The R251K Substitution in Viral Protein PB2 Increases Viral Replication and Pathogenicity of Eurasian Avian-like H1N1 Swine Influenza Viruses

• Published in: Viruses 2020-01, Vol.12 (1), p.52
• Main Authors: Cai, Mengkai, Zhong, Ruting, Qin, Chenxiao, Yu, Zhiqing, Wen, Xiaoyan, Xian, Junsi, Chen, Yongjie, Cai, Yu, Yi, Heyou, Gong, Lang, Zhang, Guihong
• Format: Article
• Language: English
• Subjects: A549 Cells; Amino acid sequence; Amino Acid Substitution; Animals; Dogs; Epidemiology; eurasian avian-like h1n1 swine influenza viruses; Experiments; Female; Genomes; Genotypes; Humans; Infections; Influenza; Influenza A Virus, H1N1 Subtype - genetics; Influenza A Virus, H1N1 Subtype - pathogenicity; Influenza A Virus, H1N1 Subtype - physiology; Infrared imaging systems; Laboratory animals; Madin Darby Canine Kidney Cells; Mammals; Mice; Mice, Inbred BALB C; Mutation; Nucleotide sequence; Orthomyxoviridae Infections - pathology; Orthomyxoviridae Infections - virology; Pandemics; Pathogenicity; pb2 gene; pb2-r251k; Plasmids; polymerase; Proteins; Public health; Replication; RNA-Dependent RNA Polymerase - genetics; RNA-Dependent RNA Polymerase - metabolism; Swine flu; Swine influenza; Transcription; Viral infections; Viral Proteins - genetics; Viral Proteins - metabolism; Virulence; Virulence - genetics; Virus Replication - genetics; Viruses
• ISSN: 1999-4915; 1999-4915
• DOI: 10.3390/v12010052

The Eurasian avian-like swine (EA) H1N1 virus has affected the Chinese swine industry, and human infection cases have been reported occasionally. However, little is known about the pathogenic mechanism of EA H1N1 virus. In this study, we compared the mouse pathogenicity of A/swine/Guangdong/YJ4/2014 (YJ4) and A/swine/Guangdong/MS285/2017 (MS285) viruses, which had similar genotype to A/Hunan/42443/2015 (HuN-like). None of the mice inoculated with 10 TCID of YJ4 survived at 7 days post infection, while the survival rate of the MS285 group was 100%. Therefore, a series of single fragment reassortants in MS285 background and two rescued wild-type viruses were generated by using the reverse genetics method, and the pathogenicity analysis revealed that the gene contributed to the high virulence of YJ4 virus. Furthermore, there were 11 amino acid differences in PB2 between MS285 and YJ4 identified by sequence alignment, and 11 single amino acid mutant viruses were generated in the MS285 background. We found that the R251K mutation significantly increased the virulence of MS285 in mice, contributed to high polymerase activity and enhanced viral genome transcription and replication. These results indicate that PB2-R251K contributes to the virulence of the EA H1N1 virus and provide new insight into future molecular epidemiological surveillance strategies.