Submitted to: International Conference on Negative Strand Viruses
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2006
Publication Date: 5/15/2006
Citation: Matsuoka, Y., Subbarao, K., Warnes, C., Altholtz, M., Swayne, D.E., Cox, N., Donis, R. 2006. H5N1 avian influenza virus hemagglutinin glycosylation and neuraminidase stalk deletion modulate virulence for mice [abstract]. Abstracts of the 13th International Conference on Negative Strand Viruses. p. 74.
Technical Abstract: It has been noted that acquisition of additional glycosylation sites in the HA and shortening of the NA stalk are characteristic features of H5 subtype viruses after multiple cycles of replication in poultry as compared to the HA from isolates from waterfowl species. It was suggested that these changes are required for adaptation of viruses to domestic poultry. How these changes affect viral replication in mammalian hosts is not clear. H5N1 viruses that caused multiple fatal human infections in HK during 1997 were thought to have been previously adapted to poultry. We established a reverse genetics system for A/Hong Kong/486/97 virus to study the impact of glycosylation sites (aa131, aa158 and aa169) on the globular head of HA and short (wild type) or long (19 aa insertion) NA on its virulence and infectivity in mice. Viruses with longer NA were more attenuated in lethality (MLD50=>7) as compared to those with short NA (MLD50=<7). The virus lacking all three potential glycosylation sites was the most lethal among variants (MLD50=4.82). In contrast, the virus with all three glycosylation sites was the least pathogenic (MLD50=8.37). Sequence analysis of more than 90 viruses isolated from mice infected with viruses with various combinations of HA and NA revealed that the changes introduced in HA and NA were stably maintained. We conclude that the shortening of NA stalk seems to contribute to virulence. However, additional glycosylation at particular sites of the HA has less impact on virulence for mice.