Porcine deltacoronavirus (PDCoV) is a newly emerging threat to the global porcine industry. PDCoV has been successfully isolated using various medium additives including trypsin, and although we know it is important for viral replication, the mechanism has not been fully elucidated. Here, we systematically investigated the role of trypsin in PDCoV replication including cell entry, cell-to-cell membrane fusion and virus release. Using pseudovirus entry assays, we demonstrated that PDCoV entry is not trypsin dependent. Furthermore, unlike porcine epidemic diarrhea virus (PEDV), in which trypsin is important for the release of virus from infected cells, PDCoV release was not affected by trypsin. We also demonstrated that trypsin promotes PDCoV replication by enhancing cell-to-cell membrane fusion. Most importantly, our study illustrates two distinct spreading patterns from infected cells to uninfected cells during PDCoV transmission, and the role of trypsin in PDCoV replication in cells with different virus spreading types. Overall, these results clarify that trypsin promotes PDCoV replication by mediating cell-to-cell fusion transmission but is not crucial for viral entry. This knowledge can potentially contribute to improvement of virus production efficiency in culture, not only for vaccine preparation but also to develop antiviral treatments.

中文翻译：

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胰蛋白酶以细胞类型依赖性方式促进猪三角洲冠状病毒介导细胞间融合。

猪三角冠状病毒（PDCoV）是对全球猪产业的新兴威胁。PDCoV已使用多种培养基添加剂（包括胰蛋白酶）成功分离，尽管我们知道它对病毒复制很重要，但其机理尚未完全阐明。在这里，我们系统地研究了胰蛋白酶在PDCoV复制中的作用，包括细胞进入，细胞间膜融合和病毒释放。使用伪病毒进入检测，我们证明PDCoV进入不依赖胰蛋白酶。此外，与猪流行性腹泻病毒（PEDV）不同，在猪流行性腹泻病毒中，胰蛋白酶对于从感染细胞中释放病毒很重要，而PDCoV的释放不受胰蛋白酶的影响。我们还证明了胰蛋白酶通过增强细胞间膜融合来促进PDCoV复制。最重要的是，我们的研究阐明了PDCoV传播过程中从感染细胞到未感染细胞的两种不同的传播方式，以及胰蛋白酶在具有不同病毒传播类型的细胞中PDCoV复制中的作用。总体而言，这些结果表明，胰蛋白酶通过介导细胞间融合传播来促进PDCoV复制，但对于病毒进入并非至关重要。这些知识可能潜在地有助于提高培养物中病毒的生产效率，不仅可以用于疫苗制备，而且可以用于开发抗病毒治疗。这些结果表明，胰蛋白酶可通过介导细胞间融合传播来促进PDCoV复制，但对于病毒的进入并非至关重要。这些知识可能潜在地有助于提高培养物中病毒的生产效率，不仅可以用于疫苗制备，而且可以用于开发抗病毒治疗。这些结果表明，胰蛋白酶通过介导细胞间融合传播来促进PDCoV复制，但对于病毒的进入并非至关重要。这些知识可能潜在地有助于提高培养物中病毒的生产效率，不仅可以用于疫苗制备，而且可以用于开发抗病毒治疗。