College of Veterinary Medicine, Northeast Agricultural University, Harbin, China.
PLoS One. 2011 May 6;6(5):e18669. doi: 10.1371/journal.pone.0018669.
Transmissible gastroenteritis virus (TGEV) is a porcine coronavirus. Lithium chloride (LiCl) has been found to be effective against several DNA viruses, such as Herpes simplex virus and vaccinia virus. Recently, we and others have reported the inhibitory effect of LiCl on avian infectious bronchitis coronavirus (IBV) infection, an RNA virus. In the current study, the action mechanism of LiCl on cell infection by TGEV was investigated. Plaque assays and 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenyl tetrazoliumbromide (MTT) assays showed that the cell infection by TGEV was inhibited in a dose-dependent manner, when LiCl was added to virus-infected cells; the cell infection was not affected when either cells or viruses were pretreated with the drug. The inhibition of TGEV infection in vitro by LiCl was observed at different virus doses and with different cell lines. The inhibitory effect of LiCl against TGEV infection and transcription was confirmed by RT-PCR and real-time PCR targeting viral S and 3CL-protease genes. The time-of-addition effect of the drug on TGEV infection indicated that LiCl acted on the initial and late stage of TGEV infection. The production of virus was not detected at 36 h post-infection due to the drug treatment. Moreover, immunofluorescence (IF) and flow cytometry analyses based on staining of Annexin V and propidium iodide staining of nuclei indicated that early and late cell apoptosis induced by TGEV was inhibited efficiently. The ability of LiCl to inhibit apoptosis was investigated by IF analysis of caspase-3 expression. Our data indicate that LiCl inhibits TGEV infection by exerting an anti-apoptotic effect. The inhibitory effect of LiCl was also observed with porcine epidemic diarrhea coronavirus. Together with other reports concerning the inhibitory effect of lithium salts on IBV in cell culture, our results indicate that LiCl may be a potent agent against porcine and avian coronaviruses.
传染性胃肠炎病毒（TGEV）是一种猪冠状病毒。氯化锂（LiCl）已被发现对多种 DNA 病毒（如单纯疱疹病毒和牛痘病毒）有效。最近，我们和其他人报道了 LiCl 对禽类传染性支气管炎冠状病毒（IBV）感染的抑制作用，IBV 是一种 RNA 病毒。在本研究中，研究了 LiCl 对 TGEV 细胞感染的作用机制。噬斑试验和 3-(4,5)-二甲基噻唑(-z-y1)-3,5-二苯基四氮唑溴盐（MTT）试验表明，当 LiCl 被添加到感染病毒的细胞中时，TGEV 的细胞感染呈剂量依赖性被抑制；当用该药物预处理细胞或病毒时，细胞感染不受影响。LiCl 对不同病毒剂量和不同细胞系的 TGEV 体外感染均有抑制作用。通过针对病毒 S 和 3CL-蛋白酶基因的 RT-PCR 和实时 PCR 证实了 LiCl 对 TGEV 感染和转录的抑制作用。药物对 TGEV 感染的添加时间效应表明，LiCl 作用于 TGEV 感染的初始和晚期。由于药物处理，感染后 36 小时未检测到病毒的产生。此外，基于 Annexin V 染色和碘化丙啶染色核的免疫荧光（IF）和流式细胞术分析表明，TGEV 诱导的早期和晚期细胞凋亡被有效抑制。通过 IF 分析 caspase-3 表达研究了 LiCl 抑制细胞凋亡的能力。我们的数据表明，LiCl 通过发挥抗凋亡作用抑制 TGEV 感染。LiCl 对猪流行性腹泻冠状病毒的抑制作用也观察到。结合关于 LiCl 在细胞培养中对 IBV 的抑制作用的其他报道，我们的结果表明，LiCl 可能是对抗猪和禽冠状病毒的有效药物。
