Dataset Information

Kurarinone Inhibits HCoV-OC43 Infection by Impairing the Virus-Induced Autophagic Flux in MRC-5 Human Lung Cells.

ABSTRACT: Kurarinone is a prenylated flavonone isolated from the roots of Sophora flavescens. Among its known functions, kurarinone has both anti-apoptotic and anti-inflammatory properties. Coronaviruses (CoVs), including HCoV-OC43, SARS-CoV, MERS-CoV, and SARS-CoV-2, are the causative agents of respiratory virus infections that range in severity from the common cold to severe pneumonia. There are currently no effective treatments for coronavirus-associated diseases. In this report, we examined the anti-viral impact of kurarinone against infection with the human coronavirus, HCoV-OC43. We found that kurarinone inhibited HCoV-OC43 infection in human lung fibroblast MRC-5 cells in a dose-dependent manner with an IC50 of 3.458 ± 0.101 ?M. Kurarinone inhibited the virus-induced cytopathic effect, as well as extracellular and intracellular viral RNA and viral protein expression. Time-of-addition experiments suggested that kurarinone acted at an early stage of virus infection. Finally, we found that HCoV-OC43 infection increased the autophagic flux in MRC-5 cells; kurarinone inhibited viral replication via its capacity to impair the virus-induced autophagic flux. As such, we suggest that kurarinone may be a useful therapeutic for the treatment of diseases associated with coronavirus infection.

SUBMITTER: Min JS

PROVIDER: S-EPMC7408680 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Kurarinone Inhibits HCoV-OC43 Infection by Impairing the Virus-Induced Autophagic Flux in MRC-5 Human Lung Cells.

Min Jung Sun JS Kim Dong Eon DE Jin Young-Hee YH Kwon Sunoh S

Journal of clinical medicine 20200714 7

Kurarinone is a prenylated flavonone isolated from the roots of <i>Sophora flavescens</i>. Among its known functions, kurarinone has both anti-apoptotic and anti-inflammatory properties. Coronaviruses (CoVs), including HCoV-OC43, SARS-CoV, MERS-CoV, and SARS-CoV-2, are the causative agents of respiratory virus infections that range in severity from the common cold to severe pneumonia. There are currently no effective treatments for coronavirus-associated diseases. In this report, we examined the ...[more]

PMID: 32674356

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Project description:The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has renewed interest in human coronaviruses that cause the common cold, particularly as research with them at biosafety level (BSL)-2 avoids the added costs and biosafety concerns that accompany work with SARS-CoV-2, BSL-3 research. One of these, human coronavirus OC43 (HCoV-OC43), is a well-matched surrogate for SARS-CoV-2 because it is also a Betacoronavirus, targets the human respiratory system, is transmitted via respiratory aerosols and droplets and is relatively resistant to disinfectants. Unfortunately, growth of HCoV-OC43 in the recommended human colon cancer (HRT-18) cells does not produce obvious cytopathic effect (CPE) and its titration in these cells requires expensive antibody-based detection. Consequently, multiple quantification approaches for HCoV-OC43 using alternative cell lines exist, which complicates comparison of research results. Hence, we investigated the basic growth parameters of HCoV-OC43 infection in three of these cell lines (HRT-18, human lung fibroblasts (MRC-5) and African green monkey kidney (Vero E6) cells) including the differential development of cytopathic effect (CPE) and explored reducing the cost, time and complexity of antibody-based detection assay. Multi-step growth curves were conducted in each cell type in triplicate at a multiplicity of infection of 0.1 with daily sampling for seven days. Samples were quantified by tissue culture infectious dose50(TCID50)/mL or plaque assay (cell line dependent) and additionally analyzed on the Sartorius Virus Counter 3100 (VC), which uses flow virometry to count the total number of intact virus particles in a sample. We improved the reproducibility of a previously described antibody-based detection based TCID50 assay by identifying commercial sources for antibodies, decreasing antibody concentrations and simplifying the detection process. The growth curves demonstrated that HCoV-O43 grown in MRC-5 cells reached a peak titer of ˜107 plaque forming units/mL at two days post infection (dpi). In contrast, HCoV-OC43 grown on HRT-18 cells required six days to reach a peak titer of ˜106.5 TCID50/mL. HCoV-OC43 produced CPE in Vero E6 cells but these growth curve samples failed to produce CPE in a plaque assay after four days. Analysis of the VC data in combination with plaque and TCID50 assays together revealed that the defective:infectious virion ratio of MRC-5 propagated HCoV-OC43 was less than 3:1 for 1-6 dpi while HCoV-OC43 propagated in HRT-18 cells varied from 41:1 at 1 dpi, to 329:4 at 4 dpi to 94:1 at 7 dpi. These results should enable better comparison of extant HCoV-OC43 study results and prompt further standardization efforts.

Project description:Four coronaviruses (HCoV-OC43, HCoV-HKU1, HCoV-NL63, and HCoV-229E) are endemic in human populations. All these viruses are seasonal and generate short-term immunity. Like the highly pathogenic coronaviruses, the endemic coronaviruses have zoonotic origins. Thus, understanding the evolutionary dynamics of these human viruses might provide insight into the future trajectories of SARS-CoV-2 evolution. Because the zoonotic sources of HCoV-OC43 and HCoV-229E are known, we applied a population genetics-phylogenetic approach to investigate which selective events accompanied the divergence of these viruses from the animal ones. Results indicated that positive selection drove the evolution of some accessory proteins, as well as of the membrane proteins. However, the spike proteins of both viruses and the hemagglutinin-esterase (HE) of HCoV-OC43 represented the major selection targets. Specifically, for both viruses, most positively selected sites map to the receptor-binding domains (RBDs) and are polymorphic. Molecular dating for the HCoV-229E spike protein indicated that RBD Classes I, II, III, and IV emerged 3-9 years apart. However, since the appearance of Class V (with much higher binding affinity), around 25 years ago, limited genetic diversity accumulated in the RBD. These different time intervals are not fully consistent with the hypothesis that HCoV-229E spike evolution was driven by antigenic drift. An alternative, not mutually exclusive possibility is that strains with higher affinity for the cellular receptor have out-competed strains with lower affinity. The evolution of the HCoV-OC43 spike protein was also suggested to undergo antigenic drift. However, we also found abundant signals of positive selection in HE. Whereas such signals might result from antigenic drift, as well, previous data showing co-evolution of the spike protein with HE suggest that optimization for human cell infection also drove the evolution of this virus. These data provide insight into the possible trajectories of SARS-CoV-2 evolution, especially in case the virus should become endemic.

Dataset Information

Kurarinone Inhibits HCoV-OC43 Infection by Impairing the Virus-Induced Autophagic Flux in MRC-5 Human Lung Cells.

Publications

Kurarinone Inhibits HCoV-OC43 Infection by Impairing the Virus-Induced Autophagic Flux in MRC-5 Human Lung Cells.

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