Ser-Leu substitution at P2 position of the hemagglutinin cleavage site attenuates replication and pathogenicity of Eurasian avian-like H1N2 swine influenza viruses

• Published in: Veterinary microbiology 2021-02, Vol.253, p.108847-108847, Article 108847
• Main Authors: Cai, Mengkai, Zhong, Ruting, Qin, Chenxiao, Yu, Zhiqing, Huang, Junming, Wen, Xiaoyan, Ji, Chihai, Chen, Yongjie, Cai, Yu, Yi, Heyou, Gong, Lang, Zhang, Guihong
• Format: Article
• Language: English
• Subjects: Amino acids; H1N2; Hemagglutinin cleavage site; Hemagglutinins; Influenza; Leucine; Livestock; Mutation; Nose; Orthomyxoviridae; P2 position; Pathogenicity; Proteolysis; Replication; Serine; Swine flu; Swine influenza; Swine influenza virus; Tropism; Vaccine development; Viral replication; Viruses
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/j.vetmic.2020.108847

•We identify a natural Ser-Leu substitution in the HA cleavage site of EA H1N2 virus.•Ser-Leu substitution at the P2 position reduces viral replication and HA cleavage.•Ser-Leu also affects survival rates in mice infected with reassortant viruses.•This amino acid change may be valuable for influenza vaccine development. Swine influenza viruses not only constitute a potential economic problem for livestock, but also pose a substantial threat to human health. Mutation in the proteolytic cleavage site of hemagglutinin (HA) is recognized as an essential factor of tissue tropism and viral pathogenicity. However, the molecular properties of the cleavage site of Eurasian avian-like swine (EA) H1N2 virus remain largely unknown. In this study, we found a serine-leucine (Ser-Leu) substitution at the P2 position of the HA cleavage site (S328 L) in naturally occurring EA H1N2 virus. To study the effect of this substitution, we used reverse genetics to generate recombinant wild-type and mutant viruses containing a single amino acid mutation at the P2 position in A/swine/Guangdong/YJ28/2014 (YJ28) or A/swine/Guangdong/DG2/2015 (DG2) background. In vitro experiments showed that the Ser-Leu substitution at the P2 position attenuated the viral replication and HA cleavage efficiency. In vivo analyses revealed that, while all mice inoculated with r/DG2-S328 L or r/YJ28 viruses survived, the survival rates of r/DG2- and r/YJ28-L328S-inoculated animals were 20 % and 40 %, respectively. Furthermore, the Ser-Leu substitution at the P2 position attenuated the replication in nasal turbinate and lungs. In summary, this amino acid change may be useful to understand the molecular properties of the cleavage site and be valuable for vaccine development.