An avian influenza A (H7N9) virus vaccine candidate based on the fusion protein of hemagglutinin globular head and Salmonella typhimurium flagellin.
BACKGROUND
A novel influenza virus, subtype H7N9, circulated through China in 2013-2014. Its higher rates of human infection in a wide range of locations within China and the associated increased likelihood of human-to-human transmission have caused global concern. Recombinant subunit vaccines provide safe and targeted protection against viral infections. However, the protective efficacy of recombinant subunit vaccines tends to be less potent than vaccines made from whole viruses. Studies have shown that bacterial flagellin has strong adjuvant activity and induces protective immune responses.


RESULTS
In this study, we used overlap-PCR to generate an H7N9 influenza recombinant subunit vaccine that fused the globular head domain (HA1-2, aa 62-284) of the protective hemagglutinin (HA) antigen with the potent TLR5 ligand, Salmonella typhimurium flagellin (fliC). The resulting fusion protein, HA1-2-fliC, was efficiently expressed in an Escherichia coli prokaryotic expression system, and Western blotting and TLR5-stimulating activity analysis confirmed that the HA1-2-fliC moiety could be faithfully refolded to take on the native HA and fliC conformations. In a C3H/HeJ mouse model of intraperitoneal vaccination, the fusion protein elicited significant and robust HA1-2-specific serum IgG titers, maintaining high levels for at least 3 months in the vaccinated animals, and induced similar levels of HA1-2-specific IgG1 and IgG2a that were detectable 12 days after the third immunization. HA1-2-fliC was also found to be capable of triggering the production of neutralizing antibodies, as assessed by measuring hemagglutination inhibition titers.


CONCLUSIONS
We conclude that immunization with HA1-2-fliC induces potent HA1-2-specific responses, offering significant promise for the development of a successful recombinant subunit vaccine for avian influenza A (H7N9).
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China.
Li
L
Song
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China.
Dan
D
Xiong
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China.
Xilong
X
Kang
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China.
Yun
Y
Yang
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China.
Jing
J
Wang
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China.
Yaxin
Y
Guo
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China.
Hui
H
Xu
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China.
Sujuan
S
Chen
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China.
Daxin
D
Peng
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China. zmpan@yzu.edu.cn.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China. zmpan@yzu.edu.cn.
Zhiming
Z
Pan
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, China. jiao@yzu.edu.cn.|Jiangsu Key Laboratory of Zoonosis, Yangzhou University, 48 East Wenhui Road, Yangzhou, Jiangsu, 225009, China. jiao@yzu.edu.cn.
Xinan
X
Jiao
D000818:Animals; D001717:Birds; D017931:DNA Primers / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005408:Flagellin / Q000378:metabolism; D057809:HEK293 Cells; D006388:Hemagglutinins / Q000378:metabolism; D006801:Humans; D064766:Influenza A Virus, H7N9 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000235:genetics*; D005585:Influenza in Birds / Q000517:prevention & control*; D007251:Influenza, Human / Q000517:prevention & control*; D051379:Mice; D012486:Salmonella typhimurium / Q000378:metabolism; D022223:Vaccines, Subunit / Q000235:genetics*; D014614:Vaccines, Synthetic / Q000235:genetics*
D017931:DNA Primers; D006388:Hemagglutinins; D007252:Influenza Vaccines; D022223:Vaccines, Subunit; D014614:Vaccines, Synthetic; D005408:Flagellin