Fig. 3

Mx1-inducing OMVs block influenza A virus replication in THP-1 cells. A Influenza A virus replication in differentiated THP-1 cells. Cells were either pre-treated with OMVs/MVs (1 µg/mL each), or left untreated for control (–). After 20 h pre-treatment, cells were infected with A/WSN/33(H1N1) (MOI 0.001) for 24 and 48 h. IAV replication was determined by qPCR against IAV-NP normalized to 18S. Mean values ± SEM of three to five independent experiments are shown. B Differentiated THP-1 cells were pre-treated with OMVs/MVs (1 µg/mL each) or left untreated for control (–). After 20 h pre-incubation, cells were infected with A/WSN/33(H1N1) (MOI 0.1) for 4 h. After fixation, cells were stained with an α-influenza NP antibody (yellow) and DAPI (blue). A representative result from four biological independent experiments is shown. C Quantification of NP positive (NP⁺) area from (B). Bars represent mean values of four independent experiments + SEM. D THP-1 cells stably overexpressing Mx1 (Mx1oex) and empty vector control (VC) cells were infected with influenza virus A/WSN/33(H1N1) (MOI 0.1) for 4 h. After fixation and immunofluorescence staining with α-influenza NP, the NP⁺ area was quantified and is depicted relative to VC cells. Bars show mean values of four independent experiments + SEM. E Mx1oex and VC cells were infected with A/WSN/33(H1N1) (MOI 0.001) for 6 h. Viral replication was determined by plaque assay and results are depicted as plaque forming units (pfu) per mL. Bars represent mean values + SEM of four independent experiments. Statistics: 2-way ANOVA (A), 1-way ANOVA (C), unpaired t-test (D + E); *p < 0.05, **p < 0.01, ****p < 0.0001; n = 3–5