Abstract
BackgroundSwine are important hosts for influenza A viruses playing a crucial role in the epidemiology and interspecies transmission of these viruses. Respiratory epithelial cells are the primary target cells for influenza viruses.Methodology/Principal FindingsTo analyze the infection of porcine airway epithelial cells by influenza viruses, we established precision-cut lung slices as a culture system for differentiated respiratory epithelial cells. Both ciliated and mucus-producing cells were found to be susceptible to infection by swine influenza A virus (H3N2 subtype) with high titers of infectious virus released into the supernatant already one day after infection. By comparison, growth of two avian influenza viruses (subtypes H9N2 and H7N7) was delayed by about 24 h. The two avian viruses differed both in the spectrum of susceptible cells and in the efficiency of replication. As the H9N2 virus grew to titers that were only tenfold lower than that of a porcine H3N2 virus this avian virus is an interesting candidate for interspecies transmission. Lectin staining indicated the presence of both α-2,3- and α-2,6-linked sialic acids on airway epithelial cells. However, their distribution did not correlate with pattern of virus infection indicating that staining by plant lectins is not a reliable indicator for the presence of cellular receptors for influenza viruses.Conclusions/SignificanceDifferentiated respiratory epithelial cells significantly differ in their susceptibility to infection by avian influenza viruses. We expect that the newly described precision-cut lung slices from the swine lung are an interesting culture system to analyze the infection of differentiated respiratory epithelial cells by different pathogens (viral, bacterial and parasitic ones) of swine.
Highlights
Pigs are important hosts for influenza A viruses
Though natural infections by avian influenza viruses were rarely able to establish a stable lineage in pigs, they may allow the introduction of new gene segments by genetic reassortment in host cells infected with two viruses
In order to analyze the infection by porcine influenza virus, we established a culture system for differentiated respiratory epithelial cells from the porcine lung
Summary
Pigs are important hosts for influenza A viruses. Based on the surface antigens hemagglutinin and neuraminidase, influenza virus strains that are enzootic in swine populations worldwide are assigned to the subtypes H1N1, H3N2, or H1N2. E.g. H3N1, H4N6, H5N1 and H9N2 has been observed but they have not been maintained in pigs as independent lineages. Natural infections of pigs by influenza viruses from different hosts, e.g. by avian virus strains, have been reported [1,2,3]. Though natural infections by avian influenza viruses were rarely able to establish a stable lineage in pigs, they may allow the introduction of new gene segments by genetic reassortment in host cells infected with two viruses. Swine are important hosts for influenza A viruses playing a crucial role in the epidemiology and interspecies transmission of these viruses. Respiratory epithelial cells are the primary target cells for influenza viruses
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