Inhibition of Japanese encephalitis virus infection by the host zinc-finger antiviral protein

CCCH-type zinc-finger antiviral protein (ZAP) is a host factor that restricts the infection of many viruses mainly through RNA degradation, translation inhibition and innate immune responses. So far, only one flavivirus, yellow fever virus, has been reported to be ZAP-resistant. Here, we investigated the antiviral potential of human ZAP (isoform ZAP-L and ZAP-S) against three flaviviruses, Japanese encephalitis virus (JEV), dengue virus (DENV) and Zika virus (ZIKV). Infection of JEV but not DENV or ZIKV was blocked by ZAP overexpression, and depletion of endogenous ZAP enhanced JEV replication. ZAP hampered JEV translation and targeted viral RNA for 3′-5′ RNA exosome-mediated degradation. The zinc-finger motifs of ZAP were essential for RNA targeting and anti-JEV activity. JEV 3′-UTR, especially in the region with dumbbell structures and high content of CG dinucleotide, was mapped to bind ZAP and confer sensitivity to ZAP. In summary, we identified JEV as the first ZAP-sensitive flavivirus. ZAP may act as an intrinsic antiviral factor through specific RNA binding to fight against JEV infection.

CCCH型锌指抗病毒蛋白（CCCH-type zinc-finger antiviral protein，ZAP）是一种宿主因子，主要通过RNA降解、翻译抑制以及天然免疫应答等途径抑制多种病毒的感染。截至目前，仅有一种黄病毒属病毒——黄热病毒——被报道对ZAP具有抗性。本研究针对三种黄病毒——日本脑炎病毒（Japanese encephalitis virus，JEV）、登革病毒（dengue virus，DENV）以及寨卡病毒（Zika virus，ZIKV）——探究了人源ZAP的两种亚型（ZAP-L与ZAP-S）的抗病毒活性。实验结果显示，ZAP过表达可抑制日本脑炎病毒的感染，但对登革病毒与寨卡病毒并无此效果；而内源性ZAP敲低则会促进日本脑炎病毒的复制。ZAP可阻碍日本脑炎病毒的翻译过程，并靶向病毒RNA，使其通过3'-5' RNA外切体介导的途径发生降解。ZAP的锌指结构域对于其RNA靶向功能以及抗日本脑炎病毒活性至关重要。日本脑炎病毒的3'非翻译区（3'-UTR），尤其是其中带有哑铃状结构且CG二核苷酸含量较高的区域，可与ZAP结合，从而使病毒对ZAP敏感。综上，本研究证实日本脑炎病毒是首个对ZAP敏感的黄病毒属病毒；ZAP或可通过特异性结合RNA的方式，作为一种固有抗病毒因子抵御日本脑炎病毒的感染。