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Wu Y, Hu J, Jin X, Li X, Wang J, Zhang M, Chen J, Xie S, Qi W, Liao M, Jia W. Accelerated Evolution of H7N9 Subtype Influenza Virus under Vaccination Pressure. Virol Sin 2021; 36:1124-1132. [PMID: 33974230 PMCID: PMC8112217 DOI: 10.1007/s12250-021-00383-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 03/17/2021] [Indexed: 01/02/2023] Open
Abstract
No avian H7N9 outbreaks have occurred since the introduction of H7N9 inactivated vaccine in the fall of 2017. However, H7N9 is still prevalent in poultry. To surveil the prevalence, genetic characteristics, and antigenic changes of H7N9, over 7000 oropharyngeal and cloaca swab specimens were collected from live poultry markets and farms in 15 provinces of China from 2017 to 2019. A total of 85 influenza virus subtype H7N9 strains were isolated and 20 representative strains were selected for genetic analysis and antigenicity evaluation. Results indicated the decreased prevalence of low-pathogenic H7N9 strains while highly-pathogenic H7N9 strains became dominated since the introduction of vaccine. Phylogenetic analysis showed that strains from 2019 formed an independent small branch and were genetically distant to strains isolated in 2013-2018. Analysis of key amino acid sites showed that the virus strains may adapt to the host environment evolutionally through mutation. Our analysis predicted additional potential glycosylation sites for HA and NA genes in the 2019 strains. Sequence analysis of HA gene in strains isolated from 2018 to 2019 showed that there were an increased nucleotide substitution rate and an increased mutation rate in the first and second nucleotides of coding codons within the open reading frame. The hemagglutination inhibition (HI) assay showed that H7-Re1 and H7-Re2 exhibited a lower HI titer for isolates from 2019, while H7-Re3 and rLN79 showed a high HI titer. The protective effect of the vaccine decreased after 15 months of use. Overall, under vaccination pressure, the evolution of influenza virus subtype H7N9 has accelerated.
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Affiliation(s)
- Yifan Wu
- National Avian Influenza Para-Reference Laboratory (Guangzhou), College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China
| | - Jingkai Hu
- National Avian Influenza Para-Reference Laboratory (Guangzhou), College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China
| | - Xuanjiang Jin
- National Avian Influenza Para-Reference Laboratory (Guangzhou), College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China
| | - Xiao Li
- National Avian Influenza Para-Reference Laboratory (Guangzhou), College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China
| | - Jinfeng Wang
- National Avian Influenza Para-Reference Laboratory (Guangzhou), College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China
| | - Mengmeng Zhang
- National Avian Influenza Para-Reference Laboratory (Guangzhou), College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China
| | - Jianglin Chen
- National Avian Influenza Para-Reference Laboratory (Guangzhou), College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China
| | - Shumin Xie
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510642, China.,National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, Guangzhou, 510642, China.,Key Laboratory of Zoonoses Prevention and Control of Guangdong Province, Guangzhou, 510642, China
| | - Wenbao Qi
- National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, Guangzhou, 510642, China
| | - Ming Liao
- Key Laboratory of Zoonoses Prevention and Control of Guangdong Province, Guangzhou, 510642, China
| | - Weixin Jia
- National Avian Influenza Para-Reference Laboratory (Guangzhou), College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China. .,Key Laboratory of Zoonosis, Key Laboratory of Animal Vaccine Development, Ministry of Agriculture and Rural Affairs, Guangzhou, 510642, China. .,Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510642, China. .,National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, Guangzhou, 510642, China. .,Key Laboratory of Zoonoses Prevention and Control of Guangdong Province, Guangzhou, 510642, China.
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