Lethal dissemination of H5N1 influenza virus is associated with dysregulation of inflammation and lipoxin signaling in a mouse model of infection. Mus musculus

Periodic outbreaks of highly pathogenic avian H5N1 influenza viruses and the current H1N1 pandemic highlight the need for a more detailed understanding of influenza virus pathogenesis. To investigate the host transcriptional response induced by pathogenic influenza viruses, we used a functional-genomics approach to compare gene expression profiles in lungs from wild-type 129S6/SvEv and interferon receptor (IFNR) knockout mice infected with either the fully reconstructed H1N1 1918 pandemic virus (1918) or the highly pathogenic avian H5N1 virus Vietnam/1203/04 (VN/1203). Overall design: Eight- to 10-week-old female wild-type and IFNR1-/- mice (on a 129S6/SvEv background) were anesthetized by intraperitoneal injection of 0.2 ml of 2,2,2-tribromoethanol in tert-amylalcohol (Avertin; Sigma-Aldrich, Milwaukee, WI). Ten times the 50% lethal dose (LD50), 3.2 × 10^4 PFU (1918) or 7 × 10^3 PFU (VN/1203), in 50 μl of infectious virus diluted in phosphate-buffered saline (PBS) was inoculated intranasally (i.n.). Lung tissue was harvested for microarray analysis from infected animals at 1, 3, and 4 days post-innoculation. For RNA isolation, lungs were frozen in individual tubes and stored in solution D (4 M guanidinium thiocyanate, 25 mM sodium citrate, 0.5% sarcosyl, 0.1 M β-mercaptoethanol). Separate microarrays were run for each infected mouse. This included 2 animals/time point for 1918 virus-infected mice (24 animals total) or 3 animals/time point for VN/1203-infected mice (36 animals total). Lung tissue from three uninfected wild type 129S6/SvEv mice was collected as a mock control. Equal masses of total RNA from the lung tissue of the three mice were pooled prior to being run on microarray. Two-channel microarrays were used to determine gene expression in the lungs. For each individual infected lung, gene expression from an infected lung was compared to gene expression from the pooled RNA from the mock control.