Inhibition of influenza hemagglutinin with the antiviral inhibitor arbidol using a proteomics based approach and mass spectrometry

25 Years Responding to Respiratory and Other Viruses with Mass Spectrometry

This review article presents the development and application of mass spectrometry (MS) approaches, developed in the author's laboratory over the past 25 years, to detect; characterise, type and subtype; and distinguish major variants and subvariants of respiratory viruses such as influenza and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). All features make use of matrix-assisted laser desorption ionisation (MALDI) mass maps, recorded for individual viral proteins or whole virus digests. A MALDI-based immunoassay in which antibody-peptide complexes were preserved on conventional MALDI targets without their immobilisation led to an approach that enabled their indirect detection. The site of binding, and thus the molecular antigenicity of viruses, could be determined. The same approach was employed to study antivirals bound to their target viral protein, the nature of the binding residues, and relative binding affinities. The benefits of high-resolution MS were exploited to detect sequence-conserved signature peptides of unique mass within whole virus and single protein digests. These enabled viruses to be typed, subtyped, their lineage determined, and variants and subvariants to be distinguished. Their detection using selected ion monitoring improved analytical sensitivity limits to aid the identification of viruses in clinical specimens. The same high-resolution mass map data, for a wide range of viral strains, were input into a purpose-built algorithm (MassTree) in order to both chart and interrogate viral evolution. Without the need for gene or protein sequences, or any sequence alignment, this phylonumerics approach also determines and displays single-point mutations associated with viral protein evolution in a single-tree building step.

Arbidol: The current demand, strategies, and antiviral mechanisms

BACKGROUND

High morbidity and mortality of influenza virus infection have made it become one of the most lethal diseases threatening public health; the lack of drugs with strong antiviral activity against virus strains exacerbates the problem.

METHODS

Two independent researchers searched relevant studies using Embase, PubMed, Web of Science, Google Scholar, and MEDLINE databases from its inception to December 2022.

RESULTS

Based on the different antiviral mechanisms, current antiviral strategies can be mainly classified into virus-targeting approaches such as neuraminidase inhibitors, matrix protein 2 ion channel inhibitors, polymerase acidic protein inhibitors and other host-targeting antivirals. However, highly viral gene mutation has underscored the necessity of novel antiviral drug development. Arbidol (ARB) is a Russian-made indole-derivative small molecule licensed in Russia and China for the prevention and treatment of influenza and other respiratory viral infections. ARB also has inhibitory effects on many other viruses such as severe acute respiratory syndrome coronavirus 2, Coxsackie virus, respiratory syncytial virus, Hantaan virus, herpes simplex virus, and hepatitis B and C viruses. ARB is a promising drug which can not only exert activity against virus at different steps of virus replication cycle, but also directly target on hosts before infection to prevent virus invasion.

CONCLUSION

ARB is a broad-spectrum antiviral drug that inhibits several viruses in vivo and in vitro, with high safety profile and low resistance; the antiviral mechanisms of ARB deserve to be further explored and more high-quality clinical studies are required to establish the efficacy and safety of ARB.

Emerging antiviral therapies and drugs for the treatment of influenza

INTRODUCTION

Both vaccines and antiviral drugs represent the mainstay for preventing and treating influenza. However, approved M2 ion channel inhibitors, neuraminidase inhibitors, polymerase inhibitors, and various vaccines cannot meet therapeutic needs because of viral resistance. Thus, the discovery of new targets for the virus or host and the development of more effective inhibitors are essential to protect humans from the influenza virus.

AREAS COVERED

This review summarizes the latest progress in vaccines and antiviral drug research to prevent and treat influenza, providing the foothold for developing novel antiviral inhibitors.

EXPERT OPINION

Vaccines embody the most effective approach to preventing influenza virus infection, and recombinant protein vaccines show promising prospects in developing next-generation vaccines. Compounds targeting the viral components of RNA polymerase, hemagglutinin and nucleoprotein, and the modification of trusted neuraminidase inhibitors are future research directions for anti-influenza virus drugs. In addition, some host factors affect the replication of virus in vivo, which can be used to develop antiviral drugs.

Modeling the Structure-Activity Relationship of Arbidol Derivatives and Other SARS-CoV-2 Fusion Inhibitors Targeting the S2 Segment of the Spike Protein

Umifenovir (Arbidol) has been reported to exhibit some degree of efficacy in multiple clinical trials for the treatment of COVID-19 as a monotherapy. It has also demonstrated synergistic inhibition of SARS-CoV-2 with other direct-acting antivirals such as Remdesivir. A computational approach was used to identify the most favorable binding site to the SARS-CoV-2 Spike S2 segment and to perform virtual screening. Compounds selected from modeling were evaluated in a live SARS-CoV-2 infection assay. An Arbidol (ARB) derivative with substitutions at both the C-4 and C-6 positions was found to exhibit a modest improvement in activity and solubility properties in comparison to ARB. However, all of the derivatives were found to only be partial inhibitors, rather than full inhibitors in a virus-induced cytopathic effect-based assay. The binding mode is also corroborated by parallel modeling of a series of oleanolic acid trisaccharide saponin fusion inhibitors shown to bind to the S2 segment. Recently determined experimental structures of the Spike protein allowed atomic resolution modeling of fusion inhibitor binding as a function of pH, and the implications for the molecular mechanism of direct-acting fusion inhibitors targeting the S2 segment are discussed.

3-Indoleacetonitrile Is Highly Effective in Treating Influenza A Virus Infection In Vitro and In Vivo

Influenza A viruses are serious zoonotic pathogens that continuously cause pandemics in several animal hosts, including birds, pigs, and humans. Indole derivatives containing an indole core framework have been extensively studied and developed to prevent and/or treat viral infection. This study evaluated the anti-influenza activity of several indole derivatives, including 3-indoleacetonitrile, indole-3-carboxaldehyde, 3-carboxyindole, and gramine, in A549 and MDCK cells. Among these compounds, 3-indoleacetonitrile exerts profound antiviral activity against a broad spectrum of influenza A viruses, as tested in A549 cells. Importantly, in a mouse model, 3-indoleacetonitrile with a non-toxic concentration of 20 mg/kg effectively reduced the mortality and weight loss, diminished lung virus titers, and alleviated lung lesions of mice lethally challenged with A/duck/Hubei/WH18/2015 H5N6 and A/Puerto Rico/8/1934 H1N1 influenza A viruses. The antiviral properties enable the potential use of 3-indoleacetonitrile for the treatment of IAV infection.

The indole alkaloids from the roots of Isatidis Radix

The root of Isatis indigotica is used as a traditional Chinese medicine (termed Isatidis Radix) due to its antiviral effects. We examined compounds isolated from Isatidis Radix and elucidated the structures of three new natural alkaloids, and we examined the possible mechanisms or active targets of indole alkaloids occurring in blood of rats treated by gavage. Three new natural products were isolated from Radix Isatidis for the first time, including 1-methoxy-2-indoleacetonitrile, 1-hydroxy-3-indoleacetonitrile, 8-Methoxy-1, 2-dihydroquinoline, and 4 compounds isolated from this medicinal material for the first time. Their structures were elucidated using nuclear magnetic resonance. The components of Isatidis Radix were analysed using liquid chromatography tandem mass spectrometry, and 33 compounds were detected in plasma of treated rats; 24 of these compounds were indole alkaloids, and they included the newly identified compounds. Molecular docking and in vitro antithrombin activity tests showed HA inhibition activity of indoleacetonitriles.

[Assessment of the antiviral activity of 2HCl*H-His-Rim compound compared to the anti-influenza drug Arbidol for influenza caused by A/duck/Novosibirsk/56/05 (H5N1) (Influenza A virus, Alphainfluenzavirus, Orthomyxoviridae).]

INTRODUCTION

The emergence of influenza virus strains with drug resistance to antiviral drugs requires finding new compounds, potential direct-acting inhibitors. Аdamantane compounds drugs used since the 1960s have lost their activity the resulting due to resistance. Only neuraminidase inhibitors such as zanamivir and oseltamivir have been approved by WHO for influenza treatment. The Russian pharmaceutical drug Arbidol (Umifenovirum) is actively used in Russia. This drug is used to treat influenza in Russia, China and most post-Soviet republics. This work presents a new derivative of aminoadamantane - dichlorohydrate L-histidyl-1-adamantayl ethylamine (2HCl*H-His-Rim), which showed a high level of inhibition of strains of influenza virus A in vitro.

OBJECTIVES

Comparison of antiviral properties of the new synthetic low-molecular inhibitor of influenza A virus replication and Arbidol drug pharmacy.

METHODS

The compound 2HCl*H-His-Rim was obtained by classical peptide synthesis methods. It was identified by methods of mass spectrometry, infrared spectroscopy (IR) and nuclear magnetic resonance spectroscopy (NMR). Its antiviral properties have been studied in vitro for monolayer of cells Vero-E6 infected with a high-virulent strain of A/duck/Novosibirsk/56/06 (H5N1) influenza virus at various injection schemes of the investigated compounds.

THE RESULTS

The antiviral activity of the 2HCl*H-His-Rim compound against the highly pathogenic strain of the influenza A/H5N1 virus was slightly higher than for the known pharmacy drug arbidol.

DISCUSSION

The difference in antiviral activity of these two compounds is explained by different mechanisms of action on the viral particle.

CONCLUSION

The 2HCl*H-His-Rim compound can be recommended as a candidate for preclinical and clinical trials in order to obtain an etiotropic antiviral drug based on it, due to its high efficacy and economic and synthetic availability. The synthetic compound 2HCl*H-His-Rim acts on influenza A virus variants resistant to Rimantadine and Amantadine.

Quadruple therapy for asymptomatic COVID-19 infection patients

Introduction: The novel coronavirus (COVID-19) is currently in epidemic stage. After large-scale interpersonal infection, asymptomatic patients appear. Whether asymptomatic patients are contagious or not and whether they need medication are the arguments among clinical experts.

Areas covered: This paper reports a special asymptomatic couple with COVID-19, of which the male patient is an intercity bus driver but has not induced confirmed infection of his 188 passengers. The patients were treated with four combinations of lopinavir/ritonavir tablets, arbidol tablets, Lianhuaqingwen granules, and recombinant human interferon-α2b (IFN-α2b) injection via aerosol. Their clinical characteristics and medication were summarized and analyzed.

Expert opinion: The two asymptomatic patients far away from Wuhan did not seem to be highly contagious. They improved obviously, after treatment with the quadruple therapy, but the effective drug is still unknown. It should be noted that lopinavir/ritonavir tablets have many drug interactions and are the most likely drugs to cause hyperlipidemia and hyperglycemia in these two patients. IFN-α2b is more effective in the early stage of virus infection. Arbidol instruction dose may not be sufficient to inhibit the novel coronavirus in vivo. The evidence-based medicine of Lianhuaqingwen granules for treating various viral infections is just based on Chinese patients.

Study on the Antiviral Activities and Hemagglutinin-Based Molecular Mechanism of Novel Chlorogenin 3-O-β-Chacotrioside Derivatives Against H5N1 Subtype Viruses

The objective of this study was to investigate the inhibitory effect of chlorogenin 3-O-β-chacotrioside derivatives against H5N1 subtype of the highly pathogenic avian influenza (HPAI) viruses and its molecular mechanism. A series of novel small molecule pentacyclic triterpene derivatives were designed and synthesized and their antiviral activities on HPAI H5N1 viruses were detected. The results displayed that the derivatives UA-Nu-ph-5, XC-27-1 and XC-27-2 strongly inhibited wild-type A/Duck/Guangdong/212/2004 H5N1 viruses with the IC50 values of 15.59 ± 2.4 μM, 16.83 ± 1.45 μM, and 12.45 ± 2.27 μM, respectively, and had the selectivity index (SI) > 3, which was consistent with the efficacy against A/Thailand/kan353/2004 pseudo-typed viruses. Four dealt patterns were compared via PRNT. The prevention dealt pattern showed the strongest inhibitory effects than other patterns, suggesting that these derivatives act on the entry process at the early stages of H5N1 viral infection, providing protection for cells against infection. Further studies through hemagglutinin inhibition (HI) and neuraminidase inhibitory (NAI) assay confirmed that these derivatives inhibited H5N1 virus replication by interfering with the viral hemagglutinin function. The derivatives could recognize specifically HA protein with binding affinity constant KD values of 2.57 × 10-4 M and 3.67 × 10-4 M. In addition, through site-directed mutagenesis combined with a pseudovirion system, we identified that the high-affinity docking sites underlying interaction were closely associated with amino acid residues I391 and T395 of HA. However, the potential binding sites of the derivatives with HA did not locate at HA1 sialic acids receptor binding domain (RBD). Taken together, these study data manifested that chlorogenin 3-O-β-chacotrioside derivatives generated antiviral effect against HPAI H5N1 viruses by targeting the hemagglutinin fusion machinery.

Specific Influenza Therapy: Current State and Prospects (Review)

Introduction. Respiratory infections are among the leaders in morbidity and mortality worldwide. The most severe cases of the disease are most often caused by the flu virus. Currently, there are many ways of specific prevention and treatment of influenza infection, but their effectiveness is far from ideal. This is due to the high variability of the influenza virus and the subsequent occurrence of resistance to the drugs used. In this regard, the improvement and development of antiviral drugs is an urgent task.

Text. Influenza virus is an RNA-containing virus that causes massive epidemics and pandemics. Specific influenza prophylaxis includes vaccination. However, antigenic variability of the virus reduces the effectiveness of the vaccine, which requires constant costly development of its more advanced modifications. Specific treatment for influenza infection includes several classes of drugs, such as neuraminidase (NA) inhibitors oseltamivir, zanamivir and M2 protein inhibitors amantadine, rimantadine. At one time, these drugs were quite effective. But the formed resistance of influenza viruses to these drugs requires the creation of new or modifications of existing antiviral agents. Among the new domestic developments of antiviral drugs, histidyl-1-adamantainethylamine, which is a modification of the rimantadine molecule, has shown sufficient antiviral activity at the stage of preclinical studies. A representative of another class of drugs is arbidol (umifenovir), an inhibitor of hemagglutinin (HA) of the influenza virus. According to studies, the drug has high profiles of efficacy and safety, but the recommendation of the World Health Organization is to continue clinical trials. Currently, clinical studies of new classes of drugs are underway – baloxavir marboxil and favipiravir. Baloxavir marboxyl is a prodrug that is converted in vivo to baloxavir, an inhibitor of cap-dependent endonuclease. Favipiravir is an inhibitor of RNA-dependent RNA polymerase. In vitro studies in cell culture and in vivo in laboratory animals have shown higher efficacy of these drugs than the above with minimal toxicity.

Conclusion. The rapid evolution of the influenza virus leads to a gradual decrease in the effectiveness of modern antiviral drugs. New compounds targeting targets important for virus reproduction are in clinical trials. The future of the fight against influenza depends on the outcome of these tests, according to which the compounds can become effective drugs for the prevention and treatment of influenza.

Clinical efficacy of umifenovir in influenza and ARVI (study ARBITR)

AIM

The aim of the study is to obtain additional data on safety and therapeutic efficacy of the antiviral drug Arbidol (umifenovir) in patients with a diagnosis of influenza and common cold.

MATERIALS AND METHODS

Double-blind, randomized, placebo-controlled clinical study investigating efficacy and safety of Arbidol (umifenovir) in Treatment and Prophylaxis of Influenza and Common Cold (ARBITR) IV phase started in November 2011 and completed in April 2016 on the basis of 15 research centers in various regions of the Russian Federation. A total of 359 patients, aged 18 to 65 years with influenza or acute respiratory tract infection, of no more than 36 hours' duration were enrolled in the study. Patients were randomized into two groups: a group of patients (therapy group) treated by Arbidol (umifenovir) at a dosage of 800 mg/day (2 capsules) for 5 days (n=181), and a group of patients receiving placebo 4 times a day for 5 days (n=178). The primary outcome measures of the study were the duration of clinical illness among patients with common cold and influenza/ARVI, the duration and severity of the main symptoms. Number of clinical complications associated with influenza and common cold was assessed as a secondary outcome. Safety was assessed by analyzing number of adverse events that are probably or definitely related to Arbidol, assessing vital signs, examining the physical condition of patients and general clinical laboratory parameters.

RESULTS

In the group treated by umifenovir, the number of full recover patients on the 4th day from the disease onset were significantly differed from the number of such cases in the placebo group. The number of cases of complete recovery after 96 hours was 98 patients (54.1%) and 77 (43.3%), p<0.05, and after 108 hours - 117 (64.6%) and 98 (55.1%), p<0.05. Duration of intoxication was reduced with umifenovir compared to placebo, amounted to 77.76 and 88.91 hours, respectively, p=0.013. The duration of all intoxication syndrome symptoms was also lower in the group receiving umifenovir. Thus, in the therapy group and placebo group, these parameters were respectively: fever duration - 67.96 and 75.32 hours (p=0.037), muscle pain - 52.23 and 59.08 hours (p=0.023), headache - 52.78 and 63.28 hours (p=0.013), weakness - 76.90 and 88.89 hours (p=0.008). The incidence of complications in the umifenovir group was 3.8%, in the placebo group 5.62%. Cases of acute tracheobronchitis was an increase in the placebo group (p<0.02). Umifenovir and placebo were well tolerated. A total of 42 cases of adverse events were registered in 11 patients in the treatment group and in 18 patients in the placebo group, which were not associated with umifenovir or placebo.

CONCLUSION

The results of this study indicate umifenovir safety and confirm its effectiveness to the treatment of influenza and other acute respiratory viral infections in adult patients. It was found that effect of umifenovir in the treatment of influenza in adults is most pronounced in the acute stage of the disease and appears in the reduction of time to resolution of all symptoms of the disease, reducing the severity of symptoms of the disease.

Efficacy of Arbidol in the prevention of virus-induced exacerbations of bronchial asthma and chronic obstructive pulmonary disease

AIM

To assess the efficacy and safety of Arbidol in the influenza and ARVI preventing in patients with asthma and chronic obstructive pulmonary disease (COPD).

MATERIALS AND METHODS

This study was an open label and prospective during epidemic period of 2016-2017 years. 100 outpatients aged 18 to 80 years with verified asthma and/or COPD, were enrolled to therapy group, and received oral umifenovir 200 mg once daily for 14 days and then 200 mg twice a week for 3 weeks.The medical records data for the same epidemic period of 2016-2017 seasons of the same patients during witch they received no prophylaxis was taken as a control. The data analysis was made by applying parametric and nonparametric statistical methods.

RESULTS

Seasonal and post-exposure prophylaxis using umifenovir was associated with 2.6-times reduction in influenza and ARVI morbidity compared to control. In diseased patients (ARVI) of the therapy group the number of patients with mild illness prevailed (62.2%) and was significantly differed from control (37.1%). Severity of catarrhal symptoms and intoxication, was reduced with umifenovir prophylaxis course and were mild in 67.6% and 67.6% respectively of therapy group compared with 43.3% and 46.4% of control. Influenza and ARVI complications were only detected in control group (4 cases). The percentage of patients with incidents of underlying disease exacerbation was 42% in therapy group and 93% in control group. Also, exacerbation in the therapy group were mild in 59.5% and 34.4% in control group, while moderate exacerbation prevailed in control group and was in 59.1% of cases with was significantly higher then in therapy group (39.3%). Results in more frequent use of adjuvant in the control group compared with the therapy group (81.7% and 59.5% respectively). Patients of control group had a higher risk of hospitalizations due to underlying disease aggravation (11.8%), compared with therapy group (9.5%) but these differences were not significant.

CONCLUSION

Seasonal and post-exposure prophylaxis with Arbidol reduce influenza and ARVI morbidity in patients with asthma and COPD during epidemic period, frequency and severity of chronic obstructive pulmonary disease aggravations resulting in decrease in the number of hospitalizations. Also, prophylaxis with Arbidol reduced the severity of catarrhal symptoms and intoxication.

The Antiviral Drug Arbidol Inhibits Zika Virus

There are many emerging and re-emerging globally prevalent viruses for which there are no licensed vaccines or antiviral medicines. Arbidol (ARB, umifenovir), used clinically for decades in several countries as an anti-influenza virus drug, inhibits many other viruses. In the current study, we show that ARB inhibits six different isolates of Zika virus (ZIKV), including African and Asian lineage viruses in multiple cell lines and primary human vaginal and cervical epithelial cells. ARB protects against ZIKV-induced cytopathic effects. Time of addition studies indicate that ARB is most effective at suppressing ZIKV when added to cells prior to infection. Moreover, ARB inhibits pseudoviruses expressing the ZIKV Envelope glycoprotein. Thus, ARB, a broadly acting anti-viral agent with a well-established safety profile, inhibits ZIKV, likely by blocking viral entry.

Structure-based optimization and synthesis of antiviral drug Arbidol analogues with significantly improved affinity to influenza hemagglutinin

Influenza is a highly contagious respiratory viral infection responsible for up to 50,000 deaths per annum in the US alone. The need for new therapeutics with novel modes of action is of paramount importance. We determined the X-ray structure of Arbidol with influenza hemagglutinin and found it was located in a distinct binding pocket. Herein, we report a structure-activity relationship study based on the co-complex combined with bio-layer interferometry to assess the binding of our compounds. Addition of a meta-hydroxy group to the thiophenol moiety of Arbidol to replace a structured water molecule in the binding pocket resulted in a dramatic increase in affinity against both H3 (1150-fold) and H1 (98-fold) hemagglutinin subtypes. Our analogues represent novel leads to yield more potent compounds against hemagglutinin that block viral entry.

Inhibition of the infectivity and inflammatory response of influenza virus by Arbidol hydrochloride in vitro and in vivo (mice and ferret)

Influenza virus infections are the main contagious respiratory disease with high levels of morbidity and mortality worldwide. Antiviral drugs are indispensable for the prophylaxis and treatment of influenza and other respiratory viral infections. In this study, the Arbidol hydrochloride (ARB), which has been licensed in Russia and China, is used to investigate its anti-viral and anti-inflammatory efficacy in vitro and in vivo. The antiviral results in vitro showed that ARB had a better inhibition on Influenza virus A/PR/8/34 (H1N1), A/Guangdong/GIRD07/09 (H1N1), A/Aichi/2/68 (H3N2), A/HK/Y280/97 (H9N2) with IC₅₀ ranging from 4.4 to 12.1μM. The further mechanisms study demonstrated that ARB is able to inhibit hemagglutinin-mediated hemolysis at concentration of 3.91-15.63μg/mL. The anti-inflammatory efficacy in vitro indicated that IL-6, IP-10, MCP-1, RANTES and TNF-α levels were diminished by ARB at concentrations of 22.6 and 18.8μM. The in vivo results in mice model displayed that the survival rates of mice administered 25mg/mL and 45mg/mL ARB were 40% and 50% respectively. And also, ARB can inhibit the decrease of body weight at 45mg/mL and inhibit the increase of mice lung index at 25mg/mL and 45mg/mL comparing to virus group. In ferret model, the ARB-treated ferrets showed a fever that peaked at 2 dpi and gradually decreased beginning at 3 dpi while relatively high temperatures were observed until 4 dpi in the virus group. The ARB-treated group scored 0-1 in the activity level at 2 dpi and 3 dpi at all time points. The transcription levels of cytokines in the respiratory tract of ferrets were detected at 3 dpi. Several proinflammatory cytokines induced by influenza (IL-10, TNF-α, IL-8 and IL-6) were down-regulated by post-treatment with ARB. The histopathological results of ferret lung displayed that ARB can alleviate the influenza virus induced lung lesions. Our results clarified the activity of ARB in both suppressing virus propagation and modulating the expression of inflammatory cytokines in vitro and in vivo, it can be as an effective drug to treat the influenza virus infection.

Structural basis of influenza virus fusion inhibition by the antiviral drug Arbidol

The broad-spectrum antiviral drug Arbidol shows efficacy against influenza viruses by targeting the hemagglutinin (HA) fusion machinery. However, the structural basis of the mechanism underlying fusion inhibition by Arbidol has remained obscure, thereby hindering its further development as a specific and optimized influenza therapeutic. We determined crystal structures of Arbidol in complex with influenza virus HA from pandemic 1968 H3N2 and recent 2013 H7N9 viruses. Arbidol binds in a hydrophobic cavity in the HA trimer stem at the interface between two protomers. This cavity is distal to the conserved epitope targeted by broadly neutralizing stem antibodies and is ∼16 Å from the fusion peptide. Arbidol primarily makes hydrophobic interactions with the binding site but also induces some conformational rearrangements to form a network of inter- and intraprotomer salt bridges. By functioning as molecular glue, Arbidol stabilizes the prefusion conformation of HA that inhibits the large conformational rearrangements associated with membrane fusion in the low pH of the endosome. This unique binding mode compared with the small-molecule inhibitors of other class I fusion proteins enhances our understanding of how small molecules can function as fusion inhibitors and guides the development of broad-spectrum therapeutics against influenza virus.

Investigational hemagglutinin-targeted influenza virus inhibitors

INTRODUCTION

Seasonal influenza and pandemic outbreaks typically result in high mortality and morbidity associated with severe economic burdens. Vaccines and anti-influenza drugs have made great contributions to control the infection. However, antigenic drifts and shifts allow influenza viruses to easily escape immune neutralization and antiviral drug activity. Hemagglutinin (HA)is an important envelope protein for the entry of influenza viruses into host cells, thus, HA-targeted agents may be potential anti-influenza drugs. Areas covered: In this review, we describe arbidol, a unique licensed drug targeting HA; discuss and summarize HA-targeted anti-influenza agents been tested before or being tested currently in clinical trials, including monoclonal antibodies, small molecule inhibitors, proteins and peptides. Other small molecule inhibitors are also briefly introduced. Expert opinion: Exploring new clinical applications for existing drugs can provide additional anti-influenza candidates with promising safety and bioavailability, and largely shortened time and costs. To enhance therapeutic efficacy and avoid drug-resistance, combination therapy involving in HA-targeted anti-influenza agent is reasonable and attractive. For drug discovery, it is helpful to keep an eye on the development of methodology in organic synthesis and probe into the co-crystal structure of HA in complex with small molecule.

Indirect study of non-covalent protein complexes by MALDI mass spectrometry: Origins, advantages, and applications of the "intensity-fading" approach

This review article describes the origins, advantages, and application of an indirect approach with which to study protein and other macromolecular complexes and identify the nature and site of interaction interfaces by means of conventional matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). First reported in 1999, it involves the detection of ion depletion or the absence of ions associated with a binding partner or domain in the MALDI mass spectrum of a mixture of interacting components compared to that for an untreated control. Later referred to as intensity-fading in some applications, the method offers numerous advantages over the direct detection of protein and other macromolecule complexes by MALDI-MS and even electrospray ionization (ESI) MS. The origins of this indirect method, its development for use with gel-separated components, validation using companion biochemical assays, and application to a range of protein-antibody and protein-drug complexes are reviewed together with software specifically developed to aid with data interpretation. The sensitivity of the approach for revealing how subtle differences in the structure of the binding partners can be detected by MALDI-MS is also demonstrated. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 35:559-573, 2016.

The Location of the Protonated and Unprotonated Forms of Arbidol in the Membrane: A Molecular Dynamics Study

Abstract

Arbidol is a potent broad-spectrum antiviral molecule for the treatment and prophylaxis of many viral infections. Viruses that can be inhibited by arbidol include enveloped and non-enveloped viruses, RNA and DNA viruses, as well as pH-independent and pH-dependent ones. These differences in viral types highlight the broad spectrum of Arb antiviral activity and, therefore, it must affect a common viral critical step. Arbidol incorporates rapidly into biological membranes, and some of its antiviral effects might be related to its capacity to interact with and locate into the membrane. However, no information is available of the molecular basis of its antiviral mechanism/s. We have aimed to locate the protonated (Arp) and unprotonated (Arb) forms of arbidol in a model membrane system. Both Arb and Arp locate in between the hydrocarbon acyl chains of the phospholipids but its specific location and molecular interactions differ from each other. Whereas both Arb and Arp average location in the membrane palisade is a similar one, Arb tends to be perpendicular to the membrane surface, whereas Arp tends to be parallel to it. Furthermore, Arp, in contrast to Arb, seems to interact stronger with POPG than with POPC, implying the existence of a specific interaction between Arp, the protonated from, with negatively charged phospholipids. This data would suggest that the active molecule of arbidol in the membrane is the protonated one, i.e., the positively charged molecule. The broad antiviral activity of arbidol would be defined by the perturbation it exerts on membrane structure and therefore membrane functioning.

Graphical Abstract

Electronic supplementary material

The online version of this article (doi:10.1007/s00232-016-9876-3) contains supplementary material, which is available to authorized users.

Molecular basis of influenza hemagglutinin inhibition with an entry-blocker peptide by computational docking and mass spectrometry

BACKGROUND

The increased resistance of circulating strains to current antiviral inhibitors of the influenza virus necessitates that new antivirals and their mode of action are identified. Influenza hemagglutinin is an ideal target given inhibitors of its function can block the entry of the virus into host cells during the early stages of replication. This article describes the molecular basis for the inhibition of H1 and H5 hemagglutinin by an entry-blocker peptide using companion molecular docking and mass spectrometry-based experiments.

METHODS

A combination of hemagglutination inhibition assays, computational molecular docking and a novel mass spectrometry-based approach are employed to explore the mode of action of the entry-blocker peptide at a molecular level.

RESULTS

The entry-blocker peptide is shown to be able to maximally inhibit blood cell hemagglutination at a concentration of between 6.4 and 9.2 µM. The molecular basis for this inhibition is derived from the binding of the peptide to hemagglutinin in the vicinity of the reported sialic acid binding site surrounded by an α-helix (190-helix) and two loop (130-loop and 220-loop) regions in the case of a H1 hemagglutinin and the second loop region in the case of a H5 hemagglutinin.

CONCLUSIONS

The results support the recognized potential of the entry-blocker peptide as an effective antiviral agent that can inhibit the early stages of viral replication and further illustrate the power of a combination of docking and a mass spectrometry approach to screen the molecular basis of new antiviral inhibitors to the influenza virus.

The Synthetic Antiviral Drug Arbidol Inhibits Globally Prevalent Pathogenic Viruses

Arbidol (ARB) is a synthetic antiviral originally developed to combat influenza viruses. ARB is currently used clinically in several countries but not in North America. We have previously shown that ARB inhibits in vitro hepatitis C virus (HCV) by blocking HCV entry and replication. In this report, we expand the list of viruses that are inhibited by ARB and demonstrate that ARB suppresses in vitro infection of mammalian cells with Ebola virus (EBOV), Tacaribe arenavirus, and human herpesvirus 8 (HHV-8). We also confirm suppression of hepatitis B virus and poliovirus by ARB. ARB inhibited EBOV Zaire Kikwit infection when added before or at the same time as virus infection and was less effective when added 24 h after EBOV infection. Experiments with recombinant vesicular stomatitis virus (VSV) expressing the EBOV Zaire glycoprotein showed that infection was inhibited by ARB at early stages, most likely at the level of viral entry into host cells. ARB inhibited HHV-8 replication to a similar degree as cidofovir. Our data broaden the spectrum of antiviral efficacy of ARB to include globally prevalent viruses that cause significant morbidity and mortality.

IMPORTANCE

There are many globally prevalent viruses for which there are no licensed vaccines or antiviral medicines. Some of these viruses, such as Ebola virus or members of the arenavirus family, rapidly cause severe hemorrhagic diseases that can be fatal. Other viruses, such as hepatitis B virus or human herpesvirus 8 (HHV-8), establish persistent infections that cause chronic illnesses, including cancer. Thus, finding an affordable, effective, and safe drug that blocks many viruses remains an unmet medical need. The antiviral drug arbidol (ARB), already in clinical use in several countries as an anti-influenza treatment, has been previously shown to suppress the growth of many viruses. In this report, we expand the list of viruses that are blocked by ARB in a laboratory setting to include Ebola virus, Tacaribe arenavirus, and HHV-8, and we propose ARB as a broad-spectrum antiviral drug that may be useful against hemorrhagic viruses.

[Clinical efficacy of arbidol (umifenovir) in the therapy of influenza in adults: preliminary results of the multicenter double-blind randomized placebo-controlled study ARBITR]

AIM

To evaluate the efficacy and safety of Arbidol (umifenovir) in adult patients with influenza.

SUBJECTS AND METHODS

The analysis of the preliminary results of the multicenter double-blind randomized placebo-controlled post-marketing study ARBITR was performed. A total of 293 adults aged 18 to 65 years with influenza or acute respiratory tract infection of no more than 36 hours' duration were enrolled in the study. Individuals were randomized into 2 treatment groups: oral umifenovir 200 mg four times daily for 5 days or placebo four times daily for 5 days. The efficacy endpoints were time to resolution of all symptoms, severity of symptoms and illness, durations of virus shedding.

RESULTS

The efficacy of umifenovir was evaluated in the group of 119 (40.6%) patients with influenza: 45 patients with laboratory-confirmed influenza and 74 patients whom diagnosis of influenza was made based on clinical and epidemiological data. Umifenovir had influence on the time to resolution of all symptoms. All symptoms were resolved within the first 60 hours after therapy initiation in 23.8% patients with laboratory-confirmed influenza in the umifenovir group and it was 5.7 times greater compared to placebo group (4.2%) (p < 0.05). Severity of illness, catarrhal symptoms and intoxication was reduced with umifenovir compared to placebo, reducing of severity was most evidently observed within the first 2-3 days following the therapy initiation. Umifenovir had a significant effect on viral shedding. The proportion of patients still shedding influenza virus on day 4 was significantly reduced in the umifenovir group compared to placebo (25 vs 53%, respectively; p < 0.05).

CONCLUSION

It was found that the effect of umifenovir in the treatment of influenza in adults is most pronounced in the acute stage of the disease and appears in the reduction of time to resolution of all symptoms of the disease, reducing the severity of symptoms of the disease and durations of virus shedding.

Catechin inhibition of influenza neuraminidase and its molecular basis with mass spectrometry

The molecular basis for the antiviral inhibitory properties of three catechins epigallocatechin gallate, epicatechin gallate and catechin-5-gallate derived from green tea was assessed in terms of their ability to interact with influenza neuraminidase. This was investigated using a molecular based MALDI mass spectrometry approach in conjunction with companion inhibition assays employing confocal microscopy. Together with computational molecular docking, all three catechins were found to bind to influenza neuraminidase in the vicinity of a structurally conserved cavity adjacent to residue 430 that has been suggested to be a secondary sialic acid binding site. In doing so, they were effective inhibitors of the enzyme preventing the release of progeny viruses from host cells at inhibitor concentrations (IC50 values) of between 100 and 173 μM. Importantly, their different binding profiles avoid the limitations of existing neuraminidase inhibitors manifested by the evolution of antiviral resistance strains.

Arbidol as a broad-spectrum antiviral: an update

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Arbidol (ARB) is licensed in Russia and China for the treatment of influenza and other viral infections.

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ARB inhibits a large panel of viral pathogens, enveloped or not.

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ARB displays a dual binding activity to lipid membranes and to viral or cellular proteins.

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It blocks viral endocytosis and replication in membranous intracellular compartments.

Arbidol (ARB) is a Russian-made small indole-derivative molecule, licensed in Russia and China for prophylaxis and treatment of influenza and other respiratory viral infections. It also demonstrates inhibitory activity against other viruses, enveloped or not, responsible for emerging or globally prevalent infectious diseases such as hepatitis B and C, gastroenteritis, hemorrhagic fevers or encephalitis. In this review, we will explore the possibility and pertinence of ARB as a broad-spectrum antiviral, after a careful examination of its physico-chemical properties, pharmacokinetics, toxicity, and molecular mechanisms of action. Recent studies suggest that ARB’s dual interactions with membranes and aromatic amino acids in proteins may be central to its broad-spectrum antiviral activity. This could impact on the virus itself, and/or on cellular functions or critical steps in virus-cell interactions, thereby positioning ARB as both a direct-acting antiviral (DAA) and a host-targeting agent (HTA). In the context of recent studies in animals and humans, we will discuss the prospective clinical use of ARB in various viral infections.

Substituent effects on the binding of natural product anthocyanidin inhibitors to influenza neuraminidase with mass spectrometry

The binding of three closely related anthocyanins within the 430-cavity of influenza neuraminidase is studied using a combination of mass spectrometry and molecular docking. Despite their similar structures, which differ only in the number and position of the hydroxyl substituents on the phenyl group attached to the chromenylium ring, subtle differences in their binding characteristics are revealed by mass spectrometry and molecular docking that are in accord with their inhibitory properties by neuraminidase inhibition assays. The cyanidin and delphinidin, with the greatest number of hydroxyl groups, bind more strongly and are better inhibitors than pelargonidin that contains a lone hydroxyl group at the 4' position. The study demonstrates, for the first time, the sensitivity of the mass spectrometry based approach for investigating the molecular basis and relative affinity of antiviral inhibitors, with subtly different structures, to their target protein. It has broader application for the screening of other protein interactions more generally with reasonable high-throughput.

Screening of neuraminidase inhibitors from traditional Chinese medicines by integrating capillary electrophoresis with immobilized enzyme microreactor

A simple and effective neuraminidase-immobilized capillary microreactor was fabricated by glutaraldehyde cross-linking technology for screening the neuraminidase inhibitors from traditional Chinese medicines. The substrate and product were separated by CE in short-end injection mode within 2 min. Dual-wavelength ultraviolet detection was employed to eliminate the interference from the screened compounds. The parameters relating to the separation efficiency and the activity of immobilized neuraminidase were systematically evaluated. The activity of the immobilized neuraminidase remained 90% after 30 days storage at 4°C. The immobilized NA microreactor could be continuously used for more than 200 runs. The Michaelis-Menten constant of neuraminidase was determined by the microreactor as 136.6 ± 10.8 μM. In addition, six in eighteen natural products were found as potent inhibitors and the inhibition potentials were ranked in the following order: bavachinin>bavachin>baicalein>baicalin>chrysin and vitexin. The half-maximal inhibitory concentrations were 59.52 ± 4.12, 65.28 ± 1.07, 44.79 ± 1.21 and 31.62 ± 2.04 for baicalein, baicalin, bavachin and bavachinin, respectively. The results demonstrated that the neuraminidase-immobilized capillary microreactor was a very effective tool for screening neuraminidase inhibitors from traditional Chinese medicines.