Antipicornavirus flavone Ro 09-0179

Quercetin, the Potential Powerful Flavonoid for Human and Food: A Review

Flavonoids occur naturally in different types of fruits and vegetables, including tea, cabbage, cauliflower, elderberries, cranberries, red apples, lettuce, pears, spinach, green hot peppers, white and red onions, kale, blueberries, and nuts. Among these flavonoids is quercetin, a potent natural antioxidant and cytotoxic substance with a number of therapeutic functions. Nowadays, quercetin is a common ingredient in many nutraceutical and cosmeceutical products due to its antioxidant properties. Its antibacterial effects and possible action mechanisms have been explored in many studies. From these, it has been established that quercetin stops the activity of numerous Gram-negative and -positive bacteria, fungi, and viruses. This review clarifies the plant sources and extraction methods of quercetin, as well as its medicinal applications as an antibacterial, antifungal, antiviral, and antioxidant agent, with a particular emphasis on the underlying mechanisms of its biological activity. The mechanism of its antimicrobial effect involves damaging the cell membrane-e.g., by changing its permeability, preventing biofilm formation, reducing the mitochondrial expression of virulence factors, and inhibiting protein and nucleic-acid synthesis. Moreover, quercetin has been shown to impede the activity of a variety of drug-resistant bacterial strains, pointing to the possibility of using it as a strong antimicrobial substance against such strains. In addition, it has occasionally been demonstrated that specific structural alterations to quercetin can increase its antibacterial action in comparison to the parent molecule. Overall, this review synthesizes our understanding of the mode of action of quercetin and its prospects for use as a therapeutic material.

An efficient trans complementation system for in vivo replication of defective poliovirus mutants

The picornavirus genome encodes a large, single polyprotein that is processed by viral proteases to form an active replication complex. The replication complex is formed with the viral genome, host proteins, and viral proteins that are produced/translated directly from each of the viral genomes (viral proteins provided in cis). Efficient complementation in vivo of replication complex formation by viral proteins provided in trans, thus exogenous or ectopically expressed viral proteins, remains to be demonstrated. Here, we report an efficient trans complementation system for the replication of defective poliovirus (PV) mutants by a viral polyprotein precursor in HEK293 cells. Viral 3AB in the polyprotein, but not 2BC, was processed exclusively in cis. Replication of a defective PV replicon mutant, with a disrupted cleavage site for viral 3Cpro protease between 3Cpro and 3Dpol (3C/D[A/G] mutant) could be rescued by a viral polyprotein provided in trans. Only a defect of 3Dpol activity of the replicon could be rescued in trans; inactivating mutations in 2CATPase/hel, 3B, and 3Cpro of the replicon completely abrogated the trans-rescued replication. An intact N-terminus of the 3Cpro domain of the 3CDpro provided in trans was essential for the trans-active function. By using this trans complementation system, a high-titer defective PV pseudovirus (PVpv) (>107 infectious units per mL) could be produced with the defective mutants, whose replication was completely dependent on trans complementation. This work reveals potential roles of exogenous viral proteins in PV replication and offers insights into protein/protein interaction during picornavirus infection.

IMPORTANCE

Viral polyprotein processing is an elaborately controlled step by viral proteases encoded in the polyprotein; fully processed proteins and processing intermediates need to be correctly produced for replication, which can be detrimentally affected even by a small modification of the polyprotein. Purified/isolated viral proteins can retain their enzymatic activities required for viral replication, such as protease, helicase, polymerase, etc. However, when these proteins of picornavirus are exogenously provided (provided in trans) to the viral replication complex with a defective viral genome, replication is generally not rescued/complemented, suggesting the importance of viral proteins endogenously provided (provided in cis) to the replication complex. In this study, I discovered that only the viral polymerase activity of poliovirus (PV) (the typical member of picornavirus family) could be efficiently rescued by exogenously expressed viral proteins. The current study reveals potential roles for exogenous viral proteins in viral replication and offers insights into interactions during picornavirus infection.

Characterization of Anti-Poliovirus Compounds Isolated from Edible Plants

Poliovirus (PV) is the causative agent of poliomyelitis and is a target of the global eradication programs of the World Health Organization (WHO). After eradication of type 2 and 3 wild-type PVs, vaccine-derived PV remains a substantial threat against the eradication as well as type 1 wild-type PV. Antivirals could serve as an effective means to suppress the outbreak; however, no anti-PV drugs have been approved at present. Here, we screened for effective anti-PV compounds in a library of edible plant extracts (a total of 6032 extracts). We found anti-PV activity in the extracts of seven different plant species. We isolated chrysophanol and vanicoside B (VCB) as the identities of the anti-PV activities of the extracts of Rheum rhaponticum and Fallopia sachalinensis, respectively. VCB targeted the host PI4KB/OSBP pathway for its anti-PV activity (EC₅₀ = 9.2 μM) with an inhibitory effect on in vitro PI4KB activity (IC₅₀ = 5.0 μM). This work offers new insights into the anti-PV activity in edible plants that may serve as potent antivirals for PV infection.

Therapeutically important bioactive compounds of the genus Polygonum L. and their possible interventions in clinical medicine

OBJECTIVES

Increasing literature data have suggested that the genus Polygonum L. possesses pharmacologically important plant secondary metabolites. These bioactive compounds are implicated as effective agents in preclinical and clinical practice due to their pharmacological effects such as anti-inflammatory, anticancer, antidiabetic, antiaging, neuroprotective or immunomodulatory properties among many others. However, elaborate pharmacological and clinical data concerning the bioavailability, tissue distribution pattern, dosage and pharmacokinetic profiles of these compounds are still scanty.

KEY FINDINGS

The major bioactive compounds implicated in the therapeutic effects of Polygonum genus include phenolic and flavonoid compounds, anthraquinones and stilbenes, such as quercetin, resveratrol, polydatin and others, and could serve as potential drug leads or as adjuvant agents. Data from in-silico network pharmacology and computational molecular docking studies are also highly helpful in identifying the possible drug target of pathogens or host cell machinery.

SUMMARY

We provide an up-to-date overview of the data from pharmacodynamic, pharmacokinetic profiles and preclinical (in-vitro and in-vivo) investigations and the available clinical data on some of the therapeutically important compounds of genus Polygonum L. and their medical interventions, including combating the outbreak of the COVID-19 pandemic.

Essential Domains of Oxysterol-Binding Protein Required for Poliovirus Replication

Oxysterol-binding protein (OSBP) is a host factor required for enterovirus (EV) replication. OSBP locates at membrane contact site and acts as a lipid exchanger of cholesterol and phosphatidylinositol 4-phosphate (PI4P) between cellular organelles; however, the essential domains required for the viral replication remain unknown. In this study, we define essential domains of OSBP for poliovirus (PV) replication by a functional dominance assay with a series of deletion variants of OSBP. We show that the pleckstrin homology domain (PHD) and the ligand-binding domain, but not the N-terminal intrinsically disordered domain, coiled-coil region, or the FFAT motif, are essential for PV replication. The PHD serves as the primary determinant of OSBP targeting to the replication organelle in the infected cells. These results suggest that not all the domains that support important biological functions of OSBP are essential for the viral replication.

Ligand Recognition by the Lipid Transfer Domain of Human OSBP Is Important for Enterovirus Replication

Oxysterol-binding protein (OSBP), which transports cholesterol and phosphatidylinositol 4-monophosphate (PtdIns[4]P) between different organelles, serves as a conserved host factor for the replication of various viruses, and OSBP inhibitors exhibit antiviral effects. Here, we determined the crystal structure of the lipid transfer domain of human OSBP in complex with endogenous cholesterol. The hydrocarbon tail and tetracyclic ring of cholesterol interact with the hydrophobic tunnel of OSBP, and the hydroxyl group of cholesterol forms a hydrogen bond network at the bottom of the tunnel. Systematic mutagenesis of the ligand-binding region revealed that M446W and L590W substitutions confer functional tolerance to an OSBP inhibitor, T-00127-HEV2. Employing the M446W variant as a functional replacement for the endogenous OSBP in the presence of T-00127-HEV2, we have identified previously unappreciated amino acid residues required for viral replication. The combined use of the inhibitor and the OSBP variant will be useful in elucidating the enigmatic in vivo functions of OSBP.

Antimicrobial Activity of Quercetin: An Approach to Its Mechanistic Principle

Quercetin, an essential plant flavonoid, possesses a variety of pharmacological activities. Extensive literature investigates its antimicrobial activity and possible mechanism of action. Quercetin has been shown to inhibit the growth of different Gram-positive and Gram-negative bacteria as well as fungi and viruses. The mechanism of its antimicrobial action includes cell membrane damage, change of membrane permeability, inhibition of synthesis of nucleic acids and proteins, reduction of expression of virulence factors, mitochondrial dysfunction, and preventing biofilm formation. Quercetin has also been shown to inhibit the growth of various drug-resistant microorganisms, thereby suggesting its use as a potent antimicrobial agent against drug-resistant strains. Furthermore, certain structural modifications of quercetin have sometimes been shown to enhance its antimicrobial activity compared to that of the parent molecule. In this review, we have summarized the antimicrobial activity of quercetin with a special focus on its mechanistic principle. Therefore, this review will provide further insights into the scientific understanding of quercetin’s mechanism of action, and the implications for its use as a clinically relevant antimicrobial agent.

In silico discovery of 3 novel quercetin derivatives against papain-like protease, spike protein, and 3C-like protease of SARS-CoV-2

BACKGROUND

The derivatives of quercetin is known for their immune-modulating antiviral, anti-blood clotting, antioxidant, and also for its anti-inflammatory efficacy. The current study was therefore conducted to examine the noted novel derivatives of quercetin present in plant sources as an immune modulator and as an antiviral molecule in the COVID-19 disease and also to study their affinity of binding with potential three targets reported for coronavirus, i.e., papain-like protease, spike protein receptor-binding domain, and 3C-like protease. Based on the high-positive drug-likeness score, the reported derivatives of quercetin obtained from an open-source database were further filtered. Compounds with positive and high drug-likeness scores were further predicted for their potential targets using DIGEP-Pred software, and STRING was used to evaluate the interaction between modulated proteins. The associated pathways were recorded based on the Kyoto Encyclopedia of Genes and Genomes pathway database. Docking was performed finally using PyRx having AutoDock Vina to identify the efficacy of binding between quercetin derivatives with papain-like protease, spike protein receptor-binding domain, and 3C-like protease. The ligand that scored minimum binding energy was chosen to visualize the interaction between protein and ligand. Normal mode analysis in internal coordinates was done with normal mode analysis to evaluate the physical movement and stability of the best protein-ligand complexes using the iMODS server.

RESULTS

Forty bioactive compounds with the highest positive drug-likeness scores were identified. These 40 bioactives were responsible for regulating different pathways associated with antiviral activity and modulation of immunity. Finally, three lead molecules were identified based on the molecular docking and dynamics simulation studies with the highest anti-COVID-19 and immunomodulatory potentials. Standard antiviral drug remdesivir on docking showed a binding affinity of - 5.8 kcal/mol with PLpro, - 6.4 kcal/mol with 3CLpro, and - 8.6 kcal/mol with spike protein receptor-binding domain of SARS-CoV-2, the discovered hit molecules quercetin 3-O-arabinoside 7-O-rhamnoside showed binding affinity of - 8.2 kcal/mol with PLpro, whereas quercetin 3-[rhamnosyl-(1- > 2)-alpha-L-arabinopyranoside] and quercetin-3-neohesperidoside-7-rhamnoside was predicted to have a binding affinity of - 8.5 kcal/mol and - 8.8 kcal/mol with spike protein receptor-binding domain and 3CLpro respectively CONCLUSION: Docking study revealed quercetin 3-O-arabinoside 7-O-rhamnoside to possess the highest binding affinity with papain-like protease, quercetin 3-[rhamnosyl-(1- > 2)-alpha-L-arabinopyranoside] with spike protein receptor-binding domain, and quercetin-3-neohesperidoside-7-rhamnoside with 3C-like protease and all the protein-ligand complexes were found to be stable after performing the normal mode analysis of the complexes in internal coordinates.

Treatment of COVID-19 patients with quercetin: a prospective, single center, randomized, controlled trial

Scientific research continues on new preventive and therapeutic strategies against severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2). So far, there is no proven curative treatment, and a valid alternative therapeutic approach needs to be developed. This study is designed to evaluate the effect of quercetin in COVID-19 treatment. This was a single-centre, prospective randomized controlled cohort study. Routine care versus QCB (quercetin, vitamin C, bromelain) supplementation was compared between 429 patients with at least one chronic disease and moderate-to-severe respiratory symptoms. Demographic features, signs, laboratory results and drug administration data of patients were recorded. The endpoint was that QCB supplementation was continued throughout the follow-up period from study baseline to discharge, intubation, or death. The most common complaints at the time of hospital admission were fatigue (62.4%), cough (61.1%), anorexia (57%), thirst (53.7%), respiratory distress (51%) and chills (48.3%). The decrease in CRP and ferritin levels was higher in the QCB group (all Ps were < 0.05). In the QCB group, the increase in platelet and lymphocyte counts was higher (all Ps were < 0.05). QCB did not reduce the risk of events during follow-up. Adjustments for statistically significant parameters, including the lung stage, use of favipiravir and presence of comorbidity did not change the results. While there was no difference between the groups in terms of event frequency, the QCB group had more advanced pulmonary findings. QCB supplement is shown to have a positive effect on laboratory recovery. While there was no difference between the groups in terms of event frequency, QCB supplement group had more advanced pulmonar findings, and QCB supplement is shown to have a positive effect on laboratory recovery/results. Therefore, we conclude that further studies involving different doses and plasma level measurements are required to reveal the dose/response relationship and bioavailability of QCB for a better understanding of the role of QCB in the treatment of SARS CoV-2.

High-Order Epistasis and Functional Coupling of Infection Steps Drive Virus Evolution toward Independence from a Host Pathway

The phosphatidylinositol-4 kinase IIIβ (PI4KB)/oxysterol-binding protein (OSBP) family I pathway serves as an essential host pathway for the formation of viral replication complex for viral plus-strand RNA synthesis; however, poliovirus (PV) could evolve toward substantial independence from this host pathway with four mutations. Recessive epistasis of the two mutations (3A-R54W and 2B-F17L) is essential for viral RNA replication. Quantitative analysis of effects of the other two mutations (2B-Q20H and 2C-M187V) on each step of infection reveals functional couplings between viral replication, growth, and spread conferred by the 2B-Q20H mutation, while no enhancing effect was conferred by the 2C-M187V mutation. The effects of the 2B-Q20H mutation occur only via another recessive epistasis between the 3A-R54W/2B-F17L mutations. These mutations confer enhanced replication in PI4KB/OSBP-independent infection concomitantly with an increased ratio of viral plus-strand RNA to the minus-strand RNA. This work reveals the essential roles of the functional coupling and high-order, multi-tiered recessive epistasis in viral evolution toward independence from an obligatory host pathway.

IMPORTANCE Each virus has a different strategy for its replication, which requires different host factors. Enterovirus, a model RNA virus, requires host factors PI4KB and OSBP, which form an obligatory functional axis to support viral replication. In an experimental evolution system in vitro, virus mutants that do not depend on these host factors could arise only with four mutations. The two mutations (3A-R54W and 2B-F17L) are required for the replication but are not sufficient to support efficient infection. Another mutation (2B-Q20H) is essential for efficient spread of the virus. The order of introduction of the mutations in the viral genome is essential (known as “epistasis”), and functional couplings of infection steps (i.e., viral replication, growth, and spread) have substantial roles to show the effects of the 2B-Q20H mutation. These observations would provide novel insights into an evolutionary pathway of the virus to require host factors for infection.

Phytochemicals as potential drug candidates for targeting SARS CoV 2 proteins, an in silico study

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a member of the family Coronaviridae, and the world is currently witnessing a global pandemic outbreak of this viral disease called COVID-19. With no specific treatment regime, this disease is now a serious threat to humanity and claiming several lives daily. In this work, we selected 24 phytochemicals for an in silico docking study as candidate drugs, targeting four essential proteins of SARS-CoV-2 namely Spike glycoprotein (PDB id 5WRG), Nsp9 RNA binding protein (PDB id 6W4B), Main Protease (PDB id 6Y84), and RNA dependent RNA Polymerase (PDB id 6M71). After statistical validation, the results indicated that a total of 11 phytochemicals divided into two clusters might be used as potential drug candidates against SARS-CoV-2.

Ethanolic extract of Artemisia campestris subsp. glutinosa (Besser) Batt. inhibits HIV-1 replication in vitro through the activity of terpenes and flavonoids on viral entry and NF-κB pathway

ETHNO-PHARMACOLOGICAL RELEVANCE

The genus Artemisia spp. is well known for its anti-infectious properties and its high content in anti-infectious compounds, like the well-known sweet wormwood (Artemisia annua L.). Another Artemisia species, Artemisia campestris subsp. glutinosa (Besser) Batt., field wormwood, has been traditionally used as medicinal plant in the Mediterranean region.

AIM OF THE STUDY

The aim of this study is to investigate the anti-HIV activity of field wormwood, to identify the compounds responsible for this activity and their structure and mechanism of action.

MATERIALS AND METHODS

Antiviral activity of isolated compounds and extracts was evaluated in HIV-1 infections of lymphoblastoid cells. We also evaluated the mechanism of action of isolated compounds. Viral entry was studied comparing the inhibitory effect of isolated compounds on wild type HIV-1 and VSV pseudotyped HIV-1. To assess the viral transcriptional effect, plasmids encoding luciferase reporter genes under the control of the whole genome of HIV-1 or NF-κB or Sp1 transcription factors were transfected in the presence of the compounds under evaluation. Finally, antioxidant activity was assessed by quantitation of reduced and total glutathione in treated cell cultures.

RESULTS

Ethanolic and aqueous extracts of Artemisia campestris subsp. glutinosa (Besser) Batt. subsp. glutinosa displayed anti-HIV activity in vitro, although ethanolic extract was more powerful (IC₅₀ 14.62 μg/mL). Bio-guided ethanolic extract fractionation leads to the isolation and characterization of two terpenes, damsin and canrenone, and four flavonoids, 6, 2', 4'-trimethoxyflavone, acerosin, cardamonin and xanthomicrol. All the isolated compounds inhibited HIV-1 replication in vitro with IC₅₀ values between the middle nanomolar and the low micromolar range. Their anti-HIV mechanism of action is due to the bloking of viral entry and/or transcription inhibition, without correlation with the antioxidant activity, through interference with the cellular transcription factors NF-κB and Sp1, which are targets that are not currently reached by antiretroviral therapy.

CONCLUSION

We describe here the anti-HIV activity of field wormwood, Artemisia campestris subsp. glutinosa (Besser) Batt., and the isolation and study of the mechanism of action of two terpenes and four flavonoids, responsible, at least in part, for its activity, through the inhibition of two different cellular targets affecting the HIV replication cycle. The activity of these compounds in cellular targets could explain why plant extracts can be used in the treatment of different diseases. Besides, the presence of several compounds with dual and different mechanisms of action could prove useful in the treatment of HIV-1 infection, since it could aid to overcome drug resistances and simplify drug therapy. This work is a further step in understanding the anti-infectious activity of wormwood species and their use in treating infectious diseases.

Quercetin: Antiviral Significance and Possible COVID-19 Integrative Considerations

Quercetin, a naturally occurring dietary flavonoid, is well known to ameliorate chronic diseases and aging processes in humans, and its antiviral properties have been investigated in numerous studies. In silico and in vitro studies demonstrated that quercetin can interfere with various stages of the coronavirus entry and replication cycle such as PLpro, 3CLpro, and NTPase/helicase. Due to its pleiotropic activities and lack of systemic toxicity, quercetin and its derivatives may represent target compounds to be tested in future clinical trials to enrich the drug arsenal against coronavirus infections. There is evidence that quercetin in combination with, for example, vitamins C and D, may exert a synergistic antiviral action that may provide either an alternative or additional therapeutic/preventive option due to overlapping antiviral and immunomodulatory properties. This review summarizes the antiviral significance of quercetin and proposes a possible strategy for the effective utilization of natural polyphenols in our daily diet for the prevention of viral infection.

Potential Anti-SARS-CoV-2 Therapeutics That Target the Post-Entry Stages of the Viral Life Cycle: A Comprehensive Review

The coronavirus disease-2019 (COVID-19) pandemic continues to challenge health care systems around the world. Scientists and pharmaceutical companies have promptly responded by advancing potential therapeutics into clinical trials at an exponential rate. Initial encouraging results have been realized using remdesivir and dexamethasone. Yet, the research continues so as to identify better clinically relevant therapeutics that act either as prophylactics to prevent the infection or as treatments to limit the severity of COVID-19 and substantially decrease the mortality rate. Previously, we reviewed the potential therapeutics in clinical trials that block the early stage of the viral life cycle. In this review, we summarize potential anti-COVID-19 therapeutics that block/inhibit the post-entry stages of the viral life cycle. The review presents not only the chemical structures and mechanisms of the potential therapeutics under clinical investigation, i.e., listed in clinicaltrials.gov, but it also describes the relevant results of clinical trials. Their anti-inflammatory/immune-modulatory effects are also described. The reviewed therapeutics include small molecules, polypeptides, and monoclonal antibodies. At the molecular level, the therapeutics target viral proteins or processes that facilitate the post-entry stages of the viral infection. Frequent targets are the viral RNA-dependent RNA polymerase (RdRp) and the viral proteases such as papain-like protease (PLpro) and main protease (Mpro). Overall, we aim at presenting up-to-date details of anti-COVID-19 therapeutics so as to catalyze their potential effective use in fighting the pandemic.

Quercetin and Vitamin C: An Experimental, Synergistic Therapy for the Prevention and Treatment of SARS-CoV-2 Related Disease (COVID-19)

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) represents an emergent global threat which is straining worldwide healthcare capacity. As of May 27th, the disease caused by SARS-CoV-2 (COVID-19) has resulted in more than 340,000 deaths worldwide, with 100,000 deaths in the US alone. It is imperative to study and develop pharmacological treatments suitable for the prevention and treatment of COVID-19. Ascorbic acid is a crucial vitamin necessary for the correct functioning of the immune system. It plays a role in stress response and has shown promising results when administered to the critically ill. Quercetin is a well-known flavonoid whose antiviral properties have been investigated in numerous studies. There is evidence that vitamin C and quercetin co-administration exerts a synergistic antiviral action due to overlapping antiviral and immunomodulatory properties and the capacity of ascorbate to recycle quercetin, increasing its efficacy. Safe, cheap interventions which have a sound biological rationale should be prioritized for experimental use in the current context of a global health pandemic. We present the current evidence for the use of vitamin C and quercetin both for prophylaxis in high-risk populations and for the treatment of COVID-19 patients as an adjunct to promising pharmacological agents such as Remdesivir or convalescent plasma.

Flavonoids as Antiviral Agents for Enterovirus A71 (EV-A71)

Flavonoids are natural biomolecules that are known to be effective antivirals. These biomolecules can act at different stages of viral infection, particularly at the molecular level to inhibit viral growth. Enterovirus A71 (EV-A71), a non-enveloped RNA virus, is one of the causative agents of hand, foot and mouth disease (HFMD), which is prevalent in Asia. Despite much effort, no clinically approved antiviral treatment is available for children suffering from HFMD. Flavonoids from plants serve as a vast reservoir of therapeutically active constituents that have been explored as potential antiviral candidates against RNA and DNA viruses. Here, we reviewed flavonoids as evidence-based natural sources of antivirals against non-picornaviruses and picornaviruses. The detailed molecular mechanisms involved in the inhibition of EV-A71 infections are discussed.

Pachypodol, a Methoxyflavonoid Isolated from Pogostemon cablin Bentham Exerts Antioxidant and Cytoprotective Effects in HepG2 Cells: Possible Role of ERK-Dependent Nrf2 Activation

Oxidative stress has been implicated in the pathogenesis of many diseases including chronic liver diseases. Nrf2 is a master transcriptional factor regulating the induction of cellular antioxidant defense systems. Here, the Nrf2-activating effect of the crude methanol extract of dried leaves of Pogostemon cablin Bentham was demonstrated by measuring the antioxidant response element (ARE)-driven luciferase activity and pachypodol, 4′,5-dihydroxy-3,3′,7-trimethoxyflavone, was isolated by bioactivity-guided fractionation and further separation using chromatographic techniques. To our knowledge, this is the first study to evaluate the antioxidant and cytoprotective effects of pachypodol in HepG2 cells as well as the underlying molecular mechanisms. Indeed, pachypodol protected HepG2 cells from cell death caused by tert-butylhydroperoxide-induced oxidative stress and also attenuated ROS production. The ability of pachypodol to activate Nrf2/ARE pathway was further confirmed by observing Nrf2 expression in nuclear fraction, mRNA levels of Nrf2 target antioxidants, and cellular glutathione content in HepG2 cells. Extracellular signal-regulated kinase (ERK) is one of the important kinases involved in Nrf2 activation. Pachypodol increased ERK phosphorylation and ERK inhibition by PD98059 totally abrogated the increase in ARE luciferase activity, nuclear Nrf2 accumulation and mRNA levels of antioxidant enzymes by pachypodol. In conclusion, pachypodol isolated from P. cablin can protect hepatocytes from oxidative injury, possibly mediated by enhancing endogenous antioxidant defense system through ERK-dependent Nrf2 activation.

Essential domains of phosphatidylinositol-4 kinase III β required for enterovirus replication

Phosphatidylinositol-4 kinase III β (PI4KB) is a host factor that is required for enterovirus (EV) replication. In this study, the importance of host proteins that interact with PI4KB in EV replication was analyzed by trans complementation with PI4KB mutants in a PI4KB-knockout cell line. Ectopically expressed PI4KB mutants, which lack binding regions for ACBD3, RAB11, and 14-3-3 proteins, rescued replication of poliovirus and enterovirus 71. These findings suggest that interaction of PI4KB with these host proteins is not essential for EV replication once PI4KB has been expressed and that PI4KB is functionally independent from these host proteins regarding EV replication.

Poliovirus Evolution toward Independence from the Phosphatidylinositol-4 Kinase III β/Oxysterol-Binding Protein Family I Pathway

Phosphatidylinositol-4 kinase III β (PI4KB) and oxysterol-binding protein (OSBP) family I provide a conserved host pathway required for enterovirus replication. Here, we analyze the role and essentiality of this pathway in enterovirus replication. Phosphatidylinositol 4-phosphate (PI4P) production and cholesterol accumulation in the replication organelle (RO) are severely suppressed in cells infected with a poliovirus (PV) mutant isolated from a PI4KB-knockout cell line (RD[Δ PI4KB]). Major determinants of the mutant for infectivity in RD(Δ PI4KB) cells map to the A5270U(3A-R54W) and U3881C(2B-F17L) mutations. The 3A mutation is required for PI4KB-independent development of RO. The 2B mutation rather sensitizes PV to PI4KB/OSBP inhibitors by itself but confers substantially complete resistance to the inhibitors with the 3A mutation. The 2B mutation also confers hypersensitivity to interferon alpha treatment on PV. These suggest that the PI4KB/OSBP pathway is not necessarily essential for enterovirus replication in vitro. This work supports a two-step resistance model of enterovirus to PI4KB/OSBP inhibitors involving unique recessive epistasis of 3A and 2B and offers insights into a potential evolutionary pathway of enterovirus toward independence from the PI4KB/OSBP pathway.

Chemical Diversity and Biological Activity of African Propolis

Natural remedies have for centuries played a significant role in traditional medicine and continue to be a unique reservoir of new chemical entities in drug discovery and development research. Propolis is a natural substance, collected by bees mainly from plant resins, which has a long history of use as a folk remedy to treat a variety of ailments. The highly variable phytochemical composition of propolis is attributed to differences in plant diversity within the geographic regions from which it is collected. Despite the fact that the last five decades has seen significant advancements in the understanding of the chemistry and biological activity of propolis, a search of the literature has revealed that studies on African propolis to date are rather limited. The aim of this contribution is to report on the current body of knowledge of African propolis, with a particular emphasis on its chemistry and biological activity. As Africa is a continent with a rich flora and a vast diversity of ecosystems, there is a wide range of propolis phytochemicals that may be exploited in the development of new drug scaffolds.

Allosteric Regulation of Phosphatidylinositol 4-Kinase III Beta by an Antipicornavirus Compound MDL-860

MDL-860 is a broad-spectrum antipicornavirus compound discovered in 1982 and one of the few promising candidates effective in in vivo virus infection. Despite the effectiveness, the target and the mechanism of action of MDL-860 remain unknown. Here, we have characterized antipoliovirus activity of MDL-860 and identified host phosphatidylinositol-4 kinase III beta (PI4KB) as the target. MDL-860 treatment caused covalent modification and irreversible inactivation of PI4KB. A cysteine residue at amino acid 646 of PI4KB, which locates at the bottom of a surface pocket apart from the active site, was identified as the target site of MDL-860. This work reveals the mechanism of action of this class of PI4KB inhibitors and offers insights into novel allosteric regulation of PI4KB activity.

Chemical constituents and coagulation activity of Agastache rugosa

Background

In the Chinese traditional medicine, plant of Agastache rugosa (Fisch. & C.A. Mey.) Kuntze (A. rugosa) has been used to treat nausea, vomiting and dispel damp. However, currently, few reports about the chemical constituents, especially the non-volatile components of A. rugosa are available.

Methods

Through separation with various column chromatographies to elucidate the chemical constituents of A. rugosa, the biological activities of the major constituents were investigated. The extracts and main constituents of A. rugosa were evaluated for their anticoagulant effects by assaying the activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT) and fibrinogen (FIB) in vitro.

Results

Seven known compounds (namely compounds 1–7) were isolated from the aerial parts of A. rugosa. They were identified as methyl hexadecanoate (1), β-sitosterol (2), acacetin (3), ursolic acid (4), apigenin (5), protocatechuic acid (6) and tilianin (7), respectively. Compounds 1 and 6 were isolated from the genus Agastache for the first time, and compound 4 was obtained from the plants for the first time. The results showed that the extract of A. rugosa had a significant procoagulant activity by shortening the time of PT (P < 0.001) and increasing FIB content (P < 0.001), as compared with Vitamin K₁. While its major constituents acacetin and tilianin exhibited significant anticoagulant activities by prolonging the times of PT, APTT, TT and reducing FIB content (P < 0.001), as compared with blank control group.

Conclusions

The total extract of A. rugosa possessed significant procoagulant activity, while its main components, acacetin and tilianin possessed significant anticoagulant activities. Further investigation should be pursued to find out the bioactivity components responsible for the procoagulant action of the plant.

Inhibitory Effects of Viscum coloratum Extract on IgE/Antigen-Activated Mast Cells and Mast Cell-Derived Inflammatory Mediator-Activated Chondrocytes

The accumulation and infiltration of mast cells are found in osteoarthritic lesions in humans and rodents. Nonetheless, the roles of mast cells in osteoarthritis are almost unknown. Although Viscum coloratum has various beneficial actions, its effect on allergic and osteoarthritic responses is unknown. In this study, we established an in vitro model of mast cell-mediated osteoarthritis and investigated the effect of the ethanol extract of Viscum coloratum (VEE) on IgE/antigen (IgE/Ag)-activated mast cells and mast cell-derived inflammatory mediator (MDIM)-stimulated chondrocytes. The anti-allergic effect of VEE was evaluated by degranulation, inflammatory mediators, and the FcεRI signaling cascade in IgE/Ag-activated RBL-2H3 cells. The anti-osteoarthritic action of VEE was evaluated by cell migration, and the expression, secretion, and activity of MMPs in MDIM-stimulated SW1353 cells. VEE significantly inhibited degranulation (IC₅₀: 93.04 μg/mL), the production of IL-4 (IC₅₀: 73.28 μg/mL), TNF-α (IC₅₀: 50.59 μg/mL), PGD₂ and LTC₄, and activation of the FcεRI signaling cascade in IgE/Ag-activated RBL-2H3 cells. Moreover, VEE not only reduced cell migration but also inhibited the expression, secretion, and/or activity of MMP-1, MMP-3, or MMP-13 in MDIM-stimulated SW1353 cells. In conclusion, VEE possesses both anti-allergic and anti-osteoarthritic properties. Therefore, VEE could possibly be considered a new herbal drug for anti-allergic and anti-osteoarthritic therapy. Moreover, the in vitro model may be useful for the development of anti-osteoarthritic drugs.

Poliovirus Studies during the Endgame of the Polio Eradication Program

Since the beginning of Global Polio Eradication Initiative in 1988, poliomyelitis cases caused by wild poliovirus (PV) have been drastically reduced, with only 74 cases reported in 2 endemic countries in 2015. The current limited PV transmission suggests that we are in the endgame of the polio eradication program. However, specific challenges have emerged in the endgame, including tight budget, switching of the vaccines, and changes in biorisk management of PV. To overcome these challenges, several PV studies have been implemented in the eradication program. Some of the responses to the emerging challenges in the polio endgame might be valuable in other infectious diseases eradication programs. Here, I will review challenges that confront the polio eradication program and current research to address these challenges.

Isolation and Preliminary Characterization of Chalcone Ro 09-0410-Resistant Human Rhinovirus Type 2

We have isolated a human rhinovirus type-2 (HRV-2) mutant that is resistant to the antiviral agent chalcone Ro 09-0410 (4′-ethoxy-2′-hydroxy-4, 6′-dimethoxychalcone). This Ro 09-0410-resistant HRV-2 mutant (SR2-0410) exhibited altered biological properties when compared with the parental wild-type (wt) HRV-2. It was unstable when exposed to acid and heat in the presence of the drug, was incapable of producing plaques and produced an early cytopathic effect (CPE) at high temperatures (35°C and 37°C). Furthermore, compared with the parental wild-type, it showed a reduced ability to be neutralized by an anti-HRV-2 polyclonal serum and monoclonal antibodies. This SR2-0410 mutant demonstrated cross-resistance to other synthetic anti-rhinovirus compounds, which are also thought to bind to the viral capsid protein (VPI), such as 4′,6-dichloroflavan, 3-methoxy-6-[4-(3-methylphenyl)-I-piperazinyl] pyridazine (R 61837) and WIN 51711 (5-[7-[4-(4,5-dihydro-2-oxazolyl) phenoxyl] heptyl]-3-methyl-isoxazole). Furthermore, it was also resistant to various antiviral combinations synergistic against HRV-2. However, it was still sensitive to enviroxime [2-amino-I-(isopropyl sulphonyl)-6-benzimidazole phenyl ketone oxime], which has a different mode of action and is thought to interfere with viral RNA synthesis.

Antipicornavirus Drugs: Current Status

Considerable efforts have been made over the past several years to discover a broad-spectrum antipicornavirus agent. The X-ray crystal structure of several rhinovirus serotypes, as well as a coxsackievirus, has provided valuable information with respect to the virus structure as well as the location of the binding site of several capsid-binding compounds. This has aided in the design of broad-spectrum compounds. Several potential drug candidates have reached clinical status and some progress has been made in achieving efficacy. However, none of these compounds has as yet become a marketable drug. This review summarizes the current status of efforts in this area.

Antiviral Agents of Plant Origin. Antiherpetic Activity of Acacetin

The effect of acacetin isolated from Scoparia dulcis and several related flavonoids on herpes simplex virus type 1 (HSV-1) was studied in vitro by the method of plaque yield reduction. Among these compounds, acacetin was shown to be the most potent agent and caused dose-dependent inhibition of virus replication. Acacetin had a weak virucidal activity at higher concentrations. Analysis of early events following infection showed that attachment of the virus to host cells and penetration were unaffected by acacetin. Acacetin was found to exert strong inhibition of protein synthesis in virus-infected cells but not in uninfected cells. The transcription of immediate-early genes and translation of their transcripts were in particular almost stopped by acacetin even at a lower concentration. These selective effects can be attributed mainly to the antiviral activity of acacetin.

Flavonoids: Potent Inhibitors of Poliovirus RNA Synthesis

Some naturally occurring flavonoids, such as 3-methyl quercetin and Ro-090179, show potent anti-picornavirus activity. They inhibit poliovirus replication at concentrations 100-fold or 1000-fold lower than hydroxybenzyl-benzimidazole (HBB) and guanidine, respectively. Ro-090179 selectively blocks viral RNA synthesis in poliovirus-infected HeLa cells more strongly than 3-methyl quercetin and is therefore the most potent and selective inhibitor of poliovirus RNA synthesis described until now. In addition, Ro-090179 discriminates in its inhibition between plus- and minus-stranded RNA synthesis. Thus, analysis of the viral RNA made in poliovirus-infected cells when the compound is added late in the infection cycle, indicates that the synthesis of genomic RNA is potently blocked, whereas minus-stranded RNA synthesis is not inhibited. These findings make Ro-090179 a valuable compound for obtaining insight into the molecular mechanisms of poliovirus RNA replication.

Phosphatidylinositol 4-kinase III beta is the target of oxoglaucine and pachypodol (Ro 09-0179) for their anti-poliovirus activities, and is located at upstream of the target step of brefeldin A

In recent years, phosphatidylinositol 4-kinase III beta (PI4KB) has emerged as a conserved target of anti-picornavirus compounds. In the present study, PI4KB was identified as the direct target of the plant-derived anti-picornavirus compounds, oxoglaucine and pachypodol (also known as Ro 09-0179). PI4KB was also identified as the target via which pachypodol interferes with brefeldin A (BFA)-induced Golgi disassembly in non-infected cells. Oxysterol-binding protein (OSBP) inhibitor also has interfering activity against BFA. It seems that this interference is not essential for the anti-poliovirus (PV) activities of BFA and PI4KB/OSBP inhibitors. BFA inhibited early to late phase PV replication (0 to 6 hr postinfection) as well as PI4KB inhibitor, but with some delay compared to guanidine hydrochloride treatment. In contrast with PI4KB/OSBP inhibitors, BFA inhibited viral nascent RNA synthesis, suggesting that BFA targets some step of viral RNA synthesis located downstream of the PI4KB/OSBP pathway in PV replication. Our results suggest that PI4KB is a major target of anti-picornavirus compounds identified in vitro for their anti-picornavirus activities and for some uncharacterized biological phenomena caused by these compounds, and that BFA and PI4KB/OSBP inhibitors synergistically repress PV replication by targeting distinct steps in viral RNA replication.

Mechanism of Poliovirus Resistance to Host Phosphatidylinositol-4 Kinase III β Inhibitor

Phosphatidylinositol-4 kinase III β (PI4KB) and oxysterol-binding protein (OSBP) family I have been identified as the major targets of anti-enterovirus drug candidates. Resistance mutations in poliovirus (PV) to these inhibitors have been identified in viral 3A protein, represented by a G5318A (3A-Ala70Thr) mutation, but the mechanism of viral resistance to host PI4KB/OSBP inhibitors remained unknown. In this study, we found that a G5318A mutation enhances the basal levels of phosphatidylinositol 4-phosphate (PI4P) and of the 3A protein and decreases the levels of the 3AB protein during PV replication. The 3A protein acted as a major effector responsible for the resistance to PI4KB inhibitor, but did not enhance the PI4KB activity in vitro in contrast to the 2C, 2BC, 3AB, and 3D proteins. The 3AB protein acted as the primary target of a G5318A mutation and also as an effector. We identified novel resistance mutations to a PI4KB inhibitor [C5151U (3A-T14M) and C5366U (3A-H86Y) mutations] and found that there is a positive correlation between the extent of the resistance phenotype and the levels of the 3A proteins. These results suggested that the 3A protein overproduced by enhanced processing of the 3AB protein with the resistance mutations overcomes the inhibitory effect of PI4KB inhibitor on PV replication independently of the hyperactivation of the PI4KB/OSBP pathway.

Antiviral activity and possible mechanism of action of constituents identified in Paeonia lactiflora root toward human rhinoviruses

Human rhinoviruses (HRVs) are responsible for more than half of all cases of the common cold and cost billions of USD annually in medical visits and missed school and work. An assessment was made of the antiviral activities and mechanisms of action of paeonol (PA) and 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose (PGG) from Paeonia lactiflora root toward HRV-2 and HRV-4 in MRC5 cells using a tetrazolium method and real-time quantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. Results were compared with those of a reference control ribavirin. Based on 50% inhibitory concentration values, PGG was 13.4 and 18.0 times more active toward HRV-2 (17.89 μM) and HRV-4 (17.33 μM) in MRC5 cells, respectively, than ribavirin. The constituents had relatively high selective index values (3.3->8.5). The 100 μg/mL PA and 20 μg/mL PGG did not interact with the HRV-4 particles. These constituents inhibited HRV-4 infection only when they were added during the virus inoculation (0 h), the adsorption period of HRVs, but not after 1 h or later. Moreover, the RNA replication levels of HRVs were remarkably reduced in the MRC5 cultures treated with these constituents. These findings suggest that PGG and PA may block or reduce the entry of the viruses into the cells to protect the cells from the virus destruction and abate virus replication, which may play an important role in interfering with expressions of rhinovirus receptors (intercellular adhesion molecule-1 and low-density lipoprotein receptor), inflammatory cytokines (interleukin (IL)-6, IL-8, tumor necrosis factor, interferon beta, and IL-1β), and Toll-like receptor, which resulted in diminishing symptoms induced by HRV. Global efforts to reduce the level of synthetic drugs justify further studies on P. lactiflora root-derived materials as potential anti-HRV products or lead molecules for the prevention or treatment of HRV.

Antiviral activity and possible mode of action of ellagic acid identified in Lagerstroemia speciosa leaves toward human rhinoviruses

BACKGROUND

Human rhinoviruses (HRVs) are responsible for more than half of all cases of the common cold and cause billions of USD annually in medical visits and school and work absenteeism. An assessment was made of the cytotoxic and antiviral activities and possible mode of action of the tannin ellagic acid from the leaves of Lagerstroemia speciosa toward HeLa cells and three rhinoviruses, HRV-2, -3, and -4.

METHODS

The antiviral property and mechanism of action of ellagic acid were evaluated using a sulforhodamine B assay and real-time reverse transcription-PCR (RT-PCR) with SYBR Green dye. Results were compared with those of the currently used broad-spectrum antiviral agent, ribavirin.

RESULTS

As judged by 50% inhibitory concentration values, natural ellagic acid was 1.8, 2.3, and 2.2 times more toxic toward HRV-2 (38 μg/mL), HRV-3 (31 μg/mL), and HRV-4 (29 μg/mL) than ribavirin, respectively. The inhibition rate of preincubation with 50 μg/mL ellagic acid was 17%, whereas continuous presence of ellagic acid during infection led to a significant increase in the inhibition (70%). Treatment with 50 μg/mL ellagic acid considerably suppressed HRV-4 infection only when added just after the virus inoculation (0 h) (87% inhibition), but not before -1 h or after 1 h or later (<20% inhibition). These findings suggest that ellagic acid does not interact with the HRV-4 particles and may directly interact with the human cells in the early stage of HRV infections to protect the cells from the virus destruction. Furthermore, RT-PCR analysis revealed that 50 μg/mL ellagic acid strongly inhibited the RNA replication of HRV-4 in HeLa cells, suggesting that ellagic acid inhibits virus replication by targeting on cellular molecules, rather than virus molecules.

CONCLUSIONS

Global efforts to reduce the level of antibiotics justify further studies on L. speciosa leaf-derived materials containing ellagic acid as potential anti-HRV products or a lead molecule for the prevention or treatment of HRV infection.

Phytochemistry and bioactivity of aromatic and medicinal plants from the genus Agastache (Lamiaceae)

Agastache is a small genus of Lamiaceae, comprising 22 species of perennial aromatic medicinal herbs. In this article, we review recent advances in phytochemical, pharmacological, biotechnological and molecular research on Agastache. The phytochemical profile of all Agastache species studied to date is generally similar, consisted of two main metabolic classes-phenylpropanoids and terpenoids. In the relatively variable essential oils, most populations of different Agastache species contain over 50 % of a phenylallyl compound-estragole. Also, other volatile compounds (methyleugenol, pulegone, menthone, isomenthone and spathulenol) were reported in various proportions. Major non-volatile metabolites belong to phenolic compounds, such as caffeic acid derivatives, especially rosmarinic acid as well as several flavones and flavone glycosides like acacetin, tilianin, agastachoside, and a rare dimeric malonyl flavone (agastachin). Two unique lignans-agastenol and agastinol-were also isolated. Terpenoids include triterpenoids of oleanane-type (maslinic acid, oleanolic acid and β-amyrin), ursane-type (ursolic acid, corosolic acid and α-amyrin), and typical plant sterols, as well as abietane-type oxidized diterpenes (e.g., agastaquinone, agastol, and others). The bioactivity of various extracts or individual compounds in vitro and in vivo include antimicrobial, antiviral and anti-mutagenic activity, cytotoxic activity to cancer cell lines, and anti-nociceptive, anti-inflammatory, anti-atherogenic, antioxidant as well as biocidal activity to several foodstuff pests. Biotechnological and molecular studies have focused on in vitro propagation and enhancing the biosynthesis of bioactive metabolites in cell or organ cultures, as well as on the expression of genes involved in phenolic biosynthesis.

Valosin-containing protein (VCP/p97) is required for poliovirus replication and is involved in cellular protein secretion pathway in poliovirus infection

Poliovirus (PV) modifies membrane-trafficking machinery in host cells for its viral RNA replication. To date, ARF1, ACBD3, BIG1/BIG2, GBF1, RTN3, and PI4KB have been identified as host factors of enterovirus (EV), including PV, involved in membrane traffic. In this study, we performed small interfering RNA (siRNA) screening targeting membrane-trafficking genes for host factors required for PV replication. We identified valosin-containing protein (VCP/p97) as a host factor of PV replication required after viral protein synthesis, and its ATPase activity was essential for PV replication. VCP colocalized with viral proteins 2BC/2C and 3AB/3B in PV-infected cells and showed an interaction with 2BC and 3AB but not with 2C and 3A. Knockdown of VCP did not suppress the replication of coxsackievirus B3 or Aichi virus. A VCP-knockdown-resistant PV mutant had an A4881G (a mutation of E253G in 2C) mutation, which is known as a determinant of a secretion inhibition-negative phenotype. However, knockdown of VCP did not affect the inhibition of cellular protein secretion caused by overexpression of each individual viral protein. These results suggested that VCP is a host factor required for viral RNA replication of PV among membrane-trafficking proteins and provides a novel link between cellular protein secretion and viral RNA replication.

Inhibition of enterovirus 71 replication by chrysosplenetin and penduletin

In recent years, enterovirus 71 (EV71) infections have caused an increasing epidemic in young children, accompanying with more severe nervous system disease and more deaths. Unfortunately, there is no specific medication for it so far. Here we investigated the anti-EV71 activity of chrysosplenetin and penduletin, two o-methylated flavonols isolated from the leaves of Laggera pterodonta. These two compounds were found to have strong activity in vitro against EV71 with low cytotoxicity. In the cytopathic effect (CPE) inhibition assays, both plaque reduction assay and virus yield inhibition assay, the compounds showed a similar 50% inhibitory concentration (IC(50)) value of about 0.20 μM. The selectivity indices (SI) of chrysosplenetin and penduletin were 107.5 and 655.6 in African green monkey kidney (Vero) cells, and 69.5 and 200.5 in human rhabdomyosarcoma (RD) cells, accordingly. The preliminary mechanism analysis indicates that they function not through blocking virus entry or inactivating virus directly but inhibiting viral RNA replication. In the time-of-addition assay, both compounds inhibited progeny virus production and RNA replication by nearly 100% when introduced within 4h post infection. In addition to EV71, both compounds inhibited several other human enteroviruses with similar efficacy. These findings provide a significant lead for the discovery of anti-EV71 drug.

The human rhinovirus: human-pathological impact, mechanisms of antirhinoviral agents, and strategies for their discovery

As the major etiological agent of the common cold, human rhinoviruses (HRV) cause millions of lost working and school days annually. Moreover, clinical studies proved an association between harmless upper respiratory tract infections and more severe diseases e.g. sinusitis, asthma, and chronic obstructive pulmonary disease. Both the medicinal and socio-economic impact of HRV infections and the lack of antiviral drugs substantiate the need for intensive antiviral research. A common structural feature of the approximately 100 HRV serotypes is the icosahedrally shaped capsid formed by 60 identical copies of viral capsid proteins VP1-4. The capsid protects the single-stranded, positive sense RNA genome of about 7,400 bases in length. Both structural as well as nonstructural proteins produced during the viral life cycle have been identified as potential targets for blocking viral replication at the step of attachment, entry, uncoating, RNA and protein synthesis by synthetic or natural compounds. Moreover, interferon and phytoceuticals were shown to protect host cells. Most of the known inhibitors of HRV replication were discovered as a result of empirical or semi-empirical screening in cell culture. Structure-activity relationship studies are used for hit optimization and lead structure discovery. The increasing structural insight and molecular understanding of viral proteins on the one hand and the advent of innovative computer-assisted technologies on the other hand have facilitated a rationalized access for the discovery of small chemical entities with antirhinoviral (anti-HRV) activity. This review will (i) summarize existing structural knowledge about HRV, (ii) focus on mechanisms of anti-HRV agents from synthetic and natural origin, and (iii) demonstrate strategies for efficient lead structure discovery.

Selective inhibitors of picornavirus replication

Picornaviruses cover a large family of pathogens that have a major impact on human but also on veterinary health. Although most infections in man subside mildly or asymptomatically, picornaviruses can also be responsible for severe, potentially life-threatening disease. To date, no therapy has been approved for the treatment of picornavirus infections. However, efforts to develop an antiviral that is effective in treating picornavirus-associated diseases are ongoing. In 2007, Schering-Plough, under license of ViroPharma, completed a phase II clinical trial with Pleconaril, a drug that was originally rejected by the FDA after a New Drug Application in 2001. Rupintrivir, a rhinovirus protease inhibitor developed at Pfizer, reached clinical trials but was recently halted from further development. Finally, Biota's HRV drug BTA-798 is scheduled for phase II trials in 2008. Several key steps in the picornaviral replication cycle, involving structural as well as non-structural proteins, have been identified as valuable targets for inhibition. The current review aims to highlight the most important developments during the past decades in the search for antivirals against picornaviruses.

Lycopene enrichment of cultured airway epithelial cells decreases the inflammation induced by rhinovirus infection and lipopolysaccharide

Rhinovirus infection results in increased release of inflammatory mediators from airway epithelial cells in asthma. As an antioxidant, lycopene offers protection from adverse effects of inflammation. The aim of this study was to find an appropriate method of lycopene enrichment of airway epithelial cells and to determine the effects of lycopene enrichment on the inflammatory response of cells infected by rhinovirus or exposed to lipopolysaccharide. Lycopene enrichment of airway epithelial cells using solubilisation in tetrahydrofuran versus incorporation in liposomes was compared. After determining that solubilisation of lycopene in tetrahydrofuran was the most suitable method of lycopene supplementation, airway epithelial cells (Calu-3) were incubated with lycopene (dissolved in tetrahydrofuran) for 24 h, followed by rhinovirus infection or lipopolysaccharide exposure for 48 h. The release of interleukin-6, interleukin-8 and interferon-gamma induced protein-10 (IP-10) and their messenger RNA levels were measured using enzyme linked immunosorbent assay and reverse transcription polymerase chain reaction, respectively. Viral replication was measured by tissue culture infective dose of 50% assay. Lycopene concentration of cells and media were analysed using high-performance liquid chromatography. Preincubation of airway epithelial cells with lycopene (dissolved in tetrahydrofuran) delivered lycopene into the cells and resulted in a 24% reduction in interleukin-6 after rhinovirus-1B infection, 31% reduction in IP-10 after rhinovirus-43 infection and 85% reduction in rhinovirus-1B replication. Lycopene also decreased the release of IL-6 and IP-10 following exposure to lipopolysaccharide. We conclude that lycopene has a potential role in suppressing rhinovirus induced airway inflammation.

Chapter 3 Antiviral drugs: general considerations

The development of an antiviral drug as well as of other drugs is a long process. In most programmes the screening and evaluation start using inhibition of virus multiplication in cell cultures, but in some instances the screening starts in animal models of different viral diseases. In these cases, the mechanism of action has to be analyzed after the in vivo effect has been found. It is not possible to specify precisely the time and resources required in a newly started project to find a compound active against a virus infection but 5-10 years is a reasonable estimation. For some viruses such as herpesviruses, where a number of active inhibitors are already known, the task is simpler than it is to find inhibitors of a virus such as influenza against which only a few active inhibitors have been reported. Evaluation of clinical efficacy in humans is a large and difficult part of the development of an antiviral drug. The number of uncontrolled clinical studies claiming efficacy of different drugs against viral diseases is depressingly large. It is essential to perform double-blind, placebo-controlled and statistically well evaluated studies to be able to judge the clinical efficacy of an antiviral drug. As the knowledge of the detailed natural history and molecular biology of viral diseases and viruses themselves increases, one will obviously have better opportunities to find new drugs. Methods such as X-ray diffraction measurement and NMR determinations will probably lead to a detailed understanding of the structures and interactions taking place at the active site of viral enzymes and their cellular counterparts.

Chapter 4 Picornavirus infections

The oldest member of the Picornaviruses group is polio virus, which was recognized early by clinicians because of its characteristic paralytic disease. This chapter examines the polio virus in regard to its virology, disease, and prevention by vaccines and chemoprophylaxis. Polio has been well controlled in most developed countries using live or inactivated vaccines. Research work has intensified using genetic engineering techniques to produce live attenuated viruses with defined and stable mutations so as to prevent reversion to virulence, and also to produce immunogenic oligopeptides or proteins for a new generation of inactivated polio vaccines. Chemotherapy is therefore not required for polio infections. In contrast, neither vaccines have been developed against rhinovirus infections, nor are the vaccines thought to have a use, unless broadly reacting antigenic determinants can be located. Several interesting but only weakly effective antiviral compounds have been selected against rhinoviruses and this is a major research area at present. Studies continue also with interferon, but because of toxicity problems these look less interesting at present. Sequence and biochemical data is now available for several additional enterovirus strains and this could open new possibilities both with antivirals or vaccines (for example synthetic peptides) in the near future.

Chapter 12. Antiviral Agents

This chapter discusses the agents with activity primarily against RNA viruses. The communicable diseases of the respiratory tract are probably the most common cause of symptomatic human infections. The viruses that are causative agents for human respiratory disease comprise the five taxonomically distinct families: orthomyxoviridae, paramyxoviridae, picornaviridae, coronaviridae, and adenoviridae. The influenza viruses, which consist of types A, B, and C, belong to the family orthomyxoviridae. Types A and B have been associated with significant increases in mortality during epidemics. The disease may be asymptomatic or cause symptoms ranging from the common cold to fatal pneumonia. Immunization against influenza has been recommended for high-risk groups and antiviral chemotherapy (amantadine) is available for the treatment and prophylaxis of all influenza A infections. There is both a great need for and interest in developing a chemotherapeutic agent for the treatment of these two viral, respiratory tract pathogens. The family picornaviridae contains the genus Rhinovirus that is composed of over a hundred distinct serotypes. Amantadine and rimantadine are specifically active against influenza A virus infections. The amantadine recipients reported a higher incidence of side effects largely attributed to the central nervous system (CNS) symptoms. This difference in side effects may be a pharmacokinetic phenomenon that results in higher plasma concentrations of amantadine. Significant progress continues to be made in the clinical use and development of agents active against DNA viruses. Acyclovir (9-(2-h droxyethoxymethyl)guanine) has been the subject of several reviews and of a syrnposium. Considerable progress has been made in evaluating the clinical promise of acyclovir; however, there remains much to be learned concerning the best use of this drug in clinical practice. Significant strides have been made in the development of clinically useful antiviral agents, especially against the DNA viruses of the herpes family. Most of these agents are directed against viral nucleic acid synthesis and require activation by a virus-induced thymidine kinase. Researchers have begun to focus on other strategies that may produce broader spectrum anti-viral agents with different mechanisms of action.

Inhibitory effects of Morus alba on compound 48/80-induced anaphylactic reactions and anti-chicken gamma globulin IgE- mediated mast cell activation

We investigated the effects of hot-water extract from the root bark of Morus alba (HEMA) on anaphylactic reactions. Using in vitro and in vivo experiments, we examined whether HEMA could inhibit compound 48/80-induced systemic anaphylactic shock and anti-chicken gamma globulin (CGG) IgE-mediated rat peritoneal mast cell activation. HEMA significantly inhibited systemic anaphylaxis induced by the compound 48/80 in mice. HEMA also significantly inhibited the passive cutaneous anaphylaxis activated by anti-CGG IgE. HEMA had no cytotoxicity on rat peritoneal mast cells (RPMC). Moreover, HEMA dose-dependently inhibited mast cell degranulation, histamine release and calcium uptake into RPMC induced by the compound 48/80 or anti-CGG IgE. When HEMA was added, the level of intracellular cAMP in RPMC showed a transient and significant increase (5-fold) compared with that of control cells. HEMA also inhibited significantly the compound 48/80-induced cAMP reduction in RPMC. These results suggested that HEMA inhibits the compound 48/80- or anti-CGG IgE-induced mast cell activation and its inhibitory effects on mast cell activations were favorably comparable to disodium cromoglycate. And HEMA is a candidate for effective therapeutic tools of allergic diseases.