To test this idea, Dr. Tumpey infected mice intranasally with one of four types of flu virus: human seasonal flu virus from a strain that circulated in Texas in 1991; lab-made viruses containing either two or five of eight viral genes from the 1918 virus; or a reconstructed virus containing all eight 1918 flu virus genes. Lung tissue from three infected mice in each group was removed on days 1, 3 and 5 post-infection and processed to destroy any virus. The mouse genetic material (RNA) was then extracted from these lung samples and sent to the University of Washington team for analysis.
Drs. Katze and Kash and colleagues examined the mouse RNA using microarrays to determine which genes were activated when exposed to each of the four viruses. This analysis showed that the immune response to the reconstructed 1918 virus containing all eight flu genes was much greater than to any of the other viruses with all eight genes, says Dr. Katze. In particular, genes involved in promoting inflammation were strongly and immediately activated following infection by the reconstructed 1918 virus. "We clearly see a dramatic and uncontrolled immune response in the mouse lungs as early as one day following infection with the reconstructed 1918 virus," he says. A complete understanding of the host's response to the 1918 flu virus, adds Dr. Katze, requires use of a fully reconstructed virus.
A fuller picture of the host immune response to the 1918 flu virus could also be valuable to scientists working to develop therapies against such viruses as the H5N1 avian influenza, the researchers note. Besides targeting the flu virus itself, Dr. Katze explains, researchers might develop new or improved agents aimed at moderating or h
Source:NIH/National Institute of Allergy and Infectious Diseases