Characterization of the 1918 "Spanish" influenza virus neuraminidase gene

The "Spanish" influenza pandemic of 1918 was characterized by exceptionally high mortality, especially among young adults. The surface proteins of inf luenza viruses, hemagglutinin and neuraminidase, play important roles in vi rulence, host specificity, and the human immune response. The complete codi ng sequence of hemagglutinin was reported last year. This laboratory has no w determined the complete coding sequence of the neuraminidase gene of the 1918 virus. Influenza RNA fragments were isolated from lung tissue of three victims of the 1918 flu; complete sequence was generated from A/Brevig Mis sion/1/18, with confirmatory sequencing carried out on A/South Carolina/1/1 8 and A/New York/1/18. The 1918 neuraminidase gene sequence was compared wi th other N1 subtype neuraminidase genes, including 9 N1 strains newly seque nced for this study. The 1918 neuraminidase shares many sequence and struct ural characteristics with avian strains, including the conserved active sit e, wild-type stalk length, glycosylation sites, and antigenic sites. Phylog enetically, the 1918 neuraminidase gene appears to be intermediate between mammals and birds, suggesting that it was introduced into mammals just befo re the 1918 pandemic.