Centre of Influenza Research & School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
Department of Pathology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
Sci Rep. 2017 Sep 12;7(1):11361. doi: 10.1038/s41598-017-11625-y.
The 701 and 702 positions of influenza PB2 polymerase subunit are previously shown to have roles on host range. Limited polymorphisms at these two residues are identified in natural isolates, thereby limiting the study of their role in the polymerase. In this study, we generated 31 viable viruses by random mutagenesis at this region, indicating that these positions can tolerate a wide range of amino acids. These mutants demonstrated varying polymerase activities and viral replication rates in mammalian and avian cells. Notably, some mutants displayed enhanced polymerase activity, yet their replication kinetics were comparable to the wild-type virus. Surface electrostatic charge predication on the PB2 structural model revealed that the viral polymerase activity in mammalian cells generally increases as this region becomes more positively charged. One of the mutants (701A/702E) showed much reduced pathogenicity in mice while others had a pathogenicity similar to the wild-type level. Distinct tissue tropisms of the PB2-701/702 mutants were observed in infected chicken embryos. Overall, this study demonstrates that the PB2-701/702 region has a high degree of sequence plasticity and sequence changes in this region can alter virus phenotypes in vitro and in vivo.
流感 PB2 聚合酶亚基的 701 位和 702 位以前被证明在宿主范围上具有作用。在天然分离株中鉴定到这两个残基的有限多态性，从而限制了对其在聚合酶中的作用的研究。在这项研究中，我们在该区域通过随机诱变生成了 31 种有活力的病毒，表明这些位置可以耐受广泛的氨基酸。这些突变体在哺乳动物和禽类细胞中显示出不同的聚合酶活性和病毒复制率。值得注意的是，一些突变体显示出增强的聚合酶活性，但它们的复制动力学与野生型病毒相当。对 PB2 结构模型的表面静电电荷预测表明，该区域带正电荷越多，病毒聚合酶在哺乳动物细胞中的活性通常越高。一个突变体（701A/702E）在小鼠中表现出明显降低的致病性，而其他突变体的致病性与野生型水平相似。在感染的鸡胚中观察到 PB2-701/702 突变体的不同组织嗜性。总体而言，这项研究表明 PB2-701/702 区域具有高度的序列可塑性，该区域的序列变化可以改变病毒在体外和体内的表型。
