Figure 2

Expression of viral nucleoprotein and matrix protein in A549 cells. A549 cells were infected with H1N1, H9N2/G1, H9N2/Y280 or H9N2/G9 at an m.o.i. of 2 and cultured with DMEM without adding N-Tosyl-L-phenylalaninechloromethyl ketone-treated trypsin. (A) The infected cells were stained with FITC-conjugated monoclonal antibody specific for influenza nucleoproteins at 24 h post-infection (pi) and were visualized by fluorescence microscopy. Mock-treated cells (at the lower right corner) were counter-stained with DAPI. (B) A549 cells were infected with H9N2/G1, H9N2/Y280 or H9N2/G9 at an m.o.i. of 2 or mock treated. Total proteins were harvested at 8 h or 24 h post-infection (pi) and M1 proteins of influenza A were examined by Western analysis. (C) A549 cells were infected with influenza H1N1 or H9N2/G1 viruses at an m.o.i. of 2 or mock treated. Total proteins were harvested at 8 h or 24 h pi and M1 proteins of influenza A were examined by Western analysis. Equal loading of protein samples was determined with anti-actin antibodies. The densities of the protein bands were determined by using Bio-Rad Quantity One imaging software. The values in the parenthesis are relative M1 protein intensities compared with those of the corresponding actin. Mock, uninfected cells; M1, matrix protein; UT, untreated; DAPI, 4'-6-Diamidino-2-phenylindole.