Omicsynin B4 potently blocks coronavirus infection by inhibiting host proteases cathepsin L and TMPRSS2.

The emergence of SARS-CoV-2 variants represents a major threat to public health and requires identification of novel therapeutic agents to address the unmet medical needs. Small molecules impeding viral entry through inhibition of spike protein priming proteases could have potent antiviral effects against SARS-CoV-2 infection. Omicsynin B4, a pseudo-tetrapeptides identified from Streptomyces sp. 1647, has potent antiviral activity against influenza A viruses in our previous study. Here, we found omicsynin B4 exhibited broad-spectrum anti-coronavirus activity against HCoV-229E, HCoV-OC43 and SARS-CoV-2 prototype and its variants in multiple cell lines. Further investigations revealed omicsynin B4 blocked the viral entry and might be related to the inhibition of host proteases. SARS-CoV-2 spike protein mediated pseudovirus assay supported the inhibitory activity on viral entry of omicsynin B4 with a more potent inhibition of Omicron variant, especially when overexpression of human TMPRSS2. Moreover, omicsynin B4 exhibited superior inhibitory activity in the sub-nanomolar range against CTSL, and a sub-micromolar inhibition against TMPRSS2 in biochemical assays. The molecular docking analysis confirmed that omicsynin B4 fits well in the substrate binding sites and forms a covalent bond to Cys25 and Ser441 in CTSL and TMPRSS2, respectively. In conclusion, we found that omicsynin B4 may serve as a natural protease inhibitor for CTSL and TMPRSS2, blocking various coronavirus S protein-driven entry into cells. These results further highlight the potential of omicsynin B4 as an attractive candidate for broad-spectrum antiviral therapy that could rapidly respond to emerging variants of SARS-CoV-2.

Synthesis and Anti-Influenza Virus Effects of Novel Substituted Polycyclic Pyridone Derivatives Modified from Baloxavir.

In this work, a series of novel substituted polycyclic pyridone derivatives were designed and synthesized as potent anti-influenza agents. The cytopathic effect (CPE) assay and cytotoxicity assay indicated that all of the compounds possessed potent anti-influenza virus activity and relatively low cytotoxicity; some of them inhibited the replication of influenza A virus (IAV) at picomolar concentrations. Further studies revealed that, at a concentration of 3 nM, three compounds (10a, 10d, and 10g) could significantly reduce the M2 RNA amounts and M2 protein expression of IAV and inhibit the activity of RNA-dependent RNA polymerase (RdRp). Among them, (R)-12-(5H-dibenzo[a,d][7]annulen-5-yl)-7-hydroxy-3,4,12,12a-tetrahydro-1H-[1,4]oxazino[3,4-c]pyrido[2,1-f][1,2,4]triazine-6,8-dione (10a) was found to be a promising anti-influenza drug candidate with good human liver microsomal stability, as well as with better selectivity index and oral bioavailability than Baloxavir.

ISGylation in Innate Antiviral Immunity and Pathogen Defense Responses: A Review.

The interferon-stimulating gene 15 (ISG15) protein is a ubiquitin-like protein induced by interferons or pathogens. ISG15 can exist in free form or covalently bind to the target protein through an enzymatic cascade reaction, which is called ISGylation. ISGylation has been found to play an important role in the innate immune responses induced by type I interferon, and is, thus, critical for the defense of host cells against RNA, DNA, and retroviruses. Through covalent binding with the host and viral target proteins, ISG15 inhibits the release of viral particles, hinder viral replication, and regulates the incubation period of viruses, thereby exerting strong antiviral effects. The SARS-CoV-2 papain-like protease, a virus-encoded deubiquitinating enzyme, has demonstrated activity on both ubiquitin and ISG15 chain conjugations, thus playing a suppressive role against the host antiviral innate immune response. Here we review the recent research progress in understanding ISG15-type ubiquitin-like modifications, with an emphasis on the underlying molecular mechanisms. We provide comprehensive references for further studies on the role of ISG15 in antiviral immunity, which may enable development of new antiviral drugs.

Engineering Extracellular Vesicles Enriched with Palmitoylated ACE2 as COVID-19 Therapy (Adv. Mater. 49/2021)

COVID-19 Therapy In their work reported in article number 2103471, Long Zhang, Fangfang Zhou, and co-workers fuse the S-palmitoylation-dependent plasma membrane (PM) targeting sequence with angiotensin converting enzyme 2 (ACE2) and engineer extracellular vesicles (EVs) on their surface enriched with palmitoylated ACE2 (PM-ACE2-EVs). The PM-ACE2-EVs can bind to the SARS-CoV-2 S-RBD with high affinity and block its interaction with cell-surface ACE2, thereby preventing SARS-CoV-2 from entering the host cell. This study provides a novel EV-based candidate for prophylactic and therapeutic treatment against COVID-19.

The way of SARS-CoV-2 vaccine development: success and challenges.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019 (COVID-19). To halt the pandemic, multiple SARS-CoV-2 vaccines have been developed and several have been allowed for emergency use and rollout worldwide. With novel SARS-CoV-2 variants emerging and circulating widely, whether the original vaccines that were designed based on the wild-type SARS-CoV-2 were effective against these variants has been a contentious discussion. Moreover, some studies revealed the long-term changes of immune responses post SARS-CoV-2 infection or vaccination and the factors that might impact the vaccine-induced immunity. Thus, in this review, we have summarized the influence of mutational hotspots on the vaccine efficacy and characteristics of variants of interest and concern. We have also discussed the reasons that might result in discrepancies in the efficacy of different vaccines estimated in different trials. Furthermore, we provided an overview of the duration of immune responses after natural infection or vaccination and shed light on the factors that may affect the immunity induced by the vaccines, such as special disease conditions, sex, and pre-existing immunity, with the aim of aiding in combating COVID-19 and distributing SARS-CoV-2 vaccines under the prevalence of diverse SARS-CoV-2 variants.

Engineering Extracellular Vesicles Enriched with Palmitoylated ACE2 as COVID-19 Therapy.

Angiotensin converting enzyme 2 (ACE2) is a key receptor present on cell surfaces that directly interacts with the viral spike (S) protein of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). It is proposed that inhibiting this interaction can be promising in treating COVID-19. Here, the presence of ACE2 in extracellular vesicles (EVs) is reported and the EV-ACE2 levels are determined by protein palmitoylation. The Cys141 and Cys498 residues on ACE2 are S-palmitoylated by zinc finger DHHC-Type Palmitoyltransferase 3 (ZDHHC3) and de-palmitoylated by acyl protein thioesterase 1 (LYPLA1), which is critical for the membrane-targeting of ACE2 and their EV secretion. Importantly, by fusing the S-palmitoylation-dependent plasma membrane (PM) targeting sequence with ACE2, EVs enriched with ACE2 on their surface (referred to as PM-ACE2-EVs) are engineered. It is shown that PM-ACE2-EVs can bind to the SARS-CoV-2 S-RBD with high affinity and block its interaction with cell surface ACE2 in vitro. PM-ACE2-EVs show neutralization potency against pseudotyped and authentic SARS-CoV-2 in human ACE2 (hACE2) transgenic mice, efficiently block viral load of authentic SARS-CoV-2, and thus protect host against SARS-CoV-2-induced lung inflammation. The study provides an efficient engineering protocol for constructing a promising, novel biomaterial for application in prophylactic and therapeutic treatments against COVID-19.

Repurposing carrimycin as an antiviral agent against human coronaviruses, including the currently pandemic SARS-CoV-2.

COVID-19 pandemic caused by SARS-CoV-2 infection severely threatens global health and economic development. No effective antiviral drug is currently available to treat COVID-19 and any other human coronavirus infections. We report herein that a macrolide antibiotic, carrimycin, potently inhibited the cytopathic effects (CPE) and reduced the levels of viral protein and RNA in multiple cell types infected by human coronavirus 229E, OC43, and SARS-CoV-2. Time-of-addition and pseudotype virus infection studies indicated that carrimycin inhibited one or multiple post-entry replication events of human coronavirus infection. In support of this notion, metabolic labelling studies showed that carrimycin significantly inhibited the synthesis of viral RNA. Our studies thus strongly suggest that carrimycin is an antiviral agent against a broad-spectrum of human coronaviruses and its therapeutic efficacy to COVID-19 is currently under clinical investigation.

Inhibitory effect of Qing-Fei-Pai-Du decoction on coronavirus in vitro

Qing-Fei-Pai-Du decoction (QFPDD) is a combination of traditional Chinese medicine and plays an important role in the treatment of coronavirus disease 2019 (COVID-19). This study investigated the inhibitory effect of QFPDD on coronavirus replication and antiviral mechanism. The cytotoxicity of QFPDD was determined by PrestoBlue cell viability assay. Quantitive reverse transcription PCR (qRT-PCR) and immunofluorescence assay (IF) were used to detect the inhibitory effects of QFPDD on coronavirus at RNA and protein levels. qRT-PCR was used to detect the adsorption and penetration of coronavirus after QFPDD treatment. The effects of QFPDD on interferon (IFN) and interferon-stimulated genes (ISGs) were also detected by qRT-PCR. The results showed that QFPDD inhibited coronavirus at RNA and protein levels in a dose-dependent manner at non-toxic concentration, and QFPDD targeted in the early stages of coronavirus infection cycle. Preliminary mechanism studies have shown that QFPDD can directly block the virus entry into the cell by inhibiting virus adsorption, and QFPDD can also play an antiviral role by up-regulating the expression of IFN and ISGs. These results indicate QFPDD as a drug potential to treat coronavirus infection.

[Mechanism and material basis of Lianhua Qingwen capsule for improving clinical cure rate of COVID-19: a study based on network pharmacology and molecular docking technology].

OBJECTIVE: To explore the potential targets, signal pathways and biological functions that mediate the effect of Lianhua Qingwen capsule in improving clinical cure rate of COVID-19 in light of network pharmacology and molecular docking technology. METHODS: TCMSP, Target, Prediction, CooLGeN, GeneCards, DAVID and other databases were searched for the active components and their target proteins from 13 herbs including Forsythia, Honeysuckle and roasted Ephedra used in Lianhua Qingwen capsule. The common target proteins, signal pathways and biological functions shared by these components and the clinical manifestations of COVID-19 (fever, cough, and fatigue) were identified to construct the network consisting of the component drugs in Lianhua Qingwen capsule, the active ingredients of, their targets of action, and the biological functions involved using Gephi software. RESULTS: A total 160 active components including MOL000522, and MOL003283, MOL003365, MOL003006, MOL003014 in 13 component drugs in Lianhua Qingwen capsule produced therapeutic effects against COVID-19 through 57 target proteins including MAPK1, IL6, HSP90AA1, TNF, and CCL2, involving 35 signaling pathways including NOD-like receptor signaling pathway and Toll-like receptor signaling pathway. The results of molecular docking showed that 83 chemical components had total scores no less than 5.0 for docking with 12 target proteins (including MAPK1, IL6, and HSP90AA1) with high binding activities to form stable conformations. The binding of MOL000522, MOL004989, and MOL003330 with MAPK1; MOL001495 and MOL001494 with NLRP3; MOL004908, MOL004863 and MOL004806 with HSP90AA1; MOL001749 with TLR9; and MOL001495 with AKT1 all had total scores exceeding 9.0. CONCLUSIONS: Lianhua Qingwen capsule contains multiple effective ingredients to improve clinical cure rate of COVID-19, and its therapeutic effect is mediated by multiple protein targets, signal pathways and biological functions.

[Mechanism of Qingfei Paidu decoction for treatment of COVID-19: analysis based on network pharmacology and molecular docking technology].

OBJECTIVE: To explore the target, signaling pathways and their biological functions of Qingfei Paidu Decoction in the treatment of COVID-19 based on network pharmacology and molecular docking technology. METHODS: The active components and target proteins in 21 drugs such as Ephedrae Herba and Pinelliae Rhizoma in Qingfei Paidu decoction were analyzed, and the signaling pathways and biological functions of the target proteins common with COVID-19 were screened by using TCMSP, Swiss Target Prediction, CooLGeN, GeneCards, DAVID and other databases. The network diagram of Qingfei Paidu decoction was constructed using Gephi software. RESULTS: We identified 163 active ingredients, including MOL004798, MOL000519, MOL004824, MOL000554, MOL010428, and MOL013443, from 18 drugs in Qingfei Paidu decoction (such as Ephedrae Herba, Pinelliae Rhizoma, Glycyrrhizae Radix Et Rhiizoma, Farfarae Flos, Asteris Radix Et Rhizoma and Aurantii Fructus Immaturus). These ingredients activate renin-angiotensin system signaling pathway and apoptosis signaling pathway by regulating 10 protein targets (ACE, ACE2, AGTR1, FURIN, TNF, CASP3, CASP6, DPP4, MCL1 and POLD1) to execute 42 biological functions such as renin-angiotensin regulation of blood volume and systemic arterial blood pressure to treat COVID-19. The results of preliminary molecular docking showed that MOL000519 (from Pinelliae Rhizoma), MOL000554 (from Farfarae Flos), MOL004798 (from Ephedrae Herba), MOL004824 (from Glycyrrhizae Radix Et Rhiizoma), MOL010428 (from Asteris Radix Et Rhizoma), and MOL013443 (from Aurantii Fructus Immaturus) had good affinity with SARS-CoV-2 3CL hydrolase to form complexes with stable conformations and high binding activity (binding energy ≤- 5 kJ/mol). CONCLUSIONS: Qingfei Paidu decoction can treat COVID-19 through its multiple medicinal ingredients that have multiple targets and involve multiple signaling pathways for different biological functions. Our finding provides reference for further investigation into the pharmacological mechanism of Qingfei Paidu decoction in treating COVID-19.