Engineered mammalian RNAi can elicit antiviral protection that negates the requirement for the interferon response

While the intrinsic antiviral cell defenses of many kingdoms utilize pathogen-specific small RNAs, the antiviral response of chordates is primarily protein-based and not uniquely tailored to the incoming microbe. In an effort to explain this evolutionary bifurcation, we determined whether antiviral RNA interference (RNAi) was sufficient to replace the protein-based type I interferon (IFN-I) system of mammals. To this end, we recreated an RNAi-like response in mammals and determined its effectiveness to combat influenza A virus in vivo in the presence and absence of the canonical IFN-I system. Mammalian antiviral RNAi, elicited by either host- or virus-derived small RNAs, effectively attenuated virus and prevented disease independently of the innate immune response. These data find that chordates could have utilized RNAi as their primary antiviral cell defense and suggest that the IFN-I system emerged as a result of natural selection imposed by ancient pathogens. WT C57BL/6 and Ifnar1-/- C57BL/6 were infected with WT Influenza A virus (IAV-WT) or a miRNA-targeted virus (IAV-NPt). RNA from lungs was harvested 2 and 9 days post infection.

尽管诸多生物界的固有抗病毒细胞防御机制均依赖病原体特异性小RNA，但脊索动物（chordates）的抗病毒应答主要基于蛋白质，且并未针对入侵微生物进行专属定制。为阐释这一进化分支现象，我们探究了抗病毒RNA干扰（RNA interference, RNAi）是否足以替代哺乳动物体内基于蛋白质的I型干扰素（type I interferon, IFN-I）系统。为此，我们在哺乳动物体内重建了类RNAi应答，并分别在经典IFN-I系统存在与缺失的情况下，验证其在体内对抗甲型流感病毒（Influenza A virus, IAV）的效果。由宿主或病毒来源的小RNA诱导产生的哺乳动物抗病毒RNAi，可在不依赖固有免疫应答的前提下有效抑制病毒增殖并阻止疾病发生。本研究数据显示，脊索动物本可将RNAi作为其核心抗病毒细胞防御机制，同时提示IFN-I系统的出现乃是远古病原体施加的自然选择压力下演化而来的结果。野生型（Wild Type, WT）C57BL/6小鼠与Ifnar1基因敲除的C57BL/6小鼠（Ifnar1-/- C57BL/6）分别感染野生型甲型流感病毒（IAV-WT）或靶向微RNA（miRNA）的重组病毒（IAV-NPt）。分别于感染后第2天与第9天采集肺组织RNA样本。