Fig. 2

Influenza virus infection and replication competence in naïve neutrophils. Primary human neutrophils isolated freshly from healthy donor were infected with influenza viruses A/VN/1203/04 (H5N1), A/HK/483/97 (H5N1), A/OK/447/08 (H1N1) and A/HK/415742/09 (H1N1pdm) at a MOI of 2. The bar charts show the means and the standard error of mean of the virus quantities pooled from at least three independent experiments. (a) Influenza matrix gene expression in these infected neutrophils at 1, 3, 6, and 16 hpi were plotted. (b) At 16 hpi, the infected neutrophils were fixed in 4% PFA and stained for influenza nucleoprotein and matrix protein (Green, 1–5) with a counterstain of DNA material using DAPI (Blue, 6–10). (c) Viral load in the neutrophil cultures were monitored at 1, 6, and 16 hpi using viral titration assay (black lines). Thermal inactivation kinetics of the same virus strain without cells at 10⁶ TCID₅₀/ml was plotted for comparison (grey dashed lines). Horizontal dotted line denotes detection limit of TCID₅₀ assay. Key: *, p < 0.05 and **, p < 0.01 significant differences of viral load across the indicated group(s)