Department of Virology, Erasmus Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, Netherlands.
J Virol. 2010 Apr;84(8):3752-8. doi: 10.1128/JVI.02634-09. Epub 2010 Feb 3.
In the first 6 months of the H1N1 swine-origin influenza virus (S-OIV) pandemic, the vast majority of infections were relatively mild. It has been postulated that mutations in the viral genome could result in more virulent viruses, leading to a more severe pandemic. Mutations E627K and D701N in the PB2 protein have previously been identified as determinants of avian and pandemic influenza virus virulence in mammals. These mutations were absent in S-OIVs detected early in the 2009 pandemic. Here, using reverse genetics, mutations E627K, D701N, and E677G were introduced into the prototype S-OIV A/Netherlands/602/2009, and their effects on virus replication, virulence, and transmission were investigated. Mutations E627K and D701N caused increased reporter gene expression driven by the S-OIV polymerase complex. None of the three mutations affected virus replication in vitro. The mutations had no major impact on virus replication in the respiratory tracts of mice and ferrets or on pathogenesis. All three mutant viruses were transmitted via aerosols or respiratory droplets in ferrets. Thus, the impact of key known virulence markers in PB2 in the context of current S-OIVs was surprisingly small. This study does not exclude the possibility of emergence of S-OIVs with other virulence-associated mutations in the future. We conclude that surveillance studies aimed at detecting S-OIVs with increased virulence or transmission should not rely solely on virulence markers identified in the past but should include detailed characterization of virus phenotypes, guided by genetic signatures of viruses detected in severe cases of disease in humans.
在 H1N1 猪源流感病毒（S-OIV）大流行的前 6 个月，绝大多数感染相对较轻。有人推测病毒基因组中的突变可能导致更具毒性的病毒，从而导致更严重的大流行。PB2 蛋白中的 E627K 和 D701N 突变先前被确定为禽流感和大流行性流感病毒在哺乳动物中毒力的决定因素。这些突变在 2009 年大流行早期检测到的 S-OIV 中不存在。在这里，使用反向遗传学技术，将突变 E627K、D701N 和 E677G 引入原型 S-OIV A/Netherlands/602/2009，并研究了它们对病毒复制、毒力和传播的影响。突变 E627K 和 D701N 导致由 S-OIV 聚合酶复合物驱动的报告基因表达增加。这三个突变都没有影响病毒在体外的复制。这些突变对小鼠和雪貂呼吸道中的病毒复制或发病机制没有重大影响。三种突变病毒都可以通过气溶胶或呼吸道飞沫在雪貂中传播。因此，在当前 S-OIV 背景下，PB2 中的关键已知毒力标记物的影响出乎意料地小。本研究不排除未来出现具有其他与毒力相关突变的 S-OIV 的可能性。我们得出结论，旨在检测具有增加毒力或传播能力的 S-OIV 的监测研究不应仅依赖过去确定的毒力标记物，而应包括对人类严重疾病中检测到的病毒的遗传特征进行指导的病毒表型的详细特征描述。
