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Differential use of importin-α isoforms governs cell tropism and host adaptation of influenza virus.

Gabriel G, Klingel K, Otte A, Thiele S, Hudjetz B, Arman-Kalcek G, Sauter M, Shmidt T, Rother F, Baumgarte S, Keiner B, Hartmann E, Bader M, Brownlee GG, Fodor E, Klenk HD - Nat Commun (2011)

Bottom Line: Influenza A viruses are a threat to humans due to their ability to cross species barriers, as illustrated by the 2009 H1N1v pandemic and sporadic H5N1 transmissions.In this study, we analysed replication, host specificity and pathogenicity of avian and mammalian influenza viruses, in importin-α-silenced cells and importin-α-knockout mice, to understand the role of individual importin-α isoforms in adaptation.Thus, differences in importin-α specificity are determinants of host range underlining the importance of the nuclear envelope in interspecies transmission.

View Article: PubMed Central - PubMed

Affiliation: 1] Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany. [2] Sir William Dunn School of Pathology, University of Oxford, Oxford, UK. [3] Institute of Virology, Philipps-University Marburg, Marburg, Germany.

ABSTRACT
Influenza A viruses are a threat to humans due to their ability to cross species barriers, as illustrated by the 2009 H1N1v pandemic and sporadic H5N1 transmissions. Interspecies transmission requires adaptation of the viral polymerase to importin-α, a cellular protein that mediates transport into the nucleus where transcription and replication of the viral genome takes place. In this study, we analysed replication, host specificity and pathogenicity of avian and mammalian influenza viruses, in importin-α-silenced cells and importin-α-knockout mice, to understand the role of individual importin-α isoforms in adaptation. For efficient virus replication, the polymerase subunit PB2 and the nucleoprotein (NP) of avian viruses required importin-α3, whereas PB2 and NP of mammalian viruses showed importin-α7 specificity. H1N1v replication depended on both, importin-α3 and -α7, suggesting ongoing adaptation of this virus. Thus, differences in importin-α specificity are determinants of host range underlining the importance of the nuclear envelope in interspecies transmission.

No MeSH data available.


Related in: MedlinePlus

Pathogenicity of H5N1 and H1N1v viruses in WT and importin-α7-knockout animals.WT (black square; n=16), α7−/− (red triangle; n=16) or α7ΔIBB/ΔIBB (orange triangle; n=16) animals were infected with 50-fold LD50 of (a, b) A/Thai/KAN-1/04 (H5N1), (c, d) 10-fold LD50 of A/Sachsen-Anhalt/101/09 (H1N1v) or (e, f) 100-fold LD50 of A/Hamburg/NY1580/09 (H1N1v). Control groups received PBS (black diamond). (a, c, e) Survival was monitored for 14 days. (b, d, f) Virus titres in the lung, brain and liver homogenates and in the blood of infected WT, α7−/− and α7ΔIBB/ΔIBB animals were determined by plaque assays. The statistical significance of differences in lung titres of WT and importin-knockout animals were assessed by Student's t-test (*P<0.05; **P<0.01). The error bars indicate the standard deviation of viral titres detected in three animals per time point. The detection limit was ≥30 p.f.u.
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f4: Pathogenicity of H5N1 and H1N1v viruses in WT and importin-α7-knockout animals.WT (black square; n=16), α7−/− (red triangle; n=16) or α7ΔIBB/ΔIBB (orange triangle; n=16) animals were infected with 50-fold LD50 of (a, b) A/Thai/KAN-1/04 (H5N1), (c, d) 10-fold LD50 of A/Sachsen-Anhalt/101/09 (H1N1v) or (e, f) 100-fold LD50 of A/Hamburg/NY1580/09 (H1N1v). Control groups received PBS (black diamond). (a, c, e) Survival was monitored for 14 days. (b, d, f) Virus titres in the lung, brain and liver homogenates and in the blood of infected WT, α7−/− and α7ΔIBB/ΔIBB animals were determined by plaque assays. The statistical significance of differences in lung titres of WT and importin-knockout animals were assessed by Student's t-test (*P<0.05; **P<0.01). The error bars indicate the standard deviation of viral titres detected in three animals per time point. The detection limit was ≥30 p.f.u.

Mentions: We next assessed the pathogenicity and cell tropism of the H5N1 and the H1N1v isolates in importin-α7-knockout mice. All WT animals infected with the H5N1 virus showed systemic virus spread with high titres in lung, liver and blood, and died on day 9 p.i. (Fig. 4a,b; Supplementary Fig. S4a). All H5N1-infected α7−/− mice died, too, but virus titres were reduced in the liver and gut and abolished in blood (Fig. 4a,b). No significant differences were observed in the weight loss of α7−/− and WT mice (Supplementary Fig. S4a). H1N1v was shown to be pathogenic for several mammalian species141516. Accordingly, WT mice infected with A/Sachsen-Anhalt/101/09 (H1N1v) showed lethal pneumonia with high virus titres only in lungs (Fig. 4c,d; Supplementary Fig. S5b). Infection with A/Hamburg/NY1580/09 (H1N1v) was also lethal (Fig. 4e), but revealed systemic spread with high virus titres in the lung, liver, brain and gut (Fig. 4f; Supplementary Fig. S5c). The genetic determinants responsible for the differences in the spread of infection in different strains of H1N1v-infected WT animals (Fig. 4d,f) remain to be investigated. However, in α7−/− and α7ΔIBB/ΔIBB mice virus loads were reduced and confined to the lung (Fig. 4d,f; Supplementary Fig. S5), and all animals survived infection with marginal weight loss (Fig. 4c,e; Supplementary Fig. S4b,c). Interestingly, in H5N1- and H1N1v-infected importin-α7-knockout mice only single macrophages were found to be infected compared with WT animals, in which infected macrophages were abundant (Supplementary Fig. S5). Taken together, these results support the view that the high pathogenicity and cell tropism of H1N1v and H5N1 isolates in mice depends on importin-α7 expression.


Differential use of importin-α isoforms governs cell tropism and host adaptation of influenza virus.

Gabriel G, Klingel K, Otte A, Thiele S, Hudjetz B, Arman-Kalcek G, Sauter M, Shmidt T, Rother F, Baumgarte S, Keiner B, Hartmann E, Bader M, Brownlee GG, Fodor E, Klenk HD - Nat Commun (2011)

Pathogenicity of H5N1 and H1N1v viruses in WT and importin-α7-knockout animals.WT (black square; n=16), α7−/− (red triangle; n=16) or α7ΔIBB/ΔIBB (orange triangle; n=16) animals were infected with 50-fold LD50 of (a, b) A/Thai/KAN-1/04 (H5N1), (c, d) 10-fold LD50 of A/Sachsen-Anhalt/101/09 (H1N1v) or (e, f) 100-fold LD50 of A/Hamburg/NY1580/09 (H1N1v). Control groups received PBS (black diamond). (a, c, e) Survival was monitored for 14 days. (b, d, f) Virus titres in the lung, brain and liver homogenates and in the blood of infected WT, α7−/− and α7ΔIBB/ΔIBB animals were determined by plaque assays. The statistical significance of differences in lung titres of WT and importin-knockout animals were assessed by Student's t-test (*P<0.05; **P<0.01). The error bars indicate the standard deviation of viral titres detected in three animals per time point. The detection limit was ≥30 p.f.u.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3105303&req=5

f4: Pathogenicity of H5N1 and H1N1v viruses in WT and importin-α7-knockout animals.WT (black square; n=16), α7−/− (red triangle; n=16) or α7ΔIBB/ΔIBB (orange triangle; n=16) animals were infected with 50-fold LD50 of (a, b) A/Thai/KAN-1/04 (H5N1), (c, d) 10-fold LD50 of A/Sachsen-Anhalt/101/09 (H1N1v) or (e, f) 100-fold LD50 of A/Hamburg/NY1580/09 (H1N1v). Control groups received PBS (black diamond). (a, c, e) Survival was monitored for 14 days. (b, d, f) Virus titres in the lung, brain and liver homogenates and in the blood of infected WT, α7−/− and α7ΔIBB/ΔIBB animals were determined by plaque assays. The statistical significance of differences in lung titres of WT and importin-knockout animals were assessed by Student's t-test (*P<0.05; **P<0.01). The error bars indicate the standard deviation of viral titres detected in three animals per time point. The detection limit was ≥30 p.f.u.
Mentions: We next assessed the pathogenicity and cell tropism of the H5N1 and the H1N1v isolates in importin-α7-knockout mice. All WT animals infected with the H5N1 virus showed systemic virus spread with high titres in lung, liver and blood, and died on day 9 p.i. (Fig. 4a,b; Supplementary Fig. S4a). All H5N1-infected α7−/− mice died, too, but virus titres were reduced in the liver and gut and abolished in blood (Fig. 4a,b). No significant differences were observed in the weight loss of α7−/− and WT mice (Supplementary Fig. S4a). H1N1v was shown to be pathogenic for several mammalian species141516. Accordingly, WT mice infected with A/Sachsen-Anhalt/101/09 (H1N1v) showed lethal pneumonia with high virus titres only in lungs (Fig. 4c,d; Supplementary Fig. S5b). Infection with A/Hamburg/NY1580/09 (H1N1v) was also lethal (Fig. 4e), but revealed systemic spread with high virus titres in the lung, liver, brain and gut (Fig. 4f; Supplementary Fig. S5c). The genetic determinants responsible for the differences in the spread of infection in different strains of H1N1v-infected WT animals (Fig. 4d,f) remain to be investigated. However, in α7−/− and α7ΔIBB/ΔIBB mice virus loads were reduced and confined to the lung (Fig. 4d,f; Supplementary Fig. S5), and all animals survived infection with marginal weight loss (Fig. 4c,e; Supplementary Fig. S4b,c). Interestingly, in H5N1- and H1N1v-infected importin-α7-knockout mice only single macrophages were found to be infected compared with WT animals, in which infected macrophages were abundant (Supplementary Fig. S5). Taken together, these results support the view that the high pathogenicity and cell tropism of H1N1v and H5N1 isolates in mice depends on importin-α7 expression.

Bottom Line: Influenza A viruses are a threat to humans due to their ability to cross species barriers, as illustrated by the 2009 H1N1v pandemic and sporadic H5N1 transmissions.In this study, we analysed replication, host specificity and pathogenicity of avian and mammalian influenza viruses, in importin-α-silenced cells and importin-α-knockout mice, to understand the role of individual importin-α isoforms in adaptation.Thus, differences in importin-α specificity are determinants of host range underlining the importance of the nuclear envelope in interspecies transmission.

View Article: PubMed Central - PubMed

Affiliation: 1] Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany. [2] Sir William Dunn School of Pathology, University of Oxford, Oxford, UK. [3] Institute of Virology, Philipps-University Marburg, Marburg, Germany.

ABSTRACT
Influenza A viruses are a threat to humans due to their ability to cross species barriers, as illustrated by the 2009 H1N1v pandemic and sporadic H5N1 transmissions. Interspecies transmission requires adaptation of the viral polymerase to importin-α, a cellular protein that mediates transport into the nucleus where transcription and replication of the viral genome takes place. In this study, we analysed replication, host specificity and pathogenicity of avian and mammalian influenza viruses, in importin-α-silenced cells and importin-α-knockout mice, to understand the role of individual importin-α isoforms in adaptation. For efficient virus replication, the polymerase subunit PB2 and the nucleoprotein (NP) of avian viruses required importin-α3, whereas PB2 and NP of mammalian viruses showed importin-α7 specificity. H1N1v replication depended on both, importin-α3 and -α7, suggesting ongoing adaptation of this virus. Thus, differences in importin-α specificity are determinants of host range underlining the importance of the nuclear envelope in interspecies transmission.

No MeSH data available.


Related in: MedlinePlus