Department of Microbiology and Immunology, School of Medicine and Dentistry, University of Rochestergrid.16416.34, Rochester, New York, USA.
Animal Health Research Centre (CISA), Centro Nacional Instituto de Investigación y Tecnología Agraria y Alimentaria (INIA, CSIC), Madrid, Spain.
Microbiol Spectr. 2022 Jun 29;10(3):e0007822. doi: 10.1128/spectrum.00078-22. Epub 2022 May 18.
Influenza A viruses (IAV) remain emerging threats to human public health. Live-attenuated influenza vaccines (LAIV) are one of the most effective prophylactic options to prevent disease caused by influenza infections. However, licensed LAIV remain restricted for use in 2- to 49-year-old healthy and nonpregnant people. Therefore, development of LAIV with increased safety, immunogenicity, and protective efficacy is highly desired. The U.S.-licensed LAIV is based on the master donor virus (MDV) A/Ann Arbor/6/60 H2N2 backbone, which was generated by adaptation of the virus to growth at low temperatures. Introducing the genetic signature of the U.S. MDV into the backbone of other IAV strains resulted in varying levels of attenuation. While the U.S. MDV mutations conferred an attenuated phenotype to other IAV strains, the same amino acid changes did not significantly attenuate the pandemic A/California/04/09 H1N1 (pH1N1) strain. To attenuate pH1N1, we replaced the conserved leucine at position 319 with glutamine (L319Q) in PB1 and analyzed the and properties of pH1N1 viruses containing either PB1 L319Q alone or in combination with the U.S. MDV mutations using two animal models of influenza infection and transmission, ferrets and guinea pigs. Our results demonstrated that L319Q substitution in the pH1N1 PB1 alone or in combination with the mutations of the U.S. MDV resulted in reduced pathogenicity (ferrets) and transmission (guinea pigs), and an enhanced temperature sensitive phenotype. These results demonstrate the feasibility of generating an attenuated MDV based on the backbone of a contemporary pH1N1 IAV strain. Vaccination represents the most effective strategy to reduce the impact of seasonal IAV infections. Although LAIV are superior in inducing protection and sterilizing immunity, they are not recommended for many individuals who are at high risk for severe disease. Thus, development of safer and more effective LAIV are needed. A concern with the current MDV used to generate the U.S.-licensed LAIV is that it is based on a virus isolated in 1960. Moreover, mutations that confer the temperature-sensitive, cold-adapted, and attenuated phenotype of the U.S. MDV resulted in low level of attenuation in the contemporary pandemic A/California/04/09 H1N1 (pH1N1). Here, we show that introduction of PB1 L319Q substitution, alone or in combination with the U.S. MDV mutations, resulted in pH1N1 attenuation. These findings support the development of a novel LAIV MDV based on a contemporary pH1N1 strain as a medical countermeasure against currently circulating H1N1 IAV.
甲型流感病毒（IAV）仍然是人类公共卫生的新兴威胁。减毒活流感疫苗（LAIV）是预防流感感染引起疾病的最有效预防选择之一。然而，许可的 LAIV 仍然限于 2 至 49 岁健康且未怀孕的人群使用。因此，开发具有更高安全性、免疫原性和保护效力的 LAIV 是非常需要的。美国许可的 LAIV 基于主供体病毒（MDV）A/Ann Arbor/6/60 H2N2 骨架，该骨架是通过使病毒适应低温生长而产生的。将美国 MDV 的遗传特征引入其他 IAV 株的骨架中，导致不同程度的衰减。虽然美国 MDV 的突变赋予了其他 IAV 株减毒表型，但相同的氨基酸变化并没有显著减弱大流行的 A/California/04/09 H1N1（pH1N1）株。为了减弱 pH1N1，我们用谷氨酰胺（L319Q）替换 PB1 中的保守亮氨酸 319 位，并分析含有 PB1 L319Q 单独或与美国 MDV 突变组合的 pH1N1 病毒的 和 特性，使用两种流感感染和传播的动物模型，雪貂和豚鼠。我们的结果表明，pH1N1 PB1 中的 L319Q 取代单独或与美国 MDV 的突变结合使用会降低致病性（雪貂）和传播性（豚鼠），并增强温度敏感表型。这些结果表明，可以基于当代 pH1N1 IAV 株的骨架生成减毒的 MDV。疫苗接种是减少季节性 IAV 感染影响的最有效策略。尽管 LAIV 在诱导保护和杀菌免疫方面更优越，但它们不推荐用于许多患有严重疾病风险高的个体。因此，需要开发更安全、更有效的 LAIV。目前用于生成美国许可的 LAIV 的 MDV 存在一个问题，即它基于 1960 年分离的病毒。此外，赋予美国 MDV 温度敏感、冷适应和减毒表型的突变导致当代大流行的 A/California/04/09 H1N1（pH1N1）株的衰减程度较低。在这里，我们表明单独引入 PB1 L319Q 取代或与美国 MDV 突变结合使用会导致 pH1N1 衰减。这些发现支持开发一种基于当代 pH1N1 株的新型 LAIV MDV，作为针对当前流行的 H1N1 IAV 的医疗对策。
