Comparison of suspension MDCK cells, adherent MDCK cells, and LLC-MK2 cells for selective isolation of influenza viruses to be used as vaccine seeds
Harada, Y.; Takahashi, H.; Trusheim, H.; Roth, B.; Mizuta, K.; Hirata-Saito, A.; Ogane, T.; Odagiri, T.; Tashiro, M.; Yamamoto, N.
Influenza and other Respiratory Viruses 14(2): 204-209
2020
ISSN/ISBN: 1750-2659
PMID: 31651085
DOI: 10.1111/irv.12694
Accession: 069451443
Cell-based influenza vaccines can solve the problem of the frequent occurrence of egg adaptation-associated antigenic changes observed in egg-based vaccines. Seed viruses for cell-based vaccines can be prepared from clinical specimens by cell culture; however, clinical samples risk harboring respiratory viruses other than influenza virus. Therefore, it is necessary to investigate the patterns of co-infection in clinical samples and explore whether cell culture technology can selectively propagate influenza viruses from samples containing other respiratory viruses. A total of 341 clinical specimens were collected from patients with influenza or influenza-like illness and analyzed by ResPlex II assay to detect 18 respiratory viruses. The patterns of co-infection were statistically analyzed with Fisher's exact test. The samples with double or triple infections were passaged in suspension MDCK cells (MDCK-S), adherent MDCK cells (MDCK-A), and LLC-MK2D cells. Cell-passaged samples were analyzed by ResPlex II assay again to investigate whether each cell line could amplify influenza viruses and eliminate other respiratory viruses. Double infections were detected in 8.5% and triple infections in 0.9% of the collected clinical specimens. We identified four pairs of viruses with significant correlation. For all samples with double and triple infection, MDCK-S and MDCK-A could selectively propagate influenza viruses, while eliminating all contaminating viruses. In contrast, LLC-MK2D showed lower isolation efficiency for influenza virus and higher isolation efficiency for coxsackievirus/echovirus than MDCK-S and MDCK-A. Both MDCK-S and MDCK-A are considered suitable for the preparation of influenza vaccine seed viruses without adventitious agents or egg-adaptation mutations.