Metallodrug ranitidine bismuth citrate suppresses SARS-CoV-2 replication and relieves virus-associated pneumonia in Syrian hamsters

The Coronavirus helicase in replication

The coronavirus nonstructural protein (nsp) 13 encodes an RNA helicase (nsp13-HEL) with multiple enzymatic functions, including unwinding and nucleoside phosphatase (NTPase) activities. Attempts for enzymatic inactivation have defined the nsp13-HEL as a critical enzyme for viral replication and a high-priority target for antiviral development. Helicases have been shown to play numerous roles beyond their canonical ATPase and unwinding activities, though these functions are just beginning to be explored in coronavirus biology. Recent genetic and biochemical studies, as well as work in structurally-related helicases, have provided evidence that supports new hypotheses for the helicase's potential role in coronavirus replication. Here, we review several aspects of the coronavirus nsp13-HEL, including its reported and proposed functions in viral replication and highlight fundamental areas of research that may aid the development of helicase inhibitors.

A Repurposed Drug Interferes with Nucleic Acid to Inhibit the Dual Activities of Coronavirus Nsp13

The recent pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) highlighted a critical need to discover more effective antivirals. While therapeutics for SARS-CoV-2 exist, its nonstructural protein 13 (Nsp13) remains a clinically untapped target. Nsp13 is a helicase responsible for unwinding double-stranded RNA during viral replication and is essential for propagation. Like other helicases, Nsp13 has two active sites: a nucleotide binding site that hydrolyzes nucleoside triphosphates (NTPs) and a nucleic acid binding channel that unwinds double-stranded RNA or DNA. Targeting viral helicases with small molecules, as well as the identification of ligand binding pockets, have been ongoing challenges, partly due to the flexible nature of these proteins. Here, we use a virtual screen to identify ligands of Nsp13 from a collection of clinically used drugs. We find that a known ion channel inhibitor, IOWH-032, inhibits the dual ATPase and helicase activities of SARS-CoV-2 Nsp13 at low micromolar concentrations. Kinetic and binding assays, along with computational and mutational analyses, indicate that IOWH-032 interacts with the RNA binding interface, leading to displacement of nucleic acid substrate, but not bound ATP. Evaluation of IOWH-032 with microbial helicases from other superfamilies reveals that it is selective for coronavirus Nsp13. Furthermore, it remains active against mutants representative of observed SARS-CoV-2 variants. Overall, this work provides a new inhibitor for Nsp13 and provides a rationale for a recent observation that IOWH-032 lowers SARS-CoV-2 viral loads in human cells, setting the stage for the discovery of other potent viral helicase modulators.

Mechanistic insights into bismuth(iii) inhibition of SARS-CoV-2 helicase

The COVID-19 pandemic caused by SARS-CoV-2 resulted in a global public health crisis. In addition to vaccines, the development of effective therapy is highly desirable. Targeting a protein that plays a critical role in virus replication may allow pan-spectrum antiviral drugs to be developed. Among SARS-CoV-2 proteins, helicase (i.e., non-structural protein 13) is considered as a promising antiviral drug target due to its highly conserved sequence, unique structure and function. Herein, we demonstrate SARS-CoV-2 helicase as a target of bismuth-based antivirals in virus-infected mammalian cells by a metal-tagged antibody approach. To search for more potent bismuth-based antivirals, we further screened a panel of bismuth compounds towards inhibition of ATPase and DNA unwinding activity of nsp13 and identified a highly potent bismuth compound Bi(5-aminotropolonate)3, namely Bi(Tro-NH2)3 with an IC50 of 30 nM for ATPase. We show that bismuth-based compounds inhibited nsp13 unwinding activity via disrupting the binding of ATP and the DNA substrate to viral helicase. Binding of Bi(iii) to nsp13 also abolished the interaction between nsp12 and nsp13 as evidenced by immunofluorescence and co-immunoprecipitation assays. Finally, we validate our in vitro data in SARS-CoV-2 infected mammalian cells. Notably, Bi(6-TG)3 exhibited an EC50 of 1.18 ± 0.09 μM with a selective index of 847 in VeroE6-TMPRSS2 infected cells. This study highlights the important role of helicase for the development of more effective antiviral drugs to combat SARS-CoV-2 infection.

Allosteric Regulation and Inhibition of Coronavirus 3CLpro Revealed by HDX-MS

Coronavirus (CoV) infections have caused contagious and fatal respiratory diseases in humans worldwide. CoV 3-chymotrypsin-like proteases (3CLpro or Mpro) play an important role in viral maturation, and maintenance of their dimeric conformation is crucial for viral activity. Therefore, allosterically regulated dimerization of 3CLpro can be employed as a drug development target. Here, we investigated the allosteric regulatory mechanism of 3CLpro dimerization by using hydrogen/deuterium exchange coupled with mass spectrometry (HDX-MS) technology. We found that the FLAG tag directly coupled to the N-finger of 3CLpro significantly increased HDX kinetics at the dimer interface, and 3CLpro transformed from a dimer to a monomer. The 3CLpro mutants of SARS-CoV-2, which are monomeric, also exhibited increased deuterium exchange. Binding of the allosteric inhibitor Gastrodenol to most betacoronavirus 3CLpros led to increased allosteric deuterium exchange, resulting in the monomeric conformation of the CoV 3CLpro upon binding. Molecular dynamics (MD) simulation analysis further indicated the molecular mechanism of action of Gastrodenol on CoV 3CLpro: binding of Gastrodenol to SARS-CoV-2 3CLpro destroyed the hydrogen bond in the dimer interface. These results suggest that Gastrodenol may be a potential broad-spectrum anti-betacoronavirus drug.

COVID-19 drug discovery and treatment options

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused substantial morbidity and mortality, and serious social and economic disruptions worldwide. Unvaccinated or incompletely vaccinated older individuals with underlying diseases are especially prone to severe disease. In patients with non-fatal disease, long COVID affecting multiple body systems may persist for months. Unlike SARS-CoV and Middle East respiratory syndrome coronavirus, which have either been mitigated or remained geographically restricted, SARS-CoV-2 has disseminated globally and is likely to continue circulating in humans with possible emergence of new variants that may render vaccines less effective. Thus, safe, effective and readily available COVID-19 therapeutics are urgently needed. In this Review, we summarize the major drug discovery approaches, preclinical antiviral evaluation models, representative virus-targeting and host-targeting therapeutic options, and key therapeutics currently in clinical use for COVID-19. Preparedness against future coronavirus pandemics relies not only on effective vaccines but also on broad-spectrum antivirals targeting conserved viral components or universal host targets, and new therapeutics that can precisely modulate the immune response during infection.

Strategies for the development of metalloimmunotherapies

Metal ions play crucial roles in the regulation of immune pathways. In fact, metallodrugs have a long record of accomplishment as effective treatments for a wide range of diseases. Here we argue that the modulation of interactions of metal ions with molecules and cells involved in the immune system forms the basis of a new class of immunotherapies. By examining how metal ions modulate the innate and adaptive immune systems, as well as host-microbiota interactions, we discuss strategies for the development of such metalloimmunotherapies for the treatment of cancer and other immune-related diseases.

Role of the RAAS in mediating the pathophysiology of COVID-19

The renin-angiotensin-aldosterone system (RAAS) holds a position of paramount importance as enzymatic and endocrine homeostatic regulator concerning the water-electrolyte and acid-base balance. Nevertheless, its intricacy is influenced by the presence of various complementary angiotensins and their specific receptors, thereby modifying the primary RAAS actions. Angiotensin-converting enzyme 2 (ACE2) acts as a surface receptor for SARS-CoV-2, establishing an essential connection between RAAS and COVID-19 infection. Despite the recurring exploration of the RAAS impact on the trajectory of COVID-19 along with the successful resolution of many inquiries, its complete role in the genesis of delayed consequences encompassing long COVID and cardiovascular thrombotic outcomes during the post-COVID phase as well as post-vaccination, remains not fully comprehended. Particularly noteworthy is the involvement of the RAAS in the molecular mechanisms underpinning procoagulant processes throughout COVID-19. These processes significantly contribute to the pathogenesis of organ complications as well as determine clinical outcomes and are discussed in this manuscript.

Fusing Bismuth and Mercaptocarboranes: Design and Biological Evaluation of Low-Toxicity Antimicrobial Thiolato Complexes

This study proposes an innovative strategy to enhance the pharmacophore model of antimicrobial bismuth thiolato complex drugs by substituting hydrocarbon ligand structures with boron clusters, particularly icosahedral closo-dicarbadodecaborane (C2B10H12, carboranes). The hetero- and homoleptic mercaptocarborane complexes BiPh2L (1) and BiL3 (2) (L=9-S-1,2-C2B10H11) were prepared from 9-mercaptocarborane (HL) and triphenylbismuth. Comprehensive characterization using NMR, IR, MS, and XRD techniques confirmed their successful synthesis. Evaluation of antimicrobial activity in a liquid broth microdilution assay demonstrated micromolar to submicromolar minimum inhibitory concentrations (MIC) suggesting high effectiveness against S. aureus and limited efficacy against E. coli. This study highlights the potential of boron-containing bismuth complexes as promising antimicrobial agents, especially targeting Gram-positive bacteria, thus contributing to the advancement of novel therapeutic approaches.

UiO-66 nanoparticles combat influenza A virus in mice by activating the RIG-I-like receptor signaling pathway

The Influenza A virus (IAV) is a zoonotic pathogen that infects humans and various animal species. Infection with IAV can cause fever, anorexia, and dyspnea and is often accompanied by pneumonia characterized by an excessive release of cytokines (i.e., cytokine storm). Nanodrug delivery systems and nanoparticles are a novel approach to address IAV infections. Herein, UiO-66 nanoparticles (NPs) are synthesized using a high-temperature melting reaction. The in vitro and in vivo optimal concentrations of UiO-66 NPs for antiviral activity are 200 μg mL-1 and 60 mg kg-1, respectively. Transcriptome analysis revealed that UiO-66 NPs can activate the RIG-I-like receptor signaling pathway, thereby enhancing the downstream type I interferon antiviral effect. These NPs suppress inflammation-related pathways, including the FOXO, HIF, and AMPK signaling pathways. The inhibitory effect of UiO-66 NPs on the adsorption and entry of IAV into A549 cells is significant. This study presents novel findings that demonstrate the effective inhibition of IAV adsorption and entry into cells via UiO-66 NPs and highlights their ability to activate the cellular RIG-I-like receptor signaling pathway, thereby exerting an anti-IAV effect in vitro or in mice. These results provide valuable insights into the mechanism of action of UiO-66 NPs against IAV and substantial data for advancing innovative antiviral nanomedicine.

Development of Pan-Anti-SARS-CoV-2 Agents through Allosteric Inhibition of nsp14/nsp10 Complex

SARS-CoV-2 nsp14 functions both as an exoribonuclease (ExoN) together with its critical cofactor nsp10 and as an S-adenosyl methionine-dependent (guanine-N7) methyltransferase (MTase), which makes it an attractive target for the development of pan-anti-SARS-CoV-2 drugs. Herein, we screened a panel of compounds (and drugs) and found that certain compounds, especially Bi(III)-based compounds, could allosterically inhibit both MTase and ExoN activities of nsp14 potently. We further demonstrated that Bi(III) binds to both nsp14 and nsp10, resulting in the release of Zn(II) ions from the enzymes as well as alternation of protein quaternary structures. The in vitro activities of the compounds were also validated in SARS-CoV-2-infected mammalian cells. Importantly, we showed that nsp14 serves as an authentic target of Bi(III)-based antivirals in SARS-CoV-2-infected mammalian cells by quantification of both the protein and inhibitor. This study highlights the importance of nsp14/nsp10 as a potential target for the development of pan-antivirals against SARS-CoV-2 infection.

PMI-controlled mannose metabolism and glycosylation determines tissue tolerance and virus fitness

Host survival depends on the elimination of virus and mitigation of tissue damage. Herein, we report the modulation of D-mannose flux rewires the virus-triggered immunometabolic response cascade and reduces tissue damage. Safe and inexpensive D-mannose can compete with glucose for the same transporter and hexokinase. Such competitions suppress glycolysis, reduce mitochondrial reactive-oxygen-species and succinate-mediated hypoxia-inducible factor-1α, and thus reduce virus-induced proinflammatory cytokine production. The combinatorial treatment by D-mannose and antiviral monotherapy exhibits in vivo synergy despite delayed antiviral treatment in mouse model of virus infections. Phosphomannose isomerase (PMI) knockout cells are viable, whereas addition of D-mannose to the PMI knockout cells blocks cell proliferation, indicating that PMI activity determines the beneficial effect of D-mannose. PMI inhibition suppress a panel of virus replication via affecting host and viral surface protein glycosylation. However, D-mannose does not suppress PMI activity or virus fitness. Taken together, PMI-centered therapeutic strategy clears virus infection while D-mannose treatment reprograms glycolysis for control of collateral damage.

H. Pylori Treatment in the COVID-19 Era. What Have We Learned So Far?

PURPOSE OF REVIEW

CoronaVirus Disease of 2019 (COVID-19) has negatively influenced the management of multiple conditions in regards to the gastroenterology patient. An equivalent change in the management of Helicobacter pylori (H. pylori)-related diseases was reported, as practically no eradication treatment was offered during most of the pandemic. Given the scarcity of published data, we performed a literature review trying to elucidate the effect of COVID-19 on H. pylori treatment.

RECENT FINDINGS

COVID-19 has produced more questions than answers as to the outcome of COVID-19 in H. Pylori infected patients, post-COVID-19 patients treated for H. pylori, acid suppression and COVID-19 incidence and outcomes, and H. pylori eradication treatment in patients having recovered from COVID-19. We strongly believe that this scientific uncertainty produced by the COVID-19 pandemic has set up the stage for an incremental change in H. pylori treatment as COVID-19 has offered us the chance to speed up how we will, in the near future, approach patients with a possible Η. pylori infection.

Bioactive Bismuth Compounds: Is Their Toxicity a Barrier to Therapeutic Use?

Bismuth compounds are considered relatively non-toxic, with their low solubility in aqueous solutions (e.g., biological fluids) being the major contributing factor to this property. Bismuth derivatives are widely used for the treatment of peptic ulcers, functional dyspepsia, and chronic gastritis. Moreover, the properties of bismuth compounds have also been extensively explored in two main fields of action: antimicrobial and anticancer. Despite the clinical interest of bismuth-based drugs, several side effects have also been reported. In fact, excessive acute ingestion of bismuth, or abuse for an extended period of time, can lead to toxicity. However, evidence has demonstrated that the discontinuation of these compounds usually reverses their toxic effects. Notwithstanding, the continuously growing use of bismuth products suggests that it is indeed part of our environment and our daily lives, which urges a more in-depth review and investigation into its possible undesired activities. Therefore, this review aims to update the pharmaco-toxicological properties of bismuth compounds. A special focus will be given to in vitro, in vivo, and clinical studies exploring their toxicity.

Multi-omics for COVID-19: driving development of therapeutics and vaccines

The ongoing COVID-19 pandemic caused by SARS-CoV-2 has raised global concern for public health and economy. The development of therapeutics and vaccines to combat this virus is continuously progressing. Multi-omics approaches, including genomics, transcriptomics, proteomics, metabolomics, epigenomics and metallomics, have helped understand the structural and molecular features of the virus, thereby assisting in the design of potential therapeutics and accelerating vaccine development for COVID-19. Here, we provide an up-to-date overview of the latest applications of multi-omics technologies in strategies addressing COVID-19, in order to provide suggestions towards the development of highly effective knowledge-based therapeutics and vaccines.

Biological Activities of Bismuth Compounds: An Overview of the New Findings and the Old Challenges Not Yet Overcome

Bismuth-based drugs have been used primarily to treat ulcers caused by Helicobacter pylori and other gastrointestinal ailments. Combined with antibiotics, these drugs also possess synergistic activity, making them ideal for multiple therapy regimens and overcoming bacterial resistance. Compounds based on bismuth have a low cost, are safe for human use, and some of them are also effective against tumoral cells, leishmaniasis, fungi, and viruses. However, these compounds have limited bioavailability in physiological environments. As a result, there is a growing interest in developing new bismuth compounds and approaches to overcome this challenge. Considering the beneficial properties of bismuth and the importance of discovering new drugs, this review focused on the last decade's updates involving bismuth compounds, especially those with potent activity and low toxicity, desirable characteristics for developing new drugs. In addition, bismuth-based compounds with dual activity were also highlighted, as well as their modes of action and structure-activity relationship, among other relevant discoveries. In this way, we hope this review provides a fertile ground for rationalizing new bismuth-based drugs.

Silver N-heterocyclic carbene complexes are potent uncompetitive inhibitors of the papain-like protease with antiviral activity against SARS-CoV-2

The ongoing SARS-CoV-2 pandemic has caused a high demand for novel innovative antiviral drug candidates. Despite promising results, metal complexes have been relatively unexplored as antiviral agents in general and in particular against SARS-CoV-2. Here we report on silver NHC complexes with chloride or iodide counter ligands that are potent inhibitors of the SARS-CoV-2 papain-like protease (PL^pro) but inactive against 3C-like protease (3CL^pro) as another SARS-CoV-2 protease. Mechanistic studies on a selected complex confirmed zinc removal from a zinc binding domain of PL^pro as relevant factor of their activity. In addition, enzyme kinetic experiments revealed that the complex is an uncompetitive inhibitor and with this rare type of inhibition it offers great pharmacological advantages in terms selectivity. The silver NHC complexes with iodide ligands showed very low or absent host cell toxicity and triggered strong effects on viral replication in cells infected with SARS-CoV-2, making them promising future antiviral drug candidates.

Exploring the Inhibitory Effect of AgBiS2 Nanoparticles on Influenza Viruses

Influenza viruses are respiratory pathogens that are major threats to human health. Due to the emergence of drug-resistant strains, the use of traditional anti-influenza drugs has been hindered. Therefore, the development of new antiviral drugs is critical. In this article, AgBiS₂ nanoparticles were synthesized at room temperature, using the bimetallic properties of the material itself to explore its inhibitory effect on the influenza virus. By comparing the synthesized Bi₂S₃ and Ag₂S nanoparticles, it is found that after adding the silver element, the synthesized AgBiS₂ nanoparticles have a significantly better inhibitory effect on influenza virus infection than Bi₂S₃ and Ag₂S nanoparticles. Recent studies have shown that the inhibitory effect of AgBiS₂ nanoparticles on the influenza virus mainly occurs in the stages of influenza virus-cell internalization and intracellular replication. In addition, it is found that AgBiS₂ nanoparticles also have prominent antiviral properties against α and β coronaviruses, indicating that AgBiS₂ nanoparticles have significant potential in inhibiting viral activity.

In vitro high-content tissue models to address precision medicine challenges

The field of precision medicine allows for tailor-made treatments specific to a patient and thereby improve the efficiency and accuracy of disease prevention, diagnosis, and treatment and at the same time would reduce the cost, redundant treatment, and side effects of current treatments. Here, the combination of organ-on-a-chip and bioprinting into engineering high-content in vitro tissue models is envisioned to address some precision medicine challenges. This strategy could be employed to tackle the current coronavirus disease 2019 (COVID-19), which has made a significant impact and paradigm shift in our society. Nevertheless, despite that vaccines against COVID-19 have been successfully developed and vaccination programs are already being deployed worldwide, it will likely require some time before it is available to everyone. Furthermore, there are still some uncertainties and lack of a full understanding of the virus as demonstrated in the high number new mutations arising worldwide and reinfections of already vaccinated individuals. To this end, efficient diagnostic tools and treatments are still urgently needed. In this context, the convergence of bioprinting and organ-on-a-chip technologies, either used alone or in combination, could possibly function as a prominent tool in addressing the current pandemic. This could enable facile advances of important tools, diagnostics, and better physiologically representative in vitro models specific to individuals allowing for faster and more accurate screening of therapeutics evaluating their efficacy and toxicity. This review will cover such technological advances and highlight what is needed for the field to mature for tackling the various needs for current and future pandemics as well as their relevancy towards precision medicine.

Protein structure-based in-silico approaches to drug discovery: Guide to COVID-19 therapeutics

With more than 5 million fatalities and close to 300 million reported cases, COVID-19 is the first documented pandemic due to a coronavirus that continues to be a major health challenge. Despite being rapid, uncontrollable, and highly infectious in its spread, it also created incentives for technology development and redefined public health needs and research agendas to fast-track innovations to be translated. Breakthroughs in computational biology peaked during the pandemic with renewed attention to making all cutting-edge technology deliver agents to combat the disease. The demand to develop effective treatments yielded surprising collaborations from previously segregated fields of science and technology. The long-standing pharmaceutical industry's aversion to repurposing existing drugs due to a lack of exponential financial gain was overrun by the health crisis and pressures created by front-line researchers and providers. Effective vaccine development even at an unprecedented pace took more than a year to develop and commence trials. Now the emergence of variants and waning protections during the booster shots is resulting in breakthrough infections that continue to strain health care systems. As of now, every protein of SARS-CoV-2 has been structurally characterized and related host pathways have been extensively mapped out. The research community has addressed the druggability of a multitude of possible targets. This has been made possible due to existing technology for virtual computer-assisted drug development as well as new tools and technologies such as artificial intelligence to deliver new leads. Here in this article, we are discussing advances in the drug discovery field related to target-based drug discovery and exploring the implications of known target-specific agents on COVID-19 therapeutic management. The current scenario calls for more personalized medicine efforts and stratifying patient populations early on for their need for different combinations of prognosis-specific therapeutics. We intend to highlight target hotspots and their potential agents, with the ultimate goal of using rational design of new therapeutics to not only end this pandemic but also uncover a generalizable platform for use in future pandemics.

Coronaviruses SARS-CoV, MERS-CoV, and SARS-CoV-2 helicase inhibitors: A systematic review of in vitro studies

Introduction

The recent outbreak of SARS-CoV-2 significantly increased the need to find inhibitors that target the essential enzymes for virus replication in the host cells. This systematic review was conducted to identify potential inhibitors of SARS-CoV, MERS-CoV, and SARS-CoV-2 helicases that have been tested by in vitro methods. The inhibition mechanisms of these compounds were discussed in this review, in addition to their cytotoxic and viral infection protection properties.

Methods

The databases PUBMED/MEDLINE, EMBASE, SCOPUS, and Web of Science were searched using different combinations of the keywords "helicase", "nsp13", "inhibitors", "coronaviridae", "coronaviruses", "virus replication", "replication", and "antagonists and inhibitors".

Results

By the end of this search, a total of 6854 articles had been identified. Thirty-one articles were included in this review. These studies reported the inhibitory effects of 309 compounds on SARS-CoV, MERS-CoV, and SARS-CoV-2 helicase activities measured by in vitro methods. Helicase inhibitors were categorized according to the type of coronavirus and the type of tested enzymatic activity, nature, approval, inhibition level, cytotoxicity, and viral infection protection effects. These inhibitors are classified according to the site of their interaction with the coronavirus helicases into four types: zinc-binding site inhibitors, nucleic acid binding site inhibitors, nucleotide-binding site inhibitors, and inhibitors with no clear interaction site.

Conclusion

Evidence from in vitro studies suggests that helicase inhibitors have a high potential as antiviral agents. Several helicase inhibitors tested in vitro showed good antiviral activities while maintaining moderate cytotoxicity. These inhibitors should be clinically investigated to determine their efficiency in treating different coronavirus infections, particularly COVID-19.

Organic-Inorganic Hybrid Nanocomposites for Nanotheranostics: Special Focus on Preventing Emerging Variants of SARS-COV-2

The worldwide emerging cases of various respiratory viral diseases and the current escalation of novel coronavirus disease (COVID-19) make people considerably attentive to controlling these viruses through innovative methods. Most re-emerging respiratory diseases envelop RNA viruses that employ attachment between the virus and host cell to get an entry form using the host cell machinery. Emerging variants of COVD-19 also bring about a constant threat to public health as it has wide infectivity and can quickly spread to infect humans. This review focuses on insights into the current investigations to prevent the progression of incipient variants of Severe Acute Respiratory Syndrome Coronavirus (SARS-COV-2) along with similar enveloped RNA viruses that cause respiratory illness in humans and animals. Nanotheranostics is a trailblazing arena of nanomedicine that simultaneously helps prevent or treat diseases and diagnoses. Nanoparticle coating and nanofibers were extensively explored, preventing viral contaminations. Several studies have proven the virucidal activities of metal nanoparticles like copper, silver, and titanium against respiratory viral pathogens. Worldwide many researchers have shown surfaces coated with ionic nanoparticles like zinc or titanium act as potent antiviral agents against RNA viruses. Carbon nanotubes, quantum dots, silica nanoparticles (NPs), polymeric and metallic nanoparticles have also been explored in the field of nanotheranostics in viral detection. In this review, we have comprehensively discussed different types of metallic, ionic, organic nanoparticles and their hybrids showing substantial antiviral properties to stop the progression of the novel coronavirus disease focused on three key classes: prevention, diagnostics, and treatment.

A Comprehensive Survey on the Expediated Anti-COVID-19 Options Enabled by Metal Complexes-Tasks and Trials

Contemporary pharmacology dating back to the late 19th/early 20th centuries has benefitted largely from the incorporation of metal complexes. Various biological attributes have been successfully realized using metal/metal complex-based drugs. Among anticancer, antimicrobial, and antiviral applications, anticancer applications have extracted the maximum benefit from the metal complex, Cisplatin. The following review has compiled the various antiviral benefits harnessed through inputs from metal complexes. As a result of exploiting the pharmacological aspects of metal complexes, the anti-COVID-19 deliverables have been summarized. The challenges ahead, the gaps in this research area, the need to improvise incorporating nanoaspects in metal complexes, and the need to test metal complex-based drugs in clinical trials have been discussed and deliberated. The pandemic shook the entire world and claimed quite a percentage of the global population. Metal complex-based drugs are already established for their antiviral property with respect to enveloped viruses and extrapolating them for COVID-19 can be an effective way to manipulate drug resistance and mutant issues that the current anti-COVID-19 drugs are facing.

Inorganic Drugs as a Tool for Protein Structure Solving and Studies on Conformational Changes

Inorganic drugs are capable of tight interactions with proteins through coordination towards aminoacidic residues, and this feature is recognized as a key aspect for their pharmacological action. However, the "protein metalation process" is exploitable for solving the phase problem and structural resolution. In fact, the use of inorganic drugs bearing specific metal centers and ligands capable to drive the binding towards the desired portions of the protein target could represent a very intriguing and fruitful strategy. In this context, a theoretical approach may further contribute to solve protein structures and their refinement. Here, we delineate the main features of a reliable experimental-theoretical integrated approach, based on the use of metallodrugs, for protein structure solving.

Antiviral Potential of Selected N-Methyl-N-phenyl Dithiocarbamate Complexes against Human Immunodeficiency Virus (HIV)

Despite the use of highly active antiretroviral therapy approved by the United States Food and Drug Administration (FDA) for the treatment of human immunodeficiency virus (HIV) infection, HIV remains a public health concern due to the inability of the treatment to eradicate the virus. In this study, N-methyl-N-phenyl dithiocarbamate complexes of indium(III), bismuth(III), antimony(III), silver(I), and copper(II) were synthesized. The complexes were characterized by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The N-methyl-N-phenyl dithiocarbamate complexes were then evaluated for their antiviral effects against HIV-1 subtypes A (Q168), B (QHO.168), and C (CAP210 and ZM53). The results showed that the copper(II)-bis (N-methyl-N-phenyl dithiocarbamate) complex had a neutralization efficiency of 94% for CAP210, 54% for ZM53, 45% for Q168, and 63% for QHO.168. The silver(I)-bis (N-methyl-N-phenyl dithiocarbamate) complex showed minimal neutralization efficiency against HIV, while indium(III) and antimony(III) N-methyl-N-phenyl dithiocarbamate complexes had no antiviral activity against HIV-1. The findings revealed that copper(II)-bis (N-methyl-N-phenyl dithiocarbamate), with further improvement, could be explored as an alternative entry inhibitor for HIV.

In Silico Binding of 2-Aminocyclobutanones to SARS-CoV-2 Nsp13 Helicase and Demonstration of Antiviral Activity

The landscape of viral strains and lineages of SARS-CoV-2 keeps changing and is currently dominated by Delta and Omicron variants. Members of the latest Omicron variants, including BA.1, are showing a high level of immune evasion, and Omicron has become a prominent variant circulating globally. In our search for versatile medicinal chemistry scaffolds, we prepared a library of substituted ɑ-aminocyclobutanones from an ɑ-aminocyclobutanone synthon (11). We performed an in silico screen of this actual chemical library as well as other virtual 2-aminocyclobutanone analogs against seven SARS-CoV-2 nonstructural proteins to identify potential drug leads against SARS-CoV-2, and more broadly against coronavirus antiviral targets. Several of these analogs were initially identified as in silico hits against SARS-CoV-2 nonstructural protein 13 (Nsp13) helicase through molecular docking and dynamics simulations. Antiviral activity of the original hits as well as ɑ-aminocyclobutanone analogs that were predicted to bind more tightly to SARS-CoV-2 Nsp13 helicase are reported. We now report cyclobutanone derivatives that exhibit anti-SARS-CoV-2 activity. Furthermore, the Nsp13 helicase enzyme has been the target of relatively few target-based drug discovery efforts, in part due to a very late release of a high-resolution structure accompanied by a limited understanding of its protein biochemistry. In general, antiviral agents initially efficacious against wild-type SARS-CoV-2 strains have lower activities against variants due to heavy viral loads and greater turnover rates, but the inhibitors we are reporting have higher activities against the later variants than the wild-type (10–20X). We speculate this could be due to Nsp13 helicase being a critical bottleneck in faster replication rates of the new variants, so targeting this enzyme affects these variants to an even greater extent. This work calls attention to cyclobutanones as a useful medicinal chemistry scaffold, and the need for additional focus on the discovery of Nsp13 helicase inhibitors to combat the aggressive and immune-evading variants of concern (VOCs).

A micro-sized vaccine based on recombinant Lactiplantibacillus plantarum fights against SARS-CoV-2 infection via intranasal immunization

COVID-19 has globally spread to burden the medical system. Even with a massive vaccination, a mucosal vaccine offering more comprehensive and convenient protection is imminent. Here, a micro-sized vaccine based on recombinant Lactiplantibacillus plantarum (rLP) displaying spike or receptor-binding domain (RBD) was characterized as microparticles, and its safety and protective effects against SARS-CoV-2 were evaluated. We found a 66.7% mortality reduction and 100% protection with rLP against SARS-CoV-2 in a mouse model. The histological analysis showed decreased hemorrhage symptoms and increased leukocyte infiltration in the lung. Especially, rLP:RBD significantly decreased pulmonary viral loads. For the first time, our study provides a Lactiplantibacillus plantarum-vectored vaccine to prevent COVID-19 progress and transmission via intranasal vaccination.

Hypothesis: Efficacy of early treatments with some NSAIDs in COVID-19: Might it also depend on their direct and/or indirect zinc chelating ability?

The present work argues for the involvement of the zinc chelating ability of some non-steroidal anti-inflammatory drugs as an additive mechanism able to increase their efficacy against COVID-19.

Bafilomycin A1 inhibits SARS-CoV-2 infection in a human lung xenograft mouse model

Coronavirus disease 2019 is a global pandemic caused by SARS-CoV-2. The emergence of its variant strains has posed a considerable challenge to clinical treatment. Therefore, drugs capable of inhibiting SARS-CoV-2 infection, regardless of virus variations, are in urgently need. Our results showed that the endosomal acidification inhibitor, Bafilomycin A1 (Baf-A1), had an inhibitory effect on the viral RNA synthesis of SARS-CoV-2, and its Beta and Delta variants at the concentration of 500 nM. Moreover, the human lung xenograft mouse model was used to investigate the anti-SARS-CoV-2 effect of Baf-A1. It was found that Baf-A1 significantly inhibited SARS-CoV-2 replication in the human lung xenografts by in situ hybridization and RT-PCR assays. Histopathological examination showed that Baf-A1 alleviated SARS-CoV-2-induced diffuse inflammatory infiltration of granulocytes and macrophages and alveolar endothelial cell death in human lung xenografts. In addition, immunohistochemistry analysis indicated that Baf-A1 decreased inflammatory exudation and infiltration in SARS-CoV-2-infected human lung xenografts. Therefore, Baf-A1 may be a candidate drug for SARS-CoV-2 treatment.

Interaction of copper potential metallodrugs with TMPRSS2: A comparative study of docking tools and its implications on COVID-19

SARS-CoV-2 is the virus responsible for the COVID-19 pandemic. For the virus to enter the host cell, its spike (S) protein binds to the ACE2 receptor, and the transmembrane protease serine 2 (TMPRSS2) cleaves the binding for the fusion. As part of the research on COVID-19 treatments, several Casiopeina-analogs presented here were looked at as TMPRSS2 inhibitors. Using the DFT and conceptual-DFT methods, it was found that the global reactivity indices of the optimized molecular structures of the inhibitors could be used to predict their pharmacological activity. In addition, molecular docking programs (AutoDock4, Molegro Virtual Docker, and GOLD) were used to find the best potential inhibitors by looking at how they interact with key amino acid residues (His296, Asp 345, and Ser441) in the catalytic triad. The results show that in many cases, at least one of the amino acids in the triad is involved in the interaction. In the best cases, Asp435 interacts with the terminal nitrogen atoms of the side chains in a similar way to inhibitors such as nafamostat, camostat, and gabexate. Since the copper compounds localize just above the catalytic triad, they could stop substrates from getting into it. The binding energies are in the range of other synthetic drugs already on the market. Because serine protease could be an excellent target to stop the virus from getting inside the cell, the analyzed complexes are an excellent place to start looking for new drugs to treat COVID-19.

Metalloproteome of human-infective RNA viruses: a study towards understanding the role of metal ions in virology

Metalloproteins and metal-based inhibitors have been shown to effectively combat infectious diseases, particularly those caused by RNA viruses. In this study, a diverse set of bioinformatics methods was employed to identify metal-binding proteins of human RNA viruses. Seventy-three viral proteins with a high probability of being metal-binding proteins were identified. These proteins included 40 zinc-, 47 magnesium- and 14 manganese-binding proteins belonging to 29 viral species and eight significant viral families, including Coronaviridae, Flaviviridae and Retroviridae. Further functional characterization has revealed that these proteins play a critical role in several viral processes, including viral replication, fusion and host viral entry. They fall under the essential categories of viral proteins, including polymerase and protease enzymes. Magnesium ion is abundantly predicted to interact with these viral enzymes, followed by zinc. In addition, this study also examined the evolutionary aspects of predicted viral metalloproteins, offering essential insights into the metal utilization patterns among different viral species. The analysis indicates that the metal utilization patterns are conserved within the functional classes of the proteins. In conclusion, the findings of this study provide significant knowledge on viral metalloproteins that can serve as a valuable foundation for future research in this area.

Therapeutic potential of compounds targeting SARS-CoV-2 helicase

The economical and societal impact of COVID-19 has made the development of vaccines and drugs to combat SARS-CoV-2 infection a priority. While the SARS-CoV-2 spike protein has been widely explored as a drug target, the SARS-CoV-2 helicase (nsp13) does not have any approved medication. The helicase shares 99.8% similarity with its SARS-CoV-1 homolog and was shown to be essential for viral replication. This review summarizes and builds on existing research on inhibitors of SARS-CoV-1 and SARS-CoV-2 helicases. Our analysis on the toxicity and specificity of these compounds, set the road going forward for the repurposing of existing drugs and the development of new SARS-CoV-2 helicase inhibitors.

Age-associated SARS-CoV-2 breakthrough infection and changes in immune response in a mouse model

Older individuals are at higher risk of SARS-CoV-2 infection and severe outcomes, but the underlying mechanisms are incompletely understood. In addition, how age modulates SARS-CoV-2 re-infection and vaccine breakthrough infections remain largely unexplored. Here, we investigated age-associated SARS-CoV-2 pathogenesis, immune responses, and the occurrence of re-infection and vaccine breakthrough infection utilizing a wild-type C57BL/6N mouse model. We demonstrated that interferon and adaptive antibody response upon SARS-CoV-2 challenge are significantly impaired in aged mice compared to young mice, which results in more effective virus replications and severe disease manifestations in the respiratory tract. Aged mice also showed increased susceptibility to re-infection due to insufficient immune protection acquired during the primary infection. Importantly, two-dose COVID-19 mRNA vaccination conferred limited adaptive immune response among the aged mice, making them susceptible to SARS-CoV-2 infection. Collectively, our findings call for tailored and optimized treatments and prevention strategies against SARS-CoV-2 among older individuals.

Rapid synthesis of bismuth-organic frameworks as selective antimicrobial materials against microbial biofilms

Antibiotic resistance is a global public health threat, and urgent actions should be undertaken for developing alternative antimicrobial strategies and approaches. Notably, bismuth drugs exhibit potent antimicrobial effects on various pathogens and promising efficacy in tackling SARS-CoV-2 and related infections. As such, bismuth-based materials could precisely combat pathogenic bacteria and effectively treat the resultant infections and inflammatory diseases through a controlled release of Bi ions for targeted drug delivery. Currently, it is a great challenge to rapidly and massively manufacture bismuth-based particles, and yet there are no reports on effectively constructing such porous antimicrobial-loaded particles. Herein, we have developed two rapid approaches (i.e., ultrasound-assisted and agitation-free methods) to synthesizing bismuth-based materials with ellipsoid- (Ellipsoids) and rod-like (Rods) morphologies respectively, and fully characterized physicochemical properties. Rods with a porous structure were confirmed as bismuth metal-organic frameworks (Bi-MOF) and aligned with the crystalline structure of CAU-17. Importantly, the formation of Rods was a 'two-step' crystallization process of growing almond-flake-like units followed by stacking into the rod-like structure. The size of Bi-MOF was precisely controlled from micro-to nano-scales by varying concentrations of metal ions and their ratio to the ligand. Moreover, both Ellipsoids and Rods showed excellent biocompatibility with human gingival fibroblasts and potent antimicrobial effects on the Gram-negative oral pathogens including Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Fusobacterium nucleatum. Both Ellipsoids and Rods at 50 ​μg/mL could disrupt the bacterial membranes, and particularly eliminate P. gingivalis biofilms. This study demonstrates highly efficient and facile approaches to synthesizing bismuth-based particles. Our work could enrich the administration modalities of metallic drugs for promising antibiotic-free healthcare.

Targeting papain-like protease for broad-spectrum coronavirus inhibition

The emergence of SARS-CoV-2 variants of concern and repeated outbreaks of coronavirus epidemics in the past two decades emphasize the need for next-generation pan-coronaviral therapeutics. Drugging the multi-functional papain-like protease (PLpro) domain of the viral nsp3 holds promise. However, none of the known coronavirus PLpro inhibitors has been shown to be in vivo active. Herein, we screened a structurally diverse library of 50,080 compounds for potential coronavirus PLpro inhibitors and identified a noncovalent lead inhibitor F0213 that has broad-spectrum anti-coronaviral activity, including against the Sarbecoviruses (SARS-CoV-1 and SARS-CoV-2), Merbecovirus (MERS-CoV), as well as the Alphacoronavirus (hCoV-229E and hCoV-OC43). Importantly, F0213 confers protection in both SARS-CoV-2-infected hamsters and MERS-CoV-infected human DPP4-knockin mice. F0213 possesses a dual therapeutic functionality that suppresses coronavirus replication via blocking viral polyprotein cleavage, as well as promoting antiviral immunity by antagonizing the PLpro deubiquitinase activity. Despite the significant difference of substrate recognition, mode of inhibition studies suggest that F0213 is a competitive inhibitor against SARS2-PLpro via binding with the 157K amino acid residue, whereas an allosteric inhibitor of MERS-PLpro interacting with its 271E position. Our proof-of-concept findings demonstrated that PLpro is a valid target for the development of broad-spectrum anti-coronavirus agents. The orally administered F0213 may serve as a promising lead compound for combating the ongoing COVID-19 pandemic and future coronavirus outbreaks.

Human early syncytiotrophoblasts are highly susceptible to SARS-CoV-2 infection

Direct in vivo investigation of human placenta trophoblast's susceptibility to SARS-CoV-2 is challenging. Here we report that human trophoblast stem cells (hTSCs) and their derivatives are susceptible to SARS-CoV-2 infection, which reveals heterogeneity in hTSC cultures. Early syncytiotrophoblasts (eSTBs) generated from hTSCs have enriched transcriptomic features of peri-implantation trophoblasts, express high levels of angiotensin-converting enzyme 2 (ACE2), and are productively infected by SARS-CoV-2 and its Delta and Omicron variants to produce virions. Antiviral drugs suppress SARS-CoV-2 replication in eSTBs and antagonize the virus-induced blockage of STB maturation. Although less susceptible to SARS-CoV-2 infection, trophoblast organoids originating from hTSCs show detectable viral replication reminiscent of the uncommon placental infection. These findings implicate possible risk of COVID-19 infection in peri-implantation embryos, which may go unnoticed. Stem cell-derived human trophoblasts such as eSTBs can potentially provide unlimited amounts of normal and genome-edited cells and facilitate coronavirus research and antiviral discovery.

A molecularly engineered, broad-spectrum anti-coronavirus lectin inhibits SARS-CoV-2 and MERS-CoV infection in vivo

"Pan-coronavirus" antivirals targeting conserved viral components can be designed. Here, we show that the rationally engineered H84T-banana lectin (H84T-BanLec), which specifically recognizes high mannose found on viral proteins but seldom on healthy human cells, potently inhibits Middle East respiratory syndrome coronavirus (MERS-CoV), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (including Omicron), and other human-pathogenic coronaviruses at nanomolar concentrations. H84T-BanLec protects against MERS-CoV and SARS-CoV-2 infection in vivo. Importantly, intranasally and intraperitoneally administered H84T-BanLec are comparably effective. Mechanistic assays show that H84T-BanLec targets virus entry. High-speed atomic force microscopy depicts real-time multimolecular associations of H84T-BanLec dimers with the SARS-CoV-2 spike trimer. Single-molecule force spectroscopy demonstrates binding of H84T-BanLec to multiple SARS-CoV-2 spike mannose sites with high affinity and that H84T-BanLec competes with SARS-CoV-2 spike for binding to cellular ACE2. Modeling experiments identify distinct high-mannose glycans in spike recognized by H84T-BanLec. The multiple H84T-BanLec binding sites on spike likely account for the drug compound's broad-spectrum antiviral activity and the lack of resistant mutants.

Advances in nanotechnology application in biosafety materials: A crucial response to COVID-19 pandemic

The outbreak of coronavirus disease 2019 (COVID-19) has adversely affected the public domain causing unprecedented cases and high mortality across the globe. This has brought back the concept of biosafety into the spotlight to solve biosafety problems in developing diagnostics and therapeutics to treat COVID-19. The advances in nanotechnology and material science in combination with medicinal chemistry have provided a new perspective to overcome this crisis. Herein, we discuss the efforts of researchers in the field of material science in developing personal protective equipment (PPE), detection devices, vaccines, drug delivery systems, and medical equipment. Such a synergistic approach of disciplines can strengthen the research to develop biosafety products in solving biosafety problems.

Structural Reshaping of the Zinc-Finger Domain of the SARS-CoV-2 nsp13 Protein Using Bismuth(III) Ions: A Multilevel Computational Study

The identification of novel therapeutics against the pandemic SARS-CoV-2 infection is an indispensable new address of current scientific research. In the search for anti-SARS-CoV-2 agents as alternatives to the vaccine or immune therapeutics whose efficacy naturally degrades with the occurrence of new variants, the salts of Bi³⁺ have been found to decrease the activity of the Zn²⁺-dependent non-structural protein 13 (nsp13) helicase, a key component of the SARS-CoV-2 molecular tool kit. Here, we present a multilevel computational investigation based on the articulation of DFT calculations, classical MD simulations, and MIF analyses, focused on the examination of the effects of Bi³⁺/Zn²⁺ exchange on the structure and molecular interaction features of the nsp13 protein. Our calculations confirmed that Bi³⁺ ions can replace Zn²⁺ in the zinc-finger metal centers and cause slight but appreciable structural modifications in the zinc-binding domain of nsp13. Nevertheless, by employing an in-house-developed ATOMIF tool, we evidenced that such a Bi³⁺/Zn²⁺ exchange may decrease the extension of a specific hydrophobic portion of nsp13, responsible for the interaction with the nsp12 protein. The present study provides for a detailed, atomistic insight into the potential anti-SARS-CoV-2 activity of Bi³⁺ and, more generally, evidences the hampering of the nsp13–nsp12 interaction as a plausible therapeutic strategy.

The Zn²⁺/Bi³⁺ exchange in the zinc finger domains of SARS-CoV-2 nsp13 hampers the viral machinery

Antiviral Activity of N1,N3-Disubstituted Uracil Derivatives against SARS-CoV-2 Variants of Concern

Despite the widespread use of the COVID-19 vaccines, the search for effective antiviral drugs for the treatment of patients infected with SARS-CoV-2 is still relevant. Genetic variability leads to the continued circulation of new variants of concern (VOC). There is a significant decrease in the effectiveness of antibody-based therapy, which raises concerns about the development of new antiviral drugs with a high spectrum of activity against VOCs. We synthesized new analogs of uracil derivatives where uracil was substituted at the N₁ and N₃ positions. Antiviral activity was studied in Vero E6 cells against VOC, including currently widely circulating SARS-CoV-2 Omicron. All synthesized compounds of the panel showed a wide antiviral effect. In addition, we determined that these compounds inhibit the activity of recombinant SARS-CoV-2 RdRp. Our study suggests that these non-nucleoside uracil-based analogs may be of future use as a treatment for patients infected with circulating SARS-CoV-2 variants.

SARS-CoV-2 ORF8 is a viral cytokine regulating immune responses

Many patients with severe COVID-19 suffer from pneumonia and the elucidation of the mechanisms underlying the development of this severe condition is important. The in vivo function of the ORF8 protein secreted by SARS-CoV-2 is not well understood. Here, we analyzed the function of ORF8 protein by generating ORF8-knockout SARS-CoV-2 and found that the lung inflammation observed in wild-type SARS-CoV-2-infected hamsters was decreased in ORF8-knockout SARS-CoV-2-infected hamsters. Administration of recombinant ORF8 protein to hamsters also induced lymphocyte infiltration into the lungs. Similar pro-inflammatory cytokine production was observed in primary human monocytes treated with recombinant ORF8 protein. Furthermore, we demonstrated that the serum ORF8 protein levels are well-correlated with clinical markers of inflammation. These results demonstrated that the ORF8 protein is a SARS-CoV-2 viral cytokine involved in the immune dysregulation observed in COVID-19 patients, and that the ORF8 protein could be a novel therapeutic target in severe COVID-19 patients.

SARS-CoV-2 hijacks macropinocytosis to facilitate its entry and promote viral spike-mediated cell-to-cell fusion

Revealing the mechanisms of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry and cell-to-cell spread might provide insights for understanding the underlying mechanisms of viral pathogenesis, tropism, and virulence. The signaling pathways involved in SARS-CoV-2 entry and viral spike–mediated cell-to-cell fusion remain elusive. In the current study, we found that macropinocytosis inhibitors significantly suppressed SARS-CoV-2 infection at both the entry and viral spike–mediated cell-to-cell fusion steps. We demonstrated that SARS-CoV-2 entry required the small GTPase Rac1 and its effector kinase p21-activated kinase 1 by dominant-negative and RNAi assays in human embryonic kidney 293T–angiotensin-converting enzyme 2 cells and that the serine protease transmembrane serine protease 2 reversed the decrease in SARS-CoV-2 entry caused by the macropinocytosis inhibitors. Moreover, in the cell-to-cell fusion assay, we confirmed that macropinocytosis inhibitors significantly decreased viral spike–mediated cell-to-cell fusion. Overall, we provided evidence that SARS-CoV-2 utilizes a macropinocytosis pathway to enter target cells and to efficiently promote viral spike–mediated cell-to-cell fusion.

The SARS-CoV-2 main protease (Mpro): Structure, function, and emerging therapies for COVID-19

The main proteases (M^pro), also termed 3‐chymotrypsin‐like proteases (3CL^pro), are a class of highly conserved cysteine hydrolases in β‐coronaviruses. Increasing evidence has demonstrated that 3CL^pros play an indispensable role in viral replication and have been recognized as key targets for preventing and treating coronavirus‐caused infectious diseases, including COVID‐19. This review is focused on the structural features and biological function of the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) main protease M^pro (also known as 3CL^pro), as well as recent advances in discovering and developing SARS‐CoV‐2 3CL^pro inhibitors. To better understand the characteristics of SARS‐CoV‐2 3CL^pro inhibitors, the inhibition activities, inhibitory mechanisms, and key structural features of various 3CL^pro inhibitors (including marketed drugs, peptidomimetic, and non‐peptidomimetic synthetic compounds, as well as natural compounds and their derivatives) are summarized comprehensively. Meanwhile, the challenges in this field are highlighted, while future directions for designing and developing efficacious 3CL^pro inhibitors as novel anti‐coronavirus therapies are also proposed. Collectively, all information and knowledge presented here are very helpful for understanding the structural features and inhibitory mechanisms of SARS‐CoV‐2 3CL^pro inhibitors, which offers new insights or inspiration to medicinal chemists for designing and developing more efficacious 3CL^pro inhibitors as novel anti‐coronavirus agents.

Low Environmental Temperature Exacerbates Severe Acute Respiratory Syndrome Coronavirus 2 Infection in Golden Syrian Hamsters

BACKGROUND

The effect of low environmental temperature on viral shedding and disease severity of Coronavirus Disease 2019 (COVID-19) is uncertain.

METHODS

We investigated the virological, clinical, pathological, and immunological changes in hamsters housed at room (21°C), low (12-15°C), and high (30-33°C) temperature after challenge by 105 plaque-forming units of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

RESULTS

The nasal turbinate, trachea, and lung viral load and live virus titer were significantly higher (~0.5-log10 gene copies/β-actin, P < .05) in the low-temperature group at 7 days postinfection (dpi). The low-temperature group also demonstrated significantly higher level of tumor necrosis factor-α, interferon-γ (IFN-γ), interleukin-1β, and C-C motif chemokine ligand 3, and lower level of the antiviral IFN-α in lung tissues at 4 dpi than the other 2 groups. Their lungs were grossly and diffusely hemorrhagic, with more severe and diffuse alveolar and peribronchiolar inflammatory infiltration, bronchial epithelial cell death, and significantly higher mean total lung histology scores. By 7 dpi, the low-temperature group still showed persistent and severe alveolar inflammation and hemorrhage, and little alveolar cell proliferative changes of recovery. The viral loads in the oral swabs of the low-temperature group were significantly higher than those of the other two groups from 10 to 17 dpi by about 0.5-1.0 log10 gene copies/β-actin. The mean neutralizing antibody titer of the low-temperature group was significantly (P < .05) lower than that of the room temperature group at 7 dpi and 30 dpi.

CONCLUSIONS

This study provided in vivo evidence that low environmental temperature exacerbated the degree of virus shedding, disease severity, and tissue proinflammatory cytokines/chemokines expression, and suppressed the neutralizing antibody response of SARS-CoV-2-infected hamsters. Keeping warm in winter may reduce the severity of COVID-19.

The spike receptor-binding motif G496S substitution determines the replication fitness of SARS-CoV-2 Omicron sublineage

AbstractThe replication and pathogenicity of SARS-CoV-2 Omicron BA.2 is comparable to that of BA.1 in experimental animal models. However, BA.2 has rapidly emerged to overtake BA.1 to become the predominant circulating SARS-CoV-2 variant worldwide. Here, we compared the replication fitness of BA.1 and BA.2 in cell culture and in the Syrian hamster model of COVID-19. Using a reverse genetics approach, we found that the BA.1-specific spike mutation G496S compromises its replication fitness, which may contribute to BA.1 being outcompeted by BA.2 in the real world. Additionally, the BA.1-unique G496S substitution confers differentiated sensitivity to therapeutic monoclonal antibodies, which partially recapitulates the immunoevasive phenotype of BA.1 and BA.2. In summary, our study identified G496S as an important determinant during the evolutionary trajectory of SARS-CoV-2.

Synthesis and characterization of violurate - based Mn(II) and Cu(II) complexes nano-crystallites as DNA-binders and therapeutics agents against SARS-CoV-2 virus

Synthesis and structural characterization of nano crystallites of bis-violurate-based manganese(II) and copper(II) chelates is the subject of the present study. Analytical data and mass spectra as well as thermal analysis determined the molecular formulas of the present metal chelates. Spectroscopic and magnetic measurements assigned the structural formula of the present violurate metal complexes. The spectroscopic and magnetic investigations along with structural analysis results indicated the square planar geometry of both the Mn(II) and Cu(II) complexes. The structural analysis of the synthesized metal complexes was achieved by processing the PXRD data using specialized software Expo 2014. Spectrophotometeric and viscosity measurements showed that violuric acid and its Mn(II) and Cu(II) complexes successfully bind to DNA with intrinsic binding constants K_b from 38.2 × 10⁵ to 26.4 × 10⁶ M⁻¹. The antiviral activity study displayed that the inhibitory concentrations (IC₅₀) of SARS-CoV-2 by violuric acid and its Mn(II) and Cu(II) complexes are 84.01, 39.58 and 44.86 μM respectively. Molecular docking calculations were performed on the SARS-CoV-2 virus protein and the computed binding energy values are −0.8, −3.860 −5.187 and −4.790, kcal/mol for the native ligand, violuric acid and its Mn(II) and Cu(II) complexes respectively. Insights into the relationship between structures of the current compounds and their degree of reactivity are discussed.

The zinc proteome of SARS-CoV-2

Zinc is an essential element for human health. Among its many functions, zinc(II) modulates the immune response to infections and, at high concentrations or in the presence of ionophores, inhibits the replication of various RNA viruses. Structural biology studies on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) revealed that zinc(II) is the most common metal ion that binds to viral proteins. However, the number of zinc(II)-binding sites identified by experimental methods is far from exhaustive, as metal ions may be lost during protein purification protocols. To better define the zinc(II)-binding proteome of coronavirus, we leveraged the wealth of deposited structural data and state-of-the-art bioinformatics methods. Through this in silico approach, 15 experimental zinc(II) sites were identified and a further 22 were predicted in Spike, open reading frame (ORF)3a/d, ORF8, and several nonstructural proteins, highlighting an essential role of zinc(II) in viral replication. Furthermore, the structural relationships between viral and eukaryotic sites (typically zinc fingers) indicate that SARS-CoV-2 can compete with human proteins for zinc(II) binding. Given the double-edged effect of zinc(II) ions, both essential and toxic to coronavirus, only the complete elucidation of the structural and regulatory zinc(II)-binding sites can guide selective antiviral strategies based on zinc supplementation.

Medicinal Hypervalent Tellurium Prodrugs Bearing Different Ligands: A Comparative Study of the Chemical Profiles of AS101 and Its Halido Replaced Analogues

Ammonium trichloro (dioxoethylene-O,O′) tellurate (AS101) is a potent immunomodulator prodrug that, in recent years, entered various clinical trials and was tested for a variety of potential therapeutic applications. It has been demonstrated that AS101 quickly activates in aqueous milieu, producing TeOCl3−, which likely represents the pharmacologically active species. Here we report on the study of the activation process of AS101 and of two its analogues. After the synthesis and characterization of AS101 and its derivatives, we have carried out a comparative study through a combined experimental and computational analysis. Based on the obtained results, we describe here, for the first time, the detailed reaction that AS101 and its bromido- and iodido-replaced analogues undergo in presence of water, allowing the conversion of the original molecule to the likely true pharmacophore. Interestingly, moving down in the halogens’ group we observed a higher tendency to react, attributable to the ligands’ effect. The chemical and mechanistic implications of these meaningful differences are discussed.