Inhibition of viral suppressor of RNAi proteins by designer peptides protects from enteroviral infection in vivo

RNA interference (RNAi) is the major antiviral mechanism in plants and invertebrates, but the absence of detectable viral (v)siRNAs in mammalian cells upon viral infection has questioned the functional relevance of this pathway in mammalian immunity. We designed a series of peptides specifically targeting enterovirus A71 (EV-A71)-encoded protein 3A, a viral suppressor of RNAi (VSR). These peptides abrogated the VSR function of EV-A71 in infected cells and resulted in the accumulation of vsiRNAs and reduced viral replication. These vsiRNAs were functional, as evidenced by RISC-loading and silencing of target RNAs. The effects of VSR-targeting peptides (VTPs) on infection with EV-A71 as well as another enterovirus, Coxsackievirus-A16, were ablated upon deletion of Dicer1 or AGO2, core components of the RNAi pathway. In vivo, VTP treatment protected mice against lethal EV-A71 challenge, with detectable vsiRNAs. Our findings provide evidence for the functional relevance of RNAi in mammalian immunity and present a therapeutic strategy for infectious disease. [Display omitted] •We design peptides targeting viral RNAi suppressor (VSR) of enterovirus A71 (EV-A71)•They abrogate EV-A71 VSR function and induce viral siRNA production in cells and mice•These viral siRNAs are functional to load into AGO and silence cognate EV-A71 RNA•The peptides show in vitro and in vivo anti-enteroviral efficacy that depends on RNAi The physiological relevance of RNAi in mammalian antiviral immunity remains to be addressed. Fang et al. demonstrate that the antiviral potency of RNAi can be successfully unlocked by abrogating enterovirus-encoded RNAi suppressor via rationally designed peptides, which exert potent anti-enteroviral efficacy in vitro and in vivo in an RNAi-dependent manner.