Arias Armando, Thorne Lucy, Ghurburrun Elsa, Bailey Dalan, Goodfellow Ian
Division of Virology, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom.
mSphere. 2016 Oct 19;1(5). doi: 10.1128/mSphere.00279-16. eCollection 2016 Sep-Oct.
Intrahost genetic diversity and replication error rates are intricately linked to RNA virus pathogenesis, with alterations in viral polymerase fidelity typically leading to attenuation during infections . We have previously shown that norovirus intrahost genetic diversity also influences viral pathogenesis using the murine norovirus model, as increasing viral mutation frequency using a mutagenic nucleoside resulted in clearance of a persistent infection in mice. Given the role of replication fidelity and genetic diversity in pathogenesis, we have now investigated whether polymerase fidelity can also impact virus transmission between susceptible hosts. We have identified a high-fidelity norovirus RNA-dependent RNA polymerase mutant (I391L) which displays delayed replication kinetics but not in cell culture. The I391L polymerase mutant also exhibited lower transmission rates between susceptible hosts than the wild-type virus and, most notably, another replication defective mutant that has wild-type levels of polymerase fidelity. These results provide the first experimental evidence that norovirus polymerase fidelity contributes to virus transmission between hosts and that maintaining diversity is important for the establishment of infection. This work supports the hypothesis that the reduced polymerase fidelity of the pandemic GII.4 human norovirus isolates may contribute to their global dominance. Virus replication fidelity and hence the intrahost genetic diversity of viral populations are known to be intricately linked to viral pathogenesis and tropism as well as to immune and antiviral escape during infection. In this study, we investigated whether changes in replication fidelity can impact the ability of a virus to transmit between susceptible hosts by the use of a mouse model for norovirus. We show that a variant encoding a high-fidelity polymerase is transmitted less efficiently between mice than the wild-type strain. This constitutes the first experimental demonstration that the polymerase fidelity of viruses can impact transmission of infection in their natural hosts. These results provide further insight into potential reasons for the global emergence of pandemic human noroviruses that display alterations in the replication fidelity of their polymerases compared to nonpandemic strains.
宿主体内的遗传多样性和复制错误率与RNA病毒的发病机制密切相关，病毒聚合酶保真度的改变通常会导致感染期间病毒毒力减弱。我们之前使用鼠诺如病毒模型表明，宿主体内诺如病毒的遗传多样性也会影响病毒发病机制，因为使用诱变核苷增加病毒突变频率会导致小鼠持续性感染的清除。鉴于复制保真度和遗传多样性在发病机制中的作用，我们现在研究了聚合酶保真度是否也会影响病毒在易感宿主之间的传播。我们鉴定出一种高保真诺如病毒RNA依赖性RNA聚合酶突变体（I391L），其在细胞培养中复制动力学延迟，但在宿主体内并非如此。I391L聚合酶突变体在易感宿主之间的传播率也低于野生型病毒，最值得注意的是，另一种复制缺陷型突变体具有野生型水平的聚合酶保真度。这些结果提供了首个实验证据，表明诺如病毒聚合酶保真度有助于病毒在宿主之间传播，且维持多样性对于感染的建立很重要。这项工作支持了这样一种假说，即大流行的GII.4型人类诺如病毒分离株聚合酶保真度降低可能有助于它们在全球的优势地位。已知病毒复制保真度以及病毒群体在宿主体内的遗传多样性与病毒发病机制和嗜性以及感染期间的免疫和抗病毒逃逸密切相关。在本研究中，我们通过使用诺如病毒小鼠模型研究了复制保真度的变化是否会影响病毒在易感宿主之间传播的能力。我们表明，编码高保真聚合酶的变体在小鼠之间的传播效率低于野生型菌株。这构成了首个实验证明，即病毒的聚合酶保真度会影响其在天然宿主中的感染传播。这些结果进一步深入了解了与非大流行株相比，聚合酶复制保真度发生改变的大流行人类诺如病毒在全球出现的潜在原因。
