Article Figures & Data
Figures
- FIG 1
Structural model of zanamivir bound to the NA of A/Indiana/12/2012 A(H3N2)v virus. The 240-aa loop does not interact directly with the NAI but instead contributes to a hydrogen bond network that involves R224, R292, and N294 in binding zanamivir.
Tables
- TABLE 1
Assessment of influenza A(H3N2)v virus susceptibilities to NAIs in the fluorescent NI assay
NA source Subtype NA substitution(s)a IC50, nM (fold)b Oseltamivir Zanamivir Peramivir Laninamivir A-315675 Test viruses Test viruses (n = 165) H3N2v — 0.16 ± 0.11 [0.15] 0.52 ± 0.09 [0.51] 0.17 ± 0.04 [0.16] 0.77 ± 0.19 [0.75] 0.29 ± 0.05 [0.28] A/Ohio/88/2012 H3N2v S245N, S247P 4.69 ± 0.25 (31) 33.86 ± 3.73 (66) 0.20 ± 0.01 (1) 4.85 ± 0.39 (7) 0.51 ± 0.06 (2) A/Ohio/83/2012 H3N2v S245N 0.13 ± 0.01 (1) 0.51 ± 0.02 (1) 0.15 ± 0.01 (1) 0.84 ± 0.06 (1) 0.29 ± 0.04 (1) A/Indiana/12/2012 H3N2v — 0.15 ± 0.01 (1) 0.42 ± 0.06 (1) 0.13 ± 0.02 (1) 0.61 ± 0.08 (1) 0.22 ± 0.04 (1) Recombinant NAs recNA-1 — 0.09 ± 0.01 0.15 ± 0.01 0.11 ± 0.01 0.44 ± 0.04 0.15 ± 0.01 recNA-2 (A/Ohio/88/2012-like) S245N, S247P 3.60 ± 0.13 (40) 35.32 ± 1.66 (235) 0.17 ± 0.02 (2) 3.84 ± 0.37 (9) 0.32 ± 0.05 (2) recNA-3c S247P 4.23 ± 0.12 (42) 39.91 ± 3.84 (266) 0.21 ± 0.02 (2) 3.79 ± 0.16 (9) 0.62 ± 0.01 (4) recNA-4 (A/Ohio/83/2012-like) S245N 0.09 ± 0.01 (1) 0.17 ± 0.03 (1) 0.13 ± 0.01 (1) 0.50 ± 0.02 (1) 0.17 ± 0.01 (1) Reference viruses A/Washington/01/2007, oseltamivir sensitive H3N2 — 0.06 ± 0.01 0.46 ± 0.15 0.08 ± 0.01 0.33 ± 0.06 0.23 ± 0.16 A/Texas/12/2007, oseltamivir resistant H3N2 E119V 38.10 ± 2.35 (635) 0.36 ± 0.06 (1) 0.10 ± 0.01 (1) 0.34 ± 0.03 (1) 0.23 ± 0.15 (1) ↵a Amino acid substitution in the NA known or suspected to affect susceptibility to NAIs; —, absence of known or suspected markers of NAI resistance.
↵b Values are means ± SD, based on at least three independent experiments. IC50 for A/Ohio/88/2012 virus was excluded from calculation of the mean and median IC50s. Fold values (in parentheses): for A(H3N2)v viruses, compared to a median IC50; for recNA, compared to an IC50 of recNA lacking changes at aa 245 and 247 in the NA; for the reference A(H3N2) viruses, compared to an IC50 for A/Washington/01/2007. Median IC50s for A(H3N2)v viruses are shown in square brackets.
↵c No corresponding virus available.
- TABLE 2
Reduction of A(H3N2)v infectious yields in MDCK cells in the presence of nitazoxanide
Virus name Subtype NA substitution(s) Mean virus titers ± SDa in the presence of nitazoxanide at concn of: 0 μM 0.5 μM 1 μM 2 μM 4 μM 10 μM Test viruses A/Ohio/88/2012 H3N2v S245N, S247P 8.3 ± 0.3 7.8 ± 0.9 7.3 ± 0.8 6.4 ± 1.3 4.6 ± 1.5 2.1 ± 0.9 A/Ohio/83/2012 H3N2v S245N 8.9 ± 0.4 8.6 ± 0.2 8.6 ± 0.1 7.8 ± 0.3 7.0 ± 1.0 5.9 ± 0.4 Reference viruses A/Washington/01/2007 H3N2 —b 8.6 ± 0.4 8.9 ± 0.2 8.6 ± 0.1 8.3 ± 0.1 8.3 ± 0.3 7.6 ± 0.2 A/Texas/12/2007 H3N2 E119V 8.1 ± 0.3 7.9 ± 0.4 7.8 ± 0.5 7.2 ± 0.4 5.4 ± 0.4 3.6 ± 0.5 A/California/04/2009 H1N1pdm09 — 6.4 ± 0.5 6.3 ± 0.5 6.0 ± 0.6 5.4 ± 0.5 4.8 ± 0.3 3.0 ± 0.8 - TABLE 3
Reduction of influenza A(H3N2)v infectious yields in MDCK-SIAT1 cells in the presence of favipiravir
Virus name Subtype NA substitution(s) Mean virus titers ± SDa in the presence of favipiravir at concn of: 0 μM 0.5 μM 2 μM 8 μM 32 μM 128 μM Test viruses A/Ohio/88/2012 H3N2v S245N, S247P 5.9 ± 0.3 5.5 ± 0.3 5.1 ± 0.2 4.7 ± 0.2 2.6 ± 0.6 <1 A/Ohio/83/2012 H3N2v S245N 6.6 ± 0.3 6.5 ± 0.1 5.9 ± 0.3 5.5 ± 0.6 3.3 ± 0.4 <1 Reference viruses A/Washington/01/2007 H3N2 —b 6.5 ± 0.5 6.0 ± 0.1 6.2 ± 0.1 5.2 ± 0.4 2.3 ± 0.6 <1 A/Texas/12/2007 H3N2 E119V 7.0 ± 0.1 6.7 ± 0.2 6.4 ± 0.2 5.6 ± 0.4 2.8 ± 0.2 <1 A/California/04/2009 H1N1pdm09 — 5.5 ± 0.1 5.1 ± 0.4 4.3 ± 0.7 3.9 ± 0.5 2.2 ± 0.3 <1 - TABLE 4
Reduction in focus formation in MDCK-SIAT1 cell monolayers pretreated with fludase
Virus name Subtype NA substitution(s) Mean FFU ± SD (no. of foci in each expt)a at fludase concn of: 0 μM 0.02 μM 0.06 μM 0.25 μM 1 μM 4 μM Test viruses A/Ohio/88/2012 H3N2v S245N, S247P 18.5 ± 1.8 1.8 ± 0.8 2.0 ± 1.2 (2;2;0) (2;3;0) (2;1;0) A/Ohio/83/2012 H3N2v S245N 24.3 ± 3.4 4.3 ± 0.8 2.5 ± 1.0 0.8 ± 0.4 0.5 ± 0.5 1.3 ± 0.8 Reference viruses A/Washington/01/2007 H3N2 —b 31.5 ± 6.6 5.8 ± 1.5 2.0 ± 0.7 3.5 ± 1.7 1.8 ± 0.4 2.5 ± 1.1 A/Texas/12/2007 H3N2 E119V 27.5 ± 3.2 4.0 ± 0.7 2.5 ± 0.9 2.0 ± 1.2 1.3 ± 0.4 1.8 ± 0.4 A/California/04/2009 H1N1pdm09 — 15.0 ± 2.3 2.7 ± 0.8 1.3 ± 0.4 (1;1;0) (1;0;0) (1;0;0) - TABLE 5
IC90a values determined in cell culture-based assays
Virus name Subtype NA substitution(s) Mean IC90 ± SD Nitazoxanide Favipiravir Fludase μM μg/ml μM μg/ml μM μg/ml Test viruses A/Ohio/88/2012 H3N2v S245N, S247P 1.09 ± 0.54 0.34 ± 0.17 2.85 ± 0.77 0.45 ± 0.12 0.03 ± 0.02 1.41 ± 1.09 A/Ohio/83/2012 H3N2v S245N 0.86 ± 0.32 0.27 ± 0.10 2.77 ± 0.49 0.43 ± 0.08 0.05 ± 0.01 2.36 ± 0.67 Reference viruses A/Washington/01/2007 H3N2 —b 5.63 ± 0.15 1.75 ± 0.05 8.99 ± 1.56 1.40 ± 0.24 0.06 ± 0.05 2.63 ± 2.33 A/Texas/12/2007 H3N2 E119V 1.61 ± 0.25 0.50 ± 0.08 2.88 ± 0.19 0.45 ± 0.03 0.03 ± 0.01 1.43 ± 0.65 A/California/04/2009 H1N1pdm09 — 2.33 ± 0.21 0.72 ± 0.07 2.13 ± 0.44 0.33 ± 0.07 0.05 ± 0.03 2.58 ± 1.54 ↵a IC90 (the concentration of antiviral agent reducing the virus replication by 90%) values were determined in the infectious viral yield reduction (nitazoxanide and favipiravir) and the focus-forming reduction (fludase) assays (see also Tables 2 to 4). Results are from three independently performed experiments.
↵b —, absence of known or suspected markers of NAI resistance.
