[show abstract][hide abstract] ABSTRACT: Following circulation of avian influenza H5 and H7 viruses in poultry, the hemagglutinin (HA) can acquire additional glycosylation sites, and the neuraminidase (NA) stalk becomes shorter. We investigated whether these features play a role in the pathogenesis of infection in mammalian hosts. From 1996 to 2007, H5N1 viruses with a short NA stalk have become widespread in several avian species. Compared to viruses with a long-stalk NA, viruses with a short-stalk NA showed a decreased capacity to elute from red blood cells and an increased virulence in mice, but not in chickens. The presence of additional HA glycosylation sites had less of an effect on virulence than did NA stalk length. The short-stalk NA of H5N1 viruses circulating in Asia may contribute to virulence in humans.
Journal of Virology 03/2009; 83(9):4704-8. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: Pandemic vaccine seed viruses for H5N1, H5N2 and H9N2 subtypes were prepared and evaluated. Formalin-inactivated reassortant vaccines using A/Puerto Rico/8/34 (PR8) as a donor of internal genes with surface glycoprotein genes, hemagglutinin (HA) and neuraminidase (NA), of H5N2 and H9N2 subtypes, were generated by conventional reassortment. A reassortant virus for the highly pathogenic H5N1 subtype was prepared using reverse genetics with a genetically modified HA gene. All candidate vaccines were immunogenic in mice and ferrets, and mice immunized with inactivated vaccines were completely protected against challenge infection with wild-type parent viruses. All viruses were non-pathogenic for chickens in the standard USDA pathotyping test.
International Congress Series 01/2004; 1263:813-817.