Contribution of 2009 pandemic swine-origin influenza virus gene segments to virulence and immunity (67.23)

Abstract Influenza A viruses cause annual epidemics and occasional global pandemics as seen in 1918, 1957, 1968 and most recently in 2009. On the 11th of June 2009 the first global pandemic of the 21st century was declared as a result of a triple reassortant virus containing gene segments from circulating swine, avian and human influenza viruses. Reverse genetics technology was used to study swine-origin influenza virus (S-OIV) virulence through the generation of reassortant influenza viruses expressing gene segments from the 2009 pandemic strain. Our results show that S-OIV gene segments are capable of altering virulence in both X31 and PR8 reassortant influenza viruses. In particular one specific X31-(S-OIV) reassortant virus showed a significant increase in virulence in mice with substantial weight loss, high virus titers and elevated levels of inflammatory mediators in the lung following infection. Moreover these findings suggest that the current H1N1 pandemic S-OIV has the potential to influence the virulence of other circulating influenza viruses in the future.