%0 Journal Article %A Sedmak, J. J. %A Grossberg, S. E. %T Interferon Bioassay: Reduction in Yield of Myxovirus Neuraminidases %D 1973 %J Journal of General Virology, %V 21 %N 1 %P 1-7 %@ 1465-2099 %R https://doi.org/10.1099/0022-1317-21-1-1 %I Microbiology Society, %X SUMMARY Interferon reduced the production of virus neuraminidase during single-cycle growth of A2/HK/1/68 or recombinant X7(F1) influenza viruses in chicken embryo cell cultures. Neuraminidase activity, measurable within 6 h after infection, was reduced as much as 70 to 80% below control levels in interferon-treated cultures. X7(F1) neuraminidase yield was at least as sensitive a measure of interferon inhibition as vesicular stomatitis virus in the standard plaque-reduction assay. Interferon titre, expressed as the 30% neuraminidase reduction dose or NRD30, is derived from semi-logarithmic sigmoidal dose—response curves. The advantages that recommend the neuraminidase reduction bioassay for interferon assay include the precision of the enzyme assay (±1.0%), the precision of measurement of replicate samples of interferon (±9%), the reproducibility of interferon titres obtained sequentially (±20%), as well as the rapidity and economy of the method. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-21-1-1