The current coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), highlights major gaps in our knowledge on the prevention control and cross-species transmission mechanisms of animal coronaviruses. Transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), and porcine delta coronavirus (PDCoV) are three common swine coronaviruses and have similar clinical features. In the absence of effective treatments, they have led to significant economic losses in the swine industry worldwide. We reported that indoles exerted potent activity against swine coronaviruses, the molecules used included melatonin, indole, tryptamine, and L-tryptophan. Herein, we did further systematic studies with melatonin, a ubiquitous and versatile molecule, and found it inhibited TGEV, PEDV, and PDCoV infection in PK-15, Vero, or LLC-PK1 cells by reducing viral entry and replication, respectively. Collectively, we provide the molecular basis for the development of new treatments based on the ability of indoles to control TGEV, PEDV, and PDCoV infection and spread.

中文翻译：

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褪黑激素和其他吲哚在药理浓度下在体外对猪冠状病毒显示出抗病毒活性

当前由严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 引起的 2019 年冠状病毒病 (COVID-19) 大流行凸显了我们对动物冠状病毒的预防控制和跨物种传播机制的认识存在重大差距。传染性胃肠炎病毒（TGEV）、猪流行性腹泻病毒（PEDV）和猪三角洲冠状病毒（PDCoV）是三种常见的猪冠状病毒，具有相似的临床特征。由于缺乏有效的治疗方法，它们已导致全球养猪业遭受重大经济损失。我们报道了吲哚对猪冠状病毒具有强效活性，使用的分子包括褪黑激素、吲哚、色胺和 L-色氨酸。在此，我们对褪黑激素（一种普遍存在且用途广泛的分子）进行了进一步的系统研究，发现它可以抑制 TGEV、PEDV、和 PDCoV 感染 PK-15、Vero 或 LLC-PK1 细胞，分别通过减少病毒进入和复制。总的来说，我们为基于吲哚控制 TGEV、PEDV 和 PDCoV 感染和传播的能力开发新疗法提供了分子基础。