High genetic stability in MDCK-SIAT1 passaged human influenza viruses

MDCK-induced amino acid (AA) mutation, such as D151G/N in the neuraminidase (NA) of influenza A/H3N2 viruses, is of concern. MDCK-SIAT1 cells, modified derivatives with an increased expression of α2,6-linked sialic acid receptors are increasingly used due to their superiority in a viral recovery. However, MDCK-SIAT1 induced AA mutations have not been fully examined. In this study, we compared NA and hemagglutinin (HA) genes of recent circulating influenza viruses isolated after an MDCK-SIAT1 passage with those directly obtained from the original samples. A total of 22 samples collected during the 2016-17 seasons included 9 A/H3N2, 5 H1N1pdm, and 8 B viruses. None of the deduced AA mutations in the NA or HA segments were detected after an MDCK-SIAT1 passage, except for one AA mutation in the NA of an influenza B virus sample. NA D151G/N changes were not seen in any of the MDCK-SIAT1 passaged A/H3N2 viruses, even in the small variants analysis conducted using deep sequencing. AA mutations induced by an MDCK-SIAT1 passage are currently rare, although careful observation is needed in the future.