Aprotinin Inhibits SARS-CoV-2 Replication

Clinical development of antivirals against SARS-CoV-2 and its variants

The unceasing global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) calls for the development of novel therapeutics. Although many newly developed antivirals and repurposed antivirals have been applied to the treatment of coronavirus disease 2019 (COVID-19), antivirals showing satisfactory clinical efficacy are few in number. In addition, the loss of sensitivity to variants of concern (VOCs) and lack of oral bioavailability have also limited the clinical application of some antivirals. These facts remind us to develop more potent and broad-spectrum antivirals with better pharmacokinetic/pharmacodynamic properties to fight against infections from SARS-CoV-2, its variants, and other human coronaviruses (HCoVs). In this review, we summarize the latest advancements in the clinical development of antivirals against infections by SARS-CoV-2 and its variants.

Development of lung tissue models and their applications

The lungs are important organs that play a critical role in the development of specific diseases, as well as responding to the effects of drugs, chemicals, and environmental pollutants. Due to the ethical concerns around animal testing, alternative methods have been sought which are more time-effective, do not pose ethical issues for animals, do not involve species differences, and provide easy investigation of the pathobiology of lung diseases. Several national and international organizations are working to accelerate the development and implementation of structurally and functionally complex tissue models as alternatives to animal testing, particularly for the lung. Unfortunately, to date, there is no lung tissue model that has been accepted by regulatory agencies for use in inhalation toxicology. This review discusses the challenges involved in developing a relevant lung tissue model derived from human cells such as cell lines, primary cells, and pluripotent stem cells. It also introduces examples of two-dimensional (2D) air-liquid interface and monocultured and co-cultured three-dimensional (3D) culture techniques, particularly organoid culture and 3D bioprinting. Furthermore, it reviews development of the lung-on-a-chip model to mimic the microenvironment and physiological performance. The applications of lung tissue models in various studies, especially disease modeling, viral respiratory infection, and environmental toxicology will be also introduced. The development of a relevant lung tissue model is extremely important for standardizing and validation the in vitro models for inhalation toxicity and other studies in the future.

The SMYD3-dependent H3K4me3 status of IGF2 intensifies local Th2 differentiation in CRSwNP via positive feedback

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a heterogeneous and common upper airway disease divided into various inflammatory endotypes. Recent epidemiological findings showed a T helper 2 (Th2)-skewed dominance in CRSwNP patients. Histone modification alterations can regulate transcriptional and translational expression, resulting in abnormal pathogenic changes and the occurrence of diseases. Trimethylation of histone H3 lysine 4 (H3K4me3) is considered an activator of gene expression through modulation of accessibility for transcription, which is closely related to CRSwNP. H3K4me3 levels in the human nasal epithelium may change under Th2-biased inflammatory conditions, resulting in exaggerated local nasal Th2 responses via the regulation of naïve CD4+ T-cell differentiation. Here, we revealed that the level of SET and MYND domain-containing protein 3 (SMYD3)-mediated H3K4me3 was increased in NPs from Th2 CRSwNP patients compared with those from healthy controls. We demonstrated that SMYD3-mediated H3K4me3 is increased in human nasal epithelial cells under Th2-biased inflammatory conditions via S-adenosyl-L-methionine (SAM) production and further found that the H3K4me3high status of insulin-like growth factor 2 (IGF2) produced in primary human nasal epithelial cells could promote naïve CD4+ T-cell differentiation into Th2 cells. Moreover, we found that SAM production was dependent on the c-Myc/methionine adenosyltransferase 2A (MAT2A) axis in the nasal epithelium. Understanding histone modifications in the nasal epithelium has immense potential utility in the development of novel classes of therapeutics targeting Th2 polarization in Th2 CRSwNP. Video Abstract.

Aprotinin-Drug against Respiratory Diseases

Aprotinin (APR) was discovered in 1930. APR is an effective pan-protease inhibitor, a typical "magic shotgun". Until 2007, APR was widely used as an antithrombotic and anti-inflammatory drug in cardiac and noncardiac surgeries for reduction of bleeding and thus limiting the need for blood transfusion. The ability of APR to inhibit proteolytic activation of some viruses leads to its use as an antiviral drug for the prevention and treatment of acute respiratory virus infections. However, due to incompetent interpretation of several clinical trials followed by incredible controversy in the literature, the usage of APR was nearly stopped for a decade worldwide. In 2015-2020, after re-analysis of these clinical trials' data the restrictions in APR usage were lifted worldwide. This review discusses antiviral mechanisms of APR action and summarizes current knowledge and prospective regarding the use of APR treatment for diseases caused by RNA-containing viruses, including influenza and SARS-CoV-2 viruses, or as a part of combination antiviral treatment.

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.

Analysis of Nipah Virus Replication and Host Proteome Response Patterns in Differentiated Porcine Airway Epithelial Cells Cultured at the Air-Liquid Interface

Respiratory tract epithelium infection plays a primary role in Nipah virus (NiV) pathogenesis and transmission. Knowledge about infection dynamics and host responses to NiV infection in respiratory tract epithelia is scarce. Studies in non-differentiated primary respiratory tract cells or cell lines indicate insufficient interferon (IFN) responses. However, studies are lacking in the determination of complex host response patterns in differentiated respiratory tract epithelia for the understanding of NiV replication and spread in swine. Here we characterized infection and spread of NiV in differentiated primary porcine bronchial epithelial cells (PBEC) cultivated at the air-liquid interface (ALI). After the initial infection of only a few apical cells, lateral spread for 12 days with epithelium disruption was observed without releasing substantial amounts of infectious virus from the apical or basal sides. Deep time course proteomics revealed pronounced upregulation of genes related to type I/II IFN, immunoproteasomal subunits, transporter associated with antigen processing (TAP)-mediated peptide transport, and major histocompatibility complex (MHC) I antigen presentation. Spliceosomal factors were downregulated. We propose a model in which NiV replication in PBEC is slowed by a potent and broad type I/II IFN host response with conversion from 26S proteasomes to immunoproteasomal antigen processing and improved MHC I presentation for adaptive immunity priming. NiV induced cytopathic effects could reflect the focal release of cell-associated NiV, which may contribute to efficient airborne viral spread between pigs.

A Monoclonal Human Alveolar Epithelial Cell Line ("Arlo") with Pronounced Barrier Function for Studying Drug Permeability and Viral Infections

In the development of orally inhaled drug products preclinical animal models regularly fail to predict pharmacological as well as toxicological responses in humans. Models based on human cells and tissues are potential alternatives to animal experimentation allowing for the isolation of essential processes of human biology and making them accessible in vitro. Here, the generation of a novel monoclonal cell line "Arlo," derived from the polyclonal human alveolar epithelium lentivirus immortalized cell line hAELVi via single-cell printing, and its characterization as a model for the human alveolar epithelium as well as a building block for future complex in vitro models is described. "Arlo" is systematically compared in vitro to primary human alveolar epithelial cells (hAEpCs) as well as to the polyclonal hAELVi cell line. "Arlo" cells show enhanced barrier properties with high transepithelial electrical resistance (TEER) of ≈3000 Ω cm2 and a potential difference (PD) of ≈30 mV under air-liquid interface (ALI) conditions, that can be modulated. The cells grow in a polarized monolayer and express genes relevant to barrier integrity as well as homeostasis as is observed in hAEpCs. Successful productive infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a proof-of-principle study offers an additional, attractive application of "Arlo" beyond biopharmaceutical experimentation.

Identification of novel antiviral drug candidates using an optimized SARS-CoV-2 phenotypic screening platform

Reliable, easy-to-handle phenotypic screening platforms are needed for the identification of anti-SARS-CoV-2 compounds. Here, we present caspase 3/7 activity as a readout for monitoring the replication of SARS-CoV-2 isolates from different variants, including a remdesivir-resistant strain, and of other coronaviruses in numerous cell culture models, independently of cytopathogenic effect formation. Compared to other models, the Caco-2 subline Caco-2-F03 displayed superior performance. It possesses a stable SARS-CoV-2 susceptibility phenotype and does not produce false-positive hits due to drug-induced phospholipidosis. A proof-of-concept screen of 1,796 kinase inhibitors identified known and novel antiviral drug candidates including inhibitors of phosphoglycerate dehydrogenase (PHGDH), CDC like kinase 1 (CLK-1), and colony stimulating factor 1 receptor (CSF1R). The activity of the PHGDH inhibitor NCT-503 was further increased in combination with the hexokinase II (HK2) inhibitor 2-deoxy-D-glucose, which is in clinical development for COVID-19. In conclusion, caspase 3/7 activity detection in SARS-CoV-2-infected Caco-2-F03 cells provides a simple phenotypic high-throughput screening platform for SARS-CoV-2 drug candidates that reduces false-positive hits.

Strategies Tackling Viral Replication and Inflammatory Pathways as Early Pharmacological Treatment for SARS-CoV-2 Infection: Any Potential Role for Ketoprofen Lysine Salt?

COVID-19 is an infective disease resulting in widespread respiratory and non-respiratory symptoms prompted by SARS-CoV-2 infection. Interaction between SARS-CoV-2 and host cell receptors prompts activation of pro-inflammatory pathways which are involved in epithelial and endothelial damage mechanisms even after viral clearance. Since inflammation has been recognized as a critical step in COVID-19, anti-inflammatory therapies, including both steroids and non-steroids as well as cytokine inhibitors, have been proposed. Early treatment of COVID-19 has the potential to affect the clinical course of the disease regardless of underlying comorbid conditions. Non-steroidal anti-inflammatory drugs (NSAIDs), which are widely used for symptomatic relief of upper airway infections, became the mainstay of early phase treatment of COVID-19. In this review, we discuss the current evidence for using NSAIDs in early phases of SARS-CoV-2 infection with focus on ketoprofen lysine salt based on its pharmacodynamic and pharmacokinetic features.

[130th anniversary of virology]

130 years ago, in 1892, our great compatriot Dmitry Iosifovich Ivanovsky (18641920) discovered a new type of pathogen viruses. Viruses have existed since the birth of life on Earth and for more than three billion years, as the biosphere evolved, they are included in interpopulation interactions with representatives of all kingdoms of life: archaea, bacteria, protozoa, algae, fungi, plants, invertebrates, and vertebrates, including the Homo sapiens (Hominidae, Homininae). Discovery of D.I. Ivanovsky laid the foundation for a new science virology. The rapid development of virology in the 20th century was associated with the fight against emerging and reemerging infections, epidemics (epizootics) and pandemics (panzootics) of which posed a threat to national and global biosecurity (tick-borne and other encephalitis, hemorrhagic fevers, influenza, smallpox, poliomyelitis, HIV, parenteral hepatitis, coronaviral and other infections). Fundamental research on viruses created the basis for the development of effective methods of diagnostics, vaccine prophylaxis, and antiviral drugs. Russian virologists continue to occupy leading positions in some priority areas of modern virology in vaccinology, environmental studies oz zoonotic viruses, studies of viral evolution in various ecosystems, and several other areas. A meaningful combination of theoretical approaches to studying the evolution of viruses with innovative methods for studying their molecular genetic properties and the creation of new generations of vaccines and antiviral drugs on this basis will significantly reduce the consequences of future pandemics or panzootics. The review presents the main stages in the formation and development of virology as a science in Russia with an emphasis on the most significant achievements of soviet and Russian virologists in the fight against viral infectious diseases.

As the virus evolves, so too must we: a drug developer's perspective : We need a new paradigm in searching for next-generation countermeasures

The SARS-CoV-2 virus has been raging globally for over 2 years with no end in sight. It has become clear that this virus possesses enormous genetic plasticity, and it will not be eradicated. Under increasing selective pressure from population immunity, the evolution of SARS-CoV-2 has driven it towards greater infectivity, and evasion of humoral and cellular immunity. Omicron and its expanding army of subvariants and recombinants have impaired vaccine protection and made most antibody drugs obsolete. Antiviral drugs, though presently effective, may select for more resistant strains over time. It may be inevitable, then, that future SARS-CoV-2 variants will be immune to our current virus-directed countermeasures. Thus, to gain control over the virus, we need to adopt a new paradigm in searching for next-generation countermeasures and develop host-directed therapeutics (HDTx) and host-directed antivirals (HDA). Different from the virus-directed countermeasures, HDTx and HDA may offer variant agnostic treatment to reduce the risk and severity of infections. In addition, they may exert more uniform effects against the genetically diverse SARS-CoV-2 quasispecies, thereby diminishing the risk of selecting resistant variants. Some promising HDTx and HDA approaches are summarized here.

Druggable targets and therapeutic development for COVID-19

Coronavirus disease (COVID-19), which is caused by SARS-CoV-2, is the biggest challenge to the global public health and economy in recent years. Until now, only limited therapeutic regimens have been available for COVID-19 patients, sparking unprecedented efforts to study coronavirus biology. The genome of SARS-CoV-2 encodes 16 non-structural, four structural, and nine accessory proteins, which mediate the viral life cycle, including viral entry, RNA replication and transcription, virion assembly and release. These processes depend on the interactions between viral polypeptides and host proteins, both of which could be potential therapeutic targets for COVID-19. Here, we will discuss the potential medicinal value of essential proteins of SARS-CoV-2 and key host factors. We summarize the most updated therapeutic interventions for COVID-19 patients, including those approved clinically or in clinical trials.

Bovine pancreatic trypsin inhibitor and soybean Kunitz trypsin inhibitor: Differential effects on proteases and larval development of the soybean pest Anticarsia gemmatalis (Lepidoptera: Noctuidae)

Pest management is challenged with resistant herbivores and problems regarding human health and environmental issues. Indeed, the greatest challenge to modern agriculture is to protect crops from pests and still maintain environmental quality. This study aimed to analyze by in silico, in vitro, and in vivo approaches to the feasibility of using the inhibitory protein extracted from mammals - Bovine Pancreatic Trypsin Inhibitor (BPTI) as a potential inhibitor of digestive trypsins from the pest Anticarsia gemmatalis and comparing the results with the host-plant inhibitor - Soybean Kunitz Trypsin Inhibitor (SKTI). BPTI and SKTI interacts with A. gemmatalis trypsin-like enzyme competitively, through hydrogen and hydrophobic bonds. A. gemmatalis larvae exposed to BPTI did not show two common adaptative mechanisms i.e., proteolytic degradation and overproduction of proteases, presenting highly reduced trypsin-like activity. On the other hand, SKTI-fed larvae did not show reduced trypsin-like activity, presenting overproduction of proteases and SKTI digestion. In addition, the larval survival was reduced by BPTI similarly to SKTI, and additionally caused a decrease in pupal weight. The non-plant protease inhibitor BPTI presents intriguing element to compose biopesticide formulations to help decrease the use of conventional refractory pesticides into integrated pest management programs.

Dysregulation of the kallikrein-kinin system in bronchoalveolar lavage fluid of patients with severe COVID-19

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) binds to the angiotensin-converting enzyme 2 (ACE2) receptor, a critical component of the kallikrein-kinin system. Its dysregulation may lead to increased vascular permeability and release of inflammatory chemokines. Interactions between the kallikrein-kinin and the coagulation system might further contribute to thromboembolic complications in COVID-19.

Methods

In this observational study, we measured plasma and tissue kallikrein hydrolytic activity, levels of kinin peptides, and myeloperoxidase (MPO)-DNA complexes as a biomarker for neutrophil extracellular traps (NETs), in bronchoalveolar lavage (BAL) fluid from patients with and without COVID-19.

Findings

In BAL fluid from patients with severe COVID-19 (n = 21, of which 19 were mechanically ventilated), we observed higher tissue kallikrein activity (18·2 pM [1·2-1535·0], median [range], n = 9 vs 3·8 [0·0-22·0], n = 11; p = 0·030), higher levels of the kinin peptide bradykinin-(1-5) (89·6 [0·0-2425·0], n = 21 vs 0·0 [0·0-374·0], n = 19, p = 0·001), and higher levels of MPO-DNA complexes (699·0 ng/mL [66·0-142621·0], n = 21 vs 70·5 [9·9-960·0], n = 19, p < 0·001) compared to patients without COVID-19.

Interpretation

Our observations support the hypothesis that dysregulation of the kallikrein-kinin system might occur in mechanically ventilated patients with severe pulmonary disease, which might help to explain the clinical presentation of patients with severe COVID-19 developing pulmonary oedema and thromboembolic complications. Therefore, targeting the kallikrein-kinin system should be further explored as a potential treatment option for patients with severe COVID-19.

Funding

Research Foundation-Flanders (G0G4720N, 1843418N), KU Leuven COVID research fund.

Blockade of TMPRSS2-mediated priming of SARS-CoV-2 by lactoferricin

In addition to vaccines, there is an urgent need for supplemental antiviral therapeutics to dampen the persistent COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The transmembrane protease serine 2 (TMPRSS2), that is responsible for proteolytic priming of the SARS-CoV-2 spike protein, appears as a rational therapeutic target. Accordingly, selective inhibitors of TMPRSS2 represent potential tools for prevention and treatment of COVID-19. Previously, we identified the human milk glycoprotein lactoferrin as a natural inhibitor of plasminogen conversion to plasmin, a serine protease homologous to TMPRSS2. Here, we tested whether lactoferrin and lactoferricin, a biologically active natural peptide produced by pepsin-mediated digestion of lactoferrin, together with synthetic peptides derived from lactoferrin, were able to block TMPRSS2 and SARS-CoV-2 infection. Particularly, we revealed that both lactoferricin and the N-terminal synthetic peptide pLF1 significantly inhibited: i) proteolytic activity of TMPRSS2 and plasmin, ii) proteolytic processing of the SARS-CoV-2 spike protein, and iii) SARS-CoV-2 infection of SARS-CoV-2-permissive cells. Thus, natural and synthetic peptides derived from lactoferrin represent feasible candidates for supporting prevention and treatment of COVID-19.

The Efficacy of Aprotinin Combinations with Selected Antiviral Drugs in Mouse Models of Influenza Pneumonia and Coronavirus Infection Caused by SARS-CoV-2

The efficacy of aprotinin combinations with selected antiviral-drugs treatment of influenza virus and coronavirus (SARS-CoV-2) infection was studied in mice models of influenza pneumonia and COVID-19. The high efficacy of the combinations in reducing virus titer in lungs and body weight loss and in increasing the survival rate were demonstrated. This preclinical study can be considered a confirmatory step before introducing the combinations into clinical assessment.

Development and optimization of a high-throughput screening assay for in vitro anti-SARS-CoV-2 activity: Evaluation of 5676 Phase 1 Passed Structures

Although vaccines are currently used to control the coronavirus disease 2019 (COVID-19) pandemic, treatment options are urgently needed for those who cannot be vaccinated and for future outbreaks involving new severe acute respiratory syndrome coronavirus virus 2 (SARS-CoV-2) strains or coronaviruses not covered by current vaccines. Thus far, few existing antivirals are known to be effective against SARS-CoV-2 and clinically successful against COVID-19. As part of an immediate response to the COVID-19 pandemic, a high-throughput, high content imaging-based SARS-CoV-2 infection assay was developed in VeroE6 African green monkey kidney epithelial cells expressing a stable enhanced green fluorescent protein (VeroE6-eGFP cells) and was used to screen a library of 5676 compounds that passed Phase 1 clinical trials. Eight drugs (nelfinavir, RG-12915, itraconazole, chloroquine, hydroxychloroquine, sematilide, remdesivir, and doxorubicin) were identified as inhibitors of in vitro anti-SARS-CoV-2 activity in VeroE6-eGFP and/or Caco-2 cell lines. However, apart from remdesivir, toxicity and pharmacokinetic data did not support further clinical development of these compounds for COVID-19 treatment.

Aprotinin treatment against SARS-CoV-2: A randomized phase III study to evaluate the safety and efficacy of a pan-protease inhibitor for moderate COVID-19

BACKGROUND

SARS-CoV-2 virus requires host proteases to cleave its spike protein to bind to its ACE2 target through a two-step furin-mediated entry mechanism. Aprotinin is a broad-spectrum protease inhibitor that has been employed as antiviral drug for other human respiratory viruses. Also, it has important anti-inflammatory properties for inhibiting the innate immunity contact system.

METHODS

This was a multicentre, double-blind, randomized trial performed in four Spanish hospitals comparing standard treatment versus standard treatment + aprotinin for patients with COVID-19 between 20 May 2020 and 20 October 2021. The primary efficacy outcomes were length of hospital stay and ICU admission. The secondary endpoints were each of the primary efficacy outcomes and a composite of oxygen therapy, analytical parameters and death. Safety outcomes included adverse reactions to treatment during a 30-day follow-up period. Treatment was given for 11 days or till discharge.

RESULTS

With almost identical analytical profiles, significant differences were observed in treatment time, which was 2 days lower in the aprotinin group (p = .002), and length of hospital admission, which was 5 days shorter in the aprotinin group (p = .003). The incidence of discharge was 2.19 times higher (HR: 2.188 [1.182-4.047]) in the aprotinin group than in the placebo group (p = .013). In addition, the aprotinin-treated group required less oxygen therapy and had no adverse reactions or side effects.

CONCLUSION

Inhaled aprotinin may improve standard treatment and clinical outcomes in hospitalized patients with COVID-19, resulting in a shorter treatment time and hospitalization compared with the placebo group. The administration of aprotinin was safe.

Drug Repurposing for COVID-19: A Review and a Novel Strategy to Identify New Targets and Potential Drug Candidates

In December 2019, the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19) was first identified in the province of Wuhan, China. Since then, there have been over 400 million confirmed cases and 5.8 million deaths by COVID-19 reported worldwide. The urgent need for therapies against SARS-CoV-2 led researchers to use drug repurposing approaches. This strategy allows the reduction in risks, time, and costs associated with drug development. In many cases, a repurposed drug can enter directly to preclinical testing and clinical trials, thus accelerating the whole drug discovery process. In this work, we will give a general overview of the main developments in COVID-19 treatment, focusing on the contribution of the drug repurposing paradigm to find effective drugs against this disease. Finally, we will present our findings using a new drug repurposing strategy that identified 11 compounds that may be potentially effective against COVID-19. To our knowledge, seven of these drugs have never been tested against SARS-CoV-2 and are potential candidates for in vitro and in vivo studies to evaluate their effectiveness in COVID-19 treatment.

Camostat Does Not Inhibit the Proteolytic Activity of Neutrophil Serine Proteases

Coronavirus disease 2019 (COVID-19) can lead to multi-organ failure influenced by comorbidities and age. Binding of the severe acute respiratory syndrome coronavirus 2 spike protein (SARS-CoV-2 S protein) to angiotensin-converting enzyme 2 (ACE2), along with proteolytic digestion of the S protein by furin and transmembrane protease serine subtype 2 (TMPRSS2), provokes internalization of SARS-CoV-2 into the host cell. Productive infection occurs through viral replication in the cytosol and cell-to-cell transmission. The catalytic activity of TMPRSS2 can be blocked by the trypsin-like serine protease inhibitor camostat, which impairs infection by SARS-CoV-2. At the site of infection, immune cells, such as neutrophils, infiltrate and become activated, releasing neutrophil serine proteases (NSPs), including cathepsin G (CatG), neutrophil elastase (NE), and proteinase 3 (PR3), which promote the mounting of a robust immune response. However, NSPs might be involved in infection and the severe outcome of COVID-19 since the uncontrolled proteolytic activity is responsible for many complications, including autoimmunity, chronic inflammatory disorders, cardiovascular diseases, and thrombosis. Here, we demonstrate that camostat does not inhibit the catalytic activity of CatG, NE, and PR3, indicating the need for additional selective serine protease inhibitors to reduce the risk of developing severe COVID-19.

SARS-CoV-2 and human retroelements: a case for molecular mimicry?

Background

The factors driving the late phase of COVID-19 are still poorly understood. However, autoimmunity is an evolving theme in COVID-19’s pathogenesis. Additionally, deregulation of human retroelements (RE) is found in many viral infections, and has also been reported in COVID-19.

Results

Unexpectedly, coronaviruses (CoV) – including SARS-CoV-2 – harbour many RE-identical sequences (up to 35 base pairs), and some of these sequences are part of SARS-CoV-2 epitopes associated to COVID-19 severity. Furthermore, RE are expressed in healthy controls and human cells and become deregulated after SARS-CoV-2 infection, showing mainly changes in long interspersed nuclear element (LINE1) expression, but also in endogenous retroviruses.

Conclusion

CoV and human RE share coding sequences, which are targeted by antibodies in COVID-19 and thus could induce an autoimmune loop by molecular mimicry.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-022-01040-2.

Antimicrobial peptides: A plausible approach for COVID-19 treatment

INTRODUCTION

Coronavirus disease 2019 (COVID-19), which emerged as a major public health threat, has affected >400 million people globally leading to >5 million mortalities to date. Treatments of COVID-19 are still to be developed as the available therapeutic approaches are not able to combat the virus causing the disease (severe acute respiratory syndrome coronavirus-2; SARS-CoV-2) satisfactorily. However, antiviral peptides (AVPs) have demonstrated prophylactic and therapeutic effects against many coronaviruses (CoVs).

AREAS COVERED

This review critically discusses various types of AVPs evaluated for the treatment of COVID-19 along with their mechanisms of action. Furthermore, the peptides inhibiting the entry of the virus by targeting its binding to angiotensin-converting enzyme 2 (ACE2) or integrins, fusion mechanism as well as activation of proteolytic enzymes (cathepsin L, transmembrane serine protease 2 (TMPRSS2), or furin) are also discussed.

EXPERT OPINION

Although extensively investigated, successful treatment of COVID-19 is still a challenge due to emergence of virus mutants. Antiviral peptides are anticipated to be blockbuster drugs for the management of this serious infection because of their formulation and therapeutic advantages. Although they may act on different pathways, AVPs having a multi-targeted approach are considered to have the upper hand in the management of this infection.

The Transmembrane Protease TMPRSS2 as a Therapeutic Target for COVID-19 Treatment

TMPRSS2 is a type II transmembrane protease with broad expression in epithelial cells of the respiratory and gastrointestinal tract, the prostate, and other organs. Although the physiological role of TMPRSS2 remains largely elusive, several endogenous substrates have been identified. TMPRSS2 serves as a major cofactor in SARS-CoV-2 entry, and primes glycoproteins of other respiratory viruses as well. Consequently, inhibiting TMPRSS2 activity is a promising strategy to block viral infection. In this review, we provide an overview of the role of TMPRSS2 in the entry processes of different respiratory viruses. We then review the different classes of TMPRSS2 inhibitors and their clinical development, with a focus on COVID-19 treatment.

Clinically available/under trial drugs and vaccines for treatment of SARS-COV-2

Prior 2019 to work date entire world is seriously influenced by an appalling illness called COVID sickness [Coronavirus disease-2019 (COVID-19)] which is brought about by another strain of coronavirus known as severe acute respiratory syndrome-Coronavirus-2. This pandemic was first seen in the Hubei area in Wuhan city of China. To date above 170 million individuals have been influenced by this infection and more than 3 million individuals died. The race of finding specific therapeutic drugs and efficacious vaccine candidates is still going on to tackle the pandemic-associated morbidities. This chapter discussed different clinically accessible medications (remdesivir, hydroxychloroquine, azithromycin, etc.) and immunizations (mRNA-1273, Sputanik, Pfizer, etc.) which are either in use or under trial for the treatment of COVID-19.

SARS-CoV-2 Antiviral Therapy

The development of effective antiviral therapy for COVID-19 is critical for those awaiting vaccination, as well as for those who do not respond robustly to vaccination. This review summarizes 1 year of progress in the race to develop antiviral therapies for COVID-19, including research spanning preclinical and clinical drug development efforts, with an emphasis on antiviral compounds that are in clinical development or that are high priorities for clinical development. The review is divided into sections on compounds that inhibit SARS-CoV-2 enzymes, including its polymerase and proteases; compounds that inhibit virus entry, including monoclonal antibodies; interferons; and repurposed drugs that inhibit host processes required for SARS-CoV-2 replication. The review concludes with a summary of the lessons to be learned from SARS-CoV-2 drug development efforts and the challenges to continued progress.

Identification of a dual acting SARS-CoV-2 proteases inhibitor through in silico design and step-by-step biological characterization

COVID-19 pandemic, starting from the latest 2019, and caused by SARS-CoV-2 pathogen, led to the hardest health-socio-economic disaster in the last century. Despite the tremendous scientific efforts, mainly focused on the development of vaccines, identification of potent and efficient anti-SARS-CoV-2 therapeutics still represents an unmet need. Remdesivir, an anti-Ebola drug selected from a repurposing campaign, is the only drug approved, so far, for the treatment of the infection. Nevertheless, WHO in later 2020 has recommended against its use in COVID-19. In the present paper, we describe a step-by-step in silico design of a small library of compounds as main protease (M^pro) inhibitors. All the molecules were screened by an enzymatic assay on M^pro and, then, cellular activity was evaluated using Vero cells viral infection model. The cellular screening disclosed compounds 29 and 34 as in-vitro SARS-CoV-2 replication inhibitors at non-toxic concentrations (0.32 < EC₅₀ < 5.98 μM). To rationalize these results, additional in-vitro assays were performed, focusing on papain like protease (PL^pro) and spike protein (SP) as potential targets for the synthesized molecules. This pharmacological workflow allowed the identification of compound 29, as a dual acting SARS-CoV-2 proteases inhibitor featuring micromolar inhibitory potency versus M^pro (IC₅₀ = 1.72 μM) and submicromolar potency versus PL^pro (IC₅₀ = 0.67 μM), and of compound 34 as a selective SP inhibitor (IC₅₀ = 3.26 μM).

Host directed therapies: COVID-19 and beyond

The global spread of SARS-CoV-2 has necessitated the development of novel, safe and effective therapeutic agents against this virus to stop the pandemic, however the development of novel antivirals may take years, hence, the best alternative available, is to repurpose the existing antiviral drugs with known safety profile in humans. After more than one year into this pandemic, global efforts have yielded the fruits and with the launch of many vaccines in the market, the world is inching towards the end of this pandemic, nonetheless, future pandemics of this magnitude or even greater cannot be denied. The preparedness against viruses of unknown origin should be maintained and the broad-spectrum antivirals with activity against range of viruses should be developed to curb future viral pandemics. The majority of antivirals developed till date are pathogen specific agents, which target critical viral pathways and lack broad spectrum activity required to target wide range of viruses. The surge in drug resistance among pathogens has rendered a compelling need to shift our focus towards host directed factors in the treatment of infectious diseases. This gains special relevance in the case of viral infections, where the pathogen encodes a handful of genes and predominantly depends on host factors for their propagation and persistence. Therefore, future antiviral drug development should focus more on targeting molecules of host pathways that are often hijacked by many viruses. Such cellular proteins of host pathways offer attractive targets for the development of broad-spectrum anticipatory antivirals. In the present article, we have reviewed the host directed therapies (HDTs) effective against viral infections with a special focus on COVID-19. This article also discusses the strategies involved in identifying novel host targets and subsequent development of broad spectrum HDTs.

Hindrance of the Proteolytic Activity of Neutrophil-Derived Serine Proteases by Serine Protease Inhibitors as a Management of Cardiovascular Diseases and Chronic Inflammation

During inflammation neutrophils become activated and segregate neutrophil serine proteases (NSPs) to the surrounding environment in order to support a natural immune defense. However, an excess of proteolytic activity of NSPs can cause many complications, such as cardiovascular diseases and chronic inflammatory disorders, which will be elucidated on a biochemical and immunological level. The application of selective serine protease inhibitors is the logical consequence in the management of the indicated comorbidities and will be summarized in this briefing.

Targeting the Pentose Phosphate Pathway for SARS-CoV-2 Therapy

SARS-CoV-2 is causing the coronavirus disease 2019 (COVID-19) pandemic, for which effective pharmacological therapies are needed. SARS-CoV-2 induces a shift of the host cell metabolism towards glycolysis, and the glycolysis inhibitor 2-deoxy-d-glucose (2DG), which interferes with SARS-CoV-2 infection, is under development for the treatment of COVID-19 patients. The glycolytic pathway generates intermediates that supply the non-oxidative branch of the pentose phosphate pathway (PPP). In this study, the analysis of proteomics data indicated increased transketolase (TKT) levels in SARS-CoV-2-infected cells, suggesting that a role is played by the non-oxidative PPP. In agreement, the TKT inhibitor benfooxythiamine (BOT) inhibited SARS-CoV-2 replication and increased the anti-SARS-CoV-2 activity of 2DG. In conclusion, SARS-CoV-2 infection is associated with changes in the regulation of the PPP. The TKT inhibitor BOT inhibited SARS-CoV-2 replication and increased the activity of the glycolysis inhibitor 2DG. Notably, metabolic drugs like BOT and 2DG may also interfere with COVID-19-associated immunopathology by modifying the metabolism of immune cells in addition to inhibiting SARS-CoV-2 replication. Hence, they may improve COVID-19 therapy outcomes by exerting antiviral and immunomodulatory effects.

A comprehensive review of COVID-19 biology, diagnostics, therapeutics, and disease impacting the central nervous system

The ongoing COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a highly transmissible disease. SARS-CoV-2 is estimated to have infected over 153 million people and to have caused over 3.2 million global deaths since its emergence in December 2019. SARS-CoV-2 is the seventh coronavirus known to infect humans, and like other coronaviruses, SARS-CoV-2 infection is characterized by a variety of symptoms including general flu-like symptoms such as a fever, sore throat, fatigue, and shortness of breath. Severe cases often display signs of pneumonia, lymphopenia, acute kidney injury, cardiac injury, cytokine storms, lung damage, acute respiratory distress syndrome (ARDS), multiple organ failure, sepsis, and death. There is evidence that around 30% of COVID-19 cases have central nervous system (CNS) or peripheral nervous system (PNS) symptoms along with or in the absence of the previously mentioned symptoms. In cases of CNS/PNS impairments, patients display dizziness, ataxia, seizure, nerve pain, and loss of taste and/or smell. This review highlights the neurological implications of SARS-CoV-2 and provides a comprehensive summary of the research done on SARS-CoV-2 pathology, diagnosis, therapeutics, and vaccines up to May 5.

A Potential Role of the CD47/SIRPalpha Axis in COVID-19 Pathogenesis

The coronavirus SARS-CoV-2 is the cause of the ongoing COVID-19 pandemic. Most SARS-CoV-2 infections are mild or even asymptomatic. However, a small fraction of infected individuals develops severe, life-threatening disease, which is caused by an uncontrolled immune response resulting in hyperinflammation. However, the factors predisposing individuals to severe disease remain poorly understood. Here, we show that levels of CD47, which is known to mediate immune escape in cancer and virus-infected cells, are elevated in SARS-CoV-2-infected Caco-2 cells, Calu-3 cells, and air-liquid interface cultures of primary human bronchial epithelial cells. Moreover, SARS-CoV-2 infection increases SIRPalpha levels, the binding partner of CD47, on primary human monocytes. Systematic literature searches further indicated that known risk factors such as older age and diabetes are associated with increased CD47 levels. High CD47 levels contribute to vascular disease, vasoconstriction, and hypertension, conditions that may predispose SARS-CoV-2-infected individuals to COVID-19-related complications such as pulmonary hypertension, lung fibrosis, myocardial injury, stroke, and acute kidney injury. Hence, age-related and virus-induced CD47 expression is a candidate mechanism potentially contributing to severe COVID-19, as well as a therapeutic target, which may be addressed by antibodies and small molecules. Further research will be needed to investigate the potential involvement of CD47 and SIRPalpha in COVID-19 pathology. Our data should encourage other research groups to consider the potential relevance of the CD47/ SIRPalpha axis in their COVID-19 research.

Enisamium Inhibits SARS-CoV-2 RNA Synthesis

Pandemic SARS-CoV-2 causes a mild to severe respiratory disease called coronavirus disease 2019 (COVID-19). While control of the SARS-CoV-2 spread partly depends on vaccine-induced or naturally acquired protective herd immunity, antiviral strategies are still needed to manage COVID-19. Enisamium is an inhibitor of influenza A and B viruses in cell culture and clinically approved in countries of the Commonwealth of Independent States. In vitro, enisamium acts through metabolite VR17-04 and inhibits the activity of the influenza A virus RNA polymerase. Here we show that enisamium can inhibit coronavirus infections in NHBE and Caco-2 cells, and the activity of the SARS-CoV-2 RNA polymerase in vitro. Docking and molecular dynamics simulations provide insight into the mechanism of action and indicate that enisamium metabolite VR17-04 prevents GTP and UTP incorporation. Overall, these results suggest that enisamium is an inhibitor of SARS-CoV-2 RNA synthesis in vitro.

Are Host Defense Peptides and Their Derivatives Ready to be Part of the Treatment of the Next Coronavirus Pandemic?

The term host defense peptides arose at the beginning to refer to those peptides that are part of the host’s immunity. Because of their broad antimicrobial capacity and immunomodulatory activity, nowadays, they emerge as a hope to combat resistant multi-drug microorganisms and emerging viruses, such as the case of coronaviruses. Since the beginning of this century, coronaviruses have been part of different outbreaks and a pandemic, and they will be surely part of the next pandemics, this review analyses whether these peptides and their derivatives are ready to be part of the treatment of the next coronavirus pandemic.

Kallikreins emerge as new regulators of viral infections

Kallikrein-related peptidases (KLKs) or kallikreins have been linked to diverse (patho) physiological processes, such as the epidermal desquamation and inflammation, seminal clot liquefaction, neurodegeneration, and cancer. Recent mounting evidence suggests that KLKs also represent important regulators of viral infections. It is well-established that certain enveloped viruses, including influenza and coronaviruses, require proteolytic processing of their hemagglutinin or spike proteins, respectively, to infect host cells. Similarly, the capsid protein of the non-enveloped papillomavirus L1 should be proteolytically cleaved for viral uncoating. Consequently, extracellular or membrane-bound proteases of the host cells are instrumental for viral infections and represent potential targets for drug development. Here, we summarize how extracellular proteolysis mediated by the kallikreins is implicated in the process of influenza (and potentially coronavirus and papillomavirus) entry into host cells. Besides direct proteolytic activation of viruses, KLK5 and 12 promote viral entry indirectly through proteolytic cascade events, like the activation of thrombolytic enzymes that also can process hemagglutinin, while additional functions of KLKs in infection cannot be excluded. In the light of recent evidence, KLKs represent potential host targets for the development of new antivirals. Humanized animal models to validate their key functions in viral infections will be valuable.

Coronavirus disease-2019: A review on the disease exacerbation via cytokine storm and concurrent management

Setting up treatment strategies is the highest concern today to reduce the fatality of COVID-19. Due to a very new kind of virus attack, no specific treatment has been discovered to date. The most crucial way to dominate the disease severity is now the repurposing of drugs. In this review, we focused on the current treatment approaches targeting the crucial causative factors for the disease burden through cytokine storm or cytokine release syndrome. Several vaccines have been developed and have been applied already for prevention purposes, and several are on the way to be developed, although the effects and side effects are under observation. Presently, regulation of the immune response through intervention treatment methods has been adjusted on the basis of the COVID-19 severity stage and generally includes vaccines, immunotherapies including convalescent plasma and immunoglobulin treatment, monoclonal antibodies, cytokine therapy, complement inhibition, regenerative medicine, and repurposed anti-inflammatory and immune-regulatory drugs. Combination therapy is not acceptable in all respects because there is no concrete evidence in clinical trials or in vivo data. Target-specific drug therapies, such as inhibition of cytokine-producing signaling pathways, could be an excellent solution and thus reduce the severity of inflammation and disease severity. Therefore, gathering information about the mechanism of disease progression, possible goals, and drug efficacy of immune-based approaches to combat COVID-19 in the context of orderly review analysis is consequential.

COVID-19: Vaccine Delivery System, Drug Repurposing and Application of Molecular Modeling Approach

The acute respiratory syndrome coronavirus (SARS-CoV-2) has spread across the world, resulting in a pandemic COVID-19 which is a human zoonotic disease that is caused by a novel coronavirus (CoV) strain thought to have originated in wild or captive bats in the initial COVID outbreak region. The global COVID-19 outbreak started in Guangdong Province, China's southernmost province. The global response to the COVID-19 pandemic has been hampered by the sheer number of infected people, many of whom need intensive care before succumbing to the disease. The epidemic is being handled by a combination of disease control by public health interventions and compassionate treatment for those who have been impacted. There is no clear anti-COVID-19 medication available at this time. However, the need to find medications that can turn the tide has led to the development of a number of investigational drugs as potential candidates for improving outcomes, especially in the severely and critically ill. Although many of these adjunctive medications are still being studied in clinical trials, professional organizations have attempted to define the circumstances in which their use is deemed off-label or compassionate. It is important to remind readers that new information about COVID-19's clinical features, treatment options, and outcomes is released on a regular basis. The mainstay of treatment remains optimized supportive care, and the therapeutic effectiveness of the subsequent agents is still being studied.

Generation of a Sleeping Beauty Transposon-Based Cellular System for Rapid and Sensitive Screening for Compounds and Cellular Factors Limiting SARS-CoV-2 Replication

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the acute respiratory disease COVID-19, which has become a global concern due to its rapid spread. The common methods to monitor and quantitate SARS-CoV-2 infectivity in cell culture are so far time-consuming and labor-intensive. Using the Sleeping Beauty transposase system, we generated a robust and versatile cellular infection model that allows SARS-CoV-2 infection experiments compatible for high-throughput and live cell imaging. The model is based on lung derived A549 cells, which show a profound interferon response and convenient cell culture characteristics. ACE2 and TMPRSS2 were introduced for constitutive expression (A549-AT). Subclones with varying levels of ACE2/TMPRSS2 were screened for optimal SARS-CoV-2 susceptibility. Furthermore, extensive evaluation demonstrated that SARS-CoV-2 infected A549-AT cells were distinguishable from mock-infected cells and already showed approximately 12 h post infection a clear signal to noise ratio in terms of cell roughness, fluorescence and a profound visible cytopathic effect. Moreover, due to the high transfection efficiency and proliferation capacity, Sleeping Beauty transposase-based overexpression cell lines with a second inducible fluorescence reporter cassette (eGFP) can be generated in a very short time, enabling the investigation of host and restriction factors in a doxycycline-inducible manner. Thus, the novel model cell line allows rapid and sensitive monitoring of SARS-CoV-2 infection and the screening for host factors essential for viral replication.

TMPRSS2 expression dictates the entry route used by SARS-CoV-2 to infect host cells

SARS-CoV-2 is a newly emerged coronavirus that caused the global COVID-19 outbreak in early 2020. COVID-19 is primarily associated with lung injury, but many other clinical symptoms such as loss of smell and taste demonstrated broad tissue tropism of the virus. Early SARS-CoV-2-host cell interactions and entry mechanisms remain poorly understood. Investigating SARS-CoV-2 infection in tissue culture, we found that the protease TMPRSS2 determines the entry pathway used by the virus. In the presence of TMPRSS2, the proteolytic process of SARS-CoV-2 was completed at the plasma membrane, and the virus rapidly entered the cells within 10 min in a pH-independent manner. When target cells lacked TMPRSS2 expression, the virus was endocytosed and sorted into endolysosomes, from which SARS-CoV-2 entered the cytosol via acid-activated cathepsin L protease 40-60 min post-infection. Overexpression of TMPRSS2 in non-TMPRSS2 expressing cells abolished the dependence of infection on the cathepsin L pathway and restored sensitivity to the TMPRSS2 inhibitors. Together, our results indicate that SARS-CoV-2 infects cells through distinct, mutually exclusive entry routes and highlight the importance of TMPRSS2 for SARS-CoV-2 sorting into either pathway.

Effect of Aprotinin and Avifavir® Combination Therapy for Moderate COVID-19 Patients

COVID-19 is a contagious multisystem inflammatory disease caused by a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We studied the efficacy of Aprotinin (nonspecific serine proteases inhibitor) in combination with Avifavir^® or Hydroxychloroquine (HCQ) drugs, which are recommended by the Russian Ministry of Health for the treatment therapy of moderate COVID-19 patients. This prospective single-center study included participants with moderate COVID-19-related pneumonia, laboratory-confirmed SARS-CoV-2, and admitted to the hospitals. Patients received combinations of intravenous (IV) Aprotinin (1,000,000 KIU daily, 3 days) and HCQ (cohort 1), inhalation (inh) treatment with Aprotinin (625 KIU four times per day, 5 days) and HCQ (cohort 2) or IV Aprotinin (1,000,000 KIU daily for 5 days) and Avifavir (cohort 3). In cohorts 1–3, the combination therapy showed 100% efficacy in preventing the transfer of patients (n = 30) to the intensive care unit (ICU). The effect of the combination therapy in cohort 3 was the most prominent, and the median time to SARS-CoV-2 elimination was 3.5 days (IQR 3.0–4.0), normalization of the CRP concentration was 3.5 days (IQR 3–5), of the D-dimer concentration was 5 days (IQR 4 to 5); body temperature was 1 day (IQR 1–3), improvement in clinical status or discharge from the hospital was 5 days (IQR 5–5), and improvement in lung lesions of patients on 14 day was 100%.

The endogenous cellular protease inhibitor SPINT2 controls SARS-CoV-2 viral infection and is associated to disease severity

COVID-19 outbreak is the biggest threat to human health in recent history. Currently, there are over 1.5 million related deaths and 75 million people infected around the world (as of 22/12/2020). The identification of virulence factors which determine disease susceptibility and severity in different cell types remains an essential challenge. The serine protease TMPRSS2 has been shown to be important for S protein priming and viral entry, however, little is known about its regulation. SPINT2 is a member of the family of Kunitz type serine protease inhibitors and has been shown to inhibit TMPRSS2. Here, we explored the existence of a co-regulation between SPINT2/TMPRSS2 and found a tightly regulated protease/inhibitor expression balance across tissues. We found that SPINT2 negatively correlates with SARS-CoV-2 expression in Calu-3 and Caco-2 cell lines and was down-regulated in secretory cells from COVID-19 patients. We validated our findings using Calu-3 cell lines and observed a strong increase in viral load after SPINT2 knockdown, while overexpression lead to a drastic reduction of the viral load. Additionally, we evaluated the expression of SPINT2 in datasets from comorbid diseases using bulk and scRNA-seq data. We observed its down-regulation in colon, kidney and liver tumors as well as in alpha pancreatic islets cells from diabetes Type 2 patients, which could have implications for the observed comorbidities in COVID-19 patients suffering from chronic diseases.

Pharmacological Effects of Selected Medicinal Plants and Vitamins Against COVID-19

The coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). It is a serious disease that has caused multiple deaths in various countries in the world. Globally, as of May 23, 2021, the total confirmed cases of COVID-19 have reach 166,346,635 with a total of 3,449,117 deaths. Several recent scientific studies have shown that medicinal plants and vitamins can benefit and improve the health of COVID-19 patients. However, the benefits of medicinal plants and vitamins in the treatment of COVID-19 remain unproven. Therefore, the objective of this article is to expounds the benefits of using medicinal plants (Allium sativum, curcumin, Nigella sativa, Zingiber officitale) and vitamins (vitamin C and vitamin D) that possess the antiviral properties for the prevention and/or control of COVID-19. To reach our objective, we searched scientific databases of ongoing trials in the Centers for Disease Control and Prevention websites, PubMed Central, Medline databases, and Google Scholar websites. We also searched databases on World Health Organization International Clinical Trials Registry Platform to collect relevant papers. We found that all of the selected medicinal plants and vitamins possess antiviral activities, and their individual intake shows promise for the prevention and/or control of COVID-19. We conclude that, the selected medicinal plants and vitamins possess anti-viral properties that are more likely to prevent and/or disrupt the SARS-CoV-2 replication cycle, enhance the human immune system and promote good health.

Trypsin-Like Proteases and Their Role in Muco-Obstructive Lung Diseases

Trypsin-like proteases (TLPs) belong to a family of serine enzymes with primary substrate specificities for the basic residues, lysine and arginine, in the P1 position. Whilst initially perceived as soluble enzymes that are extracellularly secreted, a number of novel TLPs that are anchored in the cell membrane have since been discovered. Muco-obstructive lung diseases (MucOLDs) are characterised by the accumulation of hyper-concentrated mucus in the small airways, leading to persistent inflammation, infection and dysregulated protease activity. Although neutrophilic serine proteases, particularly neutrophil elastase, have been implicated in the propagation of inflammation and local tissue destruction, it is likely that the serine TLPs also contribute to various disease-relevant processes given the roles that a number of these enzymes play in the activation of both the epithelial sodium channel (ENaC) and protease-activated receptor 2 (PAR2). More recently, significant attention has focused on the activation of viruses such as SARS-CoV-2 by host TLPs. The purpose of this review was to highlight key TLPs linked to the activation of ENaC and PAR2 and their association with airway dehydration and inflammatory signalling pathways, respectively. The role of TLPs in viral infectivity will also be discussed in the context of the inhibition of TLP activities and the potential of these proteases as therapeutic targets.

Exploring SARS-CoV-2 Spikes Glycoproteins for Designing Potential Antiviral Targets

Till today, the globe is still struggling with the newly emerging infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and known as coronavirus disease 2019 (COVID-19). It has resulted in multiple fatalities from SARSs all around the world. A year after the global pandemic, the World Health Organization (WHO) has reported more than 79 million confirmed cases of COVID-19 and over 1.7 million deaths, making it one of the worst and most difficult pandemics encompassed in the modern history. The ongoing triad of escalating infections, mortality, and economic loss has urgently called for recognizing SARS-CoV-2 cell entry mechanisms as a crucial step in the initial stages of infection and to which possible interventional strategies should be targeted. To mediate host cell infections, Coronaviruses utilize the immunogenic studded spikes glycoproteins on its surface as a key factor for attachment, fusion, and entrance to host cells. Herein, we shed the light on a potential strategy involving disruption of SARS-CoV-2 S protein interaction with host cell receptors through design of neutralizing antibodies targeting receptor binding domain in S1 subunit, small peptide inhibitors, peptide fusion inhibitors against S2, host cell angiotensin converting enzymes 2 (ACE2), and protease inhibitors, aiming to pave the way for controlling viral cell entrance. In this review, we also highlight the recent research advances in the antiviral drugs that target the highly exposed spike protein, aiming to stem the COVID-19 pandemic.

Therapeutic approaches for SARS-CoV-2 infection

Therapeutic approaches to COVID-19 treatment require appropriate inhibitors to target crucial proteins of SARS-CoV-2 replication machinery. It’s been approximately 12 months since the pandemic started, yet no known specific drugs are available. However, research progresses with time in terms of high throughput virtual screening (HTVS) and rational design of repurposed, novel synthetic and natural products discovery by understanding the viral life cycle, immuno-pathological and clinical outcomes in patients based on host’s nutritional, metabolic, and lifestyle status. Further, complementary and alternative medicine (CAM) approaches have also improved resiliency and immune responses. In this article, we summarize all the therapeutic antiviral strategies for COVID-19 drug discovery including computer aided virtual screening, repurposed drugs, immunomodulators, vaccines, plasma therapy, various adjunct therapies, and phage technology to unravel insightful mechanistic pathways of targeting SARS-CoV-2 and host’s intrinsic, innate immunity at multiple checkpoints that aid in the containment of the disease.

Inhibitory effects of aprotinin on influenza A and B viruses in vitro and in vivo

Influenza viruses cause significant morbidity and mortality worldwide. Long-term or frequent use of approved anti-influenza agents has resulted in drug-resistant strains, thereby necessitating the discovery of new drugs. In this study, we found aprotinin, a serine protease inhibitor, as an anti-influenza candidate through screening of compound libraries. Aprotinin has been previously reported to show inhibitory effects on a few influenza A virus (IAV) subtypes (e.g., seasonal H1N1 and H3N2). However, because there were no reports of its inhibitory effects on the other types of influenza viruses, we investigated the inhibitory effects of aprotinin in vitro on a wide range of influenza viruses, including avian and oseltamivir-resistant influenza virus strains. Our cell-based assay showed that aprotinin had inhibitory effects on seasonal human IAVs (H1N1 and H3N2 subtypes), avian IAVs (H5N2, H6N5, and H9N2 subtypes), an oseltamivir-resistant IAV, and a currently circulating influenza B virus. We have also confirmed its activity in mice infected with a lethal dose of influenza virus, showing a significant increase in survival rate. Our findings suggest that aprotinin has the capacity to inhibit a wide range of influenza virus subtypes and should be considered for development as a therapeutic agent against influenza.

Targeting the intestinal TMPRSS2 protease to prevent SARS-CoV-2 entry into enterocytes-prospects and challenges

The transmembrane protease serine 2 (TMPRSS2) is a membrane anchored protease that primarily expressed by epithelial cells of respiratory and gastrointestinal systems and has been linked to multiple pathological processes in humans including tumor growth, metastasis and viral infections. Recent studies have shown that TMPRSS2 expressed on cell surface of host cells could play a crucial role in activation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein which facilitates the rapid early entry of the virus into host cells. In addition, direct suppression of TMPRSS2 using small drug inhibitors has been demonstrated to be effective in decreasing SARS-CoV-2 infection in vitro, which presents TMPRSS2 protease as a potential therapeutic strategy for SARS-CoV-2 infection. Recently, SARS-CoV-2 has been shown to be capable of infecting gastrointestinal enterocytes and to provoke gastrointestinal disorders in patients with COVID-19 disease, which is considered as a new transmission route and target organ of SARS-CoV-2. In this review, we highlight the biochemical properties of TMPRSS2 protease and discuss the potential targeting of TMPRSS2 by inhibitors to prevent the SARS-CoV-2 spreading through gastro-intestinal tract system as well as the hurdles that need to be overcome.

In Vitro Lung Models and Their Application to Study SARS-CoV-2 Pathogenesis and Disease

SARS-CoV-2 has spread across the globe with an astonishing velocity and lethality that has put scientist and pharmaceutical companies worldwide on the spot to develop novel treatment options and reliable vaccination for billions of people. To combat its associated disease COVID-19 and potentially newly emerging coronaviruses, numerous pre-clinical cell culture techniques have progressively been used, which allow the study of SARS-CoV-2 pathogenesis, basic replication mechanisms, and drug efficiency in the most authentic context. Hence, this review was designed to summarize and discuss currently used in vitro and ex vivo cell culture systems and will illustrate how these systems will help us to face the challenges imposed by the current SARS-CoV-2 pandemic.

Resources and computational strategies to advance small molecule SARS-CoV-2 discovery: Lessons from the pandemic and preparing for future health crises

There is an urgent need to identify new therapies that prevent SARS-CoV-2 infection and improve the outcome of COVID-19 patients. This pandemic has thus spurred intensive research in most scientific areas and in a short period of time, several vaccines have been developed. But, while the race to find vaccines for COVID-19 has dominated the headlines, other types of therapeutic agents are being developed. In this mini-review, we report several databases and online tools that could assist the discovery of anti-SARS-CoV-2 small chemical compounds and peptides. We then give examples of studies that combined in silico and in vitro screening, either for drug repositioning purposes or to search for novel bioactive compounds. Finally, we question the overall lack of discussion and plan observed in academic research in many countries during this crisis and suggest that there is room for improvement.