Inhibition of dengue virus replication by a class of small-molecule compounds that antagonize dopamine receptor d4 and downstream mitogen-activated protein kinase signaling.

UNLABELLED: Dengue viruses (DENV) are endemic pathogens of tropical and subtropical regions that cause significant morbidity and mortality worldwide. To date, no vaccines or antiviral therapeutics have been approved for combating DENV-associated disease. In this paper, we describe a class of tricyclic small-molecule compounds-dihydrodibenzothiepines (DHBTs), identified through high-throughput screening-with potent inhibitory activity against DENV serotype 2. SKI-417616, a highly active representative of this class, displayed activity against all four serotypes of DENV, as well as against a related flavivirus, West Nile virus (WNV), and an alphavirus, Sindbis virus (SINV). This compound was characterized to determine its mechanism of antiviral activity. Investigation of the stage of the viral life cycle affected revealed that an early event in the life cycle is inhibited. Due to the structural similarity of the DHBTs to known antagonists of the dopamine and serotonin receptors, we explored the roles of two of these receptors, serotonin receptor 2A (5HTR2A) and the D4 dopamine receptor (DRD4), in DENV infection. Antagonism of DRD4 and subsequent downstream phosphorylation of epidermal growth factor receptor (EGFR)-related kinase (ERK) were found to impact DENV infection negatively, and blockade of signaling through this network was confirmed as the mechanism of anti-DENV activity for this class of compounds. IMPORTANCE: The dengue viruses are mosquito-borne, reemerging human pathogens that are the etiological agents of a spectrum of febrile diseases. Currently, there are no approved therapeutic treatments for dengue-associated disease, nor is there a vaccine. This study identifies a small molecule, SKI-417616, with potent anti-dengue virus activity. Further analysis revealed that SKI-417616 acts through antagonism of the host cell dopamine D4 receptor and subsequent repression of the ERK phosphorylation pathway. These results suggest that SKI-417616, or other compounds targeting the same cellular pathways, may have therapeutic potential for the treatment of dengue virus infections.

Seco-pregnane steroids target the subgenomic RNA of alphavirus-like RNA viruses.

Plants have evolved multiple mechanisms to selectively suppress pathogens by production of secondary metabolites with antimicrobial activities. Therefore, direct selections for antiviral compounds from plants can be used to identify new agents with potent antiviral activity but not toxic to hosts. Here, we provide evidence that a class of compounds, seco-pregnane steroid glaucogenin C and its monosugar-glycoside cynatratoside A of Strobilanthes cusia and three new pantasugar-glycosides of glaucogenin C of Cynanchum paniculatum, are effective and selective inhibitors to alphavirus-like positive-strand RNA viruses including plant-infecting tobacco mosaic virus (TMV) and animal-infecting Sindbis virus (SINV), eastern equine encephalitis virus, and Getah virus, but not to other RNA or DNA viruses, yet they were not toxic to host cells. In vivo administration of the compounds protected BALB/c mice from lethal SINV infection without adverse effects on the mice. Using TMV and SINV as models, studies on the action mechanism revealed that the compounds predominantly suppress the expression of viral subgenomic RNA(s) without affecting the accumulation of viral genomic RNA. Our work suggested that the viral subgenomic RNA could be a new target for the discovery of antiviral drugs, and that seco-pregnane steroid and its four glycosides found in the two medicinal herbs have the potential for further development as antiviral agents against alphavirus-like positive-strand RNA viruses.

Ethnomedicinal uses of Momordicacharantia (Cucurbitaceae) in Togo and relation to its phytochemistry and biological activity.

Investigation of the traditional uses of Momordica charantia (Cucurbitaceae) in Togo (West Africa) showed that it is one of the most important local medicinal plants both for ritual and ethnomedical practices. There was a high degree of consensus (>50%) for use in the treatment of gastrointestinal and viral disease among 47 groups of village informants in the general population, while 19 traditional healers reported a larger and broader set of uses. The use by informants in Gaur and Kwa language groups was not significantly different. Lyophilized Momordica charantia extracts prepared from accessions collected in Togo showed high antiviral activity (<5 microg/ml) against Sindbis and Herpes simplex type 1 viruses and anthelmintic activity against Caenorhabditis elegans at 500 microg/ml. Presence in the leaves of the triterpene glycosides momordicins I and II follows biological activity of the plant extracts. However, momordicins were found to be anthelmintic but not antiviral. Traditional healers collected plants in dry areas where momordicin content is greater.

Synthesis and antiviral evaluation of benzimidazoles, quinoxalines and indoles from dehydroabietic acid.

Several heterocycles, such as benzimidazoles, quinoxalines and indoles incorporated into a hydrophenanthrene and naphthalene skeleton, were synthesised from two useful ortho-bromonitro precursors derived from dehydroabietic acid: methyl 12-bromo-13-nitro-deisopropyldehydroabietate and methyl 12-bromo-13,14-dinitro-deisopropyldehydroabietate. The new heterocycles were evaluated for their activity in vitro against several RNA and DNA viruses.

Biological activity of Guatteria cardoniana fractions.

Methanolic extract of leaves and twigs of Guatteria cardoniana R.E. Fries (Annonaceae), a plant from the Venezuelan rain forest, was separated in alkaloid rich fractions and their biological effect on baby hamster kidney (BHK) cell line was studied. The initial plant extract (FA) induced cell proliferation, cytotoxicity as well as antiviral activity, depending on the concentration used. Further separation of this methanolic extract allowed us to separate these biological activities. The fraction with the highest antiviral activity (F7) was chromatographed and three of the nine alkaloid-rich fractions obtained, retained this activity. One of them (F(7)11) exhibited the highest inhibitory effect against a neurotropic Sindbis virus (NSV).

Antiviral activities of medicinal plants of southern Nepal.

In a screening of plants used traditionally in Nepal to treat diseases that could be caused by viruses, twenty-one methanol extracts from twenty species were quantitatively assayed for activity against three mammalian viruses: herpes simplex virus, Sindbis virus and poliovirus. Assays were performed in ultraviolet (UV)-A or visible light, as well as dark, and cytotoxicity was also noted. Impressive antiviral activities were exhibited by species of Bauhinia (Fabaceae), Carissa (Apocynaceae), Milletia (Fabaceae), Mallotus (Fabaceae), Rumex (Polygonaceae), Streblus (Moraceae), Terminalia (Combretaceae) and Tridax (Asteraceae). The Carissa extract was the most active, showing activity against all three viruses at a concentration of 12 micrograms/ml. Many of the other extracts showed partial inactivation of one or more test viruses.

Antiviral activities of Nepalese medicinal plants.

In a screening of plants used traditionally in Nepal to treat diseases that could be caused by viruses, methanol extracts from 21 species were assayed for activity against three mammalian viruses: herpes simplex virus, Sindbis virus and poliovirus. Assays were performed in UV-A or visible light, as well as dark. Individual species of Hypericum, Lygodium, and Maesa exhibited impressive antiviral activities, although their selective effects on the three viruses suggested that the antiviral ingredients were different in each extract. In addition, many of the other extracts showed partial inactivation of one or more test viruses.

Isolation of the anthropogenic compound fluoranthene in a screening of Chinese medicinal plants for antiviral compounds.

Thirty-one species of medicinal plants used in the treatment of diseases of viral origin in Yunnan Province of China were assayed for inhibition of Sindbis and murine cytomegalovirus in mammalian cell cultures. Sixteen species displayed antiviral activity. A compound, which exhibited long wavelength UV-mediated antiviral activity, was isolated from leaves and twigs of Elsholtzia ciliata (Lamiaceae) using bioassay-guided fractionation and identified as the polycyclic aromatic hydrocarbon, fluoranthene. The discovery of an anthropogenic photosensitizer with antiviral activity in a plant has implications in studies of plants as sources of bioactive constituents.

Antiviral assays on phytochemicals: the influence of reaction parameters.

Investigations of phytochemicals for antiviral activities are assuming greater importance; but little attention has been given to the influence of various reaction parameters. We found that the activities of several known antiviral phytochemicals were profoundly affected by the presence of serum components, but in different ways. Thus, the terthiophene, alpha-terthienyl (alpha-T), was inhibited in a concentration-dependent manner by serum. In the case of a carboxylic acid derivative of alpha-T, the compound appeared to have no antiviral activity at all in the presence of serum, yet in its absence this compound was as effective as alpha-T. In contrast the complex anthraquinone hypericin required a small amount of serum for maximal antiviral activity, although too much was inhibitory. The reactions were also strongly affected by the order of incubation of the components: virus, compound, serum, and light. The antiviral effects were not influenced significantly by temperature, in contrast to a report by other workers, provided the light exposures were controlled. These effects are significant because serum is commonly used in virus assays, and plant extracts often contain polypeptides. Furthermore, when phytochemicals are used in vivo, their effects could be modulated by components of tissues and body fluids.

Constituents of Eriobotrya japonica. A study of their antiviral properties.

The CHCl3 extract of Eriobotrya japonica from an Italian source was shown to contain four new triterpene esters, namely, 23-trans-p-coumaroyltormentic acid [1], 23-cis-p-coumaroyltormentic acid [2], 3-O-trans-caffeoyltormentic acid [3], and 3-O-trans-p-coumaroylrotundic acid [4], in addition to three common ursolic acid derivatives 5, 6, and 7. An investigation of the antiviral properties of compounds 1-7 revealed that only 3 significantly reduced rhinovirus infection. The compounds were ineffective towards human immunodeficiency virus type 1 (HIV-1) and Sindbis virus replication.

Effect of electric charged molecules on Sindbis virus hemagglutination and hemolysis.

The role of electrostatic interactions in the attachment and fusion at acidic pH of Sindbis virus (SNV) with goose erythrocytes was studied, investigating the effect of several anionic and cationic polyelectrolytes on SNV hemagglutination and hemolysis. In order to establish the target of active drugs, the compounds were incubated either with the virus particles or with the erythrocytes. Dextran sulfate was the only compound able to inhibit the attachment of SNV to the erythrocytes. Fusion of virus with red cells was reduced dose-dependently by the polyanions dextran sulfate, mucin and polygalacturonic acid. On the contrary two polycations, polylysine and polybrene, enhanced viral hemolytic activity. However the effect of polyions is not exclusively related to the electric charge since ineffective molecules were found in both classes of compounds.

[The antiviral action of a modified bacterial ribonuclease]. / Izuchenie antivirusnogo deistviia modifitsirovannoi bakterial'noi ribonukleazy.

The antiviral activity of a bacterial ribonuclease conjugate with chitosane of Kamchatka crab (in a form of water soluble chito-oligosaccharides) has been studied. The conjugate inhibitory activity for A and B viruses as well as to Sindbis arbovirus in tissue cultures is shown. The preparation efficiency at intramuscular and intranasal administration was observed at experimental influenza infection of white mice.

Screening of medicinal plants from Yunnan Province in southwest China for antiviral activity.

In an ethnopharmacological screening of medicinal plants used in Yunnan province of China, ethanol extracts from 31 plant species were assayed for inhibition of murine cytomegalovirus and Sindbis virus infections. Parallel assays were carried out with and without exposure to UVA radiation to test for photo-mediation of activity. Antiviral activity was observed with 16 of the plant extracts. Eight plant extracts have been selected for further studies, with the objective of characterizing the antiviral constituents.

The antiviral action of lignans.

A total of 18 purified lignans was evaluated for antiviral activity against murine cytomegalovirus (CMV) and Sindbis virus, by means of different treatment regimens. Podophyllotoxin and alpha-peltatin were the most potent compounds, and they apparently inhibited murine CMV at an essential early step in the replication cycle after the adsorption of virus to the cells. On the other hand, justicidin B and the diphyllin derivatives were much more effective against Sindbis virus, and 12 of the lignans had no demonstrable effect at all, despite their known activities in other bioassays.

Antiviral effects of Melia azedarach L. leaves extracts on Sindbis virus-infected cells.

Partially purified extracts from leaves of Melia azedarach L. (MA) exert a broad range of antiviral effects on DNA and RNA viruses. The effect of MA on different stages of Sindbis virus replicative cycle in BHK cells was investigated. Under one-step growth conditions MA afforded a greater than 90% inhibition in virus yield if added to the cell cultures 2 h before or after infection, and when added 4 h after infection MA still caused a greater than 80% inhibition. Analysis of early events following Sindbis virus infection showed that MA did not affect viral adsorption to or penetration in BHK cell. In contrast, viral RNA and protein synthesis was almost totally inhibited in cells pretreated with MA 2 h before infection, while cellular macromolecular synthesis was similar in MA-treated and untreated cell cultures.

[Blocking of Sindbis virus replication in the body of infected mice using an inhibitor of chymotrypsin-like proteases]. / Blokirovanie replikatsii virusa Sindbis v organizme zarazhennykh myshei s pomoshch'iu ingibitora khimotripsinpodobnykh proteaz.

Parenteral administration of an inhibitor of chymotrypsin-like proteases (TPCK) to mice infected with alphavirus (Sindbis AR/339 strain) blocked virus replication in the brain and inhibited the development of viremia in the infected animals. The most likely mechanism of TPCK antiviral effect seems to consist in disturbance of proteolytic processing of viral proteins.

[Effect of virazole on the antiviral activity of poly(G) X poly(C) and other polyribonucleotide interferonogens]. / Vliianie virazola na protivovirusnuiu aktivnost' poli(G) X poli(Ts) i drugikh poliribonukleotidnykh interferonogenov.

The effect of virazole on the antiviral activity of poly (G) X poly (C), poly (G, A) X X poly (C) and poly(G, I) X poly (C) was studied in cell cultures and on mice. It was shown that virazole in concentrations not sufficient for significant inhibition of the development of vesicular stomatitis virus or Sindbis virus in chick embryo cell cultures markedly increased the antiviral effect and allowed decreasing the minimum effective doses of the synthetic polyribonucleotide complexes with respect to the above viruses. Combined administration of poly (G) X poly (C) and virazole to mice 1-2 or 24 hours after infection with tick-borne encephalitis virus provided a much more pronounced decrease in the death rate of the animals than the use of the interferonogen alone. Virazole per se was little active and had no significant effect on the intensity of interferonogenesis promoted by the use of poly (G) X poly (C). A possibility of successful therapy of viral infections with polyribonucleotide interferonogens in combination with virazole or other chemotherapeutic drugs with broad antiviral spectrum is discussed.