title: Swine Influenza Virus PA and Neuraminidase Gene Reassortment into Human H1N1 Influenza Virus Is Associated with an Altered Pathogenic Phenotype Linked to Increased MIP-2 Expression.
abstract: Swine are susceptible to infection by both avian and human influenza viruses, and this feature is thought to contribute to novel reassortant influenza viruses. In this study, the influenza virus reassortment rate in swine and human cells was determined. Coinfection of swine cells with 2009 pandemic H1N1 virus (huH1N1) and an endemic swine H1N2 (A/swine/Illinois/02860/09) virus (swH1N2) resulted in a 23% reassortment rate that was independent of α2,3- or α2,6-sialic acid distribution on the cells. The reassortants had altered pathogenic phenotypes linked to introduction of the swine virus PA and neuraminidase (NA) into huH1N1. In mice, the huH1N1 PA and NA mediated increased MIP-2 expression early postinfection, resulting in substantial pulmonary neutrophilia with enhanced lung pathology and disease. The findings support the notion that swine are a mixing vessel for influenza virus reassortants independent of sialic acid distribution. These results show the potential for continued reassortment of the 2009 pandemic H1N1 virus with endemic swine viruses and for reassortants to have increased pathogenicity linked to the swine virus NA and PA genes which are associated with increased pulmonary neutrophil trafficking that is related to MIP-2 expression.
  
  
  OBJECTIVE
  Influenza A viruses can change rapidly via reassortment to create a novel virus, and reassortment can result in possible pandemics. Reassortments among subtypes from avian and human viruses led to the 1957 (H2N2 subtype) and 1968 (H3N2 subtype) human influenza pandemics. Recent analyses of circulating isolates have shown that multiple genes can be recombined from human, avian, and swine influenza viruses, leading to triple reassortants. Understanding the factors that can affect influenza A virus reassortment is needed for the establishment of disease intervention strategies that may reduce or preclude pandemics. The findings from this study show that swine cells provide a mixing vessel for influenza virus reassortment independent of differential sialic acid distribution. The findings also establish that circulating neuraminidase (NA) and PA genes could alter the pathogenic phenotype of the pandemic H1N1 virus, resulting in enhanced disease. The identification of such factors provides a framework for pandemic modeling and surveillance.
authors.affiliation: University of Georgia, College of Veterinary Medicine, Department of Infectious Diseases, Athens, Georgia, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Dlugolenski
authors.affiliation: University of Georgia, College of Veterinary Medicine, Department of Infectious Diseases, Athens, Georgia, USA.
authors.forename: Les
authors.initials: L
authors.lastname: Jones
authors.affiliation: University of Georgia, College of Veterinary Medicine, Department of Pathology, Athens, Georgia, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Howerth
authors.affiliation: J. Craig Venter Institute, Rockville, Maryland, USA.
authors.forename: David
authors.initials: D
authors.lastname: Wentworth
authors.affiliation: University of Georgia, College of Veterinary Medicine, Department of Infectious Diseases, Athens, Georgia, USA.
authors.forename: S Mark
authors.initials: SM
authors.lastname: Tompkins
authors.affiliation: University of Georgia, College of Veterinary Medicine, Department of Infectious Diseases, Athens, Georgia, USA ratripp@uga.edu.
authors.forename: Ralph A
authors.initials: RA
authors.lastname: Tripp
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D054426:Chemokine CXCL2 / Q000235:genetics*; D016207:Cytokines / Q000096:biosynthesis; D005260:Female; D005289:Ferrets; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D058507:Host Specificity / Q000235:genetics; D006801:Humans; D007113:Immunity, Innate; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics* / Q000472:pathogenicity*; D057221:Influenza A Virus, H1N2 Subtype / Q000235:genetics* / Q000472:pathogenicity*; D007251:Influenza, Human / Q000821:virology; D007694:Killer Cells, Natural / Q000276:immunology; D008168:Lung / Q000276:immunology / Q000473:pathology; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000235:genetics; D020556:Neutrophil Infiltration; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000662:veterinary / Q000821:virology; D010641:Phenotype; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics*; D016865:Reassortant Viruses / Q000235:genetics* / Q000472:pathogenicity*; D017386:Sequence Homology, Amino Acid; D013552:Swine / Q000821:virology*; D013553:Swine Diseases / Q000821:virology; D013601:T-Lymphocytes / Q000276:immunology; D015854:Up-Regulation; D014764:Viral Proteins / Q000235:genetics*; D014774:Virulence / Q000235:genetics
chemical_list: D054426:Chemokine CXCL2; C404915:Cxcl2 protein, mouse; D016207:Cytokines; D019267:Hemagglutinin Glycoproteins, Influenza Virus; C061290:PA protein, influenza viruses; D014764:Viral Proteins; D012324:RNA-Dependent RNA Polymerase; D009439:Neuraminidase