Volume 25, Number 4—April 2019
Research Letter
Reduced Susceptibility to Neuraminidase Inhibitors in Influenza B Isolate, Canada
Table
Susceptibility profiles and NA activity of influenza B virus isolates and susceptibility profiles of recombinant influenza B NAs determined by assays using the fluorescent MUNANA substrate, Canada*
Sample type |
IC50 in nM + SD (fold increase) [phenotype]† |
NA activity, Vmax‡ |
||
Oseltamivir |
Zanamivir |
Peramivir |
||
Clinical isolate | ||||
B/Phuket/3073/2013, vaccine | 18.98 + 3.89 | 0.70 + 0.17 | 0.74 + 0.02 | ND |
B/Québec/88855/2018, WT | 17.47 ± 1.43 (1) [NI] | 0.85 ± 0.09 (1) [NI] | 0.92 ± 0.09 (1) [NI] | 2.24 ± 0.3 |
B/Québec/1182C/2018, Gly407Ser |
104 + 14.62 (5.97) [RI] |
27.58 + 2.56 (32.44) [RI] |
26.08 + 0.1 (38.34) [RI] |
2.18 + 0.47 |
Recombinant neuraminidase | ||||
B/Quebec/88855/2018, WT | 11.16 + 5.25 (1) [NI] | 0.97 + 0.27 (1) [NI] | 0.76 + 0.19 (1) [NI] | ND |
B/Quebec/88855/2018, Gly407Ser | 46.52 + 12.58 (4.16) [NI] | 9.77 + 0.90 (10.07) [RI] | 12.44 + 5.47 (16.36) [RI] | ND |
*Values are from a representative experiment performed in duplicate. IC50, 50% inhibitory concentration; MUNANA, 2 '-(4-methylumbelliferyl)-α-D-N-acteylneuraminic acid; NA, neuraminidase; NAI, neuraminidase inhibitor; ND, not done; NI, normal inhibition (<5-fold increase in IC50 over WT); RI, reduced inhibition (5- to 50-fold increase in IC50 over WT); Vmax, maximum velocity of substrate conversion; WT, wild type.
†The phenotype of susceptibility to NAI following the World Health Organization guidelines.
‡Numbers indicate mean Vmax values (U/sec) ± SD of a kinetics experiment performed in triplicate.
1These authors contributed equally to this article.