Detection of viral titers and histopathological changes in lungs of the H5N1-M2e-MAP-vaccinated mice following heterosubtypic challenge with pandemic 2009 H1N1 virus. Two weeks post-last boost, H5N1-M2e-MAP-vaccinated mice were challenged with lethal dose (10LD50) of pandemic 2009 H1N1 virus A/Beijing/501/09 strain, and lung tissues were collected three days later. (A) Viral titers in lungs of infected mice. The data are expressed as Log10TCID50/g of lung tissues, and presented as GMT ± SD of 5 mice per group. * indicates P < 0.001 compared to the Freund's adjuvant control; ** means P < 0.001 compared to the aluminum adjuvant control. Experiments were repeated three times. (B) Histopathological changes in the lungs following virus challenge. The figure indicates the representative images of histopathological damage from H & E-stained lungs of 5 mice per group (magnification, 100×).