Flaviviruses are arthropod-borne viruses that constitute a major global health problem, with millions of human infections annually. Their pathogenesis ranges from mild illness to severe manifestations such as hemorrhagic fever and fatal encephalitis. Type I interferons (IFNs) are induced in response to viral infection and stimulate the expression of interferon-stimulated genes (ISGs), including that encoding viperin (virus-inhibitory protein, endoplasmic reticulum associated, IFN inducible), which shows antiviral activity against a broad spectrum of viruses, including several flaviviruses. Here we describe a novel antiviral mechanism employed by viperin against two prominent flaviviruses, tick-borne encephalitis virus (TBEV) and Zika virus (ZIKV). Viperin was found to interact and colocalize with the structural proteins premembrane (prM) and envelope (E) of TBEV, as well as with nonstructural (NS) proteins NS2A, NS2B, and NS3. Interestingly, viperin expression reduced the NS3 protein level, and the stability of the other interacting viral proteins, but only in the presence of NS3. We also found that although viperin interacted with NS3 of mosquito-borne flaviviruses (ZIKV, Japanese encephalitis virus, and yellow fever virus), only ZIKV was sensitive to the antiviral effect of viperin. This sensitivity correlated with viperin's ability to induce proteasome-dependent degradation of NS3. ZIKV and TBEV replication was rescued completely when NS3 was overexpressed, suggesting that the viral NS3 is the specific target of viperin. In summary, we present here a novel antiviral mechanism of viperin that is selective for specific viruses in the genus Flavivirus, affording the possible availability of new drug targets that can be used for therapeutic intervention.

IMPORTANCE Flaviviruses are a group of enveloped RNA viruses that cause severe diseases in humans and animals worldwide, but no antiviral treatment is yet available. Viperin, a host protein produced in response to infection, effectively restricts the replication of several flaviviruses, but the exact molecular mechanisms have not been elucidated. Here we have identified a novel mechanism employed by viperin to inhibit the replication of two flaviviruses: tick-borne encephalitis virus (TBEV) and Zika virus (ZIKV). Viperin induced selective degradation via the proteasome of TBEV and ZIKV nonstructural 3 (NS3) protein, which is involved in several steps of the viral life cycle. Furthermore, viperin also reduced the stability of several other viral proteins in a NS3-dependent manner, suggesting a central role of NS3 in viperin's antiflavivirus activity. Taking the results together, our work shows important similarities and differences among the members of the genus Flavivirus and could lead to the possibility of therapeutic intervention.

黄病毒是节肢动物传播的病毒，是一个主要的全球健康问题，每年有数百万人感染。它们的发病机制从轻微的疾病到严重的表现，如出血热和致命性脑炎。I 型干扰素 (IFN) 响应病毒感染而被诱导，并刺激干扰素刺激基因 (ISG) 的表达，包括编码毒蛇素（病毒抑制蛋白、内质网相关、可诱导干扰素）的基因，其显示出抗病毒活性广谱病毒，包括几种黄病毒。在这里，我们描述了 viperin 针对两种主要黄病毒、蜱传脑炎病毒 (TBEV) 和寨卡病毒 (ZIKV) 所采用的新型抗病毒机制。发现 Viperin 与 TBEV 的结构蛋白前膜 (prM) 和包膜 (E) 以及非结构 (NS) 蛋白 NS2A、NS2B 和 NS3 相互作用并共定位。有趣的是，viperin 表达降低了 NS3 蛋白水平，以及其他相互作用病毒蛋白的稳定性，但仅在 NS3 存在的情况下。我们还发现，虽然 viperin 与蚊媒黄病毒（ZIKV、日本脑炎病毒和黄热病病毒）的 NS3 相互作用，但只有 ZIKV 对 Viperin 的抗病毒作用敏感。这种敏感性与 viperin 诱导 NS3 蛋白酶体依赖性降解的能力相关。当 NS3 过度表达时，ZIKV 和 TBEV 复制被完全挽救，这表明病毒 NS3 是 viperin 的特定目标。总之，黄病毒，提供可用于治疗干预的新药物靶标的可能可用性。

重要性黄病毒是一组有包膜的 RNA 病毒，可在世界范围内引起人类和动物的严重疾病，但尚无抗病毒治疗方法。Viperin 是一种响应感染而产生的宿主蛋白，它有效地限制了几种黄病毒的复制，但尚未阐明确切的分子机制。在这里，我们确定了 viperin 用于抑制两种黄病毒复制的新机制：蜱传脑炎病毒 (TBEV) 和寨卡病毒 (ZIKV)。Viperin 通过 TBEV 和 ZIKV 非结构 3 (NS3) 蛋白的蛋白酶体诱导选择性降解，这涉及病毒生命周期的几个步骤。此外，viperin 还以依赖于 NS3 的方式降低了几种其他病毒蛋白的稳定性，表明 NS3 在 vi​​perin 的抗黄病毒活性中起核心作用。黄病毒并可能导致治疗干预的可能性。