Volume 16, Number 3—March 2010
Dispatch
Rare Influenza A (H3N2) Variants with Reduced Sensitivity to Antiviral Drugs
Clyde Dapat1
, Yasushi Suzuki1, Reiko Saito, Yadanar Kyaw, Yi Yi Myint, Nay Lin, Htun Naing Oo, Khin Yi Oo, Ne Win, Makoto Naito, Go Hasegawa, Isolde C. Dapat, Hassan Zaraket, Tatiana Baranovich, Makoto Nishikawa, Takehiko Saito, and Hiroshi Suzuki
, Yasushi Suzuki1, Reiko Saito, Yadanar Kyaw, Yi Yi Myint, Nay Lin, Htun Naing Oo, Khin Yi Oo, Ne Win, Makoto Naito, Go Hasegawa, Isolde C. Dapat, Hassan Zaraket, Tatiana Baranovich, Makoto Nishikawa, Takehiko Saito, and Hiroshi SuzukiTable
Characteristics of subtype H3N2 influenza viruses with Q136K mutation in NA and S31N substitution in M2*
| 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.
