Volume 16, Number 3—March 2010
Rare Influenza A (H3N2) Variants with Reduced Sensitivity to Antiviral Drugs
|Strains||Passage history||NA mutation||IC50s of NA inhibitors
||Amantadine sensitivity† (M2 mutation)|
|Zanamivir, nM ± SD||Fold change||Oseltamivir, nM ± SD||Fold change|
|All NAI-sensitive subtype H3N2 isolates‡||MDCK2||None||1.12 ± 0.40||1||0.86 ± 0.44||1||Resistant (S31N)|
|A/Myanmar/M187/2007||MDCK2||Q136K||59.72 ± 3.83||53.3||0.13 ± 0.05||0.2||Resistant (S31N)|
|A/Myanmar/M114/2008||MDCK2||Q136K||33.37 ± 7.02||29.8||0.16 ± 0.03||0.2||Resistant (S31N)|
|A/Texas/131/2002§||None||1.43 ± 0.09||1.3||0.99 ± 0.09||1.2||Sensitive|
|A/Texas/131/2002_E119V§||E119V||5.43 ± 0.68||4.8||94.33 ± 2.06||109.7||Sensitive|
*NA, neuraminidase;IC50, inhibitory concentration; NAI, neuraminidase inhibitors.
†Amantadine sensitivity was based on M2 genotyping data.
‡Average IC50 was calculated excluding the control viruses (n = 47).
§Reference strains used as drug-sensitive and -resistant control viruses in the NAI assay.
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