Chen Christie, Zuckerman David M, Brantley Susanna, Sharpe Michka, Childress Kevin, Hoiczyk Egbert, Pendleton Amanda R
Division of Natural Science and Mathematics, Oxford College of Emory University, Oxford, GA 30054, USA.
BMC Vet Res. 2014 Jan 16;10:24. doi: 10.1186/1746-6148-10-24.
Infectious bronchitis virus (IBV) is a pathogenic chicken coronavirus. Currently, vaccination against IBV is only partially protective; therefore, better preventions and treatments are needed. Plants produce antimicrobial secondary compounds, which may be a source for novel anti-viral drugs. Non-cytotoxic, crude ethanol extracts of Rhodiola rosea roots, Nigella sativa seeds, and Sambucus nigra fruit were tested for anti-IBV activity, since these safe, widely used plant tissues contain polyphenol derivatives that inhibit other viruses.
Dose-response cytotoxicity curves on Vero cells using trypan blue staining determined the highest non-cytotoxic concentrations of each plant extract. To screen for IBV inhibition, cells and virus were pretreated with extracts, followed by infection in the presence of extract. Viral cytopathic effect was assessed visually following an additional 24 h incubation with extract. Cells and supernatants were harvested separately and virus titers were quantified by plaque assay. Variations of this screening protocol determined the effects of a number of shortened S. nigra extract treatments. Finally, S. nigra extract-treated virions were visualized by transmission electron microscopy with negative staining.Virus titers from infected cells treated with R. rosea and N. sativa extracts were not substantially different from infected cells treated with solvent alone. However, treatment with S. nigra extracts reduced virus titers by four orders of magnitude at a multiplicity of infection (MOI) of 1 in a dose-responsive manner. Infection at a low MOI reduced viral titers by six orders of magnitude and pretreatment of virus was necessary, but not sufficient, for full virus inhibition. Electron microscopy of virions treated with S. nigra extract showed compromised envelopes and the presence of membrane vesicles, which suggested a mechanism of action.
These results demonstrate that S. nigra extract can inhibit IBV at an early point in infection, probably by rendering the virus non-infectious. They also suggest that future studies using S. nigra extract to treat or prevent IBV or other coronaviruses are warranted.
传染性支气管炎病毒（IBV）是一种致病性鸡冠状病毒。目前，针对IBV的疫苗接种仅具有部分保护作用；因此，需要更好的预防和治疗方法。植物会产生抗菌次生化合物，这可能是新型抗病毒药物的一个来源。由于玫瑰红景天根、黑种草籽和接骨木果实的粗乙醇提取物安全且广泛使用，且含有抑制其他病毒的多酚衍生物，因此对其进行了抗IBV活性测试。
使用台盼蓝染色法对Vero细胞进行剂量反应细胞毒性曲线测定，确定了每种植物提取物的最高无细胞毒性浓度。为筛选IBV抑制作用，先用提取物预处理细胞和病毒，然后在提取物存在的情况下进行感染。在与提取物再孵育24小时后，通过肉眼评估病毒细胞病变效应。分别收获细胞和上清液，并通过空斑试验对病毒滴度进行定量。该筛选方案的变化确定了一些缩短的接骨木提取物处理的效果。最后，通过负染色透射电子显微镜观察接骨木提取物处理的病毒粒子。用玫瑰红景天和黑种草提取物处理的感染细胞的病毒滴度与仅用溶剂处理的感染细胞相比没有显著差异。然而，在感染复数（MOI）为1时，用接骨木提取物处理以剂量反应方式使病毒滴度降低了四个数量级。低MOI感染使病毒滴度降低了六个数量级，对病毒进行预处理是完全抑制病毒所必需的，但并不充分。对接骨木提取物处理的病毒粒子进行电子显微镜观察显示包膜受损并存在膜泡，这提示了一种作用机制。
这些结果表明，接骨木提取物可以在感染早期抑制IBV，可能是通过使病毒失去感染性。它们还表明，值得在未来开展使用接骨木提取物治疗或预防IBV或其他冠状病毒的研究。
