Dual microRNA Screens Reveal That the Immune-Responsive miR-181 Promotes Henipavirus Entry and Cell-Cell Fusion

Hendra and Nipah viruses (family Paramyxoviridae, genus Henipavirus) are bat-borne viruses that cause fatal disease in humans and a range of other mammalian species. Gaining a deeper understanding of host pathways exploited by henipaviruses for infection may identify targets for new anti-viral therapies. Here we have performed genome-wide high-throughput agonist and antagonist screens at biosafety level 4 to identify host-encoded microRNAs (miRNAs) impacting henipavirus infection in human cells. Members of the miR-181 and miR-17~93 families strongly promoted Hendra virus infection. miR-181 also promoted Nipah virus infection, but did not affect infection by paramyxoviruses from other genera, indicating specificity in the virus-host interaction. Infection promotion was primarily mediated via the ability of miR-181 to significantly enhance henipavirus-induced membrane fusion. Cell signalling receptors of ephrins, namely EphA5 and EphA7, were identified as novel negative regulators of henipavirus fusion. The expression of these receptors, as well as EphB4, were suppressed by miR-181 overexpression, suggesting that simultaneous inhibition of several Ephs by the miRNA contributes to enhanced infection and fusion. Immune-responsive miR-181 levels was also up-regulated in the biofluids of ferrets and horses infected with Hendra virus, suggesting that the host innate immune response may promote henipavirus spread and exacerbate disease severity. This study is the first genome-wide screen of miRNAs influencing infection by a clinically significant mononegavirus and nominates select miRNAs as targets for future anti-viral therapy development.亨德拉病毒（Hendra virus）与尼帕病毒（Nipah virus）隶属于副粘病毒科（Paramyxoviridae）亨尼帕病毒属（Henipavirus），是一类由蝙蝠自然携带的病毒，可引发人类及多种其他哺乳类动物的致死性感染。深入解析亨尼帕病毒劫持宿主通路以完成感染的分子机制，可为新型抗病毒治疗靶点的发掘提供关键理论依据。本研究于生物安全四级（biosafety level 4）实验室中开展全基因组范围的高通量激动剂与拮抗剂筛选，以鉴定人类细胞中影响亨尼帕病毒感染的宿主编码微RNA（microRNAs, miRNAs）。miR-181家族与miR-17~93基因簇的成员可显著促进亨德拉病毒的感染过程；miR-181同样可增强尼帕病毒的感染，但对其他属副粘病毒的感染无显著影响，这提示该病毒-宿主相互作用具有特异性。该促感染效应主要通过miR-181显著增强亨尼帕病毒诱导的膜融合过程得以实现。研究进一步鉴定出Ephrin家族的细胞信号受体EphA5与EphA7为亨尼帕病毒融合过程的新型负调控因子。miR-181过表达可抑制上述受体及EphB4的表达，提示该微RNA通过同时靶向抑制多种Eph受体，从而提升病毒感染与膜融合的效率。在感染亨德拉病毒的雪貂与马的生物体液中，免疫应答相关的miR-181水平同样出现上调，这提示宿主固有免疫应答可能促进亨尼帕病毒的播散并加重疾病严重程度。本研究是首个针对具有临床重要性的单负链病毒开展的全基因组微RNA筛选研究，同时提名部分微RNA作为未来抗病毒治疗开发的潜在靶点。