The neuraminidase and matrix genes of the 2009 pandemic influenza H1N1 virus cooperate functionally to facilitate efficient replication and transmissibility in pigs

J Gen Virol. 2012 Jun;93(Pt 6):1261-1268. doi: 10.1099/vir.0.040535-0. Epub 2012 Feb 15.


The 2009 pandemic H1N1 virus (pH1N1) contains neuraminidase (NA) and matrix (M) genes from Eurasian avian-like swine influenza viruses (SIVs), with the remaining six genes from North American triple-reassortant SIVs. To characterize the role of the pH1N1 NA and M genes in pathogenesis and transmission, their impact was evaluated in the background of an H1N1 triple-reassortant (tr1930) SIV in which the HA (H3) and NA (N2) of influenza A/swine/Texas/4199-2/98 virus were replaced with those from the classical H1N1 A/swine/Iowa/15/30 (1930) virus. The laboratory-adapted 1930 virus did not shed nor transmit in pigs, but tr1930 was able to shed in infected pigs. The NA, M or both genes of the tr1930 virus were then substituted by those of pH1N1. The resulting virus with both NA and M from pH1N1 grew to significantly higher titre in cell cultures than the viruses with single NA or M from pH1N1. In a pig model, only the virus containing both NA and M from pH1N1 was transmitted to and infected sentinels, whereas the viruses with single NA or M from pH1N1 did not. These results demonstrate that the right combination of NA and M genes is critical for the replication and transmissibility of influenza viruses in pigs.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Influenza A Virus, H1N1 Subtype / enzymology
  • Influenza A Virus, H1N1 Subtype / genetics
  • Influenza A Virus, H1N1 Subtype / physiology*
  • Iowa / epidemiology
  • Neuraminidase / genetics
  • Neuraminidase / metabolism*
  • Orthomyxoviridae Infections / epidemiology
  • Orthomyxoviridae Infections / transmission
  • Orthomyxoviridae Infections / veterinary*
  • Orthomyxoviridae Infections / virology
  • Swine
  • Swine Diseases / epidemiology
  • Swine Diseases / transmission*
  • Swine Diseases / virology*
  • Texas / epidemiology
  • Viral Matrix Proteins / genetics
  • Viral Matrix Proteins / metabolism*
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*
  • Virus Replication*


  • M1 protein, Influenza A virus
  • Viral Matrix Proteins
  • Viral Proteins
  • NA protein, influenza A virus
  • Neuraminidase