Manipulation of neuraminidase packaging signals and hemagglutinin residues improves the growth of A/Anhui/1/2013 (H7N9) influenza vaccine virus yield in eggs.
In 2013, a novel avian-origin H7N9 influenza A virus causing severe lower respiratory tract disease in humans emerged in China, with continued sporadic cases. An effective vaccine is needed for this virus in case it acquires transmissibility among humans; however, PR8-based A/Anhui/1/2013 (Anhui/1, H7N9), a WHO-recommended H7N9 candidate vaccine virus (CVV) for vaccine production, does not replicate well in chicken eggs, posing an obstacle to egg-based vaccine production. To address this issue, we explored the possibility that PR8's hemagglutinin (HA) and neuraminidase (NA) packaging signals mediate improvement of Anhui/1 CVV yield in eggs. We constructed chimeric HA and NA genes having the coding region of Anhui/1 HA and NA flanked by the 5' and 3' packaging signals of PR8's HA and NA, respectively. The growth of CVVs containing the chimeric HA was not affected, but that of those containing the chimeric NA gene grew in embryonated chicken eggs with a more than 2-fold higher titer than that of WT CVV. Upon 6 passages in eggs further yield increase was achieved although this was not associated with any changes in the chimeric NA gene. The HA of the passaged CVV, did, however, exhibit egg-adaptive mutations and one of them (HA-G218E) improved CVV growth in eggs without significantly changing antigenicity. The HA-G218E substitution and a chimeric NA, thus, combine to provide an Anhui/1 CVV with properties more favorable for vaccine manufacture.
Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA. Electronic address: subrata.barman@stjude.org.
Subrata
S
Barman
Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA. Electronic address: pskrylov@gmail.com.
Petr S
PS
Krylov
Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA. Electronic address: jasmine.turner@stjude.org.
Jasmine C
JC
Turner
Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA. Electronic address: john.franks@stjude.org.
John
J
Franks
Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA. Electronic address: robert.webster@stjude.org.
Robert G
RG
Webster
Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand. Electronic address: matloob.husain@otago.ac.nz.
Matloob
M
Husain
Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA. Electronic address: richard.webby@stjude.org.
Richard J
RJ
Webby
D000818:Animals; D002642:Chick Embryo; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000096:biosynthesis* / Q000235:genetics; D064766:Influenza A Virus, H7N9 Subtype / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D009439:Neuraminidase / Q000096:biosynthesis* / Q000235:genetics; D021382:Protein Sorting Signals / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D019562:Viral Load; D014764:Viral Proteins / Q000096:biosynthesis* / Q000235:genetics; D019065:Virus Assembly; D014776:Virus Cultivation / Q000379:methods*; D014779:Virus Replication
D019267:Hemagglutinin Glycoproteins, Influenza Virus; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase
Chimeric NA; Egg adaptation; H7 HA egg-adaptive mutations; Influenza A H7N9 virus; Packaging signals; Vaccine virus