Single gene turns flu deadly.The 1918 Spanish-influenza outbreak remains the worst pandemic pandemic /pan·dem·ic/ (pan-dem´ik) 1. a widespread epidemic of a disease. 2. widely epidemic. pan·dem·ic adj. Epidemic over a wide geographic area. n. in recorded history, killing more than 20 million people worldwide. With an eye toward preventing similar health disasters, researchers have long speculated about why the 1918 outbreak was so deadly (SN: 9/28/02, p. 196). Now, findings reported in the Oct. 7 Nature suggest that differences in a single viral gene made the 1918 flu strain particularly virulent. Using a method called reverse genetics reverse genetics methods such as antisense nucleic acids and site-directed mutagenesis that are used to selectively study gene function. Contrasts with classical genetics which depends on the isolation and analysis of cells (animals) with random mutations that can be identified. , Yoshihiro Kawaoka of the University of Wisconsin-Madison “University of Wisconsin” redirects here. For other uses, see University of Wisconsin (disambiguation). A public, land-grant institution, UW-Madison offers a wide spectrum of liberal arts studies, professional programs, and student activities. and the University of Tokyo “Todai” redirects here. For the restaurant called Todai, see Todai (restaurant). The University of Tokyo (東京大学 and his colleagues engineered a relatively mild flu virus to carry two genes from the 1918 strain. In 1990, scientists had sequenced these genes from preserved lung tissue obtained from victims of the 1918 pandemic. The genes code for the proteins hemagglutinin hemagglutinin /he·mag·glu·ti·nin/ (-gloo´ti-nin) an antibody that causes agglutination of erythrocytes. cold hemagglutinin one which acts only at temperatures near 4° C. and neuraminidase neuraminidase /neu·ra·min·i·dase/ (-ah-min´i-das) an enzyme of the surface coat of myxoviruses that destroys the neuraminic acid of the cell surface during attachment, thereby preventing hemagglutination. , which help flu viruses enter and infect cells. Mice infected with the engineered virus quickly sickened and died. By inoculating mice with engineered viruses that carried just one or the other of the two genes, Kawaoka's team found that the hemagglutinin gene alone was enough to increase the virus' pathogenicity. Within days, mice inoculated with this variety came down with severe and deadly infections. Mice infected with a virus carrying only the neuraminidase gene showed just mild flu symptoms. Although all flu viruses carry a variant of the hemagglutinin gene, Kawaoka says that the 1918 version "does something different, but we don't know how it does it."--C.B. |
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