Fig. 3. ApoBDs from IAV-infected THP1 monocytes can aid viral propagation in vitro.

a Purity of FACS-based ApoBD isolation approach depicting the levels of viable, apoptotic, and necrotic cells, and ApoBDs before and after sorting. ApoBDs (1 × 10⁵) from PR8-infected cells were incubated with A549 epithelial cells for 48 h, and flow cytometry was performed to determine: b the percentage of NP⁺ A549 cells, c the percentage of viable A549 cells, and d the percentage of NP⁺ apoptotic A549 cells. e RT-qPCR analysis was performed on A549 cells subjected to 1 × 10⁵ ApoBDs for 24 or 48 h (UV-irradiated or PR8-infected THP1 ApoBDs). Relative expression was normalised to the house keeping gene, UBC. f A549 epithelial cells were incubated with 1 × 10⁵ ApoBDs isolated from PR8- or M2SR-infected THP1 monocytes for 48 h, and the percent NP⁺ A549 cells was determined by flow cytometry. g A549 epithelial cells were treated with 1 × 10⁵ ApoBDs for 48 h in the presence of 10 or 20 µM Relenza and NP expression was determined by flow cytometry. h Apoptotic (UV-irradiated) THP1 monocytes were incubated with PR8 for 15 or 60 min, and ApoBDs isolated by differential centrifugation were analysed for HA staining. i A549 cells were co-incubated with PR8-exposed, FACS-isolated ApoBDs from THP1-UV, and flow cytometry was performed to determine A549 NP expression. Unless otherwise specified, error bars represent SEM of n = 3 biological repeats, presented data are representative of at least three independent experiments, *P < 0.05, **P < 0.01, ***P < 0.001, unpaired Student’s two-tailed t-test.