Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus (CoV) that poses economic and public health burdens. Currently, there are no effective antiviral agents against PDCoV. Cryptoporus volvatus often serves as an antimicrobial agent in Traditional Chinese Medicines. This study aimed to evaluate the antiviral activities of ergosterol peroxide (EP) from C. volvatus against PDCoV infection. The inhibitory activity of EP against PDCoV was assessed by using virus titration and performing Quantitative Reverse transcription PCR (RT-qPCR), Western blotting and immunofluorescence assays in LLC-PK1 cells. The mechanism of EP against PDCoV was analyzed by flow cytometry, RT-qPCR and Western blotting. We found that EP treatment inhibited PDCoV infection in LLC-PK1 cells in a dose-dependent manner. Subsequently, we demonstrated that EP blocked virus attachment and entry using RT-qPCR. Time-of-addition assays indicated that EP mainly exerted its inhibitory effect at the early and middle stages in the PDCoV replication cycle. EP also inactivated PDCoV infectivity directly as well as suppressed PDCoV-induced apoptosis. Furthermore, EP treatment decreased the phosphorylation of IκBα and p38 MAPK induced by PDCoV infection as well as the mRNA levels of cytokines (IL-1β, IL-6, IL-12, TNF-α, IFN-α, IFN-β, Mx1 and PKR). These results imply that EP can inhibit PDCoV infection and regulate host immune responses by downregulating the activation of the NF-κB and p38/MAPK signaling pathways in vitro. EP can be used as a potential candidate for the development of a new anti-PDCoV therapy.

猪三角型冠状病毒 (PDCoV) 是一种新出现的猪肠道致病性冠状病毒 (CoV)，会造成经济和公共卫生负担。目前，没有针对 PDCoV 的有效抗病毒药物。Cryptoporus volvatus通常在中药中用作抗菌剂。本研究旨在评估来自卷曲草的过氧化麦角甾醇 (EP) 的抗病毒活性抗PDCoV感染。通过使用病毒滴定和在 LLC-PK1 细胞中进行定量逆转录 PCR (RT-qPCR)、Western 印迹和免疫荧光测定来评估 EP 对 PDCoV 的抑制活性。通过流式细胞术、RT-​​qPCR 和 Western blotting 分析了 EP 抗 PDCoV 的机制。我们发现 EP 治疗以剂量依赖性方式抑制 LLC-PK1 细胞中的 PDCoV 感染。随后，我们证明 EP 使用 RT-qPCR 阻止病毒附着和进入。添加时间测定表明，EP 主要在 PDCoV 复制周期的早期和中期发挥其抑制作用。EP 还直接使 PDCoV 感染性失活并抑制 PDCoV 诱导的细胞凋亡。此外，EP 处理降低了 PDCoV 感染诱导的 IκBα 和 p38 MAPK 的磷酸化以及细胞因子（IL-1β、IL-6、IL-12、TNF-α、IFN-α、IFN-β、Mx1 和 PKR）的 mRNA 水平). 这些结果表明 EP 可以通过下调 NF-κB 和 p38/MAPK 信号通路的激活来抑制 PDCoV 感染并调节宿主免疫反应体外。EP 可作为开发新型抗 PDCoV 疗法的潜在候选药物。