Heparin prevents Zika virus induced-cytopathic effects in human neural progenitor cells

Promising Drug Fondaparinux for the Treatment of COVID-19: an In Silico Analysis of Low Molecular Weight Heparin, Direct Oral Anticoagulant, and Antiplatelet Drug Interactions with Host Protease Furin

PURPOSE

As of July 2022, the COVID-19 pandemic has affected over 555 million worldwide confirmed cases and caused more than 6.3 million deaths. The studies showed that the D-dimer levels were increased in non-survivors compared to survivors and heparin treatment has begun to be administered to the patients in severe clinics. As we knew that the entrance of SARS-CoV-2 to the host cell needs to be facilitated by host proteases; we published our hypothesis that heparin as a serine protease inhibitor may block the interaction between spike protein receptor-binding domain and host proteases. In our study, we aimed to investigate the interactions between not only heparins but also other antiplatelet and anticoagulant drugs including fondaparinux.

METHODS

In this study, docking studies were carried out to evaluate the interactions between low molecular weight heparins (LMWHs) (enoxaparin, dalteparin, tinzaparin), direct oral anticoagulant, and antiplatelet drugs with host proteases. Molecular docking studies were performed by using Schrödinger molecular modeling software. 3D structures of the ligands were obtained from the 2D structures by assigning the OPLS-2005 force field using the Maestro 12.7. The 3D crystal structure of the furin complexed with an inhibitor, 2,5-dideoksistreptamin derivative, was extracted from the Protein Data Bank (PDB ID: 5MIM). Docking studies were carried out using the Grid-based Ligand Docking with Energetics module of the Schrödinger Software.

RESULTS

The docking studies revealed that fondaparinux was the most relevant molecule to interact with furin with a docking score of - 12.74. It showed better interaction than the natural ligand of furin with an increased score compared to the docking score of - 8.155 of the natural ligand. AnaGA*IsA structure representing LMWH structure has shown a docking score of - 11.562 which was also better than the score of the natural ligand of furin.

CONCLUSION

Our findings have shown that LMWHs and fondaparinux can be used for their possible antiviral effects in COVID-19 patients. Our results have shown that in accordance with heparin and LMWH, fondaparinux can also be a candidate for "drug repurposing" in COVID-19 therapy, not only because of their anticoagulant but also possible antiviral effects.

Research Progress on Antiviral Activity of Heparin

Heparin, as a glycosaminoglycan, is known for its anticoagulant and antithrombotic properties for several decades. Heparin is a life-saving drug and is widely used for anticoagulation in medical practice. In recent years, there have been extensive studies that heparin plays an important role in non-anticoagulant diseases, such as anti-inflammatory, anti-viral, anti-angiogenesis, anti-neoplastic, anti-metastatic effects, and so on. Clinical observation and in vitro experiments indicate that heparin displays a potential multitarget effect. In this brief review, we will summarize heparin and its derivative's recently studied progress for the treatment of various viral infections. The aim is to maximize the benefits of drugs through medically targeted development, to meet the unmet clinical needs of serious viral diseases.

Bovine colostrum and its potential contributions for treatment and prevention of COVID-19

Bovine colostrum (BC) is the initial milk an animal produces after giving birth, particularly in the first few days. Numerous bioactive substances found in BC, including proteins, enzymes, growth factors, immunoglobulins, etc., are beneficial to human health. BC has a significant role to play as part of a healthy diet, with well-documented health and nutritional advantages for people. Therefore, the use of BC and its crucial derivatives in the development of functional food and pharmaceuticals for the prevention of several diseases such as gastrointestinal and respiratory system disorders is becoming increasingly popular around the world. A novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified as the cause of a cluster of pneumonia cases that is called Coronavirus Disease 2019 (COVID-19) in China. After the first SARS-CoV-2 virus-related fatality was announced, the illness quickly spread throughout China and to other continents, causing a pandemic. Since then, numerous studies have been initiated to develop safe and efficient treatments. To prevent viral infection and potential lingering effects, it is important to investigate alternative treatments for COVID-19. Due to its effective bioactive profile and its immunomodulatory roles in biological processes, BC might be considered a promising approach to assist in combating people affected by the SARS-CoV-2 or prevention from the virus. BC has immunomodulatory effects because to its high concentration of bioactive components such as immunoglobulins, lactoferrin, cytokines, and growth factors, etc., which might help control immunological responses, potentially fostering a balanced immune response. Furthermore, its bioactive components have a potential cross-reactivity against SARS-CoV-2, aiding in virus neutralization and its comprehensive food profile also supplies important vitamins, minerals, and amino acids, fostering a healthy immune system. Hence, the possible contributions of BC to the management of COVID-19 were reviewed in this article based on the most recent research on the subject. Additionally, the key BC components that influence immune system modulation were evaluated. These components may serve as potential mediators or therapeutic advantages in COVID-19.

Heparin Precursors with Reduced Anticoagulant Properties Retain Antiviral and Protective Effects That Potentiate the Efficacy of Sofosbuvir against Zika Virus Infection in Human Neural Progenitor Cells

Zika virus (ZIKV) infection during pregnancy can result in severe birth defects, such as microcephaly, as well as a range of other related health complications. Heparin, a clinical-grade anticoagulant, is shown to protect neural progenitor cells from death following ZIKV infection. Although heparin can be safely used during pregnancy, it retains off-target anticoagulant effects if directly employed against ZIKV infection. In this study, we investigated the effects of chemically modified heparin derivatives with reduced anticoagulant activities. These derivatives were used as experimental probes to explore the structure-activity relationships. Precursor fractions of porcine heparin, obtained during the manufacture of conventional pharmaceutical heparin with decreased anticoagulant activities, were also explored. Interestingly, these modified heparin derivatives and precursor fractions not only prevented cell death but also inhibited the ZIKV replication of infected neural progenitor cells grown as neurospheres. These effects were observed regardless of the specific sulfation position or overall charge. Furthermore, the combination of heparin with Sofosbuvir, an antiviral licensed for the treatment of hepatitis C (HCV) that also belongs to the same Flaviviridae family as ZIKV, showed a synergistic effect. This suggested that a combination therapy approach involving heparin precursors and Sofosbuvir could be a potential strategy for the prevention or treatment of ZIKV infections.

Preventative and therapeutic potential of animal milk components against COVID-19: A comprehensive review

The global pandemic of COVID-19 is considered one of the most catastrophic events on earth. During the pandemic, food ingredients may play crucial roles in preventing infectious diseases and sustaining people's general health and well-being. Animal milk acts as a super food since it has the capacity to minimize the occurrence of viral infections due to inherent antiviral properties of its ingredients. SARS-CoV-2 virus infection can be prevented by immune-enhancing and antiviral properties of caseins, α-lactalbumin, β-lactoglobulin, mucin, lactoferrin, lysozyme, lactoperoxidase, oligosaccharides, glycosaminoglycans, and glycerol monolaurate. Some of the milk proteins (i.e., lactoferrin) may work synergistically with antiviral medications (e.g., remdesivir), and enhance the effectiveness of treatment in this disease. Cytokine storm during COVID-19 can be managed by casein hydrolyzates, lactoferrin, lysozyme, and lactoperoxidase. Thrombus formation can be prevented by casoplatelins as these can inhibit human platelet aggregation. Milk vitamins (i.e., A, D, E, and B complexes) and minerals (i.e., Ca, P, Mg, Zn, and Se) can have significantly positive effects on boosting the immunity and health status of individuals. In addition, certain vitamins and minerals can also act as antioxidants, anti-inflammatory, and antivirals. Thus, the overall effect of milk might be a result of synergistic antiviral effects and host immunomodulator activities from multiple components. Due to multiple overlapping functions of milk ingredients, they can play vital and synergistic roles in prevention as well as supportive agents during principle therapy of COVID-19.

Coagulopathy and thromboembolic events a pathogenic mechanism of COVID-19 associated with mortality: An updated review

During 2019, the SARS-CoV-2 emerged from China, and during months, COVID-19 spread in many countries around the world. The expanding data about pathogenesis of this virus could elucidate the exact mechanism by which COVID-19 caused death in humans. One of the pathogenic mechanisms of this disease is coagulation. Coagulation disorders that affect both venous and arterial systems occur in patients with COVID-19. The possible mechanism involved in the coagulation could be excessive inflammation induced by SARS-CoV-2. However, it is not yet clear well how SARS-CoV-2 promotes coagulopathy. However, some factors, such as pulmonary endothelial cell damage and some anticoagulant system disorders, are assumed to have an important role. In this study, we assessed conducted studies about COVID-19-induced coagulopathy to obtain clearer vision of the wide range of manifestations and possible pathogenesis mechanisms.

Interrelationship between COVID-19 and Coagulopathy: Pathophysiological and Clinical Evidence

Since the first description of COVID-19 infection, among clinical manifestations of the disease, including fever, dyspnea, cough, and fatigue, it was observed a high incidence of thromboembolic events potentially evolving towards acute respiratory distress syndrome (ARDS) and COVID-19-associated-coagulopathy (CAC). The hypercoagulation state is based on an interaction between thrombosis and inflammation. The so-called CAC represents a key aspect in the genesis of organ damage from SARS-CoV-2. The prothrombotic status of COVID-19 can be explained by the increase in coagulation levels of D-dimer, lymphocytes, fibrinogen, interleukin 6 (IL-6), and prothrombin time. Several mechanisms have been hypothesized to explain this hypercoagulable process such as inflammatory cytokine storm, platelet activation, endothelial dysfunction, and stasis for a long time. The purpose of this narrative review is to provide an overview of the current knowledge on the pathogenic mechanisms of coagulopathy that may characterize COVID-19 infection and inform on new areas of research. New vascular therapeutic strategies are also reviewed.

High sensitivity (zeptomole) detection of BODIPY-labelled heparan sulfate (HS) disaccharides by ion-paired RP-HPLC and LIF detection enables analysis of HS from mosquito midguts

The fine structure of heparan sulfate (HS), the glycosaminoglycan polysaccharide component of cell surface and extracellular matrix HS proteoglycans, coordinates the complex cell signalling processes that control homeostasis and drive development in multicellular animals. In addition, HS is involved in the infection of mammals by viruses, bacteria and parasites. The current detection limit for fluorescently labelled HS disaccharides (low femtomole; 10^-15 mol), has effectively hampered investigations of HS composition in small, functionally-relevant populations of cells and tissues that may illuminate the structural requirements for infection and other biochemical processes. Here, an ultra-high sensitivity method is described that utilises a combination of reverse-phase HPLC, with tetraoctylammonium bromide (TOAB) as the ion-pairing reagent and laser-induced fluorescence detection of BODIPY-FL-labelled disaccharides. The method provides an unparalleled increase in the sensitivity of detection by ∼six orders of magnitude, enabling detection in the zeptomolar range (∼10^-21 moles; <1000 labelled molecules). This facilitates determination of HS disaccharide compositional analysis from minute samples of selected tissues, as demonstrated by analysis of HS isolated from the midguts of Anopheles gambiae mosquitoes that was achieved without approaching the limit of detection.

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

Heparin mimetics as potential intervention for COVID-19 and their bio-manufacturing

The COVID-19 pandemic has caused severe health problems worldwide and unprecedented decimation of the global economy. Moreover, after more than 2 years, many populations are still under pressure of infection. Thus, a broader perspective in developing antiviral strategies is still of great importance. Inspired by the observed multiple benefits of heparin in the treatment of thrombosis, the potential of low molecular weight heparin (LMWH) for the treatment of COVID-19 have been explored. Clinical applications found that LMWH decreased the level of inflammatory cytokines in COVID-19 patients, accordingly reducing lethality. Furthermore, several in vitro studies have demonstrated the important roles of heparan sulfate in SARS-CoV-2 infection and the inhibitory effects of heparin and heparin mimetics in viral infection. These clinical observations and designed studies argue for the potential to develop heparin mimetics as anti-SARS-CoV-2 drug candidates. In this review, we summarize the properties of heparin as an anticoagulant and the pharmaceutical possibilities for the treatment of virus infection, focusing on the perspectives of developing heparin mimetics via chemical synthesis, chemoenzymatic synthesis, and bioengineered production by microbial cell factories. The ultimate goal is to pave the eminent need for exploring novel compounds to treat coronavirus infection-caused diseases.

ZIKV: Epidemiology, infection mechanism and current therapeutics

The Zika virus (ZIKV) is a vector-borne flavivirus that has been detected in 87 countries worldwide. Outbreaks of ZIKV infection have been reported from various places around the world and the disease has been declared a public health emergency of international concern. ZIKV has two modes of transmission: vector and non-vector. The ability of ZIKV to vertically transmit in its competent vectors, such as Aedes aegypti and Aedes albopictus, helps it to cope with adverse conditions, and this could be the reason for the major outbreaks that occur from time to time. ZIKV outbreaks are a global threat and, therefore, there is a need for safe and effective drugs and vaccines to fight the virus. In more than 80% of cases, ZIKV infection is asymptomatic and leads to complications, such as microcephaly in newborns and Guillain–Barré syndrome (GBS) in adults. Drugs such as sofosbuvir, chloroquine, and suramin have been found to be effective against ZIKV infections, but further evaluation of their safety in pregnant women is needed. Although temoporfin can be given to pregnant women, it needs to be tested further for side effects. Many vaccine types based on protein, vector, DNA, and mRNA have been formulated. Some vaccines, such as mRNA-1325 and VRC-ZKADNA090-00-VP, have reached Phase II clinical trials. Some new techniques should be used for formulating and testing the efficacy of vaccines. Although there have been no recent outbreaks of ZIKV infection, several studies have shown continuous circulation of ZIKV in mosquito vectors, and there is a risk of re-emergence of ZIKV in the near future. Therefore, vaccines and drugs for ZIKV should be tested further, and safe and effective therapeutic techniques should be licensed for use during outbreaks.

Biological Properties of Heparins Modified with an Arylazopyrazole-Based Photoswitch

Unfractionated heparin (UFH) and enoxaparin (Enox) were substituted with a photoswitch (PS) showing quantitative trans-cis and cis-trans photoisomerizations. Long half-life of the cis photoisomer enabled comparison of the properties of heparins substituted with both PS photoisomers. Hydrodynamic diameter, D_h, of UFH-PS decreased upon trans-cis photoisomerization, the change being more pronounced for UFH-PS with a higher degree of substitution (DS), while D_h of Enox-PS did not significantly change. The anticoagulative properties of substituted heparins were significantly attenuated compared to non-substituted compounds. The interaction of UFH-PS with HSA, lysozyme, and protamine was studied with ITC. Under serum-free conditions, UFH-PS-trans with a high DS stimulated proliferation of murine fibroblasts, while UFH-PS-cis decreased the viability of these cells. Under serum conditions, both UFH-PS-cis and UFH-PS-trans decreased cell viability, the reduction for UFH-PS-cis being higher than that for UFH-PS-trans. Neither Enox-PS-trans nor Enox-PS-cis influenced the viability at concentrations prolonging aPTT, while at higher concentrations their cytotoxicity did not differ.

Astrocytes derived from neural progenitor cells are susceptible to Zika virus infection

Zika virus (ZIKV) was first isolated in 1947. From its isolation until 2007, symptoms of ZIKV-caused disease were limited (e.g., fever, hives, and headache); however, during the epidemic in Brazil in 2014, ZIKV infection caused Guillain-Barré syndrome in adults and microcephaly in fetuses and infants of women infected during pregnancy. The neurovirulence of ZIKV has been studied using neural progenitor cells (NPCs), brain organoids, neurons, and astrocytes. NPCs and astrocytes appear to be the most susceptible cells of the Central Nervous System to ZIKV infection. In this work, we aimed to develop a culture of astrocytes derived from a human NPC cell line. We analyze how ZIKV affects human astrocytes and demonstrate that 1) ZIKV infection reduces cell viability, increases the production of Reactive Oxygen Species (ROS), and results in high viral titers; 2) there are changes in the expression of genes that facilitate the entry of the virus into the cells; 3) there are changes in the expression of genes involved in the homeostasis of the glutamatergic system; and 4) there are ultrastructural changes in mitochondria and lipid droplets associated with production of virions. Our findings reveal new evidence of how ZIKV compromises astrocytic functionality, which may help understand the pathophysiology of ZIKV-associated congenital disease.

Heparin Protects Human Neural Progenitor Cells from Zika Virus-Induced Cell Death While Preserving Their Differentiation into Mature Neuroglial Cells

Zika virus (ZIKV) is an arbovirus member of the Flaviviridae family that causes severe congenital brain anomalies in infected fetuses. The key target cells of ZIKV infection, human neural progenitor cells (hNPCs), are highly permissive to infection that causes the inhibition of cell proliferation and induces cell death. We have previously shown that pharmaceutical-grade heparin inhibits virus-induced cell death with negligible effects on in vitro virus replication in ZIKV-infected hNPCs at the “high” multiplicity of infection (MOI) of 1. Here, we show that heparin inhibits formation of ZIKV-induced intracellular vacuoles, a signature of paraptosis, and inhibits necrosis and apoptosis of hNPCs grown as neurospheres (NS). To test whether heparin preserved the differentiation of ZIKV-infected hNPCs into neuroglial cells, hNPCs were infected at the MOI of 0.001. In this experimental condition, heparin inhibited ZIKV replication by ca. 2 log₁₀, mostly interfering with virion attachment, while maintaining its protective effect against ZIKV-induced cytopathicity. Heparin preserved differentiation into neuroglial cells of hNPCs that were obtained from either human-induced pluripotent stem cells (hiPSC) or by fetal tissue. Quite surprisingly, multiple additions of heparin to hNPCs enabled prolonged virus replication while preventing virus-induced cytopathicity. Collectively, these results highlight the potential neuroprotective effect of heparin that could serve as a lead compound to develop novel agents for preventing the damage of ZIKV infection on the developing brain.

IMPORTANCE ZIKV is a neurotropic virus that invades neural progenitor cells (NPCs), causing inhibition of their proliferation and maturation into neurons and glial cells. We have shown previously that heparin, an anticoagulant also used widely during pregnancy, prevents ZIKV-induced cell death with negligible inhibition of virus replication. Here, we demonstrate that heparin also exerts antiviral activity against ZIKV replication using a much lower infectious inoculum. Moreover, heparin interferes with different modalities of virus-induced cell death. Finally, heparin-induced prevention of virus-induced NPC death allows their differentiation into neuroglial cells despite the intracellular accumulation of virions. These results highlight the potential use of heparin, or pharmacological agents derived from it, in pregnant women to prevent the devastating effects of ZIKV infection on the developing brain of their fetuses.

Antivirals and the Potential Benefits of Orally Inhaled Drug Administration in COVID-19 Treatment

Coronavirus Disease 2019 (COVID-19) pandemic has been on the agenda of humanity for more than 2 years. In the meantime, the pandemic has caused economic shutdowns, halt of daily lives and global mobility, overcrowding of the healthcare systems, panic, and worse, more than 6 million deaths. Today, there is still no specific therapy for COVID-19. Research focuses on repurposing of antiviral drugs that are licensed or currently in the research phase, with a known systemic safety profile. However, local safety profile should also be evaluated depending on the new indication, administration route and dosage form. Additionally, various vaccines have been developed. But the causative virus, Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), has undergone multiple variations, too. The premise that vaccines may suffice to eradicate new and all variants is unreliable, as they are based on earlier versions of the virus. Therefore, a specific medication therapy for COVID-19 is crucial and needed in order to prevent severe complications of the disease. Even though there is no specific drug that inhibits the replication of the disease-causing virus, among the current treatment options, systemic antivirals are the most medically appropriate. As SARS-CoV-2 directly targets the lungs and initiates lung damage, treating COVID-19 with inhalants can offer many advantages over the enteral/parenteral administration. Inhaled drug delivery provides higher drug concentration, specifically in the pulmonary system. This enables the reduction of systemic side effects and produces a rapid clinical response. In this article, the most frequently (systemically) used antiviral compounds are reviewed including Remdesivir, Favipiravir, Molnupiravir, Lopinavir-Ritonavir, Umifenovir, Chloroquine, Hydroxychloroquine and Heparin. A comprehensive literature search was conducted to provide insight into the potential inhaled use of these antiviral drugs and the current studies on inhalation therapy for COVID-19 was presented. A brief evaluation was also made on the use of inhaler devices in the treatment of COVID-19. Inhaled antivirals paired with suitable inhaler devices should be considered for COVID-19 treatment options.

The Auxiliary Role of Heparin in Bone Regeneration and its Application in Bone Substitute Materials

Bone regeneration in large segmental defects depends on the action of osteoblasts and the ingrowth of new blood vessels. Therefore, it is important to promote the release of osteogenic/angiogenic growth factors. Since the discovery of heparin, its anticoagulant, anti-inflammatory, and anticancer functions have been extensively studied for over a century. Although the application of heparin is widely used in the orthopedic field, its auxiliary effect on bone regeneration is yet to be unveiled. Specifically, approximately one-third of the transforming growth factor (TGF) superfamily is bound to heparin and heparan sulfate, among which TGF-β1, TGF-β2, and bone morphogenetic protein (BMP) are the most common growth factors used. In addition, heparin can also improve the delivery and retention of BMP-2 in vivo promoting the healing of large bone defects at hyper physiological doses. In blood vessel formation, heparin still plays an integral part of fracture healing by cooperating with the platelet-derived growth factor (PDGF). Importantly, since heparin binds to growth factors and release components in nanomaterials, it can significantly facilitate the controlled release and retention of growth factors [such as fibroblast growth factor (FGF), BMP, and PDGF] in vivo. Consequently, the knowledge of scaffolds or delivery systems composed of heparin and different biomaterials (including organic, inorganic, metal, and natural polymers) is vital for material-guided bone regeneration research. This study systematically reviews the structural properties and auxiliary functions of heparin, with an emphasis on bone regeneration and its application in biomaterials under physiological conditions.

SLC35B2 Acts in a Dual Role in the Host Sulfation Required for EV71 Infection

As an important neurotropic enterovirus, enterovirus 71 (EV71) is occasionally associated with severe neurological diseases and high mortality rates in infants and young children. Understanding the interaction between host factors and EV71 will play a vital role in developing antivirals and optimizing vaccines. Here, we performed a genome-wide CRISPR-Cas9 knockout screen and revealed that scavenger receptor class B member 2 (SCARB2), solute carrier family 35 member B2 (SLC35B2), and beta-1,3-glucuronyltransferase 3 (B3GAT3) are essential in facilitating EV71 replication. Subsequently, the exploration of molecular mechanisms suggested that the knockout of SLC35B2 or B3GAT3, not SCARB2, led to a remarkable decrease in the binding of EV71 to cells and internalization into cells. Furthermore, we found that the infection efficiency for EV71 was positively correlated with the level of host cell sulfation, not simply with the amount of heparan sulfate, suggesting that an unidentified sulfated protein(s) must contribute to EV71 infection. In support of this idea, we screened possible sulfated proteins among the proteinous receptors for EV71 and confirmed that SCARB2 could uniquely interact with both tyrosyl protein sulfotransferases in humans. We then performed mass spectrometric analysis of SCARB2, identifying five sites with tyrosine sulfation. The function verification test indicated that there were more than five tyrosine-sulfated sites on SCARB2. Finally, we constructed a model for EV71 entry in which both heparan sulfate and SCARB2 are regulated by SLC35B2 and act cooperatively to support viral binding, internalization, and uncoating. Taken together, this is the first time that we performed the pooled CRISPR-Cas9 genetic screening to investigate the interplay of host cells and EV71. Furthermore, we found that a novel host factor, SLC35B2, played a dual role in regulating the overall sulfation comprising heparan sulfate sulfation and protein tyrosine sulfation, which are critical for EV71 entry. IMPORTANCE As the most important nonpolio neurotropic enterovirus lacking specific treatments, EV71 can transmit to the central nervous system, leading to severe and fatal neurological complications in infants and young children. The identification of new factors that facilitate or inhibit EV71 replication is crucial to uncover the mechanisms of viral infection and pathogenesis. To date, only a few host factors involved in EV71 infection have been characterized. Herein, we conducted a genome-wide CRISPR-Cas9 functional knockout (GeCKO) screen for the first time to study EV71 in HeLa cells. The screening results are presented as a ranked list of candidates, including 518 hits in the positive selection that facilitate EV71 replication and 1,044 hits in the negative selection that may be essential for cell growth and survival or for suppressing EV71 infection. We subsequently concentrated on the top three hits in the positive selection: SCARB2, SLC35B2, and B3GAT3. The knockout of any of these three genes confers strong resistance against EV71 infection. We confirmed that EV71 infection is codependent on two receptors, heparan sulfate and SCARB2. We also identified a host entry factor, SLC35B2, indirectly facilitating EV71 infection through regulation of the host cell sulfation, and determined a novel posttranslational modification, protein tyrosine sulfation existing in SCARB2. This study revealed that EV71 infectivity exhibits a significant positive correlation with the level of cellular sulfation regulated by SLC35B2. Due to the sulfation pathway being required for many distinct viruses, including but not limited to EV71 and respiratory syncytial virus (RSV), which were tested in this study, SLC35B2 represents a target of broad-spectrum antiviral therapy.

In silico investigations of heparin binding to SARS-CoV-2 variants with a focus at the RBD/ACE2 interface

The increased infectivity and transmissibility of SARS-CoV-2 new variants were contributed largely by increase binding of receptor binding domain (RBD) domain of the Spike (S) protein to its cellular receptor ACE2 (Angiotensin-Converting Enzyme 2). Several studies have indicated that heparin and its derivatives interact to SARS-CoV-2 S-RBD and inhibits the binding of ACE2 which blocks the viral invasion. However, it is largely unclear how these SARS-CoV-2 variants affects ACE2 binding in the presence of heparin. Herein, using the molecular docking and interaction energy analysis, we showed that N501Y, L452R-E484Q, and E484K mutations bind strongly with heparin in the range of - 7.4 to - 8.0 kcal/mol. The triple mutations, K417N-E484K-N501Y, and K417T-E484K-N501Y displayed weaker binding affinity to heparin (-6.6 kcal/mol). Further, we showed that most of the RBD mutations increased the binding affinity of ACE2 in the absence of heparin, with the maximum increase observed for N501Y (-13.7 kcal/mol). Also, in the presence of heparin, ACE2 binds strongly to the mutant RBD as compared to WT RBD. The strong RBD/ACE2 interaction was observed in case of triple variants (-11.3 kcal/mol) whereas, N501Y showed weakest binding of RBD/ACE2 in the presence of heparin (-9.2 kcal/mol). The strong binding of ACE2 to RBD-heparin complex in these variants will leads to strong inhibition of their entry into host cells.

Pentosan polysulfate inhibits attachment and infection by SARS-CoV-2 in vitro: insights into structural requirements for binding

Two years since the outbreak of the novel coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) pandemic, there remain few clinically effective drugs to complement vaccines. One is the anticoagulant, heparin, which in 2004 was found able to inhibit invasion of SARS-CoV (CoV-1) and which has been employed during the current pandemic to prevent thromboembolic complications and moderate potentially damaging inflammation. Heparin has also been shown experimentally to inhibit SARS-CoV-2 attachment and infection in susceptible cells. At high therapeutic doses however, heparin increases the risk of bleeding and prolonged use can cause heparin-induced thrombocytopenia, a serious side effect. One alternative, with structural similarities to heparin, is the plant-derived, semi-synthetic polysaccharide, pentosan polysulfate (PPS). PPS is an established drug for the oral treatment of interstitial cystitis, is well-tolerated, and exhibits weaker anticoagulant effects than heparin. In an established Vero cell model, PPS and its fractions of varying molecular weights inhibited invasion by SARS-CoV-2. Intact PPS and its size-defined fractions were characterized by molecular weight distribution and chemical structure using nuclear magnetic resonance spectroscopy and liquid chromatography–mass spectrometry, then employed to explore the structural basis of interactions with SARS-CoV-2 spike protein receptor-binding domain (S1 RBD) and the inhibition of Vero cell invasion. PPS was as effective as unfractionated heparin, but more effective in inhibiting cell infection than low-molecular-weight heparin (on a weight/volume basis). Isothermal titration calorimetry and viral plaque-forming assays demonstrated size-dependent binding to S1 RBD and inhibition of Vero cell invasion, suggesting the potential application of PPS as a novel inhibitor of SARS-CoV-2 infection.

Host Molecules Regulating Neural Invasion of Zika Virus and Drug Repurposing Strategy

Zika virus (ZIKV) is a mosquito-borne, single-stranded RNA virus belonging to the genus Flavivirus. Although ZIKV infection is usually known to exhibit mild clinical symptoms, intrauterine ZIKV infections have been associated with severe neurological manifestations, including microcephaly and Guillain Barre syndrome (GBS). Therefore, it is imperative to understand the mechanisms of ZIKV entry into the central nervous system (CNS) and its effect on brain cells. Several routes of neuro-invasion have been identified, among which blood–brain barrier (BBB) disruption is the commonest mode of access. The molecular receptors involved in viral entry remain unknown; with various proposed molecular ZIKV-host interactions including potential non-receptor mediated cellular entry. As ZIKV invade neuronal cells, they trigger neurotoxic mechanisms via cell-autonomous and non-cell autonomous pathways, resulting in neurogenesis dysfunction, viral replication, and cell death, all of which eventually lead to microcephaly. Together, our understanding of the biological mechanisms of ZIKV exposure would aid in the development of anti-ZIKV therapies targeting host cellular and/or viral components to combat ZIKV infection and its neurological manifestations. In this present work, we review the current understanding of ZIKV entry mechanisms into the CNS and its implications on the brain. We also highlight the status of the drug repurposing approach for the development of potential antiviral drugs against ZIKV.

Is heparan sulfate a target for inhibition of RNA virus infection?

Heparan sulfate (HS) is a linear polysaccharide attached to a core protein, forming heparan sulfate proteoglycans (HSPGs) that are ubiquitously expressed on the surface of almost all mammalian cells and the extracellular matrix. HS orchestrates the binding of various signal molecules to their receptors, thus, regulating many biological processes, including homeostasis, metabolism, and various pathological processes. Due to its wide distribution and negatively charged properties, HS is exploited by many viruses as a co-factor to attach to host cells. Therefore, inhibition of the interaction between virus and HS is proposed as a promising approach to mitigate viral infection, including SARS-CoV-2. In this review, we summarize the interaction manners of HS with viruses with focus on significant pathogenic RNA viruses, including alphaviruses, flaviviruses, and coronaviruses. We also provide an overview of the challenges we may face when using HS-mimetics as antivirals for clinical treatment. More studies are needed to provide a further understanding of the interplay between HS and viruses both in vitro and in vivo, which will favor the development of specific antiviral inhibitors.

Neurogenesis and Viral Infection

Neural stem cells (NSCs) are multipotent stem cells that reside in the fetal and adult mammalian brain, which can self-renew and differentiate into neurons and supporting cells. Intrinsic and extrinsic cues, from cells in the local niche and from distant sites, stringently orchestrates the self-renewal and differentiation competence of NSCs. Ample evidence supports the important role of NSCs in neuroplasticity, aging, disease, and repair of the nervous system. Indeed, activation of NSCs or their transplantation into injured areas of the central nervous system can lead to regeneration in animal models. Viral invasion of NSCs can negatively affect neurogenesis and synaptogenesis, with consequent cell death, impairment of cell cycle progression, early differentiation, which cause neural progenitors depletion in the cortical layer of the brain. Herein, we will review the current understanding of Zika virus (ZIKV) infection of the fetal brain and the NSCs, which are the preferential population targeted by ZIKV. Furthermore, the potential neurotropic properties of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which may cause direct neurological damage, will be discussed.

Polyanionic Amphiphilic Dendritic Polyglycerols as Broad-Spectrum Viral Inhibitors with a Virucidal Mechanism

Heparin has been known to be a broad-spectrum inhibitor of viral infection for almost 70 years, and it has been used as a medication for almost 90 years due to its anticoagulant effect. This nontoxic biocompatible polymer efficiently binds to many types of viruses and prevents their attachment to cell membranes. However, the anticoagulant properties are limiting their use as an antiviral drug. Many heparin-like compounds have been developed throughout the years; however, the reversible nature of the virus inhibition mechanism has prevented their translation to the clinics. In vivo, such a mechanism requires the unrealistic maintenance of the concentration above the binding constant. Recently, we have shown that the addition of long hydrophobic linkers to heparin-like compounds renders the interaction irreversible while maintaining the low-toxicity and broad-spectrum activity. To date, such hydrophobic linkers have been used to create heparin-like gold nanoparticles and β-cyclodextrins. The former achieves a nanomolar inhibition concentration on a non-biodegradable scaffold. The latter, on a fully biodegradable scaffold, shows only a micromolar inhibition concentration. Here, we report that the addition of hydrophobic linkers to a new type of multifunctional scaffold (dendritic polyglycerol, dPG) creates biocompatible compounds endowed with nanomolar activity. Furthermore, we present an in-depth analysis of the molecular design rules needed to achieve irreversible virus inhibition. The most active compound (dPG-5) showed nanomolar activity against herpes simplex virus 2 (HSV-2) and respiratory syncytial virus (RSV), giving a proof-of-principle for broad-spectrum while keeping low-toxicity. In addition, we demonstrate that the virucidal activity leads to the release of viral DNA upon the interaction between the virus and our polyanionic dendritic polymers. We believe that this paper will be a stepping stone toward the design of a new class of irreversible nontoxic broad-spectrum antivirals.

Low molecular weight heparin is useful in adult COVID-19 inpatients. Experience during the first Spanish wave: observational study

BACKGROUND

The intensity of the thromboprophylaxis needed as a potential factor for preventing inpatient mortality due to coronavirus disease-19 (COVID-19) remains unclear.

OBJECTIVE

To explore the association between anticoagulation intensity and COVID-19 survival.

DESIGN AND SETTING

Retrospective observational study in a tertiary-level hospital in Spain.

METHODS

Low-molecular-weight heparin (LMWH) status was ascertained based on prescription at admission. To control for immortal time bias, anticoagulant use was analyzed as a time-dependent variable.

RESULTS

690 patients were included (median age, 72 years). LMWH was administered to 615 patients, starting from hospital admission (89.1%). 410 (66.7%) received prophylactic-dose LMWH; 120 (19.5%), therapeutic-dose LMWH; and another 85 (13.8%) who presented respiratory failure, high D-dimer levels (> 3 mg/l) and non-worsening of inflammation markers received prophylaxis of intermediate-dose LMWH. The overall inpatient-mortality rate was 38.5%. The anticoagulant nonuser group presented higher mortality risk than each of the following groups: any LMWH users (HR 2.1; 95% CI: 1.40-3.15); the prophylactic-dose heparin group (HR 2.39; 95% CI, 1.57-3.64); and the users of heparin dose according to biomarkers (HR 6.52; 95% CI, 2.95-14.41). 3.4% of the patients experienced major hemorrhage. 2.8% of the patients developed an episode of thromboembolism.

CONCLUSIONS

This observational study showed that LMWH administered at the time of admission was associated with lower mortality among unselected adult COVID-19 inpatients. The magnitude of the benefit may have been greatest for the intermediate-dose subgroup. Randomized controlled trials to assess the benefit of heparin within different therapeutic regimes for COVID-19 patients are required.

Type I interferon receptor (IFNAR2) deficiency reveals Zika virus cytopathicity in human macrophages and microglia

Macrophages are key target cells of Zika virus (ZIKV) infection, implicated as a viral reservoir seeding sanctuary sites such as the central nervous system and testes. This rests on the apparent ability of macrophages to sustain ZIKV replication without experiencing cytopathic effects. ZIKV infection of macrophages triggers an innate immune response involving type I interferons (IFN-I), key antiviral cytokines that play a complex role in ZIKV pathogenesis in animal models. To investigate the functional role of the IFN-I response we generated human induced pluripotent stem cell (iPSC)-derived macrophages from a patient with complete deficiency of IFNAR2, the high affinity IFN-I receptor subunit. Accompanying the profound defect of IFN-I signalling in IFNAR2 deficient iPS-macrophages we observed significantly enhanced ZIKV replication and cell death, revealing the inherent cytopathicity of ZIKV towards macrophages. These observations were recapitulated by genetic and pharmacological ablation of IFN-I signalling in control iPS-macrophages and extended to a model of iPS-microglia. Thus, the capacity of macrophages to support noncytolytic ZIKV replication depends on an equilibrium set by IFN-I, suggesting that innate antiviral responses might counterintuitively promote ZIKV persistence via the maintenance of tissue viral reservoirs relevant to pathogenesis.

Surface Glycan Modification of Cellular Nanosponges to Promote SARS-CoV-2 Inhibition

Cellular binding and entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are mediated by its spike glycoprotein (S protein), which binds with not only the human angiotensin-converting enzyme 2 (ACE2) receptor but also glycosaminoglycans such as heparin. Cell membrane-coated nanoparticles ("cellular nanosponges") mimic the host cells to attract and neutralize SARS-CoV-2 through natural cellular receptors, leading to a broad-spectrum antiviral strategy. Herein, we show that increasing surface heparin density on the cellular nanosponges can promote their inhibition against SARS-CoV-2. Specifically, cellular nanosponges are made with azido-expressing host cell membranes followed by conjugating heparin to the nanosponge surfaces. Cellular nanosponges with a higher heparin density have a larger binding capacity with viral S proteins and a significantly higher inhibition efficacy against SARS-CoV-2 infectivity. Overall, surface glycan engineering of host-mimicking cellular nanosponges is a facile method to enhance SARS-CoV-2 inhibition. This approach can be readily generalized to promote the inhibition of other glycan-dependent viruses.

Early Effects of Low Molecular Weight Heparin Therapy with Soft-Mist Inhaler for COVID-19-Induced Hypoxemia: A Phase IIb Trial

In COVID-19-induced acute respiratory distress syndrome, the lungs are incapable of filling with sufficient air, leading to hypoxemia that results in high mortality among hospitalized patients. In clinical trials, low-molecular-weight heparin was administered via a specially designed soft-mist inhaler device in an investigator initiated, single-center, open-label, phase-IIb clinical trial. Patients with evidently worse clinical presentations were classed as the “Device Group”; 40 patients were given low-molecular-weight heparin via a soft mist inhaler at a dose of 4000 IU per administration, twice a day. The Control Group, also made up of 40 patients, received the standard therapy. The predetermined severity of hypoxemia and the peripheral oxygen saturation of patients were measured on the 1st and 10th days of treatment. The improvement was particularly striking in cases of severe hypoxemia. In the 10-day treatment, low-molecular-weight heparin was shown to significantly improve breathing capability when delivered via a soft-mist inhaler.

Coagulation abnormalities & thromboprophylaxis in COVID-19

The ongoing pandemic of novel coronavirus 2019 is rapidly evolving, and newer organ- and system-specific manifestations are being observed. Thrombotic complications and coagulopathy are frequent manifestations of the disease, especially in sick patients, which appear to be unique and distinct from sepsis-induced coagulopathy, disseminated intravascular coagulation and other viral infection-induced coagulation abnormalities. Elevated D-dimers and fibrinogen in the early stage of the disease with minimally deranged prothrombin time and platelet counts are prominent and distinguishing features. Venous and arterial thromboses, as opposed to bleeding events, are the major clinical correlates. There is much to be known about the pathogenesis of COVID-associated coagulopathy; however, the mechanisms overlap with thrombotic microangiopathy, haemophagocytic syndrome and antiphospholipid syndrome compounded by the diffuse endothelial damage. The recommendations regarding the treatment are still evolving, but antithrombotic therapy has a definite role in positive outcomes of sick patients.

Molecular Mechanism of the Anti-Inflammatory Action of Heparin

Our objective is to reveal the molecular mechanism of the anti-inflammatory action of low-molecular-weight heparin (LMWH) based on its influence on the activity of two key cytokines, IFNγ and IL-6. The mechanism of heparin binding to IFNγ and IL-6 and the resulting inhibition of their activity were studied by means of extensive molecular-dynamics simulations. The effect of LMWH on IFNγ signalling inside stimulated WISH cells was investigated by measuring its antiproliferative activity and the translocation of phosphorylated STAT1 in the nucleus. We found that LMWH binds with high affinity to IFNγ and is able to fully inhibit the interaction with its cellular receptor. It also influences the biological activity of IL-6 by binding to either IL-6 or IL-6/IL-6Rα, thus preventing the formation of the IL-6/IL-6Rα/gp130 signalling complex. These findings shed light on the molecular mechanism of the anti-inflammatory action of LMWH and underpin its ability to influence favourably conditions characterised by overexpression of these two cytokines. Such conditions are not only associated with autoimmune diseases, but also with inflammatory processes, in particular with COVID-19. Our results put forward heparin as a promising means for the prevention and suppression of severe CRS and encourage further investigations on its applicability as an anti-inflammatory agent.

Enhanced Antiviral Function of Magnesium Chloride-Modified Heparin on a Broad Spectrum of Viruses

Previous studies reported on the broad-spectrum antiviral function of heparin. Here we investigated the antiviral function of magnesium-modified heparin and found that modified heparin displayed a significantly enhanced antiviral function against human adenovirus (HAdV) in immortalized and primary cells. Nuclear magnetic resonance analyses revealed a conformational change of heparin when complexed with magnesium. To broadly explore this discovery, we tested the antiviral function of modified heparin against herpes simplex virus type 1 (HSV-1) and found that the replication of HSV-1 was even further decreased compared to aciclovir. Moreover, we investigated the antiviral effect against the new severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) and measured a 55-fold decreased viral load in the supernatant of infected cells associated with a 38-fold decrease in virus growth. The advantage of our modified heparin is an increased antiviral effect compared to regular heparin.

Zika Virus NS1 Suppresses VE-Cadherin and Claudin-5 via hsa-miR-101-3p in Human Brain Microvascular Endothelial Cells

Zika virus (ZIKV) is a neurotropic virus that causes microcephaly in newborns and Guillain-Barré syndrome (GBS) in adults. ZIKV is known to transmigrate through the blood-brain barrier (BBB) by utilizing different strategies. NS1 is a conserved flavivirus protein, which is secreted extracellularly. ZIKV-NS1 has been shown to target adherens junctions (AJs) and tight junctions (TJs) to disrupt the endothelial barrier integrity. The microRNAs are short non-coding RNAs, which post-transcriptionally regulate the gene expression by binding to 3' UTR of the target gene. In the present study, we studied the ZIKV-NS1-mediated effect through hsa-miR-101-3p on the junctional barrier integrity in human brain microvascular endothelial cells. We exposed hBMVECs and hCMEC/D3 cells with ZIKV-NS1 at different time points (12 h and 24 h) with the doses 500 ng/mL and 1000 ng/mL. The change in the expression of VE-cadherin and claudin-5 was quantified using immunoblotting. The expression of the hsa-miR-101-3p was quantified using qRT-PCR. To prove the targeting of hsa-miR-101-3p to VE-cadherin, we transfected hsa-miR-101-3p mimic, scramble, hsa-miR-101-3p inhibitor, and Cy3 in the ZIKV-NS1-exposed hCMEC/D3 cells. The distribution and expression of the VE-cadherin and claudin-5 were observed using immunofluorescence and immunoblotting. The ZIKV-NS1 compromises the endothelial barrier integrity by disrupting the VE-cadherin and claudin-5 protein expression via hsa-miR-101-3p. The findings of this study suggest that ZIKV-NS1 dysregulates the adherens junction and tight junction proteins through hsa-miR-101-3p, which compromises the barrier integrity of human brain microvascular endothelial cells.

Identification of SARS-CoV-2 Receptor Binding Inhibitors by In Vitro Screening of Drug Libraries

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19) global pandemic. The first step of viral infection is cell attachment, which is mediated by the binding of the SARS-CoV-2 receptor binding domain (RBD), part of the virus spike protein, to human angiotensin-converting enzyme 2 (ACE2). Therefore, drug repurposing to discover RBD-ACE2 binding inhibitors may provide a rapid and safe approach for COVID-19 therapy. Here, we describe the development of an in vitro RBD-ACE2 binding assay and its application to identify inhibitors of the interaction of the SARS-CoV-2 RBD to ACE2 by the high-throughput screening of two compound libraries (LOPAC^®1280 and DiscoveryProbeTM). Three compounds, heparin sodium, aurintricarboxylic acid (ATA), and ellagic acid, were found to exert an effective binding inhibition, with IC50 values ranging from 0.6 to 5.5 µg/mL. A plaque reduction assay in Vero E6 cells infected with a SARS-CoV-2 surrogate virus confirmed the inhibition efficacy of heparin sodium and ATA. Molecular docking analysis located potential binding sites of these compounds in the RBD. In light of these findings, the screening system described herein can be applied to other drug libraries to discover potent SARS-CoV-2 inhibitors.

The Use of the Anticoagulant Heparin and Corticosteroid Dexamethasone as Prominent Treatments for COVID-19

COVID-19 is spreading worldwide at disturbing rates, overwhelming global healthcare. Mounting death cases due to disease complications highlight the necessity of describing efficient drug therapy strategies for severe patients. COVID-19 severity associates with hypercoagulation and exacerbated inflammation, both influenced by ACE2 downregulation and cytokine storm occurrence. In this review, we discuss the applicability of the anticoagulant heparin and the anti-inflammatory corticosteroid dexamethasone for managing severe COVID-19 patients. The upregulated inflammation and blood clotting may be mitigated by administrating heparin and its derivatives. Heparin enhances the anticoagulant property of anti-thrombin (AT) and may be useful in conjunction with fibrinolytic drugs for severe COVID-19 patients. Besides, heparin can also modulate immune responses, alleviating TNF-α-mediated inflammation, impairing IL-6 production and secretion, and binding to complement proteins and leukotriene B₄ (LTB₄). Moreover, heparin may present anti-SARS-CoV-2 potential once it can impact viral infectivity and alter SARS-CoV-2 Spike protein architecture. Another feasible approach is the administration of the glucocorticoid dexamethasone. Although glucocorticoid's administration for viral infection managing is controversial, there is increasing evidence demonstrating that dexamethasone treatment is capable of drastically diminishing the death rate of patients presenting with Acute Respiratory Distress Syndrome (ARDS) that required invasive mechanical ventilation. Importantly, dexamethasone may be detrimental by impairing viral clearance and inducing hyperglycemia and sodium retention, hence possibly being deleterious for diabetics and hypertensive patients, two major COVID-19 risk groups. Therefore, while heparin's multitarget capacity shows to be strongly beneficial for severe COVID-19 patients, dexamethasone should be carefully administered taking into consideration underlying medical conditions and COVID-19 disease severity. Therefore, we suggest that the multitarget impact of heparin as an anti-viral, antithrombotic and anti-inflammatory drug in the early stage of the COVID-19 could significantly reduce the need for dexamethasone treatment in the initial phase of this disease. If the standard treatment of heparins fails on protecting against severe illness, dexamethasone must be applied as a potent anti-inflammatory shutting-down the uncontrolled and exacerbated inflammation.

Pharmacological Modulators of Autophagy as a Potential Strategy for the Treatment of COVID-19

The family of coronaviruses (CoVs) uses the autophagy machinery of host cells to promote their growth and replication; thus, this process stands out as a potential target to combat COVID-19. Considering the different roles of autophagy during viral infection, including SARS-CoV-2 infection, in this review, we discuss several clinically used drugs that have effects at different stages of autophagy. Among them, we mention (1) lysosomotropic agents, which can prevent CoVs infection by alkalinizing the acid pH in the endolysosomal system, such as chloroquine and hydroxychloroquine, azithromycin, artemisinins, two-pore channel modulators and imatinib; (2) protease inhibitors that can inhibit the proteolytic cleavage of the spike CoVs protein, which is necessary for viral entry into host cells, such as camostat mesylate, lopinavir, umifenovir and teicoplanin and (3) modulators of PI3K/AKT/mTOR signaling pathways, such as rapamycin, heparin, glucocorticoids, angiotensin-converting enzyme inhibitors (IECAs) and cannabidiol. Thus, this review aims to highlight and discuss autophagy-related drugs for COVID-19, from in vitro to in vivo studies. We identified specific compounds that may modulate autophagy and exhibit antiviral properties. We hope that research initiatives and efforts will identify novel or "off-label" drugs that can be used to effectively treat patients infected with SARS-CoV-2, reducing the risk of mortality.

Pharmacological and clinical application of heparin progress: An essential drug for modern medicine

Heparin is the earliest and most widely used anticoagulant and antithrombotic drug that is still used in a variety of clinical indications. Since it was discovered in 1916, after more than a century of repeated exploration, heparin has not been replaced by other drugs, but a great progress has been made in its basic research and clinical application. Besides anticoagulant and antithrombotic effects, heparin also has antitumor, anti-inflammatory, antiviral, and other pharmacological activities. It is widely used clinically in cardiovascular and cerebrovascular diseases, lung diseases, kidney diseases, cancer, etc., as the first anticoagulant medicine in COVID-19 exerts anticoagulant, anti-inflammatory and antiviral effects. At the same time, however, it also leads to a lot of adverse reactions, such as bleeding, thrombocytopenia, elevated transaminase, allergic reactions, and others. This article comprehensively reviews the modern research progress of heparin compounds; discusses the structure, preparation, and adverse reactions of heparin; emphasizes the pharmacological activity and clinical application of heparin; reveals the possible mechanism of the therapeutic effect of heparin in related clinical applications; provides evidence support for the clinical application of heparin; and hints on the significance of exploring the wider application fields of heparin.

Thrombosis and Haemostasis challenges in COVID-19 - Therapeutic perspectives of heparin and tissue-type plasminogen activator and potential toxicological reactions-a mini review

The coronavirus disease (COVID)-19 pandemic is a major challenge for the health systems worldwide. Acute respiratory distress syndrome (ARDS), is one of the most common complications of the COVID-19 infection. The activation of the coagulation system plays an important role in the pathogenesis of ARDS. The development of lung coagulopathy involves thrombin generation and fibrinolysis inhibition.

Unfractionated heparin and its recently introduced counterpart low molecular weight heparin (LMWH), are widely used anticoagulants with a variety of clinical indications allowing for limited and manageable physio-toxicologic side effects while the use of protamine sulfate, heparin's effective antidote, has made their use even safer. Tissue-type plasminogen activator (tPA) is approved as intravenous thrombolytic treatment. The present narrative review discusses the use of heparin and tPA in the treatment of COVID-19-induced ARDS and their related potential physio-toxicologic side effects. The article is a quick review of articles on anticoagulation in COVID infection and the potential toxicologic reactions associated with these drugs.

Heparin Inhibits Cellular Invasion by SARS-CoV-2: Structural Dependence of the Interaction of the Spike S1 Receptor-Binding Domain with Heparin

The dependence of development and homeostasis in animals on the interaction of hundreds of extracellular regulatory proteins with the peri- and extracellular glycosaminoglycan heparan sulfate (HS) is exploited by many microbial pathogens as a means of adherence and invasion. Heparin, a widely used anticoagulant drug, is structurally similar to HS and is a common experimental proxy. Exogenous heparin prevents infection by a range of viruses, including S-associated coronavirus isolate HSR1. Here, we show that heparin inhibits severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) invasion of Vero cells by up to 80% at doses achievable through prophylaxis and, particularly relevant, within the range deliverable by nebulisation. Surface plasmon resonance and circular dichroism spectroscopy demonstrate that heparin and enoxaparin, a low-molecular-weight heparin which is a clinical anticoagulant, bind and induce a conformational change in the spike (S1) protein receptor-binding domain (S1 RBD) of SARS-CoV-2. A library of heparin derivatives and size-defined fragments were used to probe the structural basis of this interaction. Binding to the RBD is more strongly dependent on the presence of 2-O or 6-O sulfate groups than on N-sulfation and a hexasaccharide is the minimum size required for secondary structural changes to be induced in the RBD. It is likely that inhibition of viral infection arises from an overlap between the binding sites of heparin/HS on S1 RBD and that of the angiotensin-converting enzyme 2. The results suggest a route for the rapid development of a first-line therapeutic by repurposing heparin and its derivatives as antiviral agents against SARS-CoV-2 and other members of the Coronaviridae.

Heparin Inhibits Cellular Invasion by SARS-CoV-2: Structural Dependence of the Interaction of the Spike S1 Receptor-Binding Domain with Heparin

The dependence of development and homeostasis in animals on the interaction of hundreds of extracellular regulatory proteins with the peri- and extracellular glycosaminoglycan heparan sulfate (HS) is exploited by many microbial pathogens as a means of adherence and invasion. Heparin, a widely used anticoagulant drug, is structurally similar to HS and is a common experimental proxy. Exogenous heparin prevents infection by a range of viruses, including S-associated coronavirus isolate HSR1. Here, we show that heparin inhibits severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) invasion of Vero cells by up to 80% at doses achievable through prophylaxis and, particularly relevant, within the range deliverable by nebulisation. Surface plasmon resonance and circular dichroism spectroscopy demonstrate that heparin and enoxaparin, a low-molecular-weight heparin which is a clinical anticoagulant, bind and induce a conformational change in the spike (S1) protein receptor-binding domain (S1 RBD) of SARS-CoV-2. A library of heparin derivatives and size-defined fragments were used to probe the structural basis of this interaction. Binding to the RBD is more strongly dependent on the presence of 2-O or 6-O sulfate groups than on N-sulfation and a hexasaccharide is the minimum size required for secondary structural changes to be induced in the RBD. It is likely that inhibition of viral infection arises from an overlap between the binding sites of heparin/HS on S1 RBD and that of the angiotensin-converting enzyme 2. The results suggest a route for the rapid development of a first-line therapeutic by repurposing heparin and its derivatives as antiviral agents against SARS-CoV-2 and other members of the Coronaviridae.

Thromboprofilaxys With Fondaparinux vs. Enoxaparin in Hospitalized COVID-19 Patients: A Multicenter Italian Observational Study

Importance: The use of anticoagulant therapy with heparins decreased mortality in hospitalized patients with severe coronavirus disease 2019 (COVID-19). Even if enoxaparin and fondaparinux have the same clinical indication for venous thromboembolism (VTE) prevention; to date, there are no data about the use of fondaparinux in terms of safety, effectiveness, and impact on clinical prognosis among COVID-19 patients. Objective: To evaluate the safety, effectiveness, and clinical impact of VTE prophylaxis with fondaparinux and enoxaparin among COVID-19 patients hospitalized in internal medicine units. Design, Setting, and Participants: This was a retrospective multicenter observation study, including consecutive symptomatic patients with laboratory-proven COVID-19 admitted to internal medicine units of five Italian hospitals from 15th February to 15th March 2020. Main Outcomes and Measures: The primary safety outcome was the composite of major bleeding and clinically relevant non-major bleeding; the primary effectiveness outcome was the composite of all events classified as pulmonary embolism and deep venous thrombosis. The secondary effectiveness outcome included acute respiratory distress syndrome and all-cause death. Results: Among 120 COVID-19 patients enrolled in the study, 74 were taking enoxaparin (4,000 or 6,000 units/day) and 46 fondaparinux (2.5 units/day). No statistically significant difference in demographic and laboratory and clinical characteristics between the two groups has been shown. During a median follow-up of 32 (interquartile range: 14-51) days, the cumulative incidence rates of VTE and bleeding events on pharmacological thromboprophylaxis with heparins were 19% and 8%, respectively. The incidence of both VTE (6.5 vs. 13.5%; P = 0.36) and bleeding events (6.5 vs. 4.1%; P = 0.68) did not show a significant difference between COVID-19 patients on fondaparinux compared with those on enoxaparin therapy. The regression model for the risk of outcome events according to different VTE prophylaxis drugs did not show significant differences. Conclusions and Relevance: Although these results need confirmation by prospective studies including a larger population, our study provides preliminary evidence of a safe and efficacy use of fondaparinux for VTE prophylaxis in hospitalized COVID-19 patients.

Prevention and Management of COVID-19-Associated Venous Thromboembolism

Распространение новой коронавирусной инфекции SARS-CoV-2, классифицируемой сейчас как COVID-19, приобрело глобальный характер. Врачи, занимающиеся лечением пациентов с COVID-19, ежедневно сталкиваются с новыми и неожиданными проблемами. Коронавирусная болезнь может быть причиной системной коагулопатии и тромботических осложнений. Недавние исследования подтвердили крайне высокую частоту встречаемости тромбоэмболических событий, в особенности в группе пациентов с тяжелым течением коронавирусной пневмонии. Сепсис-индуцированная активация коагуляционного каскада в сочетании с широкой распространенностью в общей популяции известных факторов риска венозной тромбоэмболии (ВТЭ) способствуют развитию в организме протромботического статуса. Аномальные параметры коагуляции связаны с плохим прогнозом для пациентов с COVID-19-пневмонией. Определенные гематологические биомаркеры, включая D-димер, могут выступать в качестве предикторов тромботических событий и неблагоприятных исходов заболевания. Вероятность развития тромботических осложнений следует определять у всех пациентов с COVID-19, которые входят в группу высокого риска ВТЭ и имели несколько неблагоприятных факторов до начала коронавирусной инфекции (более 8 баллов по шкале Caprini). В случаях развития сепсис-индуцированной коагулопатии антикоагулянтная терапия, по-видимому, связана с лучшим прогнозом в отношении смертности. Уровень D-димера может служить показателем эффективности антикоагулянтной терапии, однако такой подход не является общепринятым. В настоящем обзоре литературы обобщены накопленные на сегодняшний день эпидемиологические данные и текущие рекомендации по профилактике и лечению COVID-19-ассоциированной ВТЭ. Дальнейшие исследования должны быть сосредоточены на разработке оптимальных стратегий диагностики и профилактики COVID-19-ассоциированной ВТЭ и связанной с ней летальности

The disease caused by coronavirus SARS-CoV-2, named CoViD-19, has become a global emergency. Physicians that treat patients with COVID-19 face new and unexpected challenges every day. COVID-19 can lead to systemic coagulation activation and thrombotic complications. Recent studies confirmed very high cumulative incidence of thromboembolic events, particularly in critically illpatients with COVID-19 pneumonia. The sepsis-related activation of the coagulation combined with high prevalence of common thrombotic risk factors can contribute to this prothrombotic state. Abnormal coagulation parameters are associated with poor prognosis in patients with novel coronavirus pneumonia. Coagulation biomarkers, including D-dimer, can help in the identification of patients with the risk of complications and mortality. D-dimers may be used to monitor the effectiveness of anticoagulants, although this practice is not universally accepted. Risk assessment in admission is important to identify high-risk patients with multiple risk factors before the onset of the viral infection (Caprini score >8). In case of sepsis-induced coagulopathy, anticoagulant therapy appears to be associated with better prognosis in relation to mortality. In this review, we summarize available epidemiological data on venous thromboembolism and recommendations on thromboprophylaxis in COVID-19. Future research should focus on optimal diagnostic and prophylactic strategies to prevent VTE and potentially improve survival.

Anti-Zika virus and anti-Usutu virus activity of human milk and its components

The benefits of human milk are mediated by multiple nutritional, trophic, and immunological components, able to promote infant's growth, maturation of its immature gut, and to confer protection against infections. Despite these widely recognized properties, breast-feeding represents an important mother-to-child transmission route of some viral infections. Different studies show that some flaviviruses can occasionally be detected in breast milk, but their transmission to the newborn is still controversial. The aim of this study is to investigate the antiviral activity of human milk (HM) in its different stages of maturation against two emerging flaviviruses, namely Zika virus (ZIKV) and Usutu virus (USUV) and to verify whether HM-derived extracellular vesicles (EVs) and glycosaminoglycans (GAGs) contribute to the milk protective effect. Colostrum, transitional and mature milk samples were collected from 39 healthy donors. The aqueous fractions were tested in vitro with specific antiviral assays and EVs and GAGs were derived and characterized. HM showed antiviral activity against ZIKV and USUV at all the stages of lactation with no significant differences in the activity of colostrum, transitional or mature milk. Mechanism of action studies demonstrated that colostrum does not inactivate viral particles, but it hampers the binding of both flaviviruses to cells. We also demonstrated that HM-EVs and HM-GAGs contribute, at least in part, to the anti-ZIKV and anti-USUV action of HM. This study discloses the intrinsic antiviral activity of HM against ZIKV and USUV and demonstrates the contribution of two bioactive components in mediating its protective effect. Since the potential infectivity of HM during ZIKV and USUV infection is still unclear, these data support the World Health Organization recommendations about breast-feeding during ZIKV infection and could contribute to producing new guidelines for a possible USUV epidemic.

Use of Enoxaparin to Counteract COVID-19 Infection and Reduce Thromboembolic Venous Complications: A Review of the Current Evidence

The impact of the COVID-19 pandemic has been dramatic worldwide, with China, Italy, and now US at its epicenter. Researchers and clinicians are studying and testing different approaches in the attempt to prevent the infection and minimize its severity. Major efforts are focused on optimizing mechanical ventilation, antiviral, and supportive treatment; however, the role of heparin and low molecular weight (LMW) heparin in this setting has been largely overlooked. This review summarizes the available evidence about the role of heparan sulfate as a key entry mechanism for SARS-CoV-2; the efficacy of heparin and LMW heparin in counteracting its entry into the cell, the recent experimental findings obtained in in vitro studies using the LMW heparin enoxaparin Inhixa®, the role of heparin and LMW heparin in modulating the cytokine storm, and the evidence for the use of LMW heparin in the prevention and treatment of the thromboembolic complications of COVID-19. The available evidence suggests that LMW heparin appears as a promising tool in the treatment of COVID-19. Whether its systematic use is associated with a reduction in complications and ultimately mortality of these patients is being tested in several studies starting worldwide.

Heparin-binding Peptides as Novel Therapies to Stop SARS-CoV-2 Cellular Entry and Infection

Heparan sulfate proteoglycans (HSPGs) are cell surface receptors that are involved in the cellular uptake of pathologic amyloid proteins and viruses, including the novel coronavirus; severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Heparin and heparan sulfate antagonize the binding of these pathogens to HSPGs and stop their cellular internalization, but the anticoagulant effect of these agents has been limiting their use in the treatment of viral infections. Heparin-binding peptides (HBPs) are suitable nonanticoagulant agents that are capable of antagonizing binding of heparin-binding pathogens to HSPGs. Here, we review and discuss the use of HBPs as viral uptake inhibitors and will address their benefits and limitations to treat viral infections. Furthermore, we will discuss a variant of these peptides that is in the clinic and can be considered as a novel therapy in coronavirus disease 2019 (COVID-19) infection. SIGNIFICANCE STATEMENT: The need to discover treatment modalities for COVID-19 is a necessity, and therapeutic interventions such as heparin-binding peptides (HBPs), which are used for other cases, can be beneficial based on their mechanisms of actions. In this paper, we have discussed the application of HBPs as viral uptake inhibitors in COVID-19 and explained possible mechanisms of actions and the therapeutic effects.

Coagulopathy, thromboembolic complications, and the use of heparin in COVID-19 pneumonia

The SARS-CoV-2 (COVID-19) is causing a pandemic and potentially fatal disease of global public health concern. Viral infections are known to be associated with coagulation impairment; thus, thrombosis, hemorrhage, or both may occur. Understanding the pathophysiologic mechanisms underlying the development of coagulation disorders during viral infection is essential for the development of therapeutic strategies. Coagulopathy in COVID-19 infection is emerging as a precipitant factor for severe respiratory complications and death. An increase in coagulation markers, such as fibrinogen and D-dimer, has been found in severe COVID-19 cases. Heparin, clinically used as an anticoagulant, also has anti-inflammatory properties, including binding of inflammatory cytokines, inhibition of neutrophil chemotaxis, and protection of endothelial cells, and a potential antiviral effect. We hypothesized that low-molecular-weight heparin may attenuate cytokine storm in COVID-19 patients; therefore, low-molecular-weight heparin could be a valid adjunctive therapeutic drug for the treatment of COVID-19 pneumopathy. In this paper, we review potential mechanisms involved in coagulation impairment after viral infection and the possible role of heparin in the treatment of COVID-19 patients.

The Potential Role of Heparin in Patients With COVID-19: Beyond the Anticoagulant Effect. A Review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is responsible of variable clinical manifestations, ranging from no symptoms to severe pneumonia with acute respiratory distress syndrome, septic shock, and multi-organ failure resulting in death. To date no specific antiviral drug have been approved for COVID-19, so the treatment of the disease is mainly focused on symptomatic treatment and supportive care. Moreover, there are no treatments of proven efficacy to reduce the progression of the disease from mild/moderate to severe/critical. An activation of the coagulation cascade leading to severe hypercoagulability has been detected in these patients, therefore early anticoagulation may reduce coagulopathy, microthrombus formation, and the risk of organ damages. The role of heparin in COVID-19 is supported by a lot of studies describing its pleiotropic activity but it must be proven in clinical trials. Several protocols have been designed to assess the risk-benefit profile of heparin (low-molecular-weight or unfractionated heparin) in hospitalized subjects. Although prophylactic doses may be adequate in most patients, it is important to wait the results of clinical trials in order to define the appropriate effective dose able to improve disease outcome.

Viral Coagulopathy in Patients With COVID-19: Treatment and Care

COVID-19 has proven to be particularly challenging given the complex pathogenesis of SARS-CoV-2. Early data have demonstrated how the host response to this novel coronavirus leads to the proliferation of pro-inflammatory cytokines, massive endothelial damage, and generalized vascular manifestations. While SARS-CoV-2 primarily targets the upper and lower respiratory tract, other organ systems are also affected. SARS-CoV-2 relies on 2 host cell receptors for successful attachment: angiotensin-converting enzyme 2 and transmembrane protease serine 2. Clinicopathologic reports have demonstrated associations between severe COVID-19 and viral coagulopathy, resulting in pulmonary embolism; venous, arterial, and microvascular thrombosis; lung endothelial injury; and associated thrombotic complications leading to acute respiratory distress syndrome. Viral coagulopathy is not novel given similar observations with SARS classic, including the consumption of platelets, generation of thrombin, and increased fibrin degradation product exhibiting overt disseminated intravascular coagulation–like syndrome. The specific mechanism(s) behind the thrombotic complications in COVID-19 patients has yet to be fully understood. Parenteral anticoagulants, such as heparin and low-molecular-weights heparins, are widely used in the management of COVID-19 patients. Beyond the primary (anticoagulant) effects of these agents, they may exhibit antiviral, anti-inflammatory, and cytoprotective effects. Direct oral anticoagulants and antiplatelet agents are also useful in the management of these patients. Tissue plasminogen activator and other fibrinolytic modalities may also be helpful in the overall management. Catheter-directed thrombolysis can be used in patients developing pulmonary embolism. Further investigations are required to understand the molecular and cellular mechanisms involved in the pathogenesis of COVID-19-associated thrombotic complications.