Current landscape and future prospects of antiviral drugs derived from microbial products

Evaluation of the Polysaccharide "Immeran" Activity in Syrian hamsters' Model of SARS-CoV-2

COVID-19 is a highly contagious respiratory disease with a high number of lethal cases in humans, which causes the need to search for new therapeutic agents. Polysaccharides could be one of the prospective types of molecules with a large variety of biological activities, especially antiviral. The aim of this work was to study the specific antiviral activity of the drug "Immeran" on a model of a new coronavirus infection SARS-CoV-2 in hamsters. Based on the second experiment, intraperitoneal treatment with the drug according to a treatment regimen in doses of 500 and 1000 μg/kg (administration after an hour, then once a day every other day, a total of 3 administrations) was effective, reliably suppressing the replication of the virus in the lungs and, at a dose of 1000 μg/kg, prevented weight loss in animals. In all cases, the treatment stimulated the formation of virus-neutralizing antibodies to the SARS-CoV-2 virus, which suggests that the drug possesses adjuvant properties.

Tackling Influenza A virus by M2 ion channel blockers: Latest progress and limitations

Influenza outbreaks cause pandemics in millions of people. The treatment of influenza remains a challenge due to significant genetic polymorphism in the influenza virus. Also, developing vaccines to protect against seasonal and pandemic influenza infections is constantly impeded. Thus, antibiotics are the only first line of defense against antigenically distinct strains or new subtypes of influenza viruses. Among several anti-influenza targets, the M2 protein of the influenza virus performs several activities. M2 protein is an ion channel that permits proton conductance through the virion envelope and the deacidification of the Golgi apparatus. Both these functions are critical for viral replication. Thus, targeting the M2 protein of the influenza virus is an essential target. Rimantadine and amantadine are two well-known drugs that act on the M2 protein. However, these drugs acquired resistance to influenza and thus are not recommended to treat influenza infections. This review discusses an overview of anti-influenza therapy, M2 ion channel functions, and its working principle. It also discusses the M2 structure and its role, and the change in the structure leads to mutant variants of influenza A virus. We also shed light on the recently identified compounds acting against wild-type and mutated M2 proteins of influenza virus A. These scaffolds could be an alternative to M2 inhibitors and be developed as antibiotics for treating influenza infections.

Catenulopyrizomicins, new anti-Hepatitis B virus compounds, from the rare actinomycete Catenuloplanes sp. MM782L-181F7

Hepatitis B virus (HBV) causes chronic hepatitis in humans, and current antiviral therapies rarely treat viral infections. To improve the treatment efficacy, novel therapeutic agents, especially those with different mechanisms of action, need to be developed for use in combination with the current antivirals. Here, we isolated new anti-HBV compounds, named catenulopyrizomicins A-C, from the fermentation broth of rare actinomycete Catenuloplanes sp. MM782L-181F7. Structural analysis revealed that these compounds contained a structure that is composed of thiazolyl pyridine moiety. The catenulopyrizomicins reduced the amount of intracellular viral DNA in HepG2.2.15 cells with EC50 values ranging from 1.94 to 2.63 µM with small but notable selectivity. Mechanistic studies indicated that catenulopyrizomicin promotes the release of immature virion particles that fail to be enveloped through alterations in membrane permeability.

Antiviral Potential of Natural Resources against Influenza Virus Infections

Influenza is a severe contagious disease caused by influenza A and B viruses. The WHO estimates that annual outbreaks lead to 3-5 million severe infections of which approximately 10% lead to the death of the patient. While vaccination is the cornerstone of prevention, antiviral drugs represent the most important treatment option of acute infections. Only two classes of drugs are currently approved for the treatment of influenza in numerous countries: M2 channel blockers and neuraminidase inhibitors. In some countries, additional compounds such as the recently developed cap-dependent endonuclease inhibitor baloxavir marboxil or the polymerase inhibitor favipiravir are available. However, many of these compounds suffer from poor efficacy, if not applied early after infection. Furthermore, many influenza strains have developed resistances and lost susceptibility to these compounds. As a result, there is an urgent need to develop new anti-influenza drugs against a broad spectrum of subtypes. Natural products have made an important contribution to the development of new lead structures, particularly in the field of infectious diseases. Therefore, this article aims to review the research on the identification of novel lead structures isolated from natural resources suitable to treat influenza infections.

Utility of NO and H2S donating platforms in managing COVID-19: Rationale and promise

Viral infections are a continuing global burden on the human population, underscored by the ramifications of the COVID-19 pandemic. Current treatment options and supportive therapies for many viral infections are relatively limited, indicating a need for alternative therapeutic approaches. Virus-induced damage occurs through direct infection of host cells and inflammation-related changes. Severe cases of certain viral infections, including COVID-19, can lead to a hyperinflammatory response termed cytokine storm, resulting in extensive endothelial damage, thrombosis, respiratory failure, and death. Therapies targeting these complications are crucial in addition to antiviral therapies. Nitric oxide and hydrogen sulfide are two endogenous gasotransmitters that have emerged as key signaling molecules with a broad range of antiviral actions in addition to having anti-inflammatory properties and protective functions in the vasculature and respiratory system. The enhancement of endogenous nitric oxide and hydrogen sulfide levels thus holds promise for managing both early-stage and later-stage viral infections, including SARS-CoV-2. Using SARS-CoV-2 as a model for similar viral infections, here we explore the current evidence regarding nitric oxide and hydrogen sulfide's use to limit viral infection, resolve inflammation, and reduce vascular and pulmonary damage.

Inferences of actinobacterial metabolites to combat Corona virus

The entire globe is reeling under the magnitude of the current corona virus pandemic. This menace has proposed severe health and economic threats for all, thereby challenging our human existence itself. Since its outbreak, it has raised the concern and imperative need of developing novel and effective agents to combat viral diseases and now its variants as well. Despite the sincere and concerted efforts of scientists and pharma giants all over the world, there seems to be no ideal recourse found till date. Natural products are rich sources of novel compounds used in the treatment of infectious and non-infectious diseases. There are reports on natural products from microbes, plants and marine organisms that are active against viral targets. Actinobacteria, the largest phylum under the bacterial kingdom, is known for its secondary metabolite production with diverse bioactive potentials. Nearly 65% of antibiotics used in medicine are contributed by Actinobacteria. Compared to antibacterial and antifungal agents, antiviral compounds from Actinobacteria are less studied. In recent years Actinobacteria from under studied/extreme ecosystems are explored for their antiviral properties. Ivermectin and teicoplanin are examples of Actinobacteria-derived antiviral drugs available for commercial use. This review highlights the importance of actinobacteria as future sources of antiviral drug discovery.

Multi-Omics-Guided Discovery of Omicsynins Produced by Streptomyces sp. 1647: Pseudo-Tetrapeptides Active Against Influenza A Viruses and Coronavirus HCoV-229E

Many microorganisms have mechanisms that protect cells against attack from viruses. The fermentation components of Streptomyces sp. 1647 exhibit potent anti-influenza A virus (IAV) activity. This strain was isolated from soil in southern China in the 1970s, but the chemical nature of its antiviral substance(s) has remained unknown until now. We used an integrated multi-omics strategy to identify the antiviral agents from this streptomycete. The antibiotics and Secondary Metabolite Analysis Shell (antiSMASH) analysis of its genome sequence revealed 38 biosynthetic gene clusters (BGCs) for secondary metabolites, and the target BGCs possibly responsible for the production of antiviral components were narrowed down to three BGCs by bioactivity-guided comparative transcriptomics analysis. Through bioinformatics analysis and genetic manipulation of the regulators and a biosynthetic gene, cluster 36 was identified as the BGC responsible for the biosynthesis of the antiviral compounds. Bioactivity-based molecular networking analysis of mass spectrometric data from different recombinant strains illustrated that the antiviral compounds were a class of structural analogues. Finally, 18 pseudo-tetrapeptides with an internal ureido linkage, omicsynins A1-A6, B1-B6, and C1-C6, were identified and/or isolated from fermentation broth. Among them, 11 compounds (omicsynins A1, A2, A6, B1-B3, B5, B6, C1, C2, and C6) are new compounds. Omicsynins B1-B4 exhibited potent antiviral activity against IAV with the 50% inhibitory concentration (IC₅₀) of approximately 1 µmol∙L^-1 and a selectivity index (SI) ranging from 100 to 300. Omicsynins B1-B4 also showed significant antiviral activity against human coronavirus HCoV-229E. By integrating multi-omics data, we discovered a number of novel antiviral pseudo-tetrapeptides produced by Streptomyces sp. 1647, indicating that the secondary metabolites of microorganisms are a valuable source of novel antivirals.

Acetophenone 4-nitrophenylhydrazone inhibits Hepatitis B virus replication by modulating capsid assembly

Hepatitis B virus (HBV) is the causative agent of chronic liver disease and is correlated with the development of subsequent hepatic cirrhosis and hepatocellular carcinoma. Current antiviral therapy using nucleos(t)ide analogs is effective in suppressing viral replication and interrupting disease progression, but HBV is rarely cured completely. Thus, there remains an unmet need for the development of novel anti-HBV drugs. Here, we report the identification of N-(4-Nitrophenyl)-1-phenylethanone hydrazone (ANPH) as a novel structural class of selective inhibitors targeting the replication of the HBV genome using adenovirus vector-mediated HBV genome transduction. ANPH inhibited viral genome replication in HepG2.2.15 cells by inducing the formation of empty capsids devoid of pregenomic RNA without affecting its transcription and translation. Biochemical assays using a truncated core protein consisting of the assembly domain showed that ANPH accelerates the formation of morphologically intact capsids. Taken together, we propose that ANPH might provide a new structural scaffold to design a new anti-HBV drug in medicinal chemistry as well as chemical probes for HBV core protein functions in the future.

Microbial Metabolites: The Emerging Hotspot of Antiviral Compounds as Potential Candidates to Avert Viral Pandemic Alike COVID-19

The present global COVID-19 pandemic caused by the noble pleomorphic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has created a vulnerable situation in the global healthcare and economy. In this pandemic situation, researchers all around the world are trying their level best to find suitable therapeutics from various sources to combat against the SARS-CoV-2. To date, numerous bioactive compounds from different sources have been tested to control many viral diseases. However, microbial metabolites are advantageous for drug development over metabolites from other sources. We herein retrieved and reviewed literatures from PubMed, Scopus and Google relevant to antiviral microbial metabolites by searching with the keywords "antiviral microbial metabolites," "microbial metabolite against virus," "microorganism with antiviral activity," "antiviral medicine from microbial metabolite," "antiviral bacterial metabolites," "antiviral fungal metabolites," "antiviral metabolites from microscopic algae' and so on. For the same purpose, the keywords "microbial metabolites against COVID-19 and SARS-CoV-2" and "plant metabolites against COVID-19 and SARS-CoV-2" were used. Only the full text literatures available in English and pertinent to the topic have been included and those which are not available as full text in English and pertinent to antiviral or anti-SARS-CoV-2 activity were excluded. In this review, we have accumulated microbial metabolites that can be used as antiviral agents against a broad range of viruses including SARS-CoV-2. Based on this concept, we have included 330 antiviral microbial metabolites so far available to date in the data bases and were previously isolated from fungi, bacteria and microalgae. The microbial source, chemical nature, targeted viruses, mechanism of actions and IC50/EC50 values of these metabolites are discussed although mechanisms of actions of many of them are not yet elucidated. Among these antiviral microbial metabolites, some compounds might be very potential against many other viruses including coronaviruses. However, these potential microbial metabolites need further research to be developed as effective antiviral drugs. This paper may provide the scientific community with the possible secret of microbial metabolites that could be an effective source of novel antiviral drugs to fight against many viruses including SARS-CoV-2 as well as the future viral pandemics.

Nature-derived hit, lead, and drug-like small molecules: Current status and future aspects against key target proteins of Coronaviruses

BACKGROUND

COVID-19 pandemic, the most unprecedented event of the year 2020, has brought millions of scientists worldwide in a single platform to fight against it. Though several drugs are now in the clinical trial, few vaccines available on the market already but the lack of an effect of those is making the situation worse.

AIM OF THE STUDY

In this review, we demonstrated comprehensive data of natural antiviral products showing activities against different proteins of Human Coronaviruses (HCoV) that are responsible for its pathogenesis. Furthermore, we categorized the compounds into the hit, lead, and drug based on the IC50/EC50 value, drug-likeness, and lead-likeness test to portray their potentiality to be a drug. We also demonstrated the present status of our screened antiviral compounds with respect to clinical trials and reported the lead compounds that can be promoted to clinical trial against COVID-19.

METHODS

A systematic search strategy was employed focusing on Natural Products (NPs) with proven activity (in vitro, in vivo, or in silico) against human coronaviruses, in general, and data were gathered from databases like PubMed, Web of Science, Google Scholar, SciVerse, and Scopus. Information regarding clinical trials retrieved from the Clinical Trial database.

RESULTS

Total "245" natural compounds were identified initially from the literature study. Among them, Glycyrrhizin, Caffeic acid, Curcumin is in phase 3, and Tetrandrine, Cyclosporine, Tacrolimus, Everolimus are in phase 4 clinical trial. Except for Glycyrrhizin, all compounds showed activity against COVID-19.

CONCLUSIONS

In summary, our demonstrated specific small molecules with lead and drug-like capabilities clarified their position in the drug discovery pipeline and proposed their future research against COVID-19.

Reviewing Antiviral Research Against Viruses Causing Human Diseases - A Structure Guided Approach

The littlest of all the pathogens, viruses have continuously been the foremost strange microorganisms to consider. Viral Infections can cause extreme sicknesses as archived by the HIV/AIDS widespread or the later Ebola or Zika episodes. Apprehensive framework distortions are too regularly watched results of numerous viral contaminations. Besides, numerous infections are oncoviruses, which can trigger different sorts of cancer. Nearly every year a modern infection species rises debilitating the world populace with an annihilating episode. Subsequently, the need of creating antivirals to combat such rising infections. In any case, from the innovation of to begin with antiviral medicate Idoxuridine in 1962 to the revelation of Baloxavir marboxil (Xofluza) that was FDA-approved in 2018, the hone of creating antivirals has changed significantly. In this article, different auxiliary science strategies have been described that can be referral for therapeutics innovation.

Antiviral effect of silymarin against Zika virus in vitro

Zika virus (ZIKV) epidemic and its association with severe neurological syndromes have raised worldwide concern. Despite the great clinical relevance of this infection, no vaccine or specific treatment is available and the search for antiviral compounds against ZIKV is extremely necessary. Several natural compounds, such as silymarin, exhibit antioxidant, hepatoprotective, and antiviral properties; however, the antiviral potential of this compound remains partially investigated. Therefore, the objective of this study was to evaluate in vitro the antiviral activity of silymarin against ZIKV infection. Global antiviral activity, dose-dependent, plaque reduction, and time-of-drug-addition assays were used to determine the anti-ZIKV activity of silymarin. Additionally, to start characterizing the mechanisms of action we determined whether silymarin could have a virucidal effect and inhibit viral adsorption and penetration stages. Regarding its global antiviral activity, silymarin showed significant inhibition of ZIKV infection, protecting cells infected with EC₅₀ equal to 34.17μg/mL, with a selectivity index greater than 17 and 4x greater than that of the positive control (ribavirin). Its greatest efficiency was achieved at 125μg/mL, whose cell viability did not differ from the control without infection and treatment. Furthermore, treatment with silymarin reduced viral load by up to two logs (> 90%) concerning viral control, when evaluating virucidal activity and the precocious times of infection. Thus, our results set to show the promising anti-ZIKV activity of silymarin, which does not seem to have a single inhibition mechanism, acting at different times of infection, and still has the advantage of silymarin be a phytotherapy already available on the market.

Investigation of Brassica juncea, Forsythia suspensa, and Inula britannica: phytochemical properties, antiviral effects, and safety

BACKGROUND

General antiviral agents such as oseltamivir are associated with certain adverse effects and the emergence of resistance. This study investigated the phytochemical properties, antiviral activities, and safety of three herbs used in traditional Korean medicine.

METHODS

Extracts of three medicinal herbs (Brassica juncea, Forsythia suspensa, and Inula britannica) were prepared using ethanol or water. The total phenolic, flavonoid, and saponin content, condensed tannin content, and reducing sugar content of the herb extracts were determined via phytochemical screening. Tandem mass analysis was performed using an ultra-performance liquid chromatography (UPLC)-electrospray ionization (ESI)-Q/Orbitrap instrument. Virus titrations were determined via tissue culture infective dose (TCID50) and cytotoxicity assays. Hemolysis and hepatotoxicity were measured to determine safety.

RESULTS

Among the three medicinal herbs, F. suspensa showed the highest concentration of phenolic compounds, flavonoids, and saponins. The number of phytochemical compounds detected via tandem mass analysis of B. juncea, F. suspensa, and I. britannica was 5 (including sinigrin, m/z [M-H] = 358.02), 14 (including forsythoside A, m/z [M-H] = 623.19), and 18 (including chlorogenic acid, m/z [M-H] = 353.20), respectively. The antiviral effects of the B. juncea extracts (ethanol and water) and I. britannica extract (ethanol) were further investigated. The ethanol extract of B. juncea showed a 3 Log TCID50/25 μL virus titration reduction and the water extract showed a selectivity index of 13.668 against infected influenza H1N1 virus A/NWS/33. The B. juncea extracts did not show hemolysis activities and hepatotoxicity (< 20%). The ethanol extract of I. britannica showed the most effective virus titration decrease, whereas its hemolytic and hepatotoxicity values were the most significantly different compared to the control. Despite the high concentration of phytochemicals detected in F. suspensa, the extract showed approximately 1 Log TCID50/25 μL at the highest concentration.

CONCLUSION

B. juncea may show antiviral effects against H1N1 in a host. In addition, B. juncea may also show decreased disadvantages compared to other antiviral agents.

AntiVPP 1.0: A portable tool for prediction of antiviral peptides

Viruses are worldwide pathogens with a high impact on the human population. Despite the constant efforts to fight viral infections, there is a need to discover and design new drug candidates. Antiviral peptides are molecules with confirmed activity and constitute excellent alternatives for the treatment of viral infections. In the present study, we developed AntiVPP 1.0, an accurate bioinformatic tool that uses the Random Forest algorithm for antiviral peptide predictions. The model of AntiVPP 1.0 for antiviral peptide predictions uses several features of 1088 peptides for training and validation. During the validation of the model we achieved the TPR = 0.87, SPC = 0.97, ACC = 0.93 and MCC = 0.87 performance measures, which were indicative of a robust model. AntiVPP 1.0 is a fast, accurate and intuitive software focused on the assessment of antiviral peptides candidates. AntiVPP 1.0 is available at https://github.com/bio-coding/AntiVPP.

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Random Forest algorithm was used for antiviral peptides prediction.

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AntiVPP 1.0 can be used for assessing various physical and chemical properties of antiviral peptides.

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Anti VPP 1.0 is a software with a simple interface and a high performance for academic and commercial purposes.

Nanoformulations: A Valuable Tool in the Therapy of Viral Diseases Attacking Humans and Animals

Various viruses can be considered as one of the most frequent causes of human diseases, from mild illnesses to really serious sicknesses that end fatally. Numerous viruses are also pathogenic to animals and plants, and many of them, mutating, become pathogenic also to humans. Several cases of affecting humans by originally animal viruses have been confirmed. Viral infections cause significant morbidity and mortality in humans, the increase of which is caused by general immunosuppression of the world population, changes in climate, and overall globalization. In spite of the fact that the pharmaceutical industry pays great attention to human viral infections, many of clinically used antivirals demonstrate also increased toxicity against human cells, limited bioavailability, and thus, not entirely suitable therapeutic profile. In addition, due to resistance, a combination of antivirals is needed for life-threatening infections. Thus, the development of new antiviral agents is of great importance for the control of virus spread. On the other hand, the discovery and development of structurally new antivirals represent risks. Therefore, another strategy is being developed, namely the reformulation of existing antivirals into nanoformulations and investigation of various metal and metalloid nanoparticles with respect to their diagnostic, prophylactic, and therapeutic antiviral applications. This chapter is focused on nanoscale materials/formulations with the potential to be used for the treatment or inhibition of the spread of viral diseases caused by human immunodeficiency virus, influenza A viruses (subtypes H3N2 and H1N1), avian influenza and swine influenza viruses, respiratory syncytial virus, herpes simplex virus, hepatitis B and C viruses, Ebola and Marburg viruses, Newcastle disease virus, dengue and Zika viruses, and pseudorabies virus. Effective antiviral long-lasting and target-selective nanoformulations developed for oral, intravenous, intramuscular, intranasal, intrarectal, intravaginal, and intradermal applications are discussed. Benefits of nanoparticle-based vaccination formulations with the potential to secure cross protection against divergent viruses are outlined as well.

Anti-influenza virus activity of a salcomine derivative mediated by inhibition of viral RNA synthesis

Influenza virus infection is a major threat to global health. Although vaccines and anti-influenza virus drugs are available, annual influenza virus epidemics result in severe illness, and an influenza pandemic occurs every 20-30 years. To identify candidate anti-influenza virus compounds, we screened approximately 5,000 compounds in an in-house library. We identified MZ7465, a salcomine derivative, as a potent inhibitor of influenza virus propagation. We analyzed the antiviral propagation mechanism of the hit compound by determining the amounts of viral proteins and RNA in infected cells treated with or without the hit compound. Treatment of infected cells with MZ7465 decreased both viral protein and RNA synthesis. In addition, an in vitro assay showed that viral RNA synthesis was directly inhibited by MZ7465. These results suggest that salcomine and its derivatives are potential candidates for the treatment of influenza virus infections.