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.
Lipatov
A S
AS
Division of Virology, Department of Infectious Diseases, St Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, TN 38105, USA.
Yen
H-L
HL
Salomon
R
R
Ozaki
H
H
Hoffmann
E
E
Webster
R G
RG
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