Influenza virus isolation for monitoring epidemic influenza
activity and for the selection of candidate vaccine strains has traditionally
been conducted by cultivation in embryonated hen’s eggs.
Due to receptor limitations, such egg passaging can cause adaptive
mutations of the haemagglutinin [1,2]. These egg-adaptive mutations
do not revert on subsequent passage in mammalian cells, and
they may alter the antigenic properties of the receptor binding site,
which is also a critical binding site for virus inhibiting and protective
antibodies [3,4]. In contrast to egg-passaged virus, mammalian
cell-grown influenza virus preserves the sequence of the original
human clinical sample.
During the last decade the worldwide National Influenza Centres
have almost completely changed influenza virus isolation from
egg culture to cell culture, mainly using MDCK cells. This change
to cell culture was stimulated not only by the relative ease of