Morphological cell profiling of SARS-CoV-2 infection identifies drug repurposing candidates for COVID-19

Lactoferrin Decreases Enterotoxigenic Escherichia coli-Induced Fluid Secretion and Bacterial Adhesion in the Porcine Small Intestine

Enterotoxigenic Escherichia coli (ETEC) infections are one of the most prevalent causes of post-weaning diarrhea in piglets, resulting in morbidity, mortality and elevated use of antibiotics. The emergence and further spread of antimicrobial resistance together with the growing demand for high quality animal protein requires the identification of novel alternatives for antimicrobials. A promising alternative is lactoferrin, as we previously showed that it can both inhibit the growth and degrade bacterial virulence factors of porcine ETEC strains in vitro. Aiming to confirm these findings in vivo, we performed a small intestinal segment perfusion experiment in piglets. Here, we showed that lactoferrin could not only decrease ETEC-induced fluid secretion, but also their ability to colonize the small intestinal epithelium. Furthermore, while ETEC infection induced pro-inflammatory cytokine mRNA expression in this experiment, lactoferrin was not able to counteract these responses. In addition, a bacterial motility assay showed that lactoferrin can reduce the motility of ETEC. Our findings further support the use of lactoferrin as an alternative for antimicrobials and also show its potential for the prevention of ETEC infections in pigs.

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.

Antibacterial properties of lactoferrin: A bibliometric analysis from 2000 to early 2022

Background

Here, a bibliometric and knowledge map analysis are used to analyze the research hot spots and development trends regarding the antibacterial effect of lactoferrin (LF). By looking for research hot spots and new topics, we provide new clues and research directions for future research.

Methods

Articles and reviews regarding the antibacterial effect of LF were retrieved and from the Web of Science Core Collection (WoSCC) on 25 June 2022. CiteSpace and VOSviewer were used to conduct the bibliometric and knowledge map analysis.

Results

In total, 8,292 authors at 2,151 institutions from 86 countries published 1,923 articles in 770 academic journals. The United States was the leader regarding research on the antibacterial effects of LF, while the Netherlands was a pioneer in conducting research in this field. The University of California system contributed the most publications. Bolscher JGM published most articles, while Wayne Bellamy had most cocitations. However, there was insufficient cooperation among the various institutions and authors. BioMetals published most LF-antibacterial activity-related articles, whereas Infection and Immunity was most commonly cocited journal. The most influential research hot spots about the antibacterial effect of LF focused on antimicrobial peptides, casein, human milk, expression, and Escherichia coli-related research. The latest hot spots and research frontier included COVID-19, antibiofilm activity, and immune defense.

Conclusions

LF is a multifunctional protein with a broad spectrum of antimicrobial activities. The related field of antibacterial properties of LF will remain a research hot spot in future.

In Vitro Evaluation and Mitigation of Niclosamide's Liabilities as a COVID-19 Treatment

Niclosamide, an FDA-approved oral anthelmintic drug, has broad biological activity including anticancer, antibacterial, and antiviral properties. Niclosamide has also been identified as a potent inhibitor of SARS-CoV-2 infection in vitro, generating interest in its use for the treatment or prevention of COVID-19. Unfortunately, there are several potential issues with using niclosamide for COVID-19, including low bioavailability, significant polypharmacology, high cellular toxicity, and unknown efficacy against emerging SARS-CoV-2 variants of concern. In this study, we used high-content imaging-based immunofluorescence assays in two different cell models to assess these limitations and evaluate the potential for using niclosamide as a COVID-19 antiviral. We show that despite promising preliminary reports, the antiviral efficacy of niclosamide overlaps with its cytotoxicity giving it a poor in vitro selectivity index for anti-SARS-CoV-2 inhibition. We also show that niclosamide has significantly variable potency against the different SARS-CoV-2 variants of concern and is most potent against variants with enhanced cell-to-cell spread including the B.1.1.7 (alpha) variant. Finally, we report the activity of 33 niclosamide analogs, several of which have reduced cytotoxicity and increased potency relative to niclosamide. A preliminary structure-activity relationship analysis reveals dependence on a protonophore for antiviral efficacy, which implicates nonspecific endolysosomal neutralization as a dominant mechanism of action. Further single-cell morphological profiling suggests niclosamide also inhibits viral entry and cell-to-cell spread by syncytia. Altogether, our results suggest that niclosamide is not an ideal candidate for the treatment of COVID-19, but that there is potential for developing improved analogs with higher clinical translational potential in the future.

An overview on in vitro and in vivo antiviral activity of lactoferrin: its efficacy against SARS-CoV-2 infection

Beyond the absolute and indisputable relevance and efficacy of anti-SARS-CoV-2 vaccines, the rapid transmission, the severity of infection, the absence of the protection on immunocompromised patients, the propagation of variants, the onset of infection and/or disease in vaccinated subjects and the lack of availability of worldwide vaccination require additional antiviral treatments. Since 1987, lactoferrin (Lf) is well-known to possess an antiviral activity related to its physico-chemical properties and to its ability to bind to both heparan sulfate proteoglycans (HSPGs) of host cells and/or surface components of viral particles. In the present review, we summarize in vitro and in vivo studies concerning the efficacy of Lf against DNA, RNA, enveloped and non-enveloped viruses. Recent studies have revealed that the in vitro antiviral activity of Lf is also extendable to SARS-CoV-2. In vivo, Lf oral administration in early stage of SARS-CoV-2 infection counteracts COVID-19 pathogenesis. In particular, the effect of Lf on SARS-CoV-2 entry, inflammatory homeostasis, iron dysregulation, iron-proteins synthesis, reactive oxygen formation, oxidative stress, gut-lung axis regulation as well as on RNA negativization, and coagulation/fibrinolysis balance will be critically reviewed. Moreover, the molecular mechanisms underneath, including the Lf binding to HSPGs and spike glycoprotein, will be disclosed and discussed. Taken together, present data not only support the application of the oral administration of Lf alone in asymptomatic COVID-19 patients or as adjuvant of standard of care practice in symptomatic ones but also constitute the basis for enriching the limited literature on Lf effectiveness for COVID-19 treatment.

The Influence of Viral Infections on Iron Homeostasis and the Potential for Lactoferrin as a Therapeutic in the Age of the SARS-CoV-2 Pandemic

The association of hyperinflammation and hyperferritinemia with adverse outcomes in SARS-CoV-2-infected patients suggests an integral role for iron homeostasis in pathogenesis, a commonly described symptom of respiratory viral infections. This dysregulated iron homeostasis results in viral-induced lung injury, often lasting long after the acute viral infection; however, much remains to be understood mechanistically. Lactoferrin is a multipurpose glycoprotein with key immunomodulatory, antimicrobial, and antiviral functions, which can be found in various secreted fluids, but is most abundantly characterized in milk from all mammalian species. Lactoferrin is found at its highest concentrations in primate colostrum; however, the abundant availability of bovine-dairy-derived lactoferrin (bLf) has led to the use of bLf as a functional food. The recent research has demonstrated the potential value of bovine lactoferrin as a therapeutic adjuvant against SARS-CoV-2, and herein this research is reviewed and the potential mechanisms of therapeutic targeting are considered.

Imaging Techniques: Essential Tools for the Study of SARS-CoV-2 Infection

The world has seen the emergence of a new virus in 2019, SARS-CoV-2, causing the COVID-19 pandemic and millions of deaths worldwide. Microscopy can be much more informative than conventional detection methods such as RT-PCR. This review aims to present the up-to-date microscopy observations in patients, the in vitro studies of the virus and viral proteins and their interaction with their host, discuss the microscopy techniques for detection and study of SARS-CoV-2, and summarize the reagents used for SARS-CoV-2 detection. From basic fluorescence microscopy to high resolution techniques and combined technologies, this article shows the power and the potential of microscopy techniques, especially in the field of virology.

Bovine lactoferrin increases the poly(I:C)-induced antiviral response in vitro

Bovine lactoferrin (bLF) is a naturally occurring glycoprotein with antibacterial and antiviral activities. We evaluated whether bLF can prevent viral infections in the human intestinal epithelial cell line Caco-2. To assess antiviral responses, we measured the levels of interferon (IFN) expression, IFN-stimulated gene expression, and infection with a pseudotyped virus bearing either severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein or vesicular stomatitis virus (VSV)-G protein after treatment of cells with both bLF and polyinosinic-polycytidylic acid, an analog of double-stranded RNA that mimics viral infection. Combination treatment of cells with both bLF and polyinosinic-polycytidylic acid increased mRNA and protein expression of several IFN genes (IFNB, IFN L1, and IFNL2) and IFN-stimulated genes (ISG15, MX1, IFITM1, and IFITM3) in Caco-2 cells. However, treatment with bLF alone did not induce an antiviral response. Furthermore, combination treatment suppressed infection of the SARS-CoV-2 pseudotyped virus more efficiently than did bLF treatment alone, even though combination treatment increased mRNA expression of ACE2. These results indicate that bLF treatment increases the antiviral response that is associated with the double-stranded RNA-stimulated signaling pathway. Our results also suggest that bLF and double-stranded RNA analogs can be used to treat viral infection, including that by SARS-CoV-2.

Exploring the Immunomodulatory Aspect of Mesenchymal Stem Cells for Treatment of Severe Coronavirus Disease 19

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is an enveloped, positive sense, single stranded RNA (+ssRNA) virus, belonging to the genus Betacoronavirus and family Coronaviridae. It is primarily transmitted from infected persons to healthy ones through inhalation of virus-laden respiratory droplets. After an average incubation period of 2–14 days, the majority of infected individuals remain asymptomatic and/or mildly symptomatic, whereas the remaining individuals manifest a myriad of clinical symptoms, including fever, sore throat, dry cough, fatigue, chest pain, and breathlessness. SARS-CoV-2 exploits the angiotensin converting enzyme 2 (ACE-2) receptor for cellular invasion, and lungs are amongst the most adversely affected organs in the body. Thereupon, immune responses are elicited, which may devolve into a cytokine storm characterized by enhanced secretion of multitude of inflammatory cytokines/chemokines and growth factors, such as interleukin (IL)-2, IL-6, IL-7, IL-8, IL-9, tumor necrosis factor alpha (TNF-α), granulocyte colony-stimulating factor (GCSF), basic fibroblast growth factor 2 (bFGF2), monocyte chemotactic protein-1 (MCP1), interferon-inducible protein 10 (IP10), macrophage inflammatory protein 1A (MIP1A), platelet-derived growth factor subunit B (PDGFB), and vascular endothelial factor (VEGF)-A. The systemic persistence of inflammatory molecules causes widespread histological injury, leading to functional deterioration of the infected organ(s). Although multiple treatment modalities with varying effectiveness are being employed, nevertheless, there is no curative COVID-19 therapy available to date. In this regard, one plausible supportive therapeutic modality may involve administration of mesenchymal stem cells (MSCs) and/or MSC-derived bioactive factors-based secretome to critically ill COVID-19 patients with the intention of accomplishing better clinical outcome owing to their empirically established beneficial effects. MSCs are well established adult stem cells (ASCs) with respect to their immunomodulatory, anti-inflammatory, anti-oxidative, anti-apoptotic, pro-angiogenic, and pro-regenerative properties. The immunomodulatory capabilities of MSCs are not constitutive but rather are highly dependent on a holistic niche. Following intravenous infusion, MSCs are known to undergo considerable histological trapping in the lungs and, therefore, become well positioned to directly engage with lung infiltrating immune cells, and thereby mitigate excessive inflammation and reverse/regenerate damaged alveolar epithelial cells and associated tissue post SARS-CoV-2 infection. Considering the myriad of abovementioned biologically beneficial properties and emerging translational insights, MSCs may be used as potential supportive therapy to counteract cytokine storms and reduce disease severity, thereby facilitating speedy recovery and health restoration.

Cell and Animal Models for SARS-CoV-2 Research

During the last two years following the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, development of potent antiviral drugs and vaccines has been a global health priority. In this context, the understanding of virus pathophysiology, the identification of associated therapeutic targets, and the screening of potential effective compounds have been indispensable advancements. It was therefore of primary importance to develop experimental models that recapitulate the aspects of the human disease in the best way possible. This article reviews the information concerning available SARS-CoV-2 preclinical models during that time, including cell-based approaches and animal models. We discuss their evolution, their advantages, and drawbacks, as well as their relevance to drug effectiveness evaluation.

Repurposing the Antiplatelet Agent Ticlopidine to Counteract the Acute Phase of ER Stress Condition: An Opportunity for Fighting Coronavirus Infections and Cancer

Different pathological conditions, including viral infections and cancer, can have a massive impact on the endoplasmic reticulum (ER), causing severe damage to the cell and exacerbating the disease. In particular, coronavirus infections, including SARS coronavirus-2 (SARS-CoV-2), responsible for COVID-19, cause ER stress as a consequence of the enormous amounts of viral glycoproteins synthesized, the perturbation of ER homeostasis and the modification of ER membranes. Therefore, ER has a central role in the viral life cycle, thus representing one of the Achilles’ heels on which to focus therapeutic intervention. On the other hand, prolonged ER stress has been demonstrated to promote many pro-tumoral attributes in cancer cells, having a key role in tumor growth, metastasis and response to therapies. In this report, adopting a repurposing approach of approved drugs, we identified the antiplatelet agent ticlopidine as an interferent of the unfolded protein response (UPR) via sigma receptors (SRs) modulation. The promising results obtained suggest the potential use of ticlopidine to counteract ER stress induced by viral infections, such as COVID-19, and cancer.

Molecular design of a pathogen activated, self-assembling mechanopharmaceutical device

Weakly basic small molecule drugs like clofazimine can be used as building blocks for endowing cells with unnatural structural and functional elements. Here, we describe how clofazimine represents a first-in-class mechanopharmaceutical device, serving to construct inert, inactive and stimulus responsive drug depots within the endophagolysosomal compartment of cells of living organisms. Upon oral administration, clofazimine molecules self-assemble into stable, membrane-bound, crystal-like drug inclusions (CLDI) that accumulate within macrophages to form a "smart" biocompatible, pathogen activatable mechanopharmaceutical device. Upon perturbation of the mechanism maintaining pH and ion homeostasis of these CLDIs, the inert encapsulated drug precipitates are destabilized, releasing bioactive drug molecules into the cell and its surrounding. The resulting increase in clofazimine solubility activates this broad-spectrum antimicrobial, antiparasitic, antiviral or cytotoxic agent within the infected macrophage. We present a general, molecular design strategy for using clofazimine and other small molecule building blocks for the cytoplasmic construction of mechanopharmaceutical devices, aimed at rapid deployment during infectious disease outbreaks, for the purpose of pandemic prevention.

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.

The IDentif.AI-x pandemic readiness platform: Rapid prioritization of optimized COVID-19 combination therapy regimens

IDentif.AI-x, a clinically actionable artificial intelligence platform, was used to rapidly pinpoint and prioritize optimal combination therapies against COVID-19 by pairing a prospective, experimental validation of multi-drug efficacy on a SARS-CoV-2 live virus and Vero E6 assay with a quadratic optimization workflow. A starting pool of 12 candidate drugs developed in collaboration with a community of infectious disease clinicians was first narrowed down to a six-drug pool and then interrogated in 50 combination regimens at three dosing levels per drug, representing 729 possible combinations. IDentif.AI-x revealed EIDD-1931 to be a strong candidate upon which multiple drug combinations can be derived, and pinpointed a number of clinically actionable drug interactions, which were further reconfirmed in SARS-CoV-2 variants B.1.351 (Beta) and B.1.617.2 (Delta). IDentif.AI-x prioritized promising drug combinations for clinical translation and can be immediately adjusted and re-executed with a new pool of promising therapies in an actionable path towards rapidly optimizing combination therapy following pandemic emergence.

In Vitro Evaluation and Mitigation of Niclosamide’s Liabilities as a COVID-19 Treatment.. [PMID: 35860224 PMCID: PMC9298134 DOI: 10.1101/2022.06.24.497526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Niclosamide, an FDA-approved oral anthelmintic drug, has broad biological activity including anticancer, antibacterial, and antiviral properties. Niclosamide has also been identified as a potent inhibitor of SARS-CoV-2 infection in vitro, generating interest in its use for the treatment or prevention of COVID-19. Unfortunately, there are several potential issues with using niclosamide for COVID-19, including low bioavailability, significant polypharmacology, high cellular toxicity, and unknown efficacy against emerging SARS-CoV-2 variants of concern. In this study, we used high-content imaging-based immunofluorescence assays in two different cell models to assess these limitations and evaluate the potential for using niclosamide as a COVID-19 antiviral. We show that despite promising preliminary reports, the antiviral efficacy of niclosamide overlaps with its cytotoxicity giving it a poor in vitro selectivity index for anti-SARS-CoV-2 inhibition. We also show that niclosamide has significantly variable potency against the different SARS-CoV-2 variants of concern and is most potent against variants with enhanced cell-to-cell spread including B.1.1.7. Finally, we report the activity of 33 niclosamide analogs, several of which have reduced cytotoxicity and increased potency relative to niclosamide. A preliminary structure-activity relationship analysis reveals dependence on a protonophore for antiviral efficacy, which implicates nonspecific endolysosomal neutralization as a dominant mechanism of action. Further single-cell morphological profiling suggests niclosamide also inhibits viral entry and cell-to-cell spread by syncytia. Altogether, our results suggest that niclosamide is not an ideal candidate for the treatment of COVID-19, but that there is potential for developing improved analogs with higher clinical translational potential in the future.

Overview of Breastfeeding Under COVID-19 Pandemic

During the global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), pregnant and lactating women are at higher risk of infection. The potential of viral intrauterine transmission and vertical transmission by breastfeeding has raised wide concerns. Breastmilk is rich in nutrients that contribute to infant growth and development, and reduce the incidence rate of infant illness and death, as well as inhibit pathogens significantly, and protect infants from infection. Although it is controversial whether mothers infected with COVID-19 should continue to breastfeed, many countries and international organizations have provided recommendations and guidance for breastfeeding. This review presents the risks and benefits of breastfeeding for mothers infected with COVID-19, and the reasons for the absence of SARS-CoV-2 active virus in human milk. In addition, the antiviral mechanisms of nutrients in breastmilk, the levels of SARS-CoV-2 specific antibodies in breastmilk from COVID-19 infected mothers and vaccinated mothers are also summarized and discussed, aiming to provide some support and recommendations for both lactating mothers and infants to better deal with the COVID-19 pandemic.

Discovery of potential anti-SARS-CoV-2 drugs based on large-scale screening in vitro and effect evaluation in vivo

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global crisis. Clinical candidates with high efficacy, ready availability, and that do not develop resistance are in urgent need. Despite that screening to repurpose clinically approved drugs has provided a variety of hits shown to be effective against SARS-CoV-2 infection in cell culture, there are few confirmed antiviral candidates in vivo. In this study, 94 compounds showing high antiviral activity against SARS-CoV-2 in Vero E6 cells were identified from 2,580 FDA-approved small-molecule drugs. Among them, 24 compounds with low cytotoxicity were selected, and of these, 17 compounds also effectively suppressed SARS-CoV-2 infection in HeLa cells transduced with human ACE2. Six compounds disturb multiple processes of the SARS-CoV-2 life cycle. Their prophylactic efficacies were determined in vivo using Syrian hamsters challenged with SARS-CoV-2 infection. Seven compounds reduced weight loss and promoted weight regain of hamsters infected not only with the original strain but also the D614G variant. Except for cisatracurium, six compounds reduced hamster pulmonary viral load, and IL-6 and TNF-α mRNA when assayed at 4 d postinfection. In particular, sertraline, salinomycin, and gilteritinib showed similar protective effects as remdesivir in vivo and did not induce antiviral drug resistance after 10 serial passages of SARS-CoV-2 in vitro, suggesting promising application for COVID-19 treatment.

A Framework for Augmented Intelligence in Allergy and Immunology Practice and Research—A Work Group Report of the AAAAI Health Informatics, Technology, and Education Committee

Artificial and augmented intelligence (AI) and machine learning (ML) methods are expanding into the health care space. Big data are increasingly used in patient care applications, diagnostics, and treatment decisions in allergy and immunology. How these technologies will be evaluated, approved, and assessed for their impact is an important consideration for researchers and practitioners alike. With the potential of ML, deep learning, natural language processing, and other assistive methods to redefine health care usage, a scaffold for the impact of AI technology on research and patient care in allergy and immunology is needed. An American Academy of Asthma Allergy and Immunology Health Information Technology and Education subcommittee workgroup was convened to perform a scoping review of AI within health care as well as the specialty of allergy and immunology to address impacts on allergy and immunology practice and research as well as potential challenges including education, AI governance, ethical and equity considerations, and potential opportunities for the specialty. There are numerous potential clinical applications of AI in allergy and immunology that range from disease diagnosis to multidimensional data reduction in electronic health records or immunologic datasets. For appropriate application and interpretation of AI, specialists should be involved in the design, validation, and implementation of AI in allergy and immunology. Challenges include incorporation of data science and bioinformatics into training of future allergists-immunologists.

Lactoferrin as Immune-Enhancement Strategy for SARS-CoV-2 Infection in Alzheimer's Disease Patients

Coronavirus 2 (SARS-CoV2) (COVID-19) causes severe acute respiratory syndrome. Severe illness of COVID-19 largely occurs in older people and recent evidence indicates that demented patients have higher risk for COVID-19. Additionally, COVID-19 further enhances the vulnerability of older adults with cognitive damage. A balance between the immune and inflammatory response is necessary to control the infection. Thus, antimicrobial and anti-inflammatory drugs are hopeful therapeutic agents for the treatment of COVID-19. Accumulating evidence suggests that lactoferrin (Lf) is active against SARS-CoV-2, likely due to its potent antiviral and anti-inflammatory actions that ultimately improves immune system responses. Remarkably, salivary Lf levels are significantly reduced in different Alzheimer's disease (AD) stages, which may reflect AD-related immunological disturbances, leading to reduced defense mechanisms against viral pathogens and an increase of the COVID-19 susceptibility. Overall, there is an urgent necessity to protect AD patients against COVID-19, decreasing the risk of viral infections. In this context, we propose bovine Lf (bLf) as a promising preventive therapeutic tool to minimize COVID-19 risk in patients with dementia or AD.

Fluid-Phase Endocytosis and Lysosomal Degradation of Bovine Lactoferrin in Lung Cells

The iron-binding protein lactoferrin and the cell-penetrating peptides derived from its sequence utilise endocytosis to enter different cell types. The full-length protein has been extensively investigated as a potential therapeutic against a range of pathogenic bacteria, fungi, and viruses, including SARS-CoV-2. As a respiratory antiviral agent, several activity mechanisms have been demonstrated for lactoferrin, at the extracellular and plasma membrane levels, but as a protein that enters cells it may also have intracellular antiviral activity. Characterisation of lactoferrin’s binding, endocytic traffic to lysosomes, or recycling endosomes for exocytosis is lacking, especially in lung cell models. Here, we use confocal microscopy, flow cytometry, and degradation assays to evaluate binding, internalisation, endocytic trafficking, and the intracellular fate of bovine lactoferrin in human lung A549 cells. In comparative studies with endocytic probes transferrin and dextran, we show that lactoferrin binds to negative charges on the cell surface and actively enters cells via fluid-phase endocytosis, in a receptor-independent manner. Once inside the cell, we show that it is trafficked to lysosomes where it undergoes degradation within two hours. These findings provide opportunities for investigating both lactoferrin and derived cell-penetrating peptides activities of targeting intracellular pathogens.

Anti-Fungal Drug Anidulafungin Inhibits SARS-CoV-2 Spike-Induced Syncytia Formation by Targeting ACE2-Spike Protein Interaction

Drug repositioning continues to be the most effective, practicable possibility to treat COVID-19 patients. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus enters target cells by binding to the ACE2 receptor via its spike (S) glycoprotein. We used molecular docking-based virtual screening approaches to categorize potential antagonists, halting ACE2-spike interactions by utilizing 450 FDA-approved chemical compounds. Three drug candidates (i.e., anidulafungin, lopinavir, and indinavir) were selected, which show high binding affinity toward the ACE2 receptor. The conformational stability of selected docked complexes was analyzed through molecular dynamics (MD) simulations. The MD simulation trajectories were assessed and monitored for ACE2 deviation, residue fluctuation, the radius of gyration, solvent accessible surface area, and free energy landscapes. The inhibitory activities of the selected compounds were eventually tested in-vitro using Vero and HEK-ACE2 cells. Interestingly, besides inhibiting SARS-CoV-2 S glycoprotein induced syncytia formation, anidulafungin and lopinavir also blocked S-pseudotyped particle entry into target cells. Altogether, anidulafungin and lopinavir are ranked the most effective among all the tested drugs against ACE2 receptor-S glycoprotein interaction. Based on these findings, we propose that anidulafungin is a novel potential drug targeting ACE2, which warrants further investigation for COVID-19 treatment.

Evaluating the in vitro efficacy of bovine lactoferrin products against SARS-CoV-2 variants of concern

Bovine lactoferrin (bLF), a naturally occurring glycoprotein found in milk, has bioactive characteristics against many microbes, viruses, and other pathogens. Bovine lactoferrin strongly inhibits SARS-CoV-2 infection in vitro through direct entry inhibition and immunomodulatory mechanisms. This study reports on the anti-SARS-CoV-2 efficacy of commercially available bLF and common dairy ingredients in the human lung cell line H1437 using a custom high-content imaging and analysis pipeline. We also show for the first time that bLF has potent efficacy across different viral strains including the South African B.1.351, UK B.1.1.7, Brazilian P.1, and Indian Delta variants. Interestingly, we show that bLF is most potent against the B.1.1.7 variant [half-maximal inhibitory concentration (IC₅₀) = 3.7 µg/mL], suggesting that this strain relies on entry mechanisms that are strongly inhibited by bLF. We also show that one of the major proteolysis products of bLF, lactoferricin B 17-41, has a modest anti-SARS-CoV-2 activity that could add to the clinical significance of this protein for SARS-CoV-2 treatment as lactoferricin is released by pepsin during digestion. Finally, we show that custom chewable lactoferrin tablets formulated in dextrose or sorbitol have equivalent potency to unformulated samples and provide an option for future human clinical trials. Lactoferrin's broad inhibition of SARS-CoV-2 variants in conjunction with the low cost and ease of production make this an exciting clinical candidate for treatment or prevention of SARS-CoV-2 in the future.

Organoid and microfluidics-based platforms for drug screening in COVID-19

Proposing efficient prophylactic and therapeutic strategies for coronavirus 2019 (COVID-19) requires precise knowledge of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogenesis. An array of platforms, including organoids and microfluidic devices, have provided a basis for studies of SARS-CoV-2. Here, we summarize available models as well as novel drug screening approaches, from simple to more advanced platforms. Notably, organoids and microfluidic devices offer promising perspectives for the clinical translation of basic science, such as screening therapeutics candidates. Overall, modifying these advanced micro and macro 3D platforms for disease modeling and combining them with recent advances in drug screening has significant potential for the discovery of novel potent drugs against COVID-19.

In silico analysis of SARS-CoV-2 proteins as targets for clinically available drugs

The ongoing pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) requires treatments with rapid clinical translatability. Here we develop a multi-target and multi-ligand virtual screening method to identify FDA-approved drugs with potential activity against SARS-CoV-2 at traditional and understudied viral targets. 1,268 FDA-approved small molecule drugs were docked to 47 putative binding sites across 23 SARS-CoV-2 proteins. We compared drugs between binding sites and filtered out compounds that had no reported activity in an in vitro screen against SARS-CoV-2 infection of human liver (Huh-7) cells. This identified 17 "high-confidence", and 97 "medium-confidence" drug-site pairs. The "high-confidence" group was subjected to molecular dynamics simulations to yield six compounds with stable binding poses at their optimal target proteins. Three drugs-amprenavir, levomefolic acid, and calcipotriol-were predicted to bind to 3 different sites on the spike protein, domperidone to the Mac1 domain of the non-structural protein (Nsp) 3, avanafil to Nsp15, and nintedanib to the nucleocapsid protein involved in packaging the viral RNA. Our "two-way" virtual docking screen also provides a framework to prioritize drugs for testing in future emergencies requiring rapidly available clinical drugs and/or treating diseases where a moderate number of targets are known.

Identified human breastmilk compositions effectively inhibit SARS-CoV-2 and variants infection and replication

The global pandemic of COVID-19 caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection confers great threat to the public health. Human breastmilk is a complex with nutritional composition to nourish infants and protect them from different kinds of infectious diseases including COVID-19. Here, we identified lactoferrin (LF), mucin1 (MUC1) and α-lactalbumin (α-LA) from human breastmilk inhibit SARS-CoV-2 infection using a SARS-CoV-2 pseudovirus system and transcription and replication-competent SARS-CoV-2 virus-like-particles (trVLP). Additionally, LF and MUC1 inhibited multiple steps including viral attachment, entry and post-entry replication, while α-LA inhibited viral attachment and entry. Importantly, LF, MUC1 and α-LA possessed potent antiviral activities towards variants such as B.1.1.7 (alpha), B.1.351 (beta), P.1 (gamma) and B.1.617.1 (kappa). Taken together, our study provides evidence that human breastmilk components (LF, MUC1 and α-LA) are promising antiviral and potential therapeutic candidates warranting further development or treating COVID-19.

Synthesis, Structure–Activity Relationships, and Antiviral Profiling of 1-Heteroaryl-2-Alkoxyphenyl Analogs As Inhibitors of SARS-CoV-2 Replication

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, has led to a pandemic, that continues to be a huge public health burden. Despite the availability of vaccines, there is still a need for small-molecule antiviral drugs. In an effort to identify novel and drug-like hit matter that can be used for subsequent hit-to-lead optimization campaigns, we conducted a high-throughput screening of a 160 K compound library against SARS-CoV-2, yielding a 1-heteroaryl-2-alkoxyphenyl analog as a promising hit. Antiviral profiling revealed this compound was active against various beta-coronaviruses and preliminary mode-of-action experiments demonstrated that it interfered with viral entry. A systematic structure–activity relationship (SAR) study demonstrated that a 3- or 4-pyridyl moiety on the oxadiazole moiety is optimal, whereas the oxadiazole can be replaced by various other heteroaromatic cycles. In addition, the alkoxy group tolerates some structural diversity.

Antiviral properties of whey proteins and their activity against SARS-CoV-2 infection

Native and chemically modified whey proteins and their peptide derivatives are encountering the interest of nutraceutical and pharmaceutical industries, due to the numerous properties, ranging from antimicrobial to immunological and antitumorigenic, that result in the possibility to employ milk and its protein components in a wide range of treatment and prevention strategies. Importantly, whey proteins were found to exert antiviral actions against different enveloped and non-enveloped viruses. Recently, the scientific community is focusing on these proteins, especially lactoferrin, since in vitro studies have demonstrated that they exert an important antiviral activity also against SARS-CoV-2. Up-to date, several studies are investigating the efficacy of lactoferrin and other whey proteins in vivo. Aim of this review is to shed light on the most relevant findings concerning the antiviral properties of whey proteins and their potential applications in human health, focussing on their application in prevention and treatment of SARS-CoV-2 infection.

Experimental Models of COVID-19

COVID-19 is the most consequential pandemic of the 21st century. Since the earliest stage of the 2019-2020 epidemic, animal models have been useful in understanding the etiopathogenesis of SARS-CoV-2 infection and rapid development of vaccines/drugs to prevent, treat or eradicate SARS-CoV-2 infection. Early SARS-CoV-1 research using immortalized in-vitro cell lines have aided in understanding different cells and receptors needed for SARS-CoV-2 infection and, due to their ability to be easily manipulated, continue to broaden our understanding of COVID-19 disease in in-vivo models. The scientific community determined animal models as the most useful models which could demonstrate viral infection, replication, transmission, and spectrum of illness as seen in human populations. Until now, there have not been well-described animal models of SARS-CoV-2 infection although transgenic mouse models (i.e. mice with humanized ACE2 receptors with humanized receptors) have been proposed. Additionally, there are only limited facilities (Biosafety level 3 laboratories) available to contribute research to aid in eventually exterminating SARS-CoV-2 infection around the world. This review summarizes the most successful animal models of SARS-CoV-2 infection including studies in Non-Human Primates (NHPs) which were found to be susceptible to infection and transmitted the virus similarly to humans (e.g., Rhesus macaques, Cynomolgus, and African Green Monkeys), and animal models that do not require Biosafety level 3 laboratories (e.g., Mouse Hepatitis Virus models of COVID-19, Ferret model, Syrian Hamster model). Balancing safety, mimicking human COVID-19 and robustness of the animal model, the Murine Hepatitis Virus-1 Murine model currently represents the most optimal model for SARS-CoV-2/COVID19 research. Exploring future animal models will aid researchers/scientists in discovering the mechanisms of SARS-CoV-2 infection and in identifying therapies to prevent or treat COVID-19.

The acid sphingomyelinase/ceramide system in COVID-19

Acid sphingomyelinase (ASM) cleaves sphingomyelin into the highly lipophilic ceramide, which forms large gel-like rafts/platforms in the plasma membrane. We showed that SARS-CoV-2 uses these platforms for cell entry. Lowering the amount of ceramide or ceramide blockade due to inhibitors of ASM, genetic downregulation of ASM, anti-ceramide antibodies or degradation by neutral ceramidase protected against infection with SARS-CoV-2. The addition of ceramide restored infection with SARS-CoV-2. Many clinically approved medications functionally inhibit ASM and are called FIASMAs (functional inhibitors of acid sphingomyelinase). The FIASMA fluvoxamine showed beneficial effects on COVID-19 in a randomized prospective study and a prospective open-label real-world study. Retrospective and observational studies showed favorable effects of FIASMA antidepressants including fluoxetine, and the FIASMA hydroxyzine on the course of COVID-19. The ASM/ceramide system provides a framework for a better understanding of the infection of cells by SARS-CoV-2 and the clinical, antiviral, and anti-inflammatory effects of functional inhibitors of ASM. This framework also supports the development of new drugs or the repurposing of "old" drugs against COVID-19.

Artificial intelligence unifies knowledge and actions in drug repositioning

Drug repositioning aims to reuse existing drugs, shelved drugs, or drug candidates that failed clinical trials for other medical indications. Its attraction is sprung from the reduction in risk associated with safety testing of new medications and the time to get a known drug into the clinics. Artificial Intelligence (AI) has been recently pursued to speed up drug repositioning and discovery. The essence of AI in drug repositioning is to unify the knowledge and actions, i.e. incorporating real-world and experimental data to map out the best way forward to identify effective therapeutics against a disease. In this review, we share positive expectations for the evolution of AI and drug repositioning and summarize the role of AI in several methods of drug repositioning.

Capsule-dependent impact of MAPK signalling on host cell invasion and immune response during infection of the choroid plexus epithelium by Neisseria meningitidis

Background

The Gram-negative bacterium Neisseria meningitidis (Nm) can cause meningitis in humans, but the host signalling pathways manipulated by Nm during central nervous system (CNS) entry are not completely understood.

Methods

We investigate the role of the mitogen-activated protein kinases (MAPK) Erk1/2 and p38 in an in vitro model of the blood-cerebrospinal fluid barrier (BCSFB) based on human epithelial choroid plexus (CP) papilloma (HIBCPP) cells during infection with Nm serogroup B (NmB) and serogroup C (NmC) strains. A transcriptome analysis of HIBCPP cells following infection with Nm by massive analysis of cDNA ends (MACE) was done to further characterize the cellular response to infection of the barrier.

Results

Interestingly, whereas NmB and NmC wild type strains required active Erk1/2 and p38 pathways for infection, invasion by capsule-deficient mutants was independent of Erk1/2 and, in case of the NmB strain, of p38 activity. The transcriptome analysis of HIBCPP cells following infection with Nm demonstrated specific regulation of genes involved in the immune response dependent on Erk1/2 signalling. Gene ontology (GO) analysis confirmed loss of MAPK signalling after Erk1/2 inhibition and revealed an additional reduction of cellular responses including NFκB and JAK-STAT signalling. Interestingly, GO terms related to TNF signalling and production of IL6 were lost specifically following Erk1/2 inhibition during infection with wild type Nm, which correlated with the reduced infection rates by the wild type in absence of Erk1/2 signalling.

Conclusion

Our data point towards a role of MAPK signalling during infection of the CP epithelium by Nm, which is strongly influenced by capsule expression, and affects infection rates as well as the host cell response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-021-00288-7.

JAK-STAT Pathway: A Novel Target to Tackle Viral Infections

Modulation of the antiviral innate immune response has been proposed as a putative cellular target for the development of novel pan-viral therapeutic strategies. The Janus kinase–signal transducer and activator of transcription (JAK-STAT) pathway is especially relevant due to its essential role in the regulation of local and systemic inflammation in response to viral infections, being, therefore, a putative therapeutic target. Here, we review the extraordinary diversity of strategies that viruses have evolved to interfere with JAK-STAT signaling, stressing the relevance of this pathway as a putative antiviral target. Moreover, due to the recent remarkable progress on the development of novel JAK inhibitors (JAKi), the current knowledge on its efficacy against distinct viral infections is also discussed. JAKi have a proven efficacy against a broad spectrum of disorders and exhibit safety profiles comparable to biologics, therefore representing good candidates for drug repurposing strategies, including viral infections.

Clinical severe acute respiratory syndrome coronavirus 2 isolation and antiviral testing

Severe acute respiratory syndrome coronavirus 2 is an RNA virus currently causing a pandemic. Due to errors during replication, mutations can occur and result in cell adaptation by the virus or in the rise of new variants. This can change the attachment receptors' usage, result in different morphology of plaques, and can affect as well antiviral development. Indeed, a molecule can be active on laboratory strains but not necessarily on circulating strains or be effective only against some viral variants. Experiments with clinical samples with limited cell adaptation should be performed to confirm the efficiency of drugs of interest. In this protocol, we present a method to culture severe acute respiratory syndrome coronavirus 2 from nasopharyngeal swabs, obtain a high viral titer while limiting cell adaptation, and assess antiviral efficiency.

Highly Specific Sigma Receptor Ligands Exhibit Anti-Viral Properties in SARS-CoV-2 Infected Cells

(1) Background: There is a strong need for prevention and treatment strategies for COVID-19 that are not impacted by SARS-CoV-2 mutations emerging in variants of concern. After virus infection, host ER resident sigma receptors form direct interactions with non-structural SARS-CoV-2 proteins present in the replication complex. (2) Methods: In this work, highly specific sigma receptor ligands were investigated for their ability to inhibit both SARS-CoV-2 genome replication and virus induced cellular toxicity. This study found antiviral activity associated with agonism of the sigma-1 receptor (e.g., SA4503), ligation of the sigma-2 receptor (e.g., CM398), and a combination of the two pathways (e.g., AZ66). (3) Results: Intermolecular contacts between these ligands and sigma receptors were identified by structural modeling. (4) Conclusions: Sigma receptor ligands and drugs with off-target sigma receptor binding characteristics were effective at inhibiting SARS-CoV-2 infection in primate and human cells, representing a potential therapeutic avenue for COVID-19 prevention and treatment.

Molecular Mechanisms of Possible Action of Phenolic Compounds in COVID-19 Protection and Prevention

The worldwide outbreak of COVID-19 was caused by a pathogenic virus called Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). Therapies against SARS-CoV-2 target the virus or human cells or the immune system. However, therapies based on specific antibodies, such as vaccines and monoclonal antibodies, may become inefficient enough when the virus changes its antigenicity due to mutations. Polyphenols are the major class of bioactive compounds in nature, exerting diverse health effects based on their direct antioxidant activity and their effects in the modulation of intracellular signaling. There are currently numerous clinical trials investigating the effects of polyphenols in prophylaxis and the treatment of COVID-19, from symptomatic, via moderate and severe COVID-19 treatment, to anti-fibrotic treatment in discharged COVID-19 patients. Antiviral activities of polyphenols and their impact on immune system modulation could serve as a solid basis for developing polyphenol-based natural approaches for preventing and treating COVID-19.

Drug repurposing against SARS-CoV-1, SARS-CoV-2 and MERS-CoV

Since the beginning of the COVID-19 pandemic, large in silico screening studies and numerous in vitro studies have assessed the antiviral activity of various drugs on SARS-CoV-2. In the context of health emergency, drug repurposing represents the most relevant strategy because of the reduced time for approval by international medicines agencies, the low cost of development and the well-known toxicity profile of such drugs. Herein, we aim to review drugs with in vitro antiviral activity against SARS-CoV-2, combined with molecular docking data and results from preliminary clinical studies. Finally, when considering all these previous findings, as well as the possibility of oral administration, 11 molecules consisting of nelfinavir, favipiravir, azithromycin, clofoctol, clofazimine, ivermectin, nitazoxanide, amodiaquine, heparin, chloroquine and hydroxychloroquine, show an interesting antiviral activity that could be exploited as possible drug candidates for COVID-19 treatment.

Organoid models: assessing lung cell fate decisions and disease responses

Organoids can be derived from various cell types in the lung, and they provide a reproducible and tractable model for understanding the complex signals driving cell fate decisions in a regenerative context. In this review, we provide a retrospective account of organoid methodologies and outline new opportunities for optimizing these methods to further explore emerging concepts in lung biology. Moreover, we examine the benefits of integrating organoid assays with in vivo modeling to explore how the various niches and compartments in the respiratory system respond to both acute and chronic lung disease. The strategic implementation and improvement of organoid techniques will provide exciting new opportunities to understand and identify new therapeutic approaches to ameliorate lung disease states.

Diverse Mechanisms of Antimicrobial Activities of Lactoferrins, Lactoferricins, and Other Lactoferrin-Derived Peptides

Lactoferrins are an iron-binding glycoprotein that have important protective roles in the mammalian body through their numerous functions, which include antimicrobial, antitumor, anti-inflammatory, immunomodulatory, and antioxidant activities. Among these, their antimicrobial activity has been the most studied, although the mechanism behind antimicrobial activities remains to be elucidated. Thirty years ago, the first lactoferrin-derived peptide was isolated and showed higher antimicrobial activity than the native lactoferrin lactoferricin. Since then, numerous studies have investigated the antimicrobial potencies of lactoferrins, lactoferricins, and other lactoferrin-derived peptides to better understand their antimicrobial activities at the molecular level. This review defines the current antibacterial, antiviral, antifungal, and antiparasitic activities of lactoferrins, lactoferricins, and lactoferrin-derived peptides. The primary focus is on their different mechanisms of activity against bacteria, viruses, fungi, and parasites. The role of their structure, amino-acid composition, conformation, charge, hydrophobicity, and other factors that affect their mechanisms of antimicrobial activity are also reviewed.

Influence of iron binding in the structural stability and cellular internalization of bovine lactoferrin

Lactoferrin (Lf) is an iron-binding glycoprotein and a component of many external secretions with a wide diversity of functions. Structural studies are important to understand the mechanisms employed by Lf to exert so varied functions. Here, we used guanidine hydrochloride and high hydrostatic pressure to cause perturbations in the structure of bovine Lf (bLf) in apo and holo (unsaturated and iron-saturated, respectively) forms, and analyzed conformational changes by intrinsic and extrinsic fluorescence spectroscopy. Our results showed that the iron binding promotes changes on tertiary structure of bLf and increases its structural stability. In addition, we evaluated the effects of bLf structural change on the kinetics of bLf internalization in Vero cells by confocal fluorescence microscopy, and observed that the holo form was faster than the apo form. This finding may indicate that structural changes promoted by iron binding may play a key role in the intracellular traffic of bLf. Altogether, our data improve the comprehension of bLf stability and uptake, adding knowledge to its potential use as a biopharmaceutical.

Discovery of re-purposed drugs that slow SARS-CoV-2 replication in human cells

COVID-19 vaccines based on the Spike protein of SARS-CoV-2 have been developed that appear to be largely successful in stopping infection. However, therapeutics that can help manage the disease are still required until immunity has been achieved globally. The identification of repurposed drugs that stop SARS-CoV-2 replication could have enormous utility in stemming the disease. Here, using a nano-luciferase tagged version of the virus (SARS-CoV-2-ΔOrf7a-NLuc) to quantitate viral load, we evaluated a range of human cell types for their ability to be infected and support replication of the virus, and performed a screen of 1971 FDA-approved drugs. Hepatocytes, kidney glomerulus, and proximal tubule cells were particularly effective in supporting SARS-CoV-2 replication, which is in-line with reported proteinuria and liver damage in patients with COVID-19. Using the nano-luciferase as a measure of virus replication we identified 35 drugs that reduced replication in Vero cells and human hepatocytes when treated prior to SARS-CoV-2 infection and found amodiaquine, atovaquone, bedaquiline, ebastine, LY2835219, manidipine, panobinostat, and vitamin D3 to be effective in slowing SARS-CoV-2 replication in human cells when used to treat infected cells. In conclusion, our study has identified strong candidates for drug repurposing, which could prove powerful additions to the treatment of COVID.