In vitro generation and characterisation of an influenza B variant with reduced sensitivity to neuraminidase inhibitors

Abstract

A contemporary influenza type B virus was passaged in vitro in the presence of increasing concentrations of the neuraminidase inhibitors, zanamivir and oseltamivir carboxylate (0.1-1000 μM over nine passages). After the fifth passage in the presence of zanamivir (10 μM), the virus acquired a Glu 119 Asp neuraminidase mutation (influenza A N2 subtype numbering) in the enzyme active site. After a further three passages, in which growth occurred in 100 μM of zanamivir, a Gln 218 Lys mutation (A (H3) numbering) in the HA1 domain of the haemagglutinin was found. In a fluorescence-based neuraminidase inhibition assay, viruses with the Glu 119 Asp NA mutation had a 32,000-fold reduction in sensitiv..