title: Influenza A viruses escape from MxA restriction at the expense of efficient nuclear vRNP import.
abstract: To establish a new lineage in the human population, avian influenza A viruses (AIV) must overcome the intracellular restriction factor MxA. Partial escape from MxA restriction can be achieved when the viral nucleoprotein (NP) acquires the critical human-adaptive amino acid residues 100I/V, 283P, and 313Y. Here, we show that introduction of these three residues into the NP of an avian H5N1 virus renders it genetically unstable, resulting in viruses harboring additional single mutations, including G16D. These substitutions restored genetic stability yet again yielded viruses with varying degrees of attenuation in mammalian and avian cells. Additionally, most of the mutant viruses lost the capacity to escape MxA restriction, with the exception of the G16D virus. We show that MxA escape is linked to attenuation by demonstrating that the three substitutions promoting MxA escape disturbed intracellular trafficking of incoming viral ribonucleoprotein complexes (vRNPs), thereby resulting in impaired nuclear import, and that the additional acquired mutations only partially compensate for this import block. We conclude that for adaptation to the human host, AIV must not only overcome MxA restriction but also an associated block in nuclear vRNP import. This inherent difficulty may partially explain the frequent failure of AIV to become pandemic.
authors.affiliation: Institute of Virology, University Medical Center Freiburg, D-79104 Freiburg, Germany.
authors.forename: Veronika
authors.initials: V
authors.lastname: Götz
authors.affiliation: Institute of Virology, University Medical Center Freiburg, D-79104 Freiburg, Germany.
authors.forename: Linda
authors.initials: L
authors.lastname: Magar
authors.affiliation: Institute of Virology, University Medical Center Freiburg, D-79104 Freiburg, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: Dornfeld
authors.affiliation: Institute of Virology, University Medical Center Freiburg, D-79104 Freiburg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Giese
authors.affiliation: Institute of Diagnostic Virology, Friedrich-Loeffler-Institute, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Pohlmann
authors.affiliation: Institute of Diagnostic Virology, Friedrich-Loeffler-Institute, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Höper
authors.affiliation: Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701, USA.
authors.forename: Byung-Whi
authors.initials: BW
authors.lastname: Kong
authors.affiliation: Nuclear Signaling Laboratory, Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia.
authors.forename: David A
authors.initials: DA
authors.lastname: Jans
authors.affiliation: Institute of Diagnostic Virology, Friedrich-Loeffler-Institute, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Beer
authors.affiliation: Institute of Virology, University Medical Center Freiburg, D-79104 Freiburg, Germany.
authors.forename: Otto
authors.initials: O
authors.lastname: Haller
authors.affiliation: Institute of Virology, University Medical Center Freiburg, D-79104 Freiburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Schwemmle
mesh_terms: D000072283:A549 Cells; D019943:Amino Acid Substitution; D000818:Animals; D001717:Birds / Q000821:virology; D002460:Cell Line; D004285:Dogs; D057809:HEK293 Cells; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics* / Q000472:pathogenicity; D061985:Madin Darby Canine Kidney Cells; D008958:Models, Molecular; D009154:Mutation; D064547:Myxovirus Resistance Proteins / Q000378:metabolism*; D019590:Nucleocapsid Proteins; D011487:Protein Conformation; D021381:Protein Transport; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014758:Viral Core Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; C048842:NP protein, Influenza A virus; D019590:Nucleocapsid Proteins; D016601:RNA-Binding Proteins; D014758:Viral Core Proteins