Imaging of Influenza Virus Replication to Optimize Cell Culture-based Vaccine Production

Motivation

Every year, vaccines against the seasonal strains of Influenza A and B viruses are produced in large quantities. These vaccines are prepared from influenza viruses that were propagated in suitable substrates such as fertilized chicken eggs or cultured mammalian cells. To maximize the yield of cell culture-based processes, high-yield producer cell lines have to be selected, and efficient virus propagation strategies have to be developed. For sustained advances in cell culture-based influenza vaccine production, it is crucial to understand and to control virus-host cell interactions that determine the amount of viruses produced.

Aim of the project

In this project, we want to gain quantitative and qualitative insights into influenza virus replication in animal cells that will help to improve industrial influenza vaccine production (Figure 1). For this, we try to identify cellular bottlenecks and to evaluate virus-host cell interactions that may limit virus replication and vaccine yields.

To identify putative limiting processes and factors in the influenza virus life cycle, we perform state-of-the-art imaging flow cytometry with fluorescent probes (e.g., antibodies, molecular beacons) to monitor proteins, nucleic acids, and other relevant cellular and viral features (e.g., glycans, protein phosphorylation states) in infected cells. We then statistically correlate the spatial-temporal expression and distribution patterns of the cellular and viral components with the productivity of the cells, what helps us to understand the basics of influenza virus vaccine production

Figure 1: Image analysis of influenza virus replication in animal cells to improve vaccine production.
To identify limitations of influenza vaccine production in animal cell cultures, we investigate influenza virus replication at the cellular and the molecular level. Influenza virus replication occurs in the following regulated steps (1) virus uptake into the cell, (2) virus uncoating and release of the viral genome (vRNA), (3) viral protein synthesis and vRNA replication (4) transport of viral proteins and vRNA to the plasma membrane, and (5) virus assembly and release from the cell surface. The efficiency of influenza virus production largely depends on the capacity of the host cell to support viral replication. Therefore, we analyze the temporal-spatial expression and distribution of host cell and viral components to identify replication patterns and dynamics in highly productive cells. The results will contribute to the design of high-yield cell lines and cultivation strategies for influenza vaccine production.
Abbreviations: cRNA, complementary RNA; HA, hemagglutinin; M1, matrix protein 1; M2, matrix protein 2; mRNA, messenger RNA; NA, neuraminidase; NP, nucleoprotein; NEP, nuclear export protein; PA, RNA polymerase subunit (acidic); PB1, RNA polymerase subunit 1 (basic); PB2, polymerase subunit 2 (basic); vRNA, viral RNA (genome)

References

Kupke, S. Y.; Riedel, D.; Frensing, T.; Zmora, P.; Reichl, U.: A Novel Type of Influenza A Virus-Derived Defective Interfering Particle with Nucleotide Substitutions in Its Genome. Journal of Virology 93 (4), 01786-18 (2019)
Frensing, T.; Kupke, S. Y.; Bachmann, M.; Fritzsche, S.; Gallo Ramirez, L. E.; Reichl, U.: Influenza virus intracellular replication dynamics, release kinetics, and particle morphology during propagation in MDCK cells. Applied Microbiology and Biotechnology 100 (16), pp. 7181 - 7192 (2016)

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