4 PFUs/ml) or a minimum of 15 spots per well (150 virospots/ml) were required for an accurate determination of viral titers (limit of detection for the assay, represented as a dotted line). Data are representative of at least two independent experiments performed in triplicate. Error bars are SEM. (****, P ≤ 0.0001; ns, P > 0.05; one-way analysis of variance [ANOVA] with Tukey’s multiple comparative analysis).