Lipatov A S, Yen H-L, Salomon R, Ozaki H, Hoffmann E, Webster R G
Division of Virology, Department of Infectious Diseases, St Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, TN 38105, USA.
Arch Virol. 2008;153(3):427-34. doi: 10.1007/s00705-007-0003-8. Epub 2007 Dec 4.
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.
甲型流感病毒核蛋白（NP）的N端半胱天冬酶切割与病毒的宿主来源相关，因此可能是宿主范围的分子决定因素。我们研究了针对人类和禽流感病毒NP切割基序的突变如何影响病毒在体外和体内的复制。NP中“禽样”的D16→G替换使该蛋白对切割具有抗性，这在体外对人类A/波多黎各/8/34（H1N1）病毒的复制没有显著影响，但使该病毒在小鼠中的致死率降低了68倍。基因不相容性导致了重组的A/波多黎各/8/34病毒与源自A/绿头鸭/香港/w312/97（H6N1）病毒的禽NP在体外和体内表现出减毒表型。将“人类样”的G16→D突变插入禽NP中，导致其对半胱天冬酶切割敏感，但并没有挽救其毒力，反而使重组病毒更加减毒。将人类样的G16→D替换引入高致病性A/越南/1203/04（H5N1）病毒的NP中，降低了其在小鼠中的致死率。我们证实，与NP的N端半胱天冬酶切割相关的第16位对于病毒在体外和体内的最佳适应性很重要。人类病毒NP第16位的禽样突变以及禽NP中该残基的人类样替换均导致病毒减毒。
