The role of the N-terminal caspase cleavage site in the nucleoprotein of influenza A virus in vitro and in vivo.
The N-terminal caspase cleavage in the nucleoprotein (NP) of influenza A virus is correlated with the host origin of the virus, thus could be a molecular determinant for host range. We studied how mutations targeting the NP cleavage motif of human and avian influenza viruses affect virus replication in vitro and in vivo. The "avian-like" D16-->G substitution in the NP, which makes this protein resistant to cleavage, did not significantly affect the human A/Puerto Rico/8/34 (H1N1) virus replication in vitro but decreased the lethality of this virus in mice by 68-fold. Gene incompatibility contributed to the attenuated phenotype of the reassortant A/Puerto Rico/8/34 virus with avian NP derived from A/Teal/Hong Kong/w312/97 (H6N1) virus in vitro and in vivo. Insertion of the "human-like" G16-->D mutation into avian NP, which resulted in susceptibility to caspase cleavage, did not rescue virulence, but made the reassortant virus even more attenuated. Introducing the human-like G16-->D substitution into the NP of highly pathogenic A/Vietnam/1203/04 (H5N1) virus decreased lethality in mice. We confirmed that position 16, which associated with the N-terminal caspase cleavage of the NP, is important for optimal virus fitness in vitro and in vivo. An avian-like mutation at position 16 in the NP of human virus as well as a human-like substitution at this residue in avian NP both resulted in virus attenuation.
Division of Virology, Department of Infectious Diseases, St Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, TN 38105, USA.
A S
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Lipatov
H-L
HL
Yen
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R
Salomon
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H
Ozaki
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Hoffmann
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Webster
D000595:Amino Acid Sequence; D000818:Animals; D020169:Caspases / Q000378:metabolism*; D002645:Chickens / Q000821:virology; D006801:Humans; D009980:Influenza A virus / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D005585:Influenza in Birds / Q000821:virology; D007251:Influenza, Human / Q000821:virology; D051379:Mice; D009154:Mutation; D019590:Nucleocapsid Proteins; D009698:Nucleoproteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D011995:Recombination, Genetic; D014758:Viral Core Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D014779:Virus Replication / Q000235:genetics
C048842:NP protein, Influenza A virus; D019590:Nucleocapsid Proteins; D009698:Nucleoproteins; D016601:RNA-Binding Proteins; D014758:Viral Core Proteins; D020169:Caspases