Meth reduces susceptibility to influenza A virus infections in human lung epithelial A549 cells.

(A) A549 cells grown on glass coverslips were left un-treated, or treated with chloroquine (Clq.; 10 µM; as positive control) or meth at indicated concentrations, followed by the infection with influenza A/WSN/33 (H1N1) virus at an MOI of 1 PFU/cell in the absence of trypsin (single-cycle growth) and presence of the corresponding drugs at indicated concentrations. At 24 h post-infection, cells were fixed with formaldehyde and subjected to immunofluorenscence staining for detecting the infected cells by using an antibody against viral nucleoprotein (NP; green); cellular nuclei were located by DAPI staining (blue). A representative result from three independent experiments is shown. Mock: cells were neither exposed to the drugs nor infected with the virus. Scale bar: 100 µm. (B) NP-positive cells were counted from ten microscopic fields with >90% cell confluence. Data are expressed as mean values ± SD from a representative result of three independent experiments. Significant differences from the drug-untreated infected group (control) were indicated (***: p < 0.0001).