Submitted to: Research Conference on Orthomyxoviruses
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2007
Publication Date: 9/21/2007
Citation: Wasilenko, J.L., Pantin Jackwood, M.J., Lee, C., Kapczynski, D.R., Sarmento, L., Spackman, E., Suarez, D.L. 2007. Studies on H5N1 avian influenza virus gene reassortants in vivo. In: Proceedings of the 4th Orthomyxoviruses Research Conference, September 21-24, 2007, MBL, Woods Hole, MA. p.73.
Technical Abstract: In order to determine which viral gene or genes contribute to the virulence of H5N1 avian influenza viruses in chickens, we used reverse genetics to generate single-gene recombinant viruses and examined their pathogenicity in chickens. Intranasal inoculation of two week-old chickens with the recombinant avian influenza virus rEgret/HK/02 resulted in 100% mortality and high viral titers in tissues. Inoculation of chickens with rCk/Indonesia/03 resulted in 50% mortality with significantly less viral replication in tissues. Exchange of the HA gene considerably affected virulence which was reflected in decreased mortality and viral replication and spread in tissues demonstrating the importance of this gene in pathogenesis of the virus. The HA genes had identical cleavage sites however there were 5 amino acid differences located in the receptor binding site of the glycoprotein, which could explain the difference observed in pathogenicity of the viruses. Exchange of the PB2 gene resulted in higher viral replication and spread in tissues. The introduction of this gene into the rEgret backbone resulted in a replicative advantage thereby increasing its virulence. This corroborates the important role of the polymerase genes in influenza virus pathogenesis The NS gene also had an effect on viral pathogenesis; however, had no effect on mortality. Differences in interferon-alpha (IFN-alpha) mRNA cytokine levels in lung and spleen were observed among the groups, indicating a role of the innate immune response on the outcome of infection.