Table_3_miR-615 facilitates porcine epidemic diarrhea virus replication by targeting IRAK1 to inhibit type III interferon expression.XLS

Porcine epidemic diarrhea virus (PEDV) in the Coronavirus family is a highly contagious enteric pathogen in the swine industry, which has evolved mechanisms to evade host innate immune responses. The PEDV-mediated inhibition of interferons (IFNs) has been linked to the nuclear factor-kappa B (NF-κB) pathway. MicroRNAs (miRNAs) are involved in virus–host interactions and IFN-I regulation. However, the mechanism by which the PEDV regulates IFN during PEDV infection has not yet been investigated in its natural target cells. We here report a novel mechanism of viral immune escape involving miR-615, which was screened from a high-throughput sequencing library of porcine intestinal epithelial cells (IECs) infected with PEDV. PEDV infection altered the profiles of miRNAs and the activities of several pathways involved in innate immunity. Overexpression of miR-615 increased PEDV replication, inhibited IFN expression, downregulated the NF-κB pathway, and blocked p65 nuclear translocation. In contrast, knockdown of miR-615 enhanced IFN expression, suppressed PEDV replication, and activated the NF-κB pathway. We further determined that IRAK1 is the target gene of miR-615 in IECs. Our findings show that miR-615 suppresses activation of the NF-κB pathway by suppressing the IRAK1 protein and reducing the generation of IFN-IIIs, which in turn facilitates PEDV infection in IECs. Moreover, miR-615 inhibited PEDV replication and NF-κB pathway activation in both IECs and MARC-145 cells. These findings support an important role for miR-615 in the innate immune regulation of PEDV infections and provide a novel perspective for developing new treatments.

冠状病毒科的猪流行性腹泻病毒（Porcine epidemic diarrhea virus, PEDV）是养猪业中一种高传染性的肠道病原体，其演化出了逃避宿主天然免疫应答的机制。PEDV介导的干扰素（interferons, IFNs）抑制作用与核因子κB（nuclear factor-kappa B, NF-κB）通路密切相关。微小RNA（MicroRNAs, miRNAs）参与病毒-宿主互作以及I型干扰素（IFN-I）的调控，但目前尚未在PEDV的天然靶细胞中探究PEDV感染过程中调控干扰素的具体机制。本研究报道了一种涉及miR-615的新型病毒免疫逃逸机制，该微小RNA是从PEDV感染的猪肠上皮细胞（porcine intestinal epithelial cells, IECs）高通量测序文库中筛选得到的。PEDV感染会改变宿主微小RNA的表达谱以及天然免疫相关的多条通路的活性。过表达miR-615可促进PEDV复制、抑制干扰素表达、下调NF-κB通路活性并阻断p65的核转位；反之，敲低miR-615则可增强干扰素表达、抑制PEDV复制并激活NF-κB通路。本研究进一步证实，IRAK1是IECs中miR-615的靶基因。研究结果表明，miR-615通过抑制IRAK1蛋白表达、减少III型干扰素（IFN-III）的产生来抑制NF-κB通路的激活，进而促进PEDV在IECs中的感染。此外，miR-615在IECs和MARC-145细胞中均能抑制PEDV复制以及NF-κB通路的激活。上述研究结果证实了miR-615在PEDV感染的天然免疫调控中发挥重要作用，并为开发新型治疗策略提供了全新视角。