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Glutamic Acid at Position 343 in PB2 Contributes to the Virulence of H1N1 Swine Influenza Virus in Mice
Yanwen Wang1, Qiu Zhong1, Fei Meng1
1State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China.
Abstract:
The H1N1 swine influenza viruses CQ91 and CQ445, isolated from pigs in China, exhibited distinct virulence in mice despite sharing similar genomic constellations. CQ91 demonstrated higher pathogenicity (MLD50: 5.4 log10 EID50) and replication efficiency in mice compared to CQ445 (MLD50: 6.6 log10 EID50). Through reverse genetics, we found that the attenuation of CQ445 was due to a single substitution of glutamic acid (E) with lysine (K) at position 343 in the PB2 protein. Introducing the CQ445-PB2 (343K) into CQ91 significantly reduced viral replication and pathogenicity in mice, while replacing CQ445-PB2 with CQ91-PB2 (343E) restored virulence. In vitro studies showed that the K343E mutation impaired viral replication in MDCK and A549 cells and reduced polymerase activity in minigenome assays. Mechanistically, the amino acid at position 343 in the PB2 affects the transcription stage of the viral replication process. Structural modeling indicated that the charge reversal caused by E343K altered local electrostatic interactions without major conformational changes. Phylogenetic analysis revealed that PB2-343E is highly conserved (>99.9%) in human and swine H1/H3 influenza viruses, suggesting that PB2-343E confers an adaptive advantage. This study identifies PB2-343E as a critical determinant of influenza virus pathogenicity in mammals, highlighting its role in host adaptation.
Insights
A specific mutation in the PB2 protein (glutamic acid to lysine at position 343) significantly impacts H1N1 swine influenza virus virulence and replication in mice. This finding is crucial for understanding influenza virus pathogenicity and host adaptation.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- H1N1 swine influenza viruses exhibit varying virulence.
- Genomic similarities do not always predict pathogenicity.
Purpose of the Study:
- To identify genetic determinants of H1N1 swine influenza virus virulence.
- To elucidate the role of the PB2 protein in viral pathogenicity and host adaptation.
Main Methods:
- Reverse genetics to manipulate viral genes.
- In vitro assays (cell culture, minigenome assays) to assess viral replication and polymerase activity.
- Structural modeling and phylogenetic analysis.
Main Results:
- A single amino acid substitution (E343K) in the PB2 protein attenuates H1N1 virus virulence in mice.
- The E343K mutation impairs viral replication and polymerase activity.
- PB2-343E is conserved in human and swine influenza viruses, suggesting adaptive significance.
Conclusions:
- The amino acid at position 343 in the PB2 protein is a critical determinant of influenza virus pathogenicity in mammals.
- PB2-343E confers an adaptive advantage, influencing host adaptation.
- This residue plays a key role in the viral transcription stage.
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