Effective inhibition of HCoV-OC43 and SARS-CoV-2 by phytochemicals in vitro and in vivo.

OBJECTIVE: Several coronaviruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and human coronavirus OC43 (HCoV-OC43), can cause respiratory infections in humans. To address the need for reliable anti-coronavirus therapeutics, we screened 16 active phytochemicals selected from medicinal plants used in traditional applications for respiratory-related illnesses. METHODS: An initial screen was completed using HCoV-OC43 to identify compounds that inhibit virus-induced cytopathic effect (CPE) and cell death inhibition. Then the top hits were validated in vitro against both HCoV-OC43 and SARS-CoV-2 by determining virus titer in cell supernatant and virus-induced cell death. Finally, the most active phytochemical was validated in vivo in the SARS-CoV-2-infected B6.Cg-Tg(K18-ACE2)2Prlmn/J mouse model. RESULTS: The phytochemicals lycorine (LYC), capsaicin, rottlerin (RTL), piperine and chebulinic acid (CHU) inhibited HCoV-OC43-induced cytopathic effect and reduced viral titres by up to 4 log. LYC, RTL and CHU also suppressed virus replication and cell death following SARS-CoV-2 infection. In vivo, RTL significantly reduced SARS-CoV-2-induced mortality by ∼40% in human angiotensin-converting enzyme 2 (ACE2)-expressing K18 mice. CONCLUSION: Collectively, these studies indicate that RTL and other phytochemicals have therapeutic potential to reduce SARS-CoV-2 and HCoV-OC43 infections.

Pinostrobin from plants and propolis against human coronavirus HCoV-OC43 by modulating host AHR/CYP1A1 pathway and lipid metabolism.

Coronaviruses, as enveloped positive-strand RNA viruses, manipulate host lipid compositions to enable robust viral replication. Temporal modulation of the host lipid metabolism is a potential novel strategy against coronaviruses. Here, the dihydroxyflavone pinostrobin (PSB) was identified through bioassay that inhibited the increment of human coronavirus OC43 (HCoV-OC43) in human ileocecal colorectal adenocarcinoma cells. Lipid metabolomic studies showed that PSB interfered with linoleic acid and arachidonic acid metabolism pathways. PSB significantly decreased the level of 12, 13- epoxyoctadecenoic (12, 13-EpOME) and increased the level of prostaglandin E2. Interestingly, exogenous supplement of 12, 13-EpOME in HCoV-OC43-infected cells significantly stimulated HCoV-OC43 virus replication. Transcriptomic analyses showed that PSB is a negative modulator of aryl hydrocarbon receptor (AHR)/cytochrome P450 (CYP) 1A1signaling pathway and its antiviral effects can be counteracted by supplement of FICZ, a well-known AHR agonist. Integrative analyses of metabolomic and transcriptomic indicated that PSB could affect linoleic acid and arachidonic acid metabolism axis through AHR/CYP1A1 pathway. These results highlight the importance of the AHR/CYP1A1 pathway and lipid metabolism in the anti-coronavirus activity of the bioflavonoid PSB.

Epigallocatechin Gallate (EGCG), a Green Tea Polyphenol, Reduces Coronavirus Replication in a Mouse Model.

The COVID-19 pandemic has resulted in a huge number of deaths from 2020 to 2021; however, effective antiviral drugs against SARS-CoV-2 are currently under development. Recent studies have demonstrated that green tea polyphenols, particularly EGCG, inhibit coronavirus enzymes as well as coronavirus replication in vitro. Herein, we examined the inhibitory effect of green tea polyphenols on coronavirus replication in a mouse model. We used epigallocatechin gallate (EGCG) and green tea polyphenols containing more than 60% catechin (GTP60) and human coronavirus OC43 (HCoV-OC43) as a surrogate for SARS-CoV-2. Scanning electron microscopy analysis results showed that HCoV-OC43 infection resulted in virion particle production in infected cells. EGCG and GTP60 treatment reduced coronavirus protein and virus production in the cells. Finally, EGCG- and GTP60-fed mice exhibited reduced levels of coronavirus RNA in mouse lungs. These results demonstrate that green tea polyphenol treatment is effective in decreasing the level of coronavirus in vivo.

Broad antiviral and anti-inflammatory activity of Qingwenjiere mixture against SARS-CoV-2 and other human coronavirus infections.

BACKGROUND: Qingwenjiere Mixture (QJM) is a traditional Chinese medicine (TCM) that has been shown to have remarkable clinical efficacy against COVID-19. However, little is known about the antiviral and anti-inflammatory activities of QJM against a wider range of human coronavirus (HCoV) strains. PURPOSE: The study aims to investigate the antiviral and anti-inflammatory activities of QJM, as well as the underlying mechanisms against HCoV infections. METHODS: The chemical compositions from QJM were analyzed by LC-MS. The inhibitory effect of QJM on infections of HCoV-OC43, HCoV-229E, HCoV-NL63, and SARS-CoV-2 was evaluated in HRT-18 cells, Huh7 cells, LLC-MK2 cells, and Vero-E6 cells, respectively, by using cytopathic effect (CPE) inhibition assay or RT-qPCR detection of viral n, s, or RdRp/Hel genes. The expression of pro-inflammatory cytokines induced by HCoV-OC43, HCoV-229E, and SARS-CoV-2, as well as the host ace2 gene was also determined by RT-qPCR assay. Furthermore, the expression of key molecules in the NF-κB/MAPKs signaling pathways was determined by western blot. RESULTS: In alcohol-extraction groups of QJM and reference decoction pieces, 53 similar ion peaks were identified, the majority of which were phenylpropanoids, iridoids, and flavonoids. In addition, QJM reduced CPE caused by HCoVs and the expression of viral n genes or N protein. Pretreatment with QJM also exerted inhibitory effect on viral n gene expression. QJM also inhibited the expression of RdRp/Hel and s genes of SARS-CoV-2, as well as the host ace2 gene. Besides, QJM markedly reduced virus-induced mRNA expression of a panel of pro-inflammatory cytokines, such as IL-6, CXCL-8/IL-8, CXCL-10/IP-10, CCL-5/RANTES, TNF-α, IFN-α, CCL-2/MCP-1, CXCL-9/MIG, and IL1-α. We further showed that QJM inhibited the phosphorylation of NF-κB p65, and JNK, ERK 1/2, and p38 MAPKs in HCoV-OC43-infected HRT-18 cells. CONCLUSIONS: QJM has broad antiviral and anti-inflammatory activity against both common and newly emerged HCoVs possibly by inhibiting the activation of key components in NF-κB/MAPKs signaling pathway. QJM also has a prevention effect against HCoV infections and inhibits the host receptor required for virus entry. These results indicate that QJM may have the therapeutic potential in the treatment of diseases caused by a broad range of HCoVs.

Pulsed blue light inactivates two strains of human coronavirus.

Emerging evidence suggests that blue light has the potential to inactivate viruses. Therefore, we investigated the effect of 405 nm, 410 nm, 425 nm and 450 nm pulsed blue light (PBL) on human alpha coronavirus HCoV-229 E and human beta coronavirus HCoV-OC43, using Qubit fluorometry and RT-LAMP to quantitate the amount of nucleic acid in irradiated and control samples. Like SARS-CoV-2, HCoV-229E and HCoV-OC43 are single stranded RNA viruses transmitted by air and direct contact; they have similar genomic sizes as SARS-CoV-2, and are used as surrogates for SARS-CoV-2. Irradiation was carried out either at 32.4 J cm-2 using 3 mW cm-2 irradiance or at 130 J cm-2 using 12 mW cm-2 irradiance. Results: (1) At each wavelength tested, PBL was antiviral against both coronaviruses. (2) 405 nm light gave the best result, yielding 52.3% (2.37 log10) inactivation against HCoV-OC43 (p < .0001), and a significant 1.46 log 10 (44%) inactivation of HCoV-229E (p < .01). HCoV-OC43, which like SARS-CoV-2 is a beta coronavirus, was more susceptible to PBL irradiation than alpha coronavirus HCoV-229E. The latter finding suggests that PBL is potentially antiviral against multiple coronavirus strains, and that, while its potency may vary from one virus to another, it seems more antiviral against beta coronaviruses, such as HCoV-OC43. (3) Further, the antiviral effect of PBL was better at a higher irradiance than a lower irradiance, and this indicates that with further refinement, a protocol capable of yielding 100% inactivation of viruses is attainable.

Pathomechanisms, therapeutic targets and potent inhibitors of some beta-coronaviruses from bench-to-bedside.

Since the emergence of their primitive strains, the complexity surrounding their pathogenesis, constant genetic mutation and translation are contributing factors to the scarcity of a successful vaccine for coronaviruses till moment. Although, the recent announcement of vaccine breakthrough for COVID-19 renews the hope, however, there remains a major challenge of accessibility to urgently match the rapid global therapeutic demand for curtailing the pandemic, thereby creating an impetus for further search. The reassessment of results from a stream of experiments is of enormous importance in identifying bona fide lead-like candidates to fulfil this quest. This review comprehensively highlights the common pathomechanisms and pharmacological targets of HCoV-OC43, SARS-CoV-1, MERS-CoV and SARS-CoV-2, and potent therapeutic potentials from basic and clinical experimental investigations. The implicated targets for the prevention and treatment include the viral proteases (Mpro, PLpro, 3CLpro), viral structural proteins (S- and N-proteins), non-structural proteins (nsp 3, 8, 10, 14, 16), accessory protein (ns12.9), viroporins (3a, E, 8a), enzymes (RdRp, TMPRSS2, ADP-ribosyltransferase, MTase, 2'-O-MTase, TATase, furin, cathepsin, deamidated human triosephosphate isomerase), kinases (MAPK, ERK, PI3K, mTOR, AKT, Abl2), interleukin-6 receptor (IL-6R) and the human host receptor, ACE2. Notably among the 109 overviewed inhibitors include quercetin, eriodictyol, baicalin, luteolin, melatonin, resveratrol and berberine from natural products, GC373, NP164 and HR2P-M2 from peptides, 5F9, m336 and MERS-GD27 from specific human antibodies, imatinib, remdesivir, ivermectin, chloroquine, hydroxychloroquine, nafamostat, interferon-ß and HCQ from repurposing libraries, some iron chelators and traditional medicines. This review represents a model for further translational studies for effective anti-CoV therapeutic designs.

EGCG, a green tea polyphenol, inhibits human coronavirus replication in vitro.

COVID-19 pandemic results in record high deaths in many countries. Although a vaccine for SARS-CoV-2 is now available, effective antiviral drugs to treat coronavirus diseases are not available yet. Recently, EGCG, a green tea polyphenol, was reported to inhibit SARS-CoV-2 3CL-protease, however the effect of EGCG on coronavirus replication is unknown. In this report, human coronavirus HCoV-OC43 (beta coronavirus) and HCoV-229E (alpha coronavirus) were used to examine the effect of EGCG on coronavirus. EGCG treatment decreases 3CL-protease activity of HCoV-OC43 and HCoV-229E. Moreover, EGCG treatment decreased HCoV-OC43-induced cytotoxicity. Finally, we found that EGCG treatment decreased the levels of coronavirus RNA and protein in infected cell media. These results indicate that EGCG inhibits coronavirus replication.

A high-throughput drug screening strategy against coronaviruses.

The emergence and re-emergence of coronaviruses (CoV) continually cause circulating epidemics and pandemics worldwide, such as the on-going outbreak of the novel coronavirus SARS-CoV-2. The resultant disease, coronavirus disease 2019 (COVID-19), has rapidly developed into a worldwide pandemic, leading to severe health and economic burdens. Although the recently announced vaccines against COVID-19 has rekindled hope, there is still a major challenge to urgently meet the global need for rapid treatment of the pandemic. Given the urgency of the CoV outbreak, we propose a strategy to screen potential broad-spectrum drugs against CoV in a high-throughput manner, particularly against SARS-CoV-2. Since the essential functional domains of CoV are extensively homologous, the availability of two types of mild CoV, HCoV-OC43 and MHV, should provide a valuable tool for the rapid identification of promising drugs against CoV without the drawbacks of level three biological confinements. The luciferase reporter gene is introduced into HCoV-OC43 and MHV to indicate viral activity, and hence the antiviral efficiency of screened drugs can be quantified by luciferase activity. Compounds with antiviral activity against both HCoV-OC43 and MHV are further evaluated in SARS-CoV-2 after structural optimizations. This system allows large-scale compounds to be screened to search for broad-spectrum drugs against CoV in a high-throughput manner, providing potential alternatives for clinical management of SARS-CoV-2 or other CoV.

Repurposing Nucleoside Analogs for Human Coronaviruses.

Coronavirus disease 2019 (COVID-19) is a serious illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or CoV-2). Some reports claimed certain nucleoside analogs to be active against CoV-2 and thus needed confirmation. Here, we evaluated a panel of compounds and identified novel nucleoside analogs with antiviral activity against CoV-2 and HCoV-OC43 while ruling out others. Of significance, sofosbuvir demonstrated no antiviral effect against CoV-2, and its triphosphate did not inhibit CoV-2 RNA polymerase.

Potential of Flavonoid-Inspired Phytomedicines against COVID-19.

Flavonoids are widely used as phytomedicines. Here, we report on flavonoid phytomedicines with potential for development into prophylactics or therapeutics against coronavirus disease 2019 (COVID-19). These flavonoid-based phytomedicines include: caflanone, Equivir, hesperetin, myricetin, and Linebacker. Our in silico studies show that these flavonoid-based molecules can bind with high affinity to the spike protein, helicase, and protease sites on the ACE2 receptor used by the severe acute respiratory syndrome coronavirus 2 to infect cells and cause COVID-19. Meanwhile, in vitro studies show potential of caflanone to inhibit virus entry factors including, ABL-2, cathepsin L, cytokines (IL-1ß, IL-6, IL-8, Mip-1α, TNF-α), and PI4Kiiiß as well as AXL-2, which facilitates mother-to-fetus transmission of coronavirus. The potential for the use of smart drug delivery technologies like nanoparticle drones loaded with these phytomedicines to overcome bioavailability limitations and improve therapeutic efficacy are discussed.

Natural Bis-Benzylisoquinoline Alkaloids-Tetrandrine, Fangchinoline, and Cepharanthine, Inhibit Human Coronavirus OC43 Infection of MRC-5 Human Lung Cells.

Stephaniatetrandra and other related species of Menispermaceae are the major sources of the bis-benzylisoquinoline alkaloids tetrandrine (TET), fangchinoline (FAN), and cepharanthine (CEP). Although the pharmacological properties of these compounds include anticancer and anti-inflammatory activities, the antiviral effects of these compounds against human coronavirus (HCoV) remain unclear. Hence, the aims of the current study were to assess the antiviral activities of TET, FAN, and CEP and to elucidate the underlying mechanisms in HCoV-OC43-infected MRC-5 human lung cells. These compounds significantly inhibited virus-induced cell death at the early stage of virus infection. TET, FAN, and CEP treatment dramatically suppressed the replication of HCoV-OC43 as well as inhibited viral S and N protein expression. The virus-induced host response was reduced by compound treatment as compared with the vehicle control. Taken together, these findings demonstrate that TET, FAN, and CEP are potential natural antiviral agents for the prevention and treatment of HCoV-OC43 infection.

High-Throughput Screening and Identification of Potent Broad-Spectrum Inhibitors of Coronaviruses.

Coronaviruses (CoVs) act as cross-species viruses and have the potential to spread rapidly into new host species and cause epidemic diseases. Despite the severe public health threat of severe acute respiratory syndrome coronavirus and Middle East respiratory syndrome CoV (MERS-CoV), there are currently no drugs available for their treatment; therefore, broad-spectrum inhibitors of emerging and endemic CoVs are urgently needed. To search for effective inhibitory agents, we performed high-throughput screening (HTS) of a 2,000-compound library of approved drugs and pharmacologically active compounds using the established genetically engineered human CoV OC43 (HCoV-OC43) strain expressing Renilla luciferase (rOC43-ns2Del-Rluc) and validated the inhibitors using multiple genetically distinct CoVs in vitro We screened 56 hits from the HTS data and validated 36 compounds in vitro using wild-type HCoV-OC43. Furthermore, we identified seven compounds (lycorine, emetine, monensin sodium, mycophenolate mofetil, mycophenolic acid, phenazopyridine, and pyrvinium pamoate) as broad-spectrum inhibitors according to their strong inhibition of replication by four CoVs in vitro at low-micromolar concentrations. Additionally, we found that emetine blocked MERS-CoV entry according to pseudovirus entry assays and that lycorine protected BALB/c mice against HCoV-OC43-induced lethality by decreasing viral load in the central nervous system. This represents the first demonstration of in vivo real-time bioluminescence imaging to monitor the effect of lycorine on the spread and distribution of HCoV-OC43 in a mouse model. These results offer critical information supporting the development of an effective therapeutic strategy against CoV infection.IMPORTANCE Currently, there is no approved therapy to treat coronavirus infection; therefore, broad-spectrum inhibitors of emerging and endemic CoVs are needed. Based on our high-throughput screening assay using a compound library, we identified seven compounds with broad-spectrum efficacy against the replication of four CoVs in vitro Additionally, one compound (lycorine) was found to protect BALB/c mice against HCoV-OC43-induced lethality by decreasing viral load in the central nervous system. This inhibitor might offer promising therapeutic possibilities for combatting novel CoV infections in the future.