A small molecule inhibits virion attachment to heparan sulfate- or sialic acid-containing glycans

Heparan sulfate regulates amphiregulin signaling towards reparative lung mesenchymal cells during influenza A infection

Amphiregulin (Areg), a growth factor produced by regulatory T (Treg) cells to facilitate tissue repair/regeneration, contains a heparan sulfate (HS) binding domain. How HS, a highly sulfated glycan subtype that alters growth factor signaling, influences Areg repair/regeneration functions is unclear. Here we report that inhibition of HS in various cell lines and primary lung mesenchymal cells (LMC) qualitatively alters downstream signaling and highlights the existence of HS-dependent vs. -independent Areg transcriptional signatures. Utilizing a panel of cell lines with targeted deletions in HS synthesis-related genes, we found that the presence of the glypican family of heparan sulfate proteoglycans is critical for Areg signaling and confirmed this dependency in primary LMC by siRNA-mediated knockdown. Furthermore, in the context of influenza A (IAV) infection in vivo , we found that an Areg-responsive subset of reparative LMC upregulate glypican-4 and HS. Conditional deletion of HS primarily within this LMC subset resulted in reduced blood oxygen saturation following infection with IAV, with no changes in viral load. Finally, we found that co-culture of HS-knockout LMC with IAV-induced Treg cells results in reduced LMC responses. Collectively, this study reveals the essentiality of HS on a specific lung mesenchymal population as a mediator of Treg cell-derived Areg reparative signaling during IAV infection.

Novel antioxidant protein target therapy to counter the prevalence and severity of SARS-CoV-2

Background

This review analyzed the magnitude of the COVID-19 pandemic globally and in India and the measures to counter its effect using natural and innate immune booster molecules. The study focuses on two phases: the first focuses on the magnitude, and the second on the effect of antioxidants (natural compounds) on SARS-CoV-2.

Methods

The magnitude of the prevalence, mortality, and comorbidities was acquired from the World Health Organization (WHO) report, media, a report from the Ministry of Health and Family Welfare (MoHFW), newspapers, and the National Centre of Disease Control (NCDC). Research articles from PubMed as well as other sites/journals and databases were accessed to gather literature on the effect of antioxidants.

Results

In the elderly and any chronic diseases, the declined level of antioxidant molecules enhanced the reactive oxygen species, which in turn deprived the immune system.

Conclusion

Innate antioxidant proteins like sirtuin and sestrin play a vital role in enhancing immunity. Herbal products and holistic approaches can also be alternative solutions for everyday life to boost the immune system by improving the redox balance in COVID-19 attack. This review analyzed the counteractive effect of alternative therapy to boost the immune system against the magnitude of the COVID-19 pandemic.

Herbal Substances with Antiviral Effects: Features and Prospects for the Treatment of Viral Diseases with Emphasis on Pro-Inflammatory Cytokines

Viral diseases have a significant impact on human health, and three novel coronaviruses (CoV) have emerged during the 21st century. In this review, we have emphasized the potential of herbal substances with antiviral effects. Our investigation focused on the features and prospects of viral disease treatment, with a particular emphasis on proinflammatory cytokines. We conducted comprehensive searches of various databases, including Science Direct, CABI Direct, Web of Science, PubMed, and Scopus. Cytokine storm mechanisms play a crucial role in inducing a pro-inflammatory response by triggering the expression of cytokines and chemokines. This response leads to the recruitment of leukocytes and promotes antiviral effects, forming the first line of defense against viruses. Numerous studies have investigated the use of herbal medicine candidates as immunomodulators or antivirals. However, cytokine-storm-targeted therapy is recommended for patients with acute respiratory distress syndrome caused by SARS-CoV to survive severe pulmonary failure. Our reviews have demonstrated that herbal formulations could serve as alternative medicines and significantly reduce complicated viral infections. Furthermore, they hold promising potential as specific antiviral agents in experimental animal models.

Pre-Clinical Evaluation of the Antiviral Activity of Epigalocatechin-3-Gallate, a Component of Green Tea, against Influenza A(H1N1)pdm Viruses

Influenza antiviral drugs are important tools in our fight against both annual influenza epidemics and pandemics. Polyphenols are a group of compounds found in plants, some of which have demonstrated promising antiviral activity. Previous in vitro and mouse studies have outlined the anti-influenza virus effectiveness of the polyphenol epigallocatechin-3-gallate (EGCG); however, no study has utilised the ferret model, which is considered the gold-standard for influenza antiviral studies. This study aimed to explore the antiviral efficacy of EGCG in vitro and in ferrets. We first performed studies in Madin-Darby Canine Kidney (MDCK) and human lung carcinoma (Calu-3) cells, which demonstrated antiviral activity. In MDCK cells, we observed a selective index (SI, CC50/IC50) of 77 (290 µM/3.8 µM) and 96 (290 µM/3.0 µM) against A/California/07/2009 and A/Victoria/2570/2019 (H1N1)pdm09 influenza virus, respectively. Calu-3 cells demonstrated a SI of 16 (420 µM/26 µM) and 18 (420 µM/24 µM). Ferrets infected with A/California/07/2009 influenza virus and treated with EGCG (500 mg/kg/day for 4 days) had no change in respiratory tissue viral titres, in contrast to oseltamivir treatment, which significantly reduced viral load in the lungs of treated animals. Therefore, we demonstrated that although EGCG showed antiviral activity in vitro against influenza viruses, the drug failed to impair viral replication in the respiratory tract of ferrets.

Dual action of epigallocatechin-3-gallate in virus-induced cell Injury

BACKGROUND

Viral infections cause damage and long-term injury to infected human tissues, demanding therapy with antiviral and wound healing medications. Consequently, safe phytochemical molecules that may control viral infections with an ability to provide wound healing to viral-induced tissue injuries, either topically or systemically, are advantageous. Herein, we hypothesized that epigallocatechin-3-gallate (EGCG), the most abundant polyphenol in green tea, might be effective as a wound healing, antiviral, and antifibrotic therapy.

RESULTS

The antiviral activities of EGCG against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Herpes simplex virus type 2 (HSV-2) as well as its wound healing activities against different monolayer tissue (continuous and primary) systems were investigated. Consider its possible wound-healing advantages as well. To determine the safe concentrations of EGCG in green monkey kidney (Vero) and Vero-E6 cell lines, MTT assay was performed and showed high CC50 values of 405.1 and 322.9 μM, respectively. The antiviral activities of EGCG against SARS-CoV-2 and HSV-2, measured as half-maximal concentration 50 (IC50) concentrations, were 36.28 and 59.88 μM, respectively. These results confirm that the EGCG has remarkable viral inhibitory activities and could successfully suppress the replication of SARS-CoV-2 and HSV-2 in vitro with acceptable selectivity indices (SI) of 11.16 and 5.39, respectively. In parallel, the EGCG exhibits significant and dose/time-dependent anti-migration effects in human breast cancer cells (MCF-7), its resistant variation (MCF-7adr), and human skin fibroblast (HSF) indicating their potential to heal injuries in different internal and topical mammalian systems.

CONCLUSIONS

The EGCG has proven to be an efficient antiviral against SARS-CoV-2 and HSV-2, as well as a wound-healing phytochemical. We assume that EGCG may be a promising option for slowing the course of acute cellular damage induced by systemic (Coronavirus Disease 2019 (COVID-19)) or topical (HSV-2) viral infections.

Epigallocatechin Gallate-Modified Silver Nanoparticles Show Antiviral Activity against Herpes Simplex Type 1 and 2

(1) Background: Epigallocatechin gallate (EGCG) has been recognized as a flavonoid showing antiviral activity against various types of DNA and RNA viruses. In this work, we tested if EGCG-modified silver nanoparticles (EGCG-AgNPs) can become novel microbicides with additional adjuvant properties to treat herpes infections. (2) Methods: The anti-HSV and cytotoxic activities of EGCG-AgNPs were tested in human HaCaT and VK-2-E6/E7 keratinocytes. HSV-1/2 titers and immune responses after treatment with EGCG-AgNPs were tested in murine models of intranasal HSV-1 infection and genital HSV-2 infection. (3) Results: EGCG-AgNPs inhibited attachment and entry of HSV-1 and HSV-2 in human HaCaT and VK-2-E6/E7 keratinocytes much better than EGCG at the same concentration. Infected mice treated intranasally (HSV-1) or intravaginally (HSV-2) with EGCG-AgNPs showed lower virus titers in comparison to treatment with EGCG alone. After EGCG-AgNPs treatment, mucosal tissues showed a significant infiltration in dendritic cells and monocytes in comparison to NaCl-treated group, followed by significantly better infiltration of CD8+ T cells, NK cells and increased expression of IFN-α, IFN-γ, CXCL9 and CXCL10. (4) Conclusions: Our findings show that EGCG-AgNPs can become an effective novel antiviral microbicide with adjuvant properties to be applied upon the mucosal tissues.

Epigallocatechin Gallate: A Multifaceted Molecule for Neurological Disorders and Neurotropic Viral Infections

Epigallocatechin-3-gallate (EGCG), a polyphenolic moiety found in green tea extracts, exhibits pleiotropic bioactivities to combat many diseases including neurological ailments. These neurological diseases include Alzheimer's disease, multiple sclerosis, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. For instance, in the case of Alzheimer's disease, the formation of a β-sheet in the region of the 10th-21st amino acids was significantly reduced in EGCG-induced oligomeric samples of Aβ40. Its interference induces the formation of Aβ structures with an increase in intercenter-of-mass distances, reduction in interchain/intrachain contacts, reduction in β-sheet propensity, and increase in α-helix. Besides, numerous neurotropic viruses are known to instigate or aggravate neurological ailments. It exerts an effect on the oxidative damage caused in neurodegenerative disorders by acting on GSK3-β, PI3K/Akt, and downstream signaling pathways via caspase-3 and cytochrome-c. EGCG also diminishes these viral-mediated effects, such as EGCG delayed HSV-1 infection by blocking the entry for virions, inhibitory effects on NS3/4A protease or NS5B polymerase of HCV and potent inhibitor of ZIKV NS2B-NS3pro/NS3 serine protease (NS3-SP). It showed a reduction in the neurotoxic properties of HIV-gp120 and Tat in the presence of IFN-γ. EGCG also involves numerous viral-mediated inflammatory cascades, such as JAK/STAT. Nonetheless, it also inhibits the Epstein-Barr virus replication protein (Zta and Rta). Moreover, it also impedes certain viruses (influenza A and B strains) by hijacking the endosomal and lysosomal compartments. Therefore, the current article aims to describe the importance of EGCG in numerous neurological diseases and its inhibitory effect against neurotropic viruses.

Antiviral Mechanism of Virucidal Sialic Acid Modified Cyclodextrin

We have reported that CD-6'SLN [6-sialyllactosamine (6'SLN)-modified β-cyclodextrin (CD)] can be a potential anti-influenza drug because it irreversibly deactivates virions. Indeed, in vivo, CD-6'SLN improved mice survival in an H1N1 infection model even when administered 24 h post-infection. Although CD-6'SLN was designed to target the viral envelope protein hemagglutinin (HA), a natural receptor of 6'SLN, it remains unclear whether other targets exist. In this study, we confirm that CD-6'SLN inhibits the influenza virus through an extracellular mechanism by interacting with HA, but not with neuraminidase (NA), despite the latter also having a binding pocket for the sialyl group. We find that CD-6'SLN interacts with the viral envelope as it elicits the release of a fluorophore embedded in the membrane. Two similar compounds were designed to test separately the effect of 6'SLN and of the undecyl moiety that links the CD to 6'SLN. Neither showed any interaction with the membrane nor the irreversible viral inhibition (virucidal), confirming that both components are essential to membrane interaction and virucidal action. Unlike similar antiviral cyclodextrins developed against other viruses, CD-6'SLN was not able to decapsulate viral RNA. Our findings support that combining viral protein-specific epitopes with hydrophobic linkers provides a strategy for developing antiviral drugs with a virucidal mechanism.

Therapeutic potential of green tea catechin, (-)-epigallocatechin-3-O-gallate (EGCG) in SARS-CoV-2 infection: Major interactions with host/virus proteases

BACKGROUND

The current COVID-19 pandemic from the human pathogenic virus SARS-CoV-2 has resulted in a major health hazard globally. The morbidity and transmission modality of this disease are severe and uncontrollable. As no effective clinical drugs are available for treatment of COVID-19 infection till to date and only vaccination is used as prophylaxis and its efficacy is restricted due to emergent of new variants of SARS-CoV-2, there is an urgent need for effective drugs for its treatment.

PURPOSE

The aim of this review was to provide a detailed analysis of anti-SARS-CoV-2 efficacy of (-)-epigallocatechin-3-O-gallate (EGCG), a major catechin constituent of green tea (Camellia sinensis (L.) Kuntze) beverage to highlight the scope of EGCG in clinical medicine as both prophylaxis and treatment of present COVID-19 infection. In addition, the factors related to poor oral bioavailabilty of EGCG was also analysed for a suggestion for future research in this direction.

STUDY DESIGN

We collected the published articles related to anti-SARS-CoV-2 activity of EGCG against the original strain (Wuhan type) and its newly emerged variants of SARS-CoV-2 virus.

METHODS

A systematic search on the published literature was conducted in various databases including Google Scholar, PubMed, Science Direct and Scopus to collect the relevant literature.

RESULTS

The findings of this search demonstrate that EGCG shows potent antiviral activity against SARS-CoV-2 virus by preventing viral entry and replication in host cells in vitro models. The studies on the molecular mechanisms of EGCG in inhibition of SARS-CoV-2 infection in host cells reveal that EGCG blocks the entry of the virus particles by interaction with the receptor binding domain (RBD) of viral spike (S) protein to host cell surface receptor protease angiotensin-converting enzyme 2 (ACE2) as well as suppression of the expressions of host proteases, ACE2, TMPRSS2 and GRP78, required for viral entry, by Nrf2 activation in host cells. Moreover, EGCG inhibits the activities of SARS-CoV-2 main protease (Mpro), papain-like protease (PLpro), endoribonuclease Nsp15 in vitro models and of RNA-dependent RNA polymerase (RdRp) in molecular docking model for suppression of viral replication. In addition, EGCG significantly inhibits viral inflammatory cytokine production by stimulating Nrf2- dependent host immune response in virus-infected cells. EGCG significantly reduces the elevated levels of HMGB1, a biomarker of sepsis, lung fibrosis and thrombotic complications in viral infections. EGCG potentially inhibits the infection of original (Wuhan type) strain of SARS-CoV-2 and other newly emerged variants as well as the infections of SARS-CoV-2 virus spike-protein of WT and its mutants-mediated pseudotyped viruses . EGCG shows maximum inhibitory effect against SARS-CoV-2 infection when the host cells are pre-incubated with the drug prior to viral infection. A sorbitol/lecithin-based throat spray containing concentrated green tea extract rich in EGCG content significantly reduces SARS-CoV-2 infectivity in oral mucosa. Several factors including degradation in gastrointestinal environment, low absorption in small intestine and extensive metabolism of EGCG are responsible for its poor bioavailability in humans. Pharmacokinetic and metabolism studies of EGCG in humans reveal poor bioavailability of EGCG in human plasma and EGCG-4"-sulfate is its major metabolite. The concentration of EGCG-4"-sulfate in human plasma is almost equivalent to that of free EGCG (Cmax 177.9 vs 233.5 nmol/L). These findings suggest that inhibition of sulfation of EGCG is a crucial factor for improvement of its bioavailability. In vitro study on the mechanism of EGCG sulfonation indicates that sulfotransferases, SULT1A1 and SULT1A3 are responsible for sulfonation in human liver and small intestine, respectively. Some attempts including structural modifications, and nanoformulations of EGCG and addition of nutrients with EGCG have been made to improve the bioavailability of EGCG.

CONCLUSIONS

The findings of this study suggest that EGCG has strong antiviral activity against SARS-CoV-2 infection independent of viral strains (Wuhan type (WT), other variants) by inhibition of viral entry and replication in host cells in vitro models. EGCG may be useful in reduction of this viral load in salivary glands of COVID-19 patients, if it is applied in mouth and throat wash formulations in optimal concentrations. EGCG could be a promising candidate in the development of effective vaccine for prevention of the infections of newly emergent strains of SARS-CoV-2 virus. EGCG might be useful also as a clinical medicine for treatment of COVID-19 patients if its bioavailability in human plasma is enhanced.

Strictinin, a Major Ingredient in Yunnan Kucha Tea Possessing Inhibitory Activity on the Infection of Mouse Hepatitis Virus to Mouse L Cells

Theacrine and strictinin of Yunnan Kucha tea prepared from a mutant variety of wild Pu'er tea plants were two major ingredients responsible for the anti-influenza activity. As the COVID-19 outbreak is still lurking, developing safe and cost-effective therapeutics is an urgent need. This study aimed to evaluate the effects of these tea compounds on the infection of mouse hepatitis virus (MHV), a β-coronavirus serving as a surrogate for SARS-CoV. Treatment with strictinin (100 μM), but not theacrine, completely eliminated MHV infection, as indicated by a pronounced reduction in plaque formation, nucleocapsid protein expression, and progeny production of MHV. Subsequently, a time-of-drug addition protocol, including pre-, co-, or post-treatment, was exploited to further evaluate the possible mechanism of antiviral activity mediated by strictinin, and remdesivir, a potential drug for the treatment of SARS-CoV-2, was used as a positive control against MHV infection. The results showed that all three treatments of remdesivir (20 μM) completely blocked MHV infection. In contrast, no significant effect on MHV infection was observed when cells were pre-treated with strictinin (100 μM) prior to infection, while significant inhibition of MHV infection was observed when strictinin was introduced upon viral adsorption (co-treatment) and after viral entry (post-treatment). Of note, as compared with the co-treatment group, the inhibitory effect of strictinin was more striking in the post-treatment group. These results indicate that strictinin suppresses MHV infection by multiple mechanisms; it possibly interferes with viral entry and also critical step(s) of viral infection. Evidently, strictinin significantly inhibited MHV infection and might be a suitable ingredient for protection against coronavirus infection.

Effects of green tea extract epigallocatechin-3-gallate (EGCG) on oral disease-associated microbes: a review

For thousands of years, caries, periodontitis and mucosal diseases, which are closely related to oral microorganisms, have always affected human health and quality of life. These complex microbiota present in different parts of the mouth can cause chronic infections in the oral cavity under certain conditions, some of which can also lead to acute and systemic diseases. With the mutation of related microorganisms and the continuous emergence of drug-resistant strains, in order to prevent and treat related diseases, in addition to the innovation of diagnosis and treatment technology, the development of new antimicrobial drugs is also important. Catechins are polyphenolic compounds in green tea, some of which are reported to provide health benefits for a variety of diseases. Studies have shown that epigallocatechin-3-gallate (EGCG) is the most abundant and effective active ingredient in green tea catechins, which acts against a variety of gram-positive and negative bacteria, as well as some fungi and viruses. This review aims to summarize the research progress on the activity of EGCG against common oral disease-associated organisms and discuss the mechanisms of these actions, hoping to provide new medication strategies for the prevention and treatment of oral infectious diseases, the future research of EGCG and its translation into clinical practice are also discussed.

Heparan Sulfate and Sialic Acid in Viral Attachment: Two Sides of the Same Coin?

Sialic acids and heparan sulfates make up the outermost part of the cell membrane and the extracellular matrix. Both structures are characterized by being negatively charged, serving as receptors for various pathogens, and are highly expressed in the respiratory and digestive tracts. Numerous viruses use heparan sulfates as receptors to infect cells; in this group are HSV, HPV, and SARS-CoV-2. Other viruses require the cell to express sialic acids, as is the case in influenza A viruses and adenoviruses. This review aims to present, in a general way, the participation of glycoconjugates in viral entry, and therapeutic strategies focused on inhibiting the interaction between the virus and the glycoconjugates. Interestingly, there are few studies that suggest the participation of both glycoconjugates in the viruses addressed here. Considering the biological redundancy that exists between heparan sulfates and sialic acids, we propose that it is important to jointly evaluate and design strategies that contemplate inhibiting the interactions of both glycoconjugates. This approach will allow identifying new receptors and lead to a deeper understanding of interspecies transmission.

The green tea catechin EGCG provides proof-of-concept for a pan-coronavirus attachment inhibitor

The COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has emphasized the serious threat to human health posed by emerging coronaviruses. Effective broadly-acting antiviral countermeasures are urgently needed to prepare for future emerging CoVs, as vaccine development is not compatible with a rapid response to a newly emerging virus. The green tea catechin, epigallocatechin gallate (EGCG), has broad-spectrum antiviral activity, although its mechanisms against coronavirus (CoV) infection have remained unclear. Here, we show that EGCG prevents human and murine CoV infection and blocks the entry of lentiviral particles pseudotyped with spike proteins from bat or highly pathogenic CoVs, including SARS-CoV-2 variants of concern, in lung epithelial cells. Mechanistically, EGCG treatment reduces CoV attachment to target cell surfaces by interfering with attachment to cell-surface glycans. Heparan sulfate proteoglycans are a required attachment factor for SARS-CoV-2 and are shown here to be important in endemic HCoV-OC43 infection. We show that EGCG can compete with heparin, a heparan sulfate analog, for virion binding. Our results highlight heparan sulfate as a conserved cell attachment factor for CoVs, and demonstrate the potential for the development of pan-coronavirus attachment inhibitors, which may be useful to protect against future emerging CoVs.

Therapeutic effectiveness of green tea leaf extract on clinical symptoms in children suffering viral gastroenteritis: A randomized clinical trial

The use of tea plant extract has been reported to reduce viral complications, but its role in improving viral gastritis has not been investigated. The aim of this randomized clinical trial was to evaluate the effect of green tea consumption in improving pediatric viral gastroenteritis. This clinical trial study was performed on children aged 12 to 17 years with diarrhea who were not treated within 48 hours of the onset of clinical symptoms during September 2019 to September 2020. The children were randomly assigned to a green tea leaf extract (GTE) tablet. The placebo group was considered as a control. Treatment (prescribing the tablets) was continued until a Bristol Stool Scale of 3 or 4 was obtained. Two groups were compared in terms of clinical symptoms. The complete and partial improvement was revealed in 63.2% and 31.6% respectively in the GTE group while only in 15.8% and 57.9% respectively in control group indicating a significant difference (p <0.001). The increase in the number of tablets led to higher improvement rate in response to GTE prescription. The mean hospital stay in GTE and control groups was also 1.66 ± 0.63 days and 3.36 ± 0.4 days indicated shorter hospitalization in former group (p < 0.001). The use of GTE leads to effectively improve the diarrhea as well as to reduce the hospital stay in children suffering viral gastroenteritis.

Tale of Viruses in Male Infertility

Male infertility is a condition where the males either become sterile or critically infertile. The World Health Organisation assessed that approximately 9% of the couple have fertility issues where the contribution of the male partner was estimated to be 50%. There are several factors that can amalgamate to give rise to male infertility. Among them are lifestyle factors, genetic factors and as well as several environmental factors. The causes of male infertility may be acquired, congenital or sometimes idiopathic. All these factors adversely affect the spermatogenesis process as well as they impart serious threats to male genital organs thus resulting in infertility. Viruses are submicroscopic pathogenic agents that rely on host for their replication and survival. They enter the host cell, hijack the host cell machinery to aid their own replication and exit the cell for a new round of infection. With the growing abundance of different types of viruses and the havoc they have stirred in the form of pandemics, it is very essential to decipher their route of entry inside the human body and understand their diverse functional roles in order to combat them. In this chapter, we will review how viruses invade the male genital system thus in turn leading to detrimental consequence on male fertility. We will discuss the tropism of various viruses in the male genital organs and explore their sexual transmissibility. This chapter will summarise the functional and mechanistic approaches employed by the viruses in inducing oxidative stress inside spermatozoa thus leading to male infertility. Moreover, we will also highlight the various antiviral therapies that have been studied so far in order to ameliorate viral infection in order to combat the harmful consequences leading to male infertility.

Effect of Catechins on Upper Respiratory Tract Infections in Winter: A Randomized, Placebo-Controlled, Double-Blinded Trial

Tea catechins are plant-derived compounds that improve immune functions. Previous randomized control trials have demonstrated the efficacy of primarily epi-type catechins against upper respiratory tract infections (URTIs). Green tea can be consumed in several ways, including popular bottled beverages. These beverages, however, require sterilization during manufacturing, which results in catechin isomerization. We conducted a randomized, double-blinded, placebo-controlled trial involving healthy Japanese participants to evaluate whether catechin consumption via bottled beverages has an alleviating effect on the duration and severity of URTIs in winter. The catechin group (490 mg catechin, 0.14%, containing 59% epi-type catechin, n = 55) showed reduced durations of running nose, nasal congestion, and headache, compared with the placebo group (0 mg catechin, n = 54; p = 0.013, 0.018, and <0.001, respectively). Furthermore, when considering physical symptoms, the duration of nasopharyngeal symptoms improved significantly in the catechin group (p < 0.001) compared with that in the control group. The daily consumption of catechin thus reduced the duration and severity of URTIs in healthy men and women. Humans are regularly exposed to several potential infectious threats, and the oral administration of heat-epimerized tea catechins might help prevent and reduce the severity of URTIs.

In silico evaluation of Vitis amurensis Rupr. polyphenol compounds for their inhibition potency against CoVID-19 main enzymes Mpro and RdRp

The rapid transmission of the pneumonia (COVID-19) emerged as an entire worldwide health concern and it was declared as pandemic by the World Health Organization (WHO) as a consequence of the increasing reported infections number. COVID-19 disease is caused by the novel SARS-CoV-2 virus, and unfortunatly no drugs are currently approved against this desease. Accordingly, it is of outmost importance to review the possible therapeutic effects of naturally-occuring compounds that showed approved antiviral activities. The molecular docking approach offers a rapid prediction of a possible inhibition of the main enzymes M^pro and RdRp that play crucial role in the SARS-CoV-2 replication and transcription. In the present work, we review the anti-viral activities of polyphenol compounds (phenolic acids, flavonoids and stilbene) derived from the traditional Chinese medicinal Vitis amurensis. Recent molecular docking studies reported the possible binding of these polyphenols on SARS-CoV-2 enzymes M^pro and RdRp active sites and showed interesting inhibitory effects. This antiviral activity was explained by the structure-activity relationships of the studied compounds. Also, pharmacokinetic analysis of the studied molecules is simulated in the present work. Among the studied polyphenol compounds, only five, namely caffeic acid, ferulic acid, quercetin, naringenin and catechin have drug-likeness characteristics. These five polyphenols derived from Vitis amurensis are promising drug candidates for the COVID-19 treatment.

Multi-Target Approaches of Epigallocatechin-3-O-gallate (EGCG) and its Derivatives Against Influenza Viruses

Influenza viruses (INFV), Orthomyxoviridae family, are mainly transmitted among humans, via aerosols or droplets from the respiratory secretions. However, fomites could be a potential transmission pathway. Annually, seasonal INFV infections account for 290-650 thousand deaths worldwide. Currently, there are two classes of approved drugs to treat INFV infections, being neuraminidase (NA) inhibitors and blockers of matrix-2 (M2) ion channel. However, cases of resistance have been observed for both chemical classes, reducing the efficacy of treatment. The emergence of influenza outbreaks and pandemics calls for new antiviral molecules more effective and that could overcome the current resistance to anti-influenza drugs. In this context, polyphenolic compounds are found in various plants and these have displayed different multi-target approaches against diverse pathogens. Among these, green tea (Camellia sinensis) catechins, in special epigallocatechin-3-O-gallate (EGCG), have demonstrated significant activities against the two most relevant human INFV, subtypes A and lineages B. In this sense, EGCG has been found a promising multi-target agent against INFV since can act inhibiting NA, hemagglutination (HA), RNA-dependent RNA polymerase (RdRp), and viral entry/adsorption. In general, the lack of knowledge about potential multi-target natural products prevents an adequate exploration of them, increasing the time for developing multi-target drugs. Then, this review aimed to compile to most relevant studies showing the anti-INFV effects of EGCG and its derivatives, which could become antiviral drug prototypes in the future.

Epigallocatechin gallate (EGCG) combined with zinc sulfate inhibits Peste des petits ruminants virus entry and replication

Despite the fact that the Peste des petits ruminants virus (PPRV) leads to high morbidity and mortality (up to 100%), antiviral drugs against PPRV are not available. The aim of this study was to estimate the dose of epigallocatechin gallate (EGCG) co-administered with zinc (II) ions as an antiviral agent against PPRV. Treatment of PPRV-infectedVero cells with EGCG and zinc sulfate (zinc II) was administered, and antiviral activities against PPRV in infected Vero cells was evaluated by determination of virus yields, expressed as logTCID₅₀/mL. Cytotoxicity was determined using the tetrazolium-based MTS test. Zinc sulfate at 1.1 mg/mL and EGCG at 25 μM showed low potentiated and potentiated antiviral activities against PPRV, respectively. These agents caused significant inhibition of PPRV in Vero cells (p < 0.05) with a reduction in logTCID₅₀/mL by up to 3-fold. The combination of EGCG (25 μM) and zinc sulfate (1.1 mg/mL) was observed to have strong antiviral activity (p < 0.01) against PPRV with a reduction in logTCID₅₀/mL of the virus up to 4-times without causing any host cell cytotoxicity. This study is the first one to prove that the zinc II has the capability of stimulating EGCG to inhibit in vitro PPRV entry. Moreover, this combination appears capable of reducing infection resistance by hindering viral adaptation.

Epigallocatechin-3-Gallate as a Novel Vaccine Adjuvant

Vaccine adjuvants from natural resources have been utilized for enhancing vaccine efficacy against infectious diseases. This study examined the potential use of catechins, polyphenolic materials derived from green tea, as adjuvants for subunit and inactivated vaccines. Previously, catechins have been documented to have irreversible virucidal function, with the possible applicability in the inactivated viral vaccine platform. In a mouse model, the coadministration of epigallocatechin-3-gallate (EGCG) with influenza hemagglutinin (HA) antigens induced high levels of neutralizing antibodies, comparable to that induced by alum, providing complete protection against the lethal challenge. Adjuvant effects were observed for all types of HA antigens, including recombinant full-length HA and HA1 globular domain, and egg-derived inactivated split influenza vaccines. The combination of alum and EGCG further increased neutralizing (NT) antibody titers with the corresponding hemagglutination inhibition (HI) titers, demonstrating a dose-sparing effect. Remarkably, EGCG induced immunoglobulin isotype switching from IgG1 to IgG2a (approximately >64-700 fold increase), exerting a more balanced TH1/TH2 response compared to alum. The upregulation of IgG2a correlated with significant enhancement of antibody-dependent cellular cytotoxicity (ADCC) function (approximately 14 fold increase), providing a potent effector-mediated protection in addition to NT and HI. As the first report on a novel class of vaccine adjuvants with built-in virucidal activities, the results of this study will help improve the efficacy and safety of vaccines for pandemic preparedness.

Previously published ethno-pharmacological reports reveal the potentiality of plants and plant-derived products used as traditional home remedies by Bangladeshi COVID-19 patients to combat SARS-CoV-2

Several plants have traditionally been used since antiquity to treat various gastroenteritis and respiratory symptoms similar to COVID-19 outcomes. The common symptoms of COVID-19 include fever or chills, cold, cough, flu, headache, diarrhoea, tiredness/fatigue, sore throat, loss of taste or smell, asthma, shortness of breath, or difficulty breathing, etc. This study aims to find out the plants and plant-derived products which are being used by the COVID-19 infected patients in Bangladesh and how those plants are being used for the management of COVID-19 symptoms. In this study, online and partially in-person survey interviews were carried out among Bangladeshi respondents. We selected Bangladeshi COVID-19 patients who were detected Coronavirus positive (+) by RT-PCR nucleic acid test and later recovered. Furthermore, identified plant species from the surveys were thoroughly investigated for safety and efficacy based on the previous ethnomedicinal usage reports. Based on the published data, they were also reviewed for their significant potentialities as antiviral, anti-inflammatory, and immunomodulatory agents. We explored comprehensive information about a total of 26 plant species, belonging to 23 genera and 17 different botanical families, used in COVID-19 treatment as home remedies by the respondents. Most of the plants and plant-derived products were collected directly from the local marketplace. According to our survey results, greatly top 5 cited plant species measured as per the highest RFC value are Camellia sinensis (1.0) > Allium sativum (0.984) > Azadirachta indica (0.966) > Zingiber officinale (0.966) > Syzygium aromaticum (0.943). Previously published ethnomedicinal usage reports, antiviral, anti-inflammatory, and immunomodulatory activity of the concerned plant species also support our results. Thus, the survey and review analysis simultaneously reveals that these reported plants and plant-derived products might be promising candidates for the treatment of COVID-19. Moreover, this study clarifies the reported plants for their safety during COVID-19 management and thereby supporting them to include in any future pre-clinical and clinical investigation for developing herbal COVID-19 therapeutics.

Receptors and ligands for herpes simplex viruses: Novel insights for drug targeting

Human herpes simplex viruses (HSVs) belong to the Herpesviridae family. At present, no vaccine or curative treatment is available for the prevention of HSV infections. Here, we review the cell surface receptors that are recognized by HSV's glycoprotein B, glycoprotein C, glycoprotein D, and the glycoprotein H - glycoprotein L complex to facilitate entry into host cells. These receptors include heparan sulfate (HS), herpesvirus entry mediator (HVEM), and nectin-1/-2, 3-O-sulfated heparan sulfate (3-OS HS).

Natural Products and Their Derivatives against Human Herpesvirus Infection

Herpesviruses establish long-term latent infection for the life of the host and are known to cause numerous diseases. The prevalence of viral infection is significantly increased and causes a worldwide challenge in terms of health issues due to drug resistance. Prolonged treatment with conventional antiviral drugs is more likely to develop drug-resistant strains due to mutations of thymidine nucleoside kinase or DNA polymerase. Hence, the development of alternative treatments is clearly required. Natural products and their derivatives have played a significant role in treating herpesvirus infection rather than nucleoside analogs in drug-resistant strains with minimal undesirable effects and different mechanisms of action. Numerous plants, animals, fungi, and bacteria-derived compounds have been proved to be efficient and safe for treating human herpesvirus infection. This review covers the natural antiherpetic agents with the chemical structural class of alkaloids, flavonoids, terpenoids, polyphenols, anthraquinones, anthracyclines, and miscellaneous compounds, and their antiviral mechanisms have been summarized. This review would be helpful to get a better grasp of anti-herpesvirus activity of natural products and their derivatives, and to evaluate the feasibility of natural compounds as an alternative therapy against herpesvirus infections in humans.

Quercetin as an antiviral agent inhibits the Pseudorabies virus in vitro and in vivo

Pseudorabies virus (PRV) accounts for a critical swine disease incurring economic losses worldwide. Several PRV vaccines are commercially available but these vaccines are effective against only certain prevalent PRV strains in China. To prevent PRV-induced latent infection and decrease the pathogenicity, novel anti-PRV drugs are required to prevent PRV infection. Natural products show exceptional structural diversity representing an important source for developing novel therapeutic agents. Quercetin is a flavonoid with anti-oxidant, anti-cancer, anti-bacterial and anti-viral activities. This study involved quercetin for studying the anti-PRV function in vitro and in vivo. Quercetin was found to significantly decrease the PRV virulent strain HNX at a half-maximal inhibitory concentration (IC₅₀) of 2.618 μM and selectivity index 229. This anti-PRV activity of quercetin was found to be dose-dependent. Furthermore, quercetin also inhibited a wide the infections by a spectrum of PRV strains like HNX, Ea, Bartha and Fa strain. These virucidal effects of quercetin suggest the interaction between these molecules and viral particles, and quercetin is responsible for inhibiting the adsorption of PRV infections. The silico assays suggesting that quercetin might interact with the gD-protein on the surface of the PRV important for viral infection. Additional, the quercetin plantar injection protected the mice from the lethal challenge, decreasing the PRV-infected mice's brain viral loads and mortality. These results provides a anti-PRV strategy and contribute to drug discovery and development.

Epigallocatechin gallate from green tea effectively blocks infection of SARS-CoV-2 and new variants by inhibiting spike binding to ACE2 receptor

BACKGROUND

As the COVID-19 pandemic rages on, the new SARS-CoV-2 variants have emerged in the different regions of the world. These newly emerged variants have mutations in their spike (S) protein that may confer resistance to vaccine-elicited immunity and existing neutralizing antibody therapeutics. Therefore, there is still an urgent need of safe, effective, and affordable agents for prevention/treatment of SARS-CoV-2 and its variant infection.

RESULTS

We demonstrated that green tea beverage (GTB) or its major ingredient, epigallocatechin gallate (EGCG), were highly effective in inhibiting infection of live SARS-CoV-2 and human coronavirus (HCoV OC43). In addition, infection of the pseudoviruses with spikes of the new variants (UK-B.1.1.7, SA-B.1.351, and CA-B.1.429) was efficiently blocked by GTB or EGCG. Among the 4 active green tea catechins at noncytotoxic doses, EGCG was the most potent in the action against the viruses. The highest inhibitory activity was observed when the viruses or the cells were pre-incubated with EGCG prior to the infection. Mechanistic studies revealed that EGCG blocked infection at the entry step through interfering with the engagement of the receptor binding domain (RBD) of the viral spikes to angiotensin-converting enzyme 2 (ACE2) receptor of the host cells.

CONCLUSIONS

These data support further clinical evaluation and development of EGCG as a novel, safe, and cost-effective natural product for prevention/treatment of SARS-CoV-2 transmission and infection.

Design, synthesis and in vitro biological evaluation of a novel class of anti-adenovirus agents based on 3-amino-1,2-propanediol

Nowadays there is not an effective drug for the treatment of infections caused by human adenovirus (HAdV) which supposes a clinical challenge, especially for paediatric and immunosuppressed patients. Here, we describe the design, synthesis and biological evaluation as anti-adenovirus agents of a new library (57 compounds) of diester, monoester and triazole derivatives based on 3-amino-1,2-propanediol skeleton. Seven compounds (17, 20, 26, 34, 44, 60 and 66) were selected based on their high anti-HAdV activity at low micromolar concentration (IC₅₀ from 2.47 to 5.75 µM) and low cytotoxicity (CC₅₀ from 28.70 to >200 µM). In addition, our mechanistic assays revealed that compounds 20 and 44 might be targeting specifically the HAdV DNA replication process, and compound 66 would be targeting HAdV E1A mRNA transcription. For compounds 17, 20, 34 and 60, the mechanism of action seems to be associated with later steps after HAdV DNA replication.

Hepatitis C Virus Glycan-Dependent Interactions and the Potential for Novel Preventative Strategies

Chronic hepatitis C virus (HCV) infections continue to be a major contributor to liver disease worldwide. HCV treatment has become highly effective, yet there are still no vaccines or prophylactic strategies available to prevent infection and allow effective management of the global HCV burden. Glycan-dependent interactions are crucial to many aspects of the highly complex HCV entry process, and also modulate immune evasion. This review provides an overview of the roles of viral and cellular glycans in HCV infection and highlights glycan-focused advances in the development of entry inhibitors and vaccines to effectively prevent HCV infection.

Targeting the glycans: A paradigm for host-targeted and COVID-19 drug design

There is always a need for new approaches for the control of virus burdens caused by seasonal outbreaks, the emergence of novel viruses with pandemic potential and the development of resistance to current antiviral drugs. The outbreak of the 2019 novel coronavirus-disease COVID-19 represented a pandemic threat and declared a public health emergency of international concern. Herein, the role of glycans for the development of new drugs or vaccines, as a host-targeted approach, is discussed where may provide a front-line prophylactic or threats to protect against the current and any future respiratory-infecting virus and possibly against other respiratory pathogens. As a prototype, the role of glycans in the coronavirus infection, as well as, galectins (Gal) as the glycan-recognition agents (GRAs) in drug design are here summarized. Galectins, in particular, Gal-1 and Gal-3 are ubiquitous and important to biological systems, whose interactions with viral glycans modulate host immunity and homeostatic balance.

The green tea catechin epigallocatechin gallate inhibits SARS-CoV-2 infection

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection has caused a pandemic with tens of millions of cases and more than a million deaths. The infection causes COVID-19, a disease of the respiratory system of divergent severity. No treatment exists. Epigallocatechin-3-gallate (EGCG), the major component of green tea, has several beneficial properties, including antiviral activities. Therefore, we examined whether EGCG has antiviral activity against SARS-CoV-2. EGCG blocked not only the entry of SARS-CoV-2, but also MERS- and SARS-CoV pseudotyped lentiviral vectors and inhibited virus infections in vitro. Mechanistically, inhibition of the SARS-CoV-2 spike-receptor interaction was observed. Thus, EGCG might be suitable for use as a lead structure to develop more effective anti-COVID-19 drugs.

Epigallocatechin-3-gallate Can Prevent Type 2 Human Papillomavirus E7 from Suppressing Interferon-Stimulated Genes

Human papillomavirus (HPV) in high-risk groups is known to suppress the type I interferon (IFN) signaling pathway leading to the transcription of interferon-stimulated genes (ISGs), which have many antiviral functions. However, the effects of HPV on the action of various ISGs in low-risk groups are not fully understood. We aimed to investigate whether antiviral ISGs are expressed in transfected keratinocytes with type 2 HPV (HPV-2) E7. The mRNA and protein expressions of ISGs and type I IFN signaling pathway components were evaluated by quantitative real-time polymerase chain reaction, western blot, immunofluorescence, and/or immunohistochemistry. Compared with normal skin, mRNA expression of all ISGs in HPV-2 positive cutaneous warts was significantly decreased (p < 0.05). In comparison with empty vector transfection, E7 transfection significantly down-regulated the mRNA and protein expressions of ISGs and type I IFN signaling pathway components, which were significantly up-regulated by E7 siRNA transfection (p < 0.05). Interestingly, epigallocatechin-3-gallate (EGCG) pretreatment up-regulated the mRNA and protein expressions of ISGs and type I IFN signaling pathway components, which were significantly down-regulated by E7 transfection (p < 0.05). Our results demonstrate that EGCG is a potential candidate for cutaneous wart prevention.

Novel combined single dose anti-hepatitis C therapy: a pilot study

The new anti-hepatitis C virus (HCV) molecules improve treatment regimens and outcomes, but there are drawbacks. New combinations should target the HCV infectious cycle and be effective against all HCV genotypes. We developed the novel formulation Catvira, composed of epigallocatechingallate (EGCG) + sofosbuvir + ribavirin. Here, we compared Catvira to sofosbuvir + ribavirin tablets in patients with CHC genotype 4 in a randomized open-label efficacy and safety study. Treatment-naïve and treatment-experienced patients (n = 80) were randomly assigned to receive a single daily fixed dose of Catvira or sofosbuvir + ribavirin for 12 or 24 weeks. Both Catvira and sofosbuvir + ribavirin yielded similar outcomes of viral load (p < 0.001). Patients receiving Catvira had a significantly more rapid rate of viral load decline with sustained virologic response (SVR12) achieved by 90% of patients receiving 12 weeks of treatment. Catvira did not impact hemoglobin levels while sofosbuvir + ribavirin showed significant decline in hemoglobin levels after 24 weeks (p < 0.05). In this clinical trial (ClinicalTrials.gov Identifier NCT02483156), we found that Catvira administered daily for 12 or 24 weeks is safe, effective, and well-tolerated in both naïve and treatment-experienced patients with HCV genotype 4.

Emerging antiviral therapeutics for human adenovirus infection: Recent developments and novel strategies

Human adenoviruses (HAdV) are ubiquitous human pathogens that cause a significant burden of respiratory, ocular, and gastrointestinal illnesses. Although HAdV infections are generally self-limiting, pediatric and immunocompromised individuals are at particular risk for developing severe disease. Currently, no approved antiviral therapies specific to HAdV exist. Recent outbreaks underscore the need for effective antiviral agents to treat life-threatening infections. In this review we will focus on recent developments in search of potential therapeutic agents for controlling HAdV infections, with a focus on those targeting post-entry stages of the virus replicative cycle.

Epigallocatechin-3-gallate exhibits antiviral effects against the duck Tembusu virus via blocking virus entry and upregulating type I interferons

The duck Tembusu virus (DTMUV) is a novel mosquito-borne Flavivirus which caused huge economic losses for poultry industries in Southeast Asia and China. Currently, no effective antiviral drugs against this virus have been reported. (-)-Epigallocatechin-3-gallate (EGCG), a polyphenol present in abundance in green tea, has recently been demonstrated to have an antiviral activity for many viruses; however, whether EGCG can inhibit DTMUV infection remains unknown. Here, we tried to explore the anti-DTMUV effects and mechanisms of EGCG both in vitro and in vivo. Several EGCG treatment regimens were used to study the comprehensive antiviral activity of EGCG in DTMUV-infected baby hamster kidney cell line (BHK-21). The DTMUV titers of mock- and EGCG-treated infected cell cultures were determined using the tissue culture infective dose assay and the DTMUV mRNA copy number as determined using quantitative Real Time PCR. Moreover, the therapeutic efficacy of EGCG against DTMUV was assessed in DTMUV-infected ducklings. Our results suggested that EGCG significantly reduced the viral infection in BHK-21 cells in a dose-dependent manner, as reflected by the reduction of virus titers, virus copy number, and the expressions of viral E protein. We also observed that EGCG exhibited direct virucidal abilities against DTMUV. Notably, a significant reduction in virus binding ability was also observed, indicating that EGCG possesses excellent inhibitory effects on the viral adsorption step. In addition, DTMUV replication was also suppressed in BHK-21 cells treated with EGCG after viral entry, likely because of upregulation of the levels of interferon alfa and interferon beta. Finally, we also proved that EGCG exhibited anti-DTMUV efficacy in a duckling infection model because the survival rate was significantly improved. This is the first study to demonstrate the protective effect of EGCG against DTMUV, suggesting its potential use as an antiviral drug for DTMUV infection.

(-)-Epigallocatechin-3-Gallate Inhibits the Life Cycle of Pseudorabies Virus In Vitro and Protects Mice Against Fatal Infection

A newly emerged pseudorabies virus (PRV) variant with enhanced pathogenicity has been identified in many PRV-vaccinated swine in China since 2011. The PRV variant has caused great economic cost to the swine industry, and measures for the effective prevention and treatment of this PRV variant are still lacking. (–)-Epigallocatechin-3-gallate (EGCG) exhibits antiviral activity against diverse viruses and thus in this study, we investigated the anti-PRV activity of EGCG in vitro and in vivo. EGCG significantly inhibited infectivity of PRV Ra and PRV XJ5 strains in PK15 B6 cells and Vero cells. The anti-PRV activity of EGCG was dose-dependent, and 50 μM EGCG could completely block viral infection at different multiplicities of infection. We next revealed that EGCG blocked PRV adsorption and entry to PK15 B6 cells in a dose-dependent manner, but inhibition of PRV entry by EGCG was not as efficient as its inhibition of PRV adsorption. PRV replication was suppressed in PK15 B6 cells treated with EGCG post-infection. However, EGCG did not affect PRV assembly and could promote PRV release. Furthermore, 40 mg/kg EGCG provided 100% protection in BALB/c mice challenged with PRV XJ5, when EGCG was administrated both pre- and post-challenge. These results revealed that EGCG exhibits antiviral activity against PRV mainly by inhibiting virus adsorption, entry and replication in vitro. Meanwhile, EGCG increased the survival of mice challenged with PRV. Therefore, EGCG might be a potential antiviral agent against PRV infection.

Epigallocatechin-3-Gallate (EGCG) Inhibits SARS-CoV-2 Infection in Primate Epithelial Cells: (A Short Communication)

SARS-CoV-2, the novel coronavirus responsible for the COVID-19 pandemic, caused >26 million cases in the United States and >437,000 deaths as of Jan 30, 2020. Worldwide by that date, there had been 102 million cases of infections, and deaths had climbed to 2.21 million. Mutated variants of SARS-CoV-2 that have emerged from the United Kingdom, Brazil, and South Africa are associated with higher transmission rates and associated deaths. Therefore, novel therapeutic and prophylactic methods against SARS-CoV-2 are in urgent need. While some antiviral drugs, such as Remdesivir, provide relief to certain patient populations, other existing antiviral drugs or combinations of FDA approved pharmaceuticals have yet to show clinical efficacy against COVID-19. Compounds that possess strong and broad antiviral properties with different mechanisms of action against respiratory viruses may provide novel approaches to combat SARS-CoV-2 and its variants, especially if the compounds are classified as generally recognized as safe (GRAS). A large body of evidence indicates a promising potential for the use of epigallocatechin-3-gallate (EGCG) and its derivatives as effective agents against infections from a wide range of pathogenic viruses. However, EGCG or its derivatives have not been tested directly against SARS-CoV-2. The current study was designed to evaluate the potential antiviral activity of EGCG against SARS-CoV-2 infection in primate epithelial cells. Methods applied in the study include cytopathic effect (CPE) assay and virus yield reduction (VYR) assays using Vero 76 (green monkey epithelial cells) and Caco-2 (human epithelial cells) cell lines, respectively. The results demonstrated that EGCG at 0.27 μg/ml (0.59 μM) inhibited SARS-CoV-2 infection in Vero 76 cells by 50% (i.e., EC50=0.27 μg/ml). EGCG also inhibited SARS-CoV-2 infection in Caco-2 cells with EC90=28 μg/ml (61 μM). These results, to the best of our knowledge, are the first observations on the antiviral activities of EGCG against SARS-CoV-2, and suggest that EGCG and its derivatives could be used to combat COVID-19 and other respiratory viral infection-induced illness, pending in vivo and clinical studies.

Screening coronavirus and human proteins for sialic acid binding sites using a docking approach

<abstract> <p>The initial step of interaction of some pathogens with the host is driven by the interaction of glycoproteins of either side <italic>via</italic> endcaps of their glycans. These end caps consist of sialic acids or sugar molecules. Coronaviruses (CoVs), including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), are found to use this route of interaction. The strength and spatial interactions on the single molecule level of sialic acids with either the spike (S) protein of SARS coronaviruses, or human angiotensin-converting enzyme 2 (ACE2) and furin are probed and compared to the binding modes of those sugar molecules which are present in glycans of glycoproteins. The protocol of using single molecules is seen as a simplified but effective mimic of the complex mode of interaction of the glycans. Averaged estimated binding energies from a docking approach result in preferential binding of the sialic acids to a specific binding site of the S protein of human coronavirus OC43 (HCoV-OC43). Furin is proposed to provide better binding sites for sialic acids than ACE2, albeit outweighed by sites for other sugar molecules. Absolute minimal estimated binding energies indicate weak binding affinities and are indifferent to the type of sugar molecules and the proteins. Neither the proposed best binding sites of the sialic acids nor those of the sugar molecules overlap with any of the cleavage sites at the S protein and the active sites of the human proteins.</p> </abstract>

Effects of epigallocatechin-3-gallate and acyclovir on herpes simplex virus type 1 infection in oral epithelial cells

BACKGROUND/PURPOSE

Herpes simplex virus type 1 (HSV-1) is the pathogenic agent of human diseases, including gingivostomatitis and herpes labialis. The anti-viral activities of the tea polyphenol, epigallocatechin-3-gallate (EGCG), have been demonstrated. This study examined the combined effects of EGCG and the antiviral drug, acyclovir (ACV), on infection of HSV-1 in oral epithelial cells.

METHODS

Cell viability was examined using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide. Viral yields were determined using the plaque assay. Viral proteins were detected using Western blotting analysis or confocal laser scanning microscopy. Viral DNA was detected using the real-time polymerase chain reaction.

RESULTS

Cytotoxic effects of HSV-1 on the viability of oral epithelial cells were evidently reduced in the presence of EGCG (25 μg/ml) or/and ACV (50 μg/ml). Viral yields were also significantly reduced by treatment of cells with EGCG or/and ACV. Expression of viral immediate early protein, infected cell protein 0 (ICP0), was greatly inhibited when cells were treated with EGCG. Combined effects of EGCG and ACV were more evident for the expression of viral thymidine kinase, ICP5 and glycoprotein D. EGCG, but not ACV, significantly reduced the levels of viral particles and viral DNA during viral entry phase. However, at 20 h post infection, the intracellular viral DNA was evidently reduced in HSV-1 infected cells treated with EGCG and ACV. Moreover, the stimulatory effects of HSV-1 on phosphorylation of c-Jun N-terminal kinase could be reduced by ACV.

CONCLUSION

The results demonstrated the additive effects of EGCG and ACV on HSV-1 infection in oral epithelial cells.

Antiviral Role of Phenolic Compounds against Dengue Virus: A Review

Phenolic compounds have been related to multiple biological activities, and the antiviral effect of these compounds has been demonstrated in several viral models of public health concern. In this review, we show the antiviral role of phenolic compounds against dengue virus (DENV), the most widespread arbovirus globally that, after its re-emergence, has caused multiple epidemic outbreaks, especially in the last two years. Twenty phenolic compounds with anti-DENV activity are discussed, including the multiple mechanisms of action, such as those directed against viral particles or viral proteins, host proteins or pathways related to the productive replication viral cycle and the spread of the infection.

Host Factors and Pathways Involved in the Entry of Mosquito-Borne Alphaviruses

Chikungunya virus (CHIKV) is an arthropod-borne virus that has re-emerged recently and has spread to previously unaffected regions, resulting in millions of infections worldwide. The genus Alphavirus, in the family Togaviridae, contains several members with a similar potential for epidemic emergence. In order for CHIKV to replicate in targeted cell types it is essential for the virus to enter these cells. In this review, we summarize our current understanding of the versatile and promiscuous steps in CHIKV binding and entry into human and mosquito host cells. We describe the different entry pathways, receptors, and attachment factors so far described for CHIKV and other mosquito-borne alphaviruses and discuss them in the context of tissue tropism and potential therapeutic targeting.

Matrix metalloproteinase inhibitors identified from Camellia sinensis for COVID-19 prophylaxis: an in silico approach

To respond to the public panic, government and private research organizations of every country keep working on the COVID-19 pandemic, even though still there is a lack of more efficacious medicine for the choice of Coronavirus disease treatment. To counteract on this situation several approved drugs including anti-malarial (hydroxychloroquine and chloroquine), and few anti-viral (remdesvir) agents are choice of treatment for COVID-19. However, these agents suffer from certain limitation in their uses and pointed that there is no specific treatment or vaccine available to counter this contagious disease. Hence, there is urgent requirement to find a specific cure for the disease. In this view, there are several ongoing clinical trials of both western and traditional medicines. In present study, phytochemicals from Camellia sinensis were retrieved from the database and identified based on their ability to inhibit matrix metalloproteinase (MMPs) against SARS-CoV-2 main protease. Camellia sinensis entails of a massive number of phytochemicals with a good source of polyphenols such as Catechin, Epicatechin, Epigallocatechin and (–)-Epigallocatechin gallate. Molecular docking was performed using the GLIDE docking module of Schrodinger Suite software. The analysis displayed docking score for the five polyphenols i.e. theaflavin (− 8.701), 1-O-caffeoylquinic acid (− 7.795), Genistein (− 7.168), Epigallocatechin 3-gallate (− 6.282) and Ethyl trans-caffeate (− 5.356). Interestingly, theaflavin and Epigallocatechin 3-gallate have not revealed any side effects. These polyphenolic compounds had a strong binding affinity with hydrogen bonds and a good drug-likeness score. Therefore, Camellia sinensis could be the beneficial option in the prophylaxis of the COVID-19 outbreak.

Research Progress of the Antiviral Bioactivities of Natural Flavonoids

Flavonoids are now considered as an indispensable component in a variety of nutraceutical and pharmaceutical applications. Most recent researches have focused on the health aspects of flavonoids for humans. Especially, different flavonoids have been investigated for their potential antiviral activities, and several natural flavonoids exhibited significant antiviral properties both in vitro and in vivo. This review provides a survey of the literature regarding the evidence for antiviral bioactivities of natural flavonoids, highlights the cellular and molecular mechanisms of natural flavonoids on viruses, and presents the details of most reported flavonoids. Meanwhile, future perspectives on therapeutic applications of flavonoids against viral infections were discussed.

Antiviral Medicinal Plants of Veterinary Importance: A Literature Review

Viruses have a high mutation rate, and, thus, there is a continual emergence of new antiviral-resistant strains. Therefore, it becomes imperative to explore and develop new antiviral compounds continually. The search for pharmacological substances of plant origin that are effective against animal viruses, which have a high mortality rate or cause large economic losses, has garnered interest in the last few decades. This systematic review compiles 130 plant species that exhibit antiviral activity on 37 different virus species causing serious diseases in animals. The kind of extract, fraction, or compound exhibiting the antiviral activity and the design of the trial were particularly considered for review. The literature revealed details regarding plant species exhibiting antiviral activities against pathogenic animal virus species of the following families-Herpesviridae, Orthomyxoviridae, Paramyxoviridae, Parvoviridae, Poxviridae, Nimaviridae, Coronaviridae, Reoviridae, and Rhabdoviridae-that cause infections, among others, in poultry, cattle, pigs, horses, shrimps, and fish. Overall, 30 plant species exhibited activity against various influenza viruses, most of them causing avian influenza. Furthermore, 30 plant species were noted to be active against Newcastle disease virus. In addition, regarding the pathogens most frequently investigated, this review provides a compilation of 20 plant species active against bovine herpesvirus, 16 against fowlpox virus, 12 against white spot syndrome virus in marine shrimps, and 10 against suide herpesvirus. Nevertheless, some plant extracts, particularly their compounds, are promising candidates for the development of new antiviral remedies, which are urgently required.

Can phytotherapy with polyphenols serve as a powerful approach for the prevention and therapy tool of novel coronavirus disease 2019 (COVID-19)?

Much more serious than the previous severe acute respiratory syndrome (SARS) coronavirus (CoV) outbreaks, the novel SARS-CoV-2 infection has spread speedily, affecting 213 countries and causing ∼17,300,000 cases and ∼672,000 (∼+1,500/day) deaths globally (as of July 31, 2020). The potentially fatal coronavirus disease (COVID-19), caused by air droplets and airborne as the main transmission modes, clearly induces a spectrum of respiratory clinical manifestations, but it also affects the immune, gastrointestinal, hematological, nervous, and renal systems. The dramatic scale of disorders and complications arises from the inadequacy of current treatments and absence of a vaccine and specific anti-COVID-19 drugs to suppress viral replication, inflammation, and additional pathogenic conditions. This highlights the importance of understanding the SARS-CoV-2 mechanisms of actions and the urgent need of prospecting for new or alternative treatment options. The main objective of the present review is to discuss the challenging issue relative to the clinical utility of plants-derived polyphenols in fighting viral infections. Not only is the strong capacity of polyphenols highlighted in magnifying health benefits, but the underlying mechanisms are also stressed. Finally, emphasis is placed on the potential ability of polyphenols to combat SARS-CoV-2 infection via the regulation of its molecular targets of human cellular binding and replication, as well as through the resulting host inflammation, oxidative stress, and signaling pathways.

Epigallocatechin gallate and theaflavin gallate interaction in SARS-CoV-2 spike-protein central channel with reference to the hydroxychloroquine interaction: Bioinformatics and molecular docking study

SARS‐CoV‐2 or COVID‐19 pandemic global outbreak created the most unstable situation of human health–economy. In the past two decades different parts of the word experienced smaller or bigger outbreak related to human coronaviruses. The spike glycoproteins of the COVID‐19 (similar to SARS‐CoV) attach to the angiotensin‐converting enzyme (ACE2) and transit over a stabilized open state for the viral internalization to the host cells and propagate with great efficacy. Higher rate of mutability makes this virus unpredictable/less sensitive to the protein/nucleic acid based drugs. In this emergent situation, drug‐induced destabilization of spike binding to RBD could be a good strategy. In the current study we demonstrated by bioinformatics (CASTp: computed atlas of surface topography of protein, PyMol: molecular visualization) and molecular docking (PatchDock and Autodock) experiments that tea flavonoids catechin products mainly epigallocatechin gallate or other like theaflavin gallate demonstrated higher atomic contact energy (ACE) value, binding energy, Ki value, ligand efficiency, surface area and more amino acid interactions than hydroxychloroquine (HCQ) during binding in the central channel of the spike protein. Moreover, out of three distinct binding sites (I, II and III) of spike core when HCQ binds only with site III (farthest from the nCoV‐RBD of ACE2 contact), epigallocatechin gallate and theaflavin gallate bind all three sites. As sites I and II are in closer contact with open state location and viral–host contact area, these drugs might have significant effects. Taking into account the toxicity/side effects by chloroquine/HCQ, present drugs may be important. Our laboratory is working on tea flavonoids and other phytochemicals in the protection from toxicity, DNA/mitochondrial damage, inflammation and so on. The present data might be helpful for further analysis of flavonoids in this emergent pandemic situation.

Antiviral Strategies of Chinese Herbal Medicine Against PRRSV Infection

Bioactive compounds from Traditional Chinese Medicines (TCMs) are gradually becoming an effective alternative in the control of porcine reproductive and respiratory syndrome virus (PRRSV) because most of the commercially available PRRSV vaccines cannot provide full protection against the genetically diverse strains isolated from farms. Besides, the incomplete attenuation procedure involved in the production of modified live vaccines (MLV) may cause them to revert to the more virulence forms. TCMs have shown some promising potentials in bridging this gap. Several investigations have revealed that herbal extracts from TCMs contain molecules with significant antiviral activities against the various stages of the life cycle of PRRSV, and they do this through different mechanisms. They either block PRRSV attachment and entry into cells or inhibits the replication of viral RNA or viral particles assembly and release or act as immunomodulators and pathogenic pathway inhibitors through cytokines regulations. Here, we summarized the various antiviral strategies employed by some TCMs against the different stages of the life cycle of PRRSV under two major classes, including direct-acting antivirals (DAAs) and indirect-acting antivirals (IAAs). We highlighted their mechanisms of action. In conclusion, we recommended that in making plans for the use of TCMs to control PRRSV, the pathway forward must be built on a real understanding of the mechanisms by which bioactive compounds exert their effects. This will provide a template that will guide the focus of collaborative studies among researchers in the areas of bioinformatics, chemistry, and proteomics. Furthermore, available data and procedures to support the efficacy, safety, and quality control levels of TCMs should be well documented without any breach of data integrity and good manufacturing practices.

EGCG induces β-defensin 3 against influenza A virus H1N1 by the MAPK signaling pathway

Epigallocatechin gallate (EGCG) is the main component of green tea, which has been proven to inhibit a variety of viruses, including influenza A virus. However, the mechanism of EGCG against influenza virus remains to be further explored. The mechanism of EGCG against influenza virus was studied. The results showed that EGCG significantly increased the levels of HBD3 mRNA and protein, while the levels of phosphorylation of (p)-p38 MAPK, ERK and JNK after EGCG treatment were significantly up-regulated. p38 MAPK, ERK and JNK inhibitors significantly inhibited the expression of HBD3 induced by EGCG. On the other hand, EGCG significantly inhibited the expression of HA and NP proteins in influenza A virus H1N1, but attenuated the anti-influenza A virus effect of EGCG after silencing HBD3. Thus, the anti-influenza virus effect of EGCG is related to the induction of HBD3 expression. In addition, the expression of EGCG-induced HBD3 is related to the p38 MAPK, ERK and JNK signaling pathways. The research data show that EGCG can induce HBD3 expression through p38 MAPK, ERK and JNK signaling pathway to inhibit the replication of influenza A virus H1N1, providing a new and effective candidate drug for influenza virus.

Protective Effect of Epigallocatechin-3-Gallate (EGCG) in Diseases with Uncontrolled Immune Activation: Could Such a Scenario Be Helpful to Counteract COVID-19?

Some coronavirus disease 2019 (COVID-19) patients develop acute pneumonia which can result in a cytokine storm syndrome in response to Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) infection. The most effective anti-inflammatory drugs employed so far in severe COVID-19 belong to the cytokine-directed biological agents, widely used in the management of many autoimmune diseases. In this paper we analyze the efficacy of epigallocatechin 3-gallate (EGCG), the most abundant ingredient in green tea leaves and a well-known antioxidant, in counteracting autoimmune diseases, which are dominated by a massive cytokines production. Indeed, many studies registered that EGCG inhibits signal transducer and activator of transcription (STAT)1/3 and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcription factors, whose activities are crucial in a multiplicity of downstream pro-inflammatory signaling pathways. Importantly, the safety of EGCG/green tea extract supplementation is well documented in many clinical trials, as discussed in this review. Since EGCG can restore the natural immunological homeostasis in many different autoimmune diseases, we propose here a supplementation therapy with EGCG in COVID-19 patients. Besides some antiviral and anti-sepsis actions, the major EGCG benefits lie in its anti-fibrotic effect and in the ability to simultaneously downregulate expression and signaling of many inflammatory mediators. In conclusion, EGCG can be considered a potential safe natural supplement to counteract hyper-inflammation growing in COVID-19.

Influence of Herbal Medicines on HMGB1 Release, SARS-CoV-2 Viral Attachment, Acute Respiratory Failure, and Sepsis. A Literature Review

By attaching to the angiotensin converting enzyme 2 (ACE2) protein on lung and intestinal cells, Sudden Acute Respiratory Syndrome (SARS-CoV-2) can cause respiratory and homeostatic difficulties leading to sepsis. The progression from acute respiratory failure to sepsis has been correlated with the release of high-mobility group box 1 protein (HMGB1). Lack of effective conventional treatment of this septic state has spiked an interest in alternative medicine. This review of herbal extracts has identified multiple candidates which can target the release of HMGB1 and potentially reduce mortality by preventing progression from respiratory distress to sepsis. Some of the identified mixtures have also been shown to interfere with viral attachment. Due to the wide variability in chemical superstructure of the components of assorted herbal extracts, common motifs have been identified. Looking at the most active compounds in each extract it becomes evident that as a group, phenolic compounds have a broad enzyme inhibiting function. They have been shown to act against the priming of SARS-CoV-2 attachment proteins by host and viral enzymes, and the release of HMGB1 by host immune cells. An argument for the value in a nonspecific inhibitory action has been drawn. Hopefully these findings can drive future drug development and clinical procedures.

Antiviral Natural Products for Arbovirus Infections

Over the course of the last 50 years, the emergence of several arboviruses have resulted in countless outbreaks globally. With a high proportion of infections occurring in tropical and subtropical regions where arthropods tend to be abundant, Asia in particular is a region that is heavily affected by arboviral diseases caused by dengue, Japanese encephalitis, West Nile, Zika, and chikungunya viruses. Major gaps in protection against the most significant emerging arboviruses remains as there are currently no antivirals available, and vaccines are only available for some. A potential source of antiviral compounds could be discovered in natural products—such as vegetables, fruits, flowers, herbal plants, marine organisms and microorganisms—from which various compounds have been documented to exhibit antiviral activities and are expected to have good tolerability and minimal side effects. Polyphenols and plant extracts have been extensively studied for their antiviral properties against arboviruses and have demonstrated promising results. With an abundance of natural products to screen for new antiviral compounds, it is highly optimistic that natural products will continue to play an important role in contributing to antiviral drug development and in reducing the global infection burden of arboviruses.