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Volume 17, Number 11—November 2011

Dispatch

Influenza B Viruses with Mutation in the Neuraminidase Active Site, North Carolina, USA, 2010–11

Katrina Sleeman, Tiffany G. Sheu, Zack Moore, Susan Kilpatrick, Shikha Garg, Alicia M. Fry, and Larisa V. GubarevaComments to Author 
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (K. Sleeman, T.G. Sheu, S. Garg, A.M. Fry, L.V. Gubareva); Battelle, Atlanta (T.G. Sheu); North Carolina Department of Health and Human Services, Raleigh, North Carolina, USA (Z. Moore, S. Kilpatrick)

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Table 1

Comparison of influenza virus susceptibility, North Carolina, USA, 2010−11 influenza seasons*

Type/subtype and strain designation Virus subset NA change Fluorescent NAI assay,
IC50 ± SD, nmol/L (-fold)
Chemiluminescent NAI assay,
IC50 ± SD nmol/L (-fold)
Zanamivir Oseltamivir Peramivir Zanamivir Oseltamivir Peramivir
Influenza B
B/North Carolina/11/2010 Test I221V/I 8.58 (3) 20.39 (6) 2.77 (8) 5 (2) 8.97 (5) 1.26 (5)
B/North Carolina/03/2011 Test I221V/I 8.13 (3) 18.98 (6) 2.43 (7) 6.37 (2) 4.98 (3) 1.19 (4)
B/North Carolina/13/2010 Test I221V/I; K360E 6.42 (2) 17.76 (5) 2.6 (7) 3.67 (1) 4.84 (3) 1.29 (5)
B/North Carolina/07/2011 Test I221V/I; S283N 7.93 (3) 22.31 (7) 2.95 (8) 4.82 (2) 6.01 (3) 1.26 (5)
B/North Carolina/10/2011 Control WT 4.34 (2) 10.67 (2) 0.64 (2) 2.82 (1) 2.72 (1) 0.41 (1)
2010–2011 influenza B,
n = 39 Surveillance WT 3.31 ± 0.91 (1) 8.33 ± 0.28 (3) 0.61 ± 0.18 (2) 2.48 ± 0.89 (1) 2.77 ±
0.79 (1) 0.38 ± 0.20 (1)
B/Memphis/20/1996 Reference WT 2.59 ± 0.50 (1) 3.25 ± 0.9 (1) 0.35 ± 0.03 (1) 2.96 ± 0.64 (1) 1.88 ±
0.33 (1) 0.28 ± 0.04 (1)
B/Memphis/20/1996
Reference
R152K
66.14 ± 28.45 (26)
700.25 ± 61.06 (215)
269.78 ± 38.21 (771)

53.46 ± 11.59 (18)
177.20 ± 36.72 (94)
62.83 ± 38.02 (224)
Pandemic (H1N1) 2009
A/California/07/2009 Reference WT 0.26 ± 0.02 (1) 0.22 ± 0.08 (1) 0.08 ± 0.01 (1) 0.24 ± 0.04 (1) 0.21 ± 0.03 (1) 0.07 ± 0.01 (1)
A/Texas/48/2009
Reference
H275Y
0.37 ± 0.04 (1)
165.42 ± 24.15 (752)
16.32 ± 2.12 (204)

0.36 ± 0.06 (1)
58.77 ± 10.99 (280)
7.50 ± 1.30 (107)
Influenza A (H3N2)
A/Washington/01/2007 Reference WT 0.40 ± 0.07 (1) 0.12 ± 0.01 (1) 0.13 ± 0.01 (1) 0.79 ± 0.08 (1) 0.11 ± 0.02 (1) 0.13 ± 0.01 (1)
A/Texas/12/2007 Reference E119V 0.40 ± 0.05 (1) 43.81 ± 1.90 (365) 0.16 ± 0.02 (1) 0.57 ± 0.09 (1) 3.37 ± 0.63 (31) 0.16 ± 0.03 (1)

*NA, neuraminidase; NAI, neuraminidase inhibition; IC50, 50% inhibitory concentration; WT, wild type. Mean IC50 values for wild-type reference control viruses for each type/subtype are in boldface and were used to calculate the -fold differences for their respective type/subtypes as indicated in parentheses. Test, influenza B viruses from North Carolina study carrying the I221V substitution. Control, influenza B virus with identical NA sequence as B/North Carolina/11/2010 with the exception of being wild-type (I) at position 221. Surveillance, influenza B viruses collected in the US during October 2010−December 2010 tested in routine influenza surveillance activities in both the fluorescent and chemiluminescent NAI assays. Reference, susceptible and resistant reference viruses used as controls in NAI assays. IC50 values for reference viruses represent the average taken from 5 replicates.

*NA, neuraminidase; NAI, neuraminidase inhibition; IC50, 50% inhibitory concentration; WT, wild type. Mean IC50 values for wild-type reference control viruses for each type/subtype are in boldface and were used to calculate the -fold differences for their respective type/subtypes as indicated in parentheses. Test, influenza B viruses from North Carolina study carrying the I221V substitution. Control, influenza B virus with identical NA sequence as B/North Carolina/11/2010 with the exception of being wild-type (I) at position 221. Surveillance, influenza B viruses collected in the US during October 2010−December 2010 tested in routine influenza surveillance activities in both the fluorescent and chemiluminescent NAI assays. Reference, susceptible and resistant reference viruses used as controls in NAI assays. IC50 values for reference viruses represent the average taken from 5 replicates.

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