Submitted to: Archives of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2009
Publication Date: 6/8/2009
Citation: Wasilenko, J.L., Sarmento, L., Pantin Jackwood, M.J. 2009. A single substitution in amino acid 184 of the NP protein alters the replication and pathogenicity of H5N1 avian influenza viruses in chickens. Archives of Virology. 154:969-979. Interpretive Summary: Avian influenza virus can vary widely in its ability to cause disease in poultry, but few virulence characteristics have been associated to specific genes in the virus. Reverse genetics techniques were used to study the role of the NP gene in the pathogenesis of H5N1 avian influenza and to determine how the chicken immune response to the virus is altered by changes in these genes. We identified one change at position 184 in the NP protein that resulted in greatly increased virus replication and spread in tissues of infected chickens, increased mortality, and up-regulation of several host genes involved in the innate immune response as well as an increased level of nitric oxide production by the host in response to virus infection. This study provides new insights into how AIV causes disease and underlines the importance of the NP in avian influenza virus replication and pathogenicity.
Technical Abstract: Previously we found that exchanging the NP genes of recombinant avian influenza viruses (AIVs) affected viral replication and altered host gene expression and mean death times in chickens infected with these viruses. Five amino acids at positions 22, 184, 400, 406, and 423 were different between the two recombinant viruses studied. In this study we individually mutated the 5 amino acids that differed and found that the difference in virus pathogenicity after NP gene exchange was a result of an alanine to lysine change at position 184 of the NP protein. Viruses containing a lysine at NP 184 induced earlier mortality in chickens, increased virus titers and nitric oxide levels in tissues, and up-regulated host immune genes, such as a-interferon (IFN-a), g-interferon (IFN-g), orthomyxovirus resistance gene 1 (Mx1), and inducible nitric oxide synthase (iNOS). This study underlines the importance of the NP in avian influenza virus replication and pathogenicity.