Antiviral effects of Korean Red Ginseng on human coronavirus OC43

Abstract

Background: Panax ginseng Meyer is a medicinal plant well-known for its antiviral activities against various viruses, but its antiviral effect on coronavirus has not yet been studied thoroughly. The antiviral activity of Korean Red Ginseng (KRG) and ten ginsenosides against Human coronavirus OC43 (HCoV-OC43) was investigated in vitro.

Methods: The antiviral response and mechanism of action of KRG extract and ginsenoside Rc, Re, Rf, Rg1, Rg2-20 (R) and -20 (S), Rg3-20 (R) and -20 (S), and Rh2-20 (R) and -20 (S), against the human coronavirus strain OC43 were investigated by using plaque assay, time of addition assay, real-time PCR, and FACS analysis.

Results: Virus plaque formation was reduced in KRG extract-treated and HCoV-OC43-infected HCT-8 cells. KRG extract decreased the viral proteins (Nucleocapsid protein and Spike protein) and mRNA (N and M gene) expression, while increased the expression of interferon genes.

Conclusion: KRG extract exhibits antiviral activity by enhancing the expression of interferons and can be used in treating infections caused by HCoV-OC43.

Keywords: Korea Red Ginseng; aAntiviral; coronavirus; ginsenoside.

Graphical abstract

Fig. 1

Cytotoxicity and antiviral effect of KRG and ginsenosides. For cytotoxicity, HCT-8 cells were treated with KRG (100 μg/mL) or each of the 10 different ginsenosides (100 μM) for 7 days, and cell viability was measured by the MTT assay (A). For testing antiviral effect, plaque formation assay was performed (B). Cell viability is shown as relative values in each treatment compared to the untreated control group (N). HCoV-OC43 plaque formation levels were represented as the relative number of plaques compared with that obtained from DMSO-treated control (B). The data are represented as mean ± SEM of three independent experiments with similar results. One-way ANOVA plus Tukey's multiple comparison test was applied.

Fig. 2

Time of addition assay to determine the antiviral activities of KRG. HCT-8 cells were infected with HCoV-OC43, and KRG was added to the cells at 24 h before, during, or after HCoV-OC43 infection. The overall scheme of the time-of-addition assay (A). Plaque assay image of HCoV-OC43-infected HCT-8 cells with or without KRG treatment (B). The plaques of pre-, co-, and post-KRG-treated cells were quantified at 7 dpi (Fig. C–E). The data are representative of three experiments with similar results.

Fig. 3

Expression of HCoV-OC43 nucleoprotein (N protein) and spike protein (S protein) in HCT-8 cells. The cells were infected with HCoV-OC43 followed by KRG treatment, and the expression of N protein (A) and S protein (B) was analyzed by flow cytometry at 4 dpi. The FACS plot is representative of three experiments with similar results.

Fig. 4

Decrease in nucleoprotein (N) and membrane protein (M) mRNA levels in KRG-treated HCT-8 cells. HCT-8 cells were treated with 25, 50, and 100 μg/mL KRG for 4 days after infection with HCoV-OC43, and the culture supernatant was harvested at 3 dpi and 4 dpi. The viral RNA was obtained from the culture supernatant of HCoV-OC43-infected cells, and the mRNA level of HCoV-OC43 N protein (A, B) and M protein (C, D) was examined by qRT-PCR.

Fig. 5

Changes in the expression of IFN-α, IFN-β, IFN-γ, and MxA in KRG-treated, HCoV-OC43-infected HCT-8 cells. Total RNA was extracted from HCT-8 cells at 4 dpi, and the mRNA expression levels of IFN-α (A), IFN-β (B), IFN-γ (C), and MxA (D) were measured by qRT-PCR. GAPDH was used for data normalization.