Abstract
BackgroundInfluenza vaccine manufacturers traditionally use egg-derived candidate vaccine viruses (CVVs) to produce high-yield influenza viruses for seasonal or pandemic vaccines; however, these egg-derived CVVs need an adaptation process for the virus to grow in mammalian cells. The low yields of cell-based manufacturing systems using egg-derived CVVs remain an unsolved issue. This study aimed to develop high-growth cell-derived CVVs for MDCK cell-based vaccine manufacturing platforms.MethodsFour H7N9 CVVs were generated in characterized Vero and adherent MDCK (aMDCK) cells. Furthermore, reassortant viruses were amplified in adherent MDCK (aMDCK) cells with certification, and their growth characteristics were detected in aMDCK cells and new suspension MDCK (sMDCK) cells. Finally, the plaque-forming ability, biosafety, and immunogenicity of H7N9 reassortant viruses were evaluated.ResultsThe HA titers of these CVVs produced in proprietary suspension MDCK (sMDCK) cells and chicken embryos were 2- to 8-fold higher than those in aMDCK cells. All H7N9 CVVs showed attenuated characteristics by trypsin-dependent plaque assay and chicken embryo lethality test. The alum-adjuvanted NHRI-RG5 (derived from the fifth wave H7N9 virus A/Guangdong/SP440/2017) vaccine had the highest immunogenicity and cross-reactivity among the four H7N9 CVVs. Finally, we found that AddaVax adjuvant improved the cross-reactivity of low pathogenic H7N9 virus against highly pathogenic H7N9 viruses.ConclusionsOur study indicates that cell-derived H7N9 CVVs possessed high growth rate in new sMDCK cells and low pathogenicity in chicken embryo, and that CVVs generated by this platform are also suitable for both cell- and egg-based prepandemic vaccine production.
Highlights
Influenza vaccine manufacturers traditionally use egg-derived candidate vaccine viruses (CVVs) to produce high-yield influenza viruses for seasonal or pandemic vaccines; these egg-derived CVVs need an adaptation process for the virus to grow in mammalian cells
To explore the role of acquired glycosylation in the growth of H7N9 CVV in MDCK cells, we generated CVVs derived from the A/Guangdong/SP440/2017 and A/Taiwan/1/2017 H7N9 viruses, which acquired potential N-linked glycosylation site in HA protein during evolution
The HA titers of National Health Research Institutes (NHRI)-RG3 and NHRI-RG4 showed an increase from 64 hemagglutination units (HAU)/50 μL (V1aM2) to 256 HAU/50 μL (V1aM3) and were maintained at a level similar to that of V1aM10, which means in the adherent MDCK (aMDCK)-based production system, the aMDCK cell-adapted master donor viruses (MDVs) could not generate highgrowth reassortants for all H7N9 viruses and the reassortant viruses may need further adaptations to reach higher titers (Table 2)
Summary
Influenza vaccine manufacturers traditionally use egg-derived candidate vaccine viruses (CVVs) to produce high-yield influenza viruses for seasonal or pandemic vaccines; these egg-derived CVVs need an adaptation process for the virus to grow in mammalian cells. The low yields of cell-based manufacturing systems using egg-derived CVVs remain an unsolved issue. This study aimed to develop high-growth cell-derived CVVs for MDCK cell-based vaccine manufacturing platforms. The fifth epidemic wave of H7N9 avian influenza in China has raised concerns to public health. The H7N9 outbreak is under control currently, the newly emerging H7N9 viruses still pose a threat to public health. The H7N9 viruses in the fifth wave have become highly pathogenic avian influenza (HPAI) viruses that bear mutations in the HA gene [2, 3] and display reduced susceptibility to antiviral drugs [4, 5]. Antiviral medicines and H7N9 prepandemic vaccines need to be stockpiled in Taiwan
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