WHO Collaborating Centre for Reference and Research on Influenza, Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.
Department of Microbiology and Immunology, The University of Melbourne, Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.
J Virol. 2022 Aug 10;96(15):e0091822. doi: 10.1128/jvi.00918-22. Epub 2022 Jul 14.
Oseltamivir-resistant influenza viruses arise due to amino acid mutations in key residues of the viral neuraminidase (NA). These changes often come at a fitness cost; however, it is known that permissive mutations in the viral NA can overcome this cost. This result was observed in former seasonal A(H1N1) viruses in 2007 which expressed the H275Y substitution (N1 numbering) with no apparent fitness cost and lead to widespread oseltamivir resistance. Therefore, this study aims to predict permissive mutations that may similarly enable fit H275Y variants to arise in currently circulating A(H1N1)pdm09 viruses. The first approach in this study utilized analyses to predict potentially permissive mutations. The second approach involved the generation of a virus library which encompassed all possible NA mutations while keeping H275Y fixed. Fit variants were then selected by serially passaging the virus library either through ferrets by transmission or passaging once . The fitness impact of selected substitutions was further evaluated experimentally. The computational approach predicted three candidate permissive NA mutations which, in combination with each other, restored the replicative fitness of an H275Y variant. The second approach identified a stringent bottleneck during transmission between ferrets; however, three further substitutions were identified which may improve transmissibility. A comparison of fit H275Y variants and in experimentally infected animals showed a statistically significant correlation in the variants that were positively selected. Overall, this study provides valuable tools and insights into potential permissive mutations that may facilitate the emergence of a fit H275Y A(H1N1)pdm09 variant. Oseltamivir (Tamiflu) is the most widely used antiviral for the treatment of influenza infections. Therefore, resistance to oseltamivir is a public health concern. This study is important as it explores the different evolutionary pathways available to current circulating influenza viruses that may lead to widespread oseltamivir resistance. Specifically, this study develops valuable experimental and computational tools to evaluate the fitness landscape of circulating A(H1N1)pmd09 influenza viruses bearing the H275Y mutation. The H275Y substitution is most commonly reported to confer oseltamivir resistance but also leads to loss of virus replication and transmission fitness, which limits its spread. However, it is known from previous influenza seasons that influenza viruses can evolve to overcome this loss of fitness. Therefore, this study aims to prospectively predict how contemporary A(H1N1)pmd09 influenza viruses may evolve to overcome the fitness cost of bearing the H275Y NA substitution, which could result in widespread oseltamivir resistance.
奥司他韦耐药流感病毒是由于病毒神经氨酸酶（NA）关键残基的氨基酸突变而产生的。这些变化通常会带来适应性成本；然而，已知病毒 NA 中的许可性突变可以克服这种成本。这一结果在 2007 年以前的季节性 A(H1N1)病毒中得到了观察，这些病毒表达了 H275Y 取代（N1 编号），没有明显的适应性成本，并导致广泛的奥司他韦耐药性。因此，本研究旨在预测可能使适合的 H275Y 变体出现的许可性突变，这些变体在当前流行的 A(H1N1)pdm09 病毒中出现。本研究的第一种方法利用分析预测潜在的许可性突变。第二种方法涉及生成一个病毒文库，该文库在固定 H275Y 的同时包含所有可能的 NA 突变。然后通过在雪貂中传播或传代一次，连续传代病毒文库来选择适合的变体。选择的取代的适应性影响进一步通过实验进行评估。计算方法预测了三个候选许可性 NA 突变，这些突变相互结合，恢复了 H275Y 变体的复制适应性。第二种方法在雪貂之间的传播过程中发现了一个严格的瓶颈；然而，还发现了另外三个可能提高传染性的取代。在实验感染动物中比较适合的 H275Y 变体和发现，在被正选择的变体中存在统计学上显著的相关性。总体而言，本研究提供了有价值的工具和见解，了解可能促进适合的 H275Y A(H1N1)pdm09 变体出现的潜在许可性突变。奥司他韦（达菲）是治疗流感感染最广泛使用的抗病毒药物。因此，对奥司他韦的耐药性是一个公共卫生问题。本研究很重要，因为它探讨了当前流行的流感病毒可能导致广泛的奥司他韦耐药性的不同进化途径。具体来说，本研究开发了有价值的实验和计算工具来评估携带 H275Y 突变的循环 A(H1N1)pmd09 流感病毒的适应性景观。H275Y 取代最常被报道赋予奥司他韦耐药性，但也导致病毒复制和传播适应性的丧失，这限制了它的传播。然而，从以前的流感季节中已知，流感病毒可以进化以克服这种适应性丧失。因此，本研究旨在前瞻性地预测当代 A(H1N1)pmd09 流感病毒如何进化以克服携带 H275Y NA 取代的适应性成本，这可能导致广泛的奥司他韦耐药性。
