Impact of defective interfering particles on virus replication and antiviral host response in cell culture-based influenza vaccine production
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During the replication of influenza viruses, defective interfering particles (DIPs) can be generated. These are noninfectious deletion mutants that require coinfection with a wild-type virus but interfere with its helper virus replication. Consequently, coinfected cells mainly produce DIPs. Little is known about how such noninfectious virus particles affect the virus yield of cell culture-based influenza vaccine production. We compared infections of Madin-Darby canine kidney cells with two seed virus preparations of the influenza virus strain A/Puerto Rico/8/34 that contain different amounts of DIPs. A combination of conventional RT-PCR, RT-qPCR, and flow cytometry revealed that DI genomes indeed strongly accumulate in coinfected cells and impede the viral RNA synthesis. Additionally, cells infected at the higher DIP concentration showed a stronger antiviral response characterized by increased interferon-β expression and apoptosis induction. Furthermore, in the presence of DIPs, a significant fraction of cells did not show any productive accumulation of viral proteins at all. Together, these effects of DIPs significantly reduce the virus yield. Therefore, the accumulation of DIPs should be avoided during influenza vaccine production which can be achieved by quality controls of working seed viruses based on conventional RT-PCR. The strategy for the depletion of DIPs presented here can help to make cell culture-based vaccine production more reliable and robust.
KeywordsInfluenza virus Cell culture-based vaccine production Defective interfering particles
We thank Frank Stefan Heldt, Tanja Laske, and Andrew Easton for critical comments on the manuscript. In addition, the authors would like to thank Stefanie Luetzner and Nancy Wynserski for excellent technical assistance. Mandy Bachmann is supported by a grant of the German Federal Ministry of Education and Research as part of the e:Bio initiative.
Conflict of interest
The authors declare that they have no conflict of interest.
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