Figure 5. Macrophage is required for protection against influenza virus.

Liposome-DMDP or liposome alone (20 µl/dose) was intranasally administrated to mice on day 1 and day 4 after influenza virus challenge. (A) Survival rate of WT mice treated with either control liposome (black) or liposome-DMDP (red) after intranasal injection with PBS only (dotted line) or H1N1 (solid line). ***P<0.001 compared with H1N1 group treated with control liposome. (B–D) Viral load in WT mice treated with either control liposome or liposome-DMDP at 2 and 7 days after infection of influenza virus (1×10⁴ PFU). (B) TCID₅₀; Results are shown in log₁₀ scale per lobe. M1 (C) and NS (D) H1N1 viral mRNA. Results are expressed as RNA copies normalized to GAPDH expression levels, as determined by real-time PCR. *P<0.05 compared with control liposome group. (E) Cellular cytospin appearance of bronchoalveolar lavage (BAL) harvested from mice treated with either control liposome or liposome-DMDP at day 2 and 7 after influenza virus infection stained with Giemsa stain. Red arrows show macrophages. Original magnification, ×1000. (F) The number of cells harvested from BAL. *P<0.05 compared with control liposome group. (G) Quantitative real-time PCR (Taqman) was performed to measure the transcript levels of Dll1 at day 2 and 7 after inoculation of influenza virus. *P<0.05 compared with control liposome group. (H) IFN-γ production from whole lungs of WT mice treated with either control liposome or liposome-DMDP at day 2 and 7 after influenza virus infection. Cytokine levels of IFN-γ were measured using a Luminex system. *P<0.05 compared with control liposome group. Data shown indicate mean ± SEM and are from a representative experiment of 2 independent experiments. Each time point represents 5 mice per group.