Division of International Health (Public Health), Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
Antiviral Res. 2013 Sep;99(3):261-9. doi: 10.1016/j.antiviral.2013.06.003. Epub 2013 Jun 17.
Two new influenza virus neuraminidase inhibitors (NAIs), peramivir and laninamivir, were approved in 2010 which resulted to four NAIs that were used during the 2010-2011 influenza season in Japan. This study aims to monitor the susceptibility of influenza virus isolates in 2009-2010 and 2010-2011 influenza seasons in Japan to the four NAIs using the fluorescence-based 50% inhibitory concentration (IC₅₀) method. Outliers were identified using box-and-whisker plot analysis and full NA gene sequencing was performed to determine the mutations that are associated with reduction of susceptibility to NAIs. A total of 117 influenza A(H1N1)pdm09, 59 A(H3N2), and 18 type B viruses were tested before NAI treatment and eight A(H1N1)pdm09 and 1 type B viruses were examined from patients after NAI treatment in the two seasons. NA inhibition assay showed type A influenza viruses were more susceptible to NAIs than type B viruses. The peramivir and laninamivir IC₅₀ values of both type A and B viruses were significantly lower than the oseltamivir and zanamivir IC₅₀ values. Among influenza A(H1N1)pdm09 viruses, the prevalence of H274Y viruses increased from 0% in the 2009-2010 season to 3% in the 2010-2011 season. These H274Y viruses were resistant to oseltamivir and peramivir with 200-300 fold increase in IC₅₀ values but remained sensitive to zanamivir and laninamivir. Other mutations in NA, such as I222T and M241I were identified among the outliers. Among influenza A(H3N2) viruses, two outliers were identified with D151G and T148I mutations, which exhibited a reduction in susceptibility to oseltamivir and zanamivir, respectively. Among type B viruses, no outliers were identified to the four NAIs. For paired samples that were collected before and after drug treatment, three (3/11; 27.3%) H274Y viruses were identified among A(H1N1)pdm09 viruses after oseltamivir treatment but no outliers were found in the laninamivir-treatment group (n=3). Despite widespread use of NAIs in Japan, the prevalence of NAI-resistant influenza viruses is still low.
2010 年批准了两种新的流感病毒神经氨酸酶抑制剂（NAI），即帕拉米韦和拉尼米韦，这使得日本在 2010-2011 流感季中共有四种 NAI 可供使用。本研究旨在通过荧光法测定 50%抑制浓度（IC₅₀），监测 2009-2010 年和 2010-2011 年日本流感季节中流感病毒分离株对四种 NAI 的敏感性。使用箱线图分析鉴定出离群值，并对全 NA 基因进行测序，以确定与 NAI 敏感性降低相关的突变。在两个季节中，分别对 117 株甲型 H1N1pdm09、59 株甲型 H3N2 和 18 株乙型病毒进行了 NA 抑制试验，对 8 株甲型 H1N1pdm09 和 1 株乙型病毒进行了 NAI 治疗后的患者检测。NA 抑制试验表明，甲型流感病毒比乙型病毒对 NAI 更敏感。两种类型的 A 和 B 病毒的帕拉米韦和拉尼米韦 IC₅₀ 值均明显低于奥司他韦和扎那米韦 IC₅₀ 值。在甲型 H1N1pdm09 病毒中，H274Y 病毒的流行率从 2009-2010 年的 0%上升至 2010-2011 年的 3%。这些 H274Y 病毒对奥司他韦和帕拉米韦具有 200-300 倍的 IC₅₀ 值增加，表现出耐药性，但对扎那米韦和拉尼米韦仍保持敏感。在离群值中还发现了其他 NA 突变，如 I222T 和 M241I。在甲型 H3N2 病毒中，有两个离群值鉴定为 D151G 和 T148I 突变，它们对奥司他韦和扎那米韦的敏感性分别降低。在乙型病毒中，四种 NAI 均未鉴定出离群值。在药物治疗前后采集的配对样本中，在奥司他韦治疗后，甲型 H1N1pdm09 病毒中鉴定出 3 株（3/11；27.3%）H274Y 病毒，但在拉尼米韦治疗组中未发现离群值（n=3）。尽管 NAI 在日本广泛使用，但耐药性流感病毒的流行率仍然较低。
