Inhibition of herpes simplex virus type 1 and adenovirus type 5 by heterocyclic Schiff bases of aminohydroxyguanidine tosylate

Eleven heterocyclic Schiff bases of aminohydroxyguanidine tosylate (SB-AHGs), compounds I-XI, were tested for antiviral activity against herpes simplex virus type 1 (HSV-1) and adenovirus type 5 (Ad 5) via plaque reduction and virus yield reduction assays. This work was undertaken to test the hypothesis that low molecular weight SB-AHGs (MW < 235 for the free SB) make better antiviral agents than high MW SB-AHGs (MW > 300). The plaque reduction assay method demonstrated that three compounds, I, VII and IX, had moderate activity against HSV-1, with 50% inhibitory concentration (IC50) values of 38.0, 23.5 and 52.1 microM, respectively. Against Ad 5, compounds I, VIII and XI exhibited moderate activity, with IC50 values of 52.7, 19.3 and 5.1 microM, respectively. Among the compounds screened, compound I (1-[(3'-hydroxy-6'-methyl-2'-pyridyl)methylene]amino-3-hydroxyguanidi ne tosylate) was the most promising antiviral candidate, with selectivity indices (SI) of 10.2 (HSV-1) and 7.6 (Ad 5), respectively. Virus yield reduction assays indicated that compound I had less antiviral potency against HSV-1 than against Ad 5. The antiviral effects of compound I at a high input virus multiplicity of infection (MOI > 5) indicated that compound I had effective anti-adenoviral activity at 24 h post infection. This work demonstrated that some of SB-AHGs only have moderate antiviral activities against Ad 5 and HSV-1 viruses. In general, low MW SB-AHGs have low cytotoxicities to the host cells.     

Antiviral activity of Australian tea tree oil and eucalyptus oil against herpes simplex virus in cell culture

The antiviral effect of Australian tea tree oil (TTO) and eucalyptus oil (EUO) against herpes simplex virus was examined. Cytotoxicity of TTO and EUO was evaluated in a standard neutral red dye uptake assay. Toxicity of TTO and EUO was moderate for RC-37 cells and approached 50% (TC50) at concentrations of 0.006% and 0.03%, respectively. Antiviral activity of TTO and EUO against herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) was tested in vitro on RC-37 cells using a plaque reduction assay. The 50% inhibitory concentration (IC50) of TTO for herpes simplex virus plaque formation was 0.0009% and 0.0008% and the IC50 of EUO was determined at 0.009% and 0.008% for HSV-1 and HSV-2, respectively. Australian tea tree oil exhibited high levels of virucidal activity against HSV-1 and HSV-2 in viral suspension tests. At noncytotoxic concentrations of TTO plaque formation was reduced by 98.2% and 93.0% for HSV-1 and HSV-2, respectively. Noncytotoxic concentrations of EUO reduced virus titers by 57.9% for HSV-1 and 75.4% for HSV-2. Virus titers were reduced significantly with TTO, whereas EUO exhibited distinct but less antiviral activity. In order to determine the mode of antiviral action of both essential oils, either cells were pretreated before viral infection or viruses were incubated with TTO or EUO before infection, during adsorption or after penetration into the host cells. Plaque formation was clearly reduced, when herpes simplex virus was pretreated with the essential oils prior to adsorption. These results indicate that TTO and EUO affect the virus before or during adsorption, but not after penetration into the host cell. Thus TTO and EUO are capable to exert a direct antiviral effect on HSV. Although the active antiherpes components of Australian tea tree and eucalyptus oil are not yet known, their possible application as antiviral agents in recurrent herpes infection is promising.     

Inactivation of HSV-1 and HSV-2 and prevention of cell-to-cell virus spread by Santolina insularis essential oil

The essential oil obtained in toto from Santolina insularis was investigated for its antiviral activity on herpes simplex type 1 (HSV-1) and type 2 (HSV-2) in vitro. The IC(50) values, determined by plaque reduction assays, were 0.88 and 0.7 microg/ml for HSV-1 and HSV-2, respectively, while the CC(50) determined by the MTT test on Vero cells was 112 microg/ml, indicating a CC(50)/IC(50) ratio of 127 for HSV-1 and 160 for HSV-2. Results obtained by plaque reduction assays also indicated that the antiviral activity of S. insularis was principally due to direct virucidal effects. Antiviral activity against HSV-1 and HSV-2 was not observed in a post-attachment assay, and attachment assays indicated that virus adsorption was not inhibited. Up to 80% inhibition of HSV-1 was achieved at the concentration of 40 microg/ml by yield reduction assay. Furthermore, reduction of plaque formation assays also showed that S. insularis essential oil inhibits cell-to-cell transmission of both HSV-1 and HSV-2.     

Antiviral activity of hop constituents against a series of DNA and RNA viruses

We investigated whether crude hop extracts and purified hop components representing every major chemical class of hop compound have antiviral activity. These hop constituents were tested for antiviral activity against bovine viral diarrhea virus (BVDV) as a surrogate model of hepatitis C virus (HCV), human immunodeficiency virus (HIV), influenza A virus (FLU-A), influenza B virus (FLU-B), rhinovirus (Rhino), respiratory syncytial virus (RSV), yellow fever virus (YFV), cytomegalovirus (CMV), hepatitis B virus (HBV), and herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2). The extracts all failed to prevent the replication of HIV, FLU-A, FLU-B, RSV and YFV. A xanthohumol-enriched hop extract displayed a weak to moderate antiviral activity against BVDV (therapeutic index (TI)=6.0), HSV-2 (TI=>5.3), Rhino (TI=4.0) and HSV-1 (TI=>1.9) with IC(50) values in the low microg/ml range. Pure iso-alpha-acids demonstrated low to moderate antiviral activity against both BVDV (TI=9.1) and CMV (TI=4.2) with IC(50) values in the low microg/ml range. No antiviral activity was detected using beta-acids or a hop oil extract. Ultra-pure preparations (>99% pure) were used to show that xanthohumol accounted for the antiviral activity observed in the xanthohumol-enriched hop extract against BVDV, HSV-1 and HSV-2. Xanthohumol was found to be a more potent antiviral agent against these viruses than the isomer iso-xanthohumol. With Rhino, the opposite trend was observed with iso-xanthohumol showing superior antiviral activity to that observed with xanthohumol. Xanthohumol also showed antiviral activity against CMV, suggesting that it might have a generalized anti-herpesvirus antiviral activity. Again, superior antiviral activity was observed with the xanthohumol isomer against CMV. In summary, iso-alpha-acids and xanthohumol were shown to have a low-to-moderate antiviral activity against several viruses. These hop constituents might serve as interesting lead compounds from which more active anti-HCV, anti-Rhino and anti-herpesvirus antiviral agents could be synthesized.     

Antiviral activity of Plantago major extracts and related compounds in vitro

Plantago major L., a popular traditional Chinese medicine, has long been used for treating various diseases varying from cold to viral hepatitis. The aim of present study was to examine the antiviral activity of aqueous extract and pure compounds of P. major. Studies were conducted on a series of viruses, namely herpesviruses (HSV-1, HSV-2) and adenoviruses (ADV-3, ADV-8, ADV-11). The antiviral activity of EC50 was defined as the concentration achieved 50% cyto-protection against virus infection and the selectivity index (SI) was determined by the ratio of CC50 (concentration of 50% cellular cytotoxicity) to EC50. Results showed that aqueous extract of P. major possessed only a slight anti-herpes virus activity. In contrast, certain pure compounds belonging to the five different classes of chemicals found in extracts of this plant exhibited potent antiviral activity. Among them, caffeic acid exhibited the strongest activity against HSV-1 (EC50=15.3 microg/ml, SI=671), HSV-2 (EC50=87.3 microg/ml, SI=118) and ADV-3 (EC50=14.2 microg/ml, SI=727), whereas chlorogenic acid possessed the strongest anti-ADV-11 (EC50=13.3 microg/ml, SI=301) activity. The present study concludes that pure compounds of P. major, which possess antiviral activities are mainly derived from the phenolic compounds, especially caffeic acid. Its mode of action against HSV-2 and ADV-3 was found to be at multiplication stages (postinfection of HSV-1: 0-12 h; ADV-3: 0-2 h), and with SI values greater than 400, suggesting the potential use of this compound for treatment of the infection by these two viruses.     

Antiviral activities of biflavonoids

Biflavonoids such as amentoflavone (1), agathisflavone (2), robustaflavone (3), hinokiflavone (4), volkensiflavone (5), rhusflavanone (7), succedaneflavanone (9), all isolated from Rhus succedanea and Garcinia multiflora, as well as their methyl ethers and acetates, volkensiflavone hexamethyl ether (6), rhusflavanone hexaacetate (8), and succedaneflavanone hexaacetate (10) were evaluated for their antiviral activities. The inhibitory activities against a number of viruses including respiratory viruses (influenza A, influenza B, respiratory syncytial, parainfluenza type 3, adenovirus type 5, and measles) and herpes viruses (HSV-1, HSV-2, HCMV, and VZV) were investigated. The results indicated that robustaflavone exhibited strong inhibitory effects against influenza A and influenza B viruses with EC50 values of 2.0 micrograms/ml and 0.2 microgram/ml, respectively, and selectivity index values (SI) of 16 and 454, respectively. Amentoflavone and agathisflavone also demonstrated significant activity against influenza A and B viruses. Amentoflavone and robustaflavone exhibited moderate anti-HSV-1 anti-HSV-2 activities with EC50 values of 17.9 micrograms/ml (HSV-1) and 48.0 micrograms/ml (HSV-2) and SI values of > 5.6 (HSV-1) and > 2.1 (HSV-2) for amentoflavone; EC50 values of 8.6 micrograms/ml (HSV-1) and 8.5 micrograms/ml (HSV-2), and SI values of > 11.6 (HSV-1) and > 11.8 (HSV-2) for robustaflavone. Rhusflavanone demonstrated inhibitory activities against influenza B, measles, and HSV-2 viruses with SI values of 9.3, 8 and > 6.4, respectively. Succedaneaflavanone exhibited inhibitory activities against influenza B virus and VZV with SI values of 15 and < 3.0, respectively.     

Increased efficacy of acyclovir-loaded microparticles against herpes simplex virus type 1 in cell culture.

Acyclovir is one of the most effective and selective agents against viruses of the herpes group. In order to increase its antiviral activity, acyclovir loaded microparticles, prepared by an O/W solvent evaporation method were developed. Their antiviral activity against herpes simplex virus type 1 (HSV-1) and toxicity were evaluated on Vero cells and then compared with those presented by a drug solution. The 50% inhibitory concentration (IC(50)) values for acyclovir loaded microspheres determined by plaque reduction assays at 48 and 96 h, were found to be 1.06 +/- 0.01 microM and 0.15 +/- 0.03 microM, respectively, while the equivalent values obtained for an acyclovir solution were 1.28 +/- 0.04 microM at 48 h and 0.27 +/- 0.02 microM at 96 h. These results indicate that acyclovir shows a higher antiviral activity, against herpes simplex virus type 1, when this drug was loaded in microparticles rather than as a drug solution, especially after 96 h of incubation. The toxicity of these microparticles was determined by the MTT test at 48 and 96 h. At 48 h only a small toxicity was found (cell viability ranged from 72 to 82%, with the higher concentration tested) and it could not be attributed to the microparticles, since the acyclovir control solution showed similar toxicity values. However, after 96 h a higher toxicity was observed with acyclovir microparticles as well as with the unloaded ones (cell viability located between 60 and 70%). In summary, acyclovir-loaded microparticles have shown to be promising carriers for the effective delivery of acyclovir in the treatment of HSV-1 infections in cells so they can have a potential use in vivo.     

Antiviral activity of the marine alga Symphyocladia latiuscula against herpes simplex virus (HSV-1) in vitro and its therapeutic efficacy against HSV-1 infection in mice

The antiviral activities of extracts from 5 species of marine algae collected at Haeundae (Pusan, Korea), were examined using plaque reduction assays. Although the activity of a methanol (MeOH) extract of Sargassum ringoldianum (Sargassaceae) was the most potent against several types of viruses, it was also cytotoxic. A MeOH extract of Symphyocladia latiuscula (Rhodomelaceae) and its fractions exhibited antiviral activities against acyclovir (ACV) and phosphonoacetic acid (PAA)-resistant (AP(r)) herpes simplex type 1 (HSV-1), thymidine kinase (TK(-)) deficient HSV-1 and wild type HSV-1 in vitro without cytotoxicity. The major component, 2,3,6-tribromo-4,5-dihydroxybenzyl methyl ether (TDB) of a CH(2)Cl(2)-soluble fraction was active against wild type HSV-1, as well as AP(r) HSV-1 and TK(-) HSV-1 (IC(50) values of 5.48, 4.81 and 23.3 microg/ml, respectively). The therapeutic effectiveness of the MeOH extract and TDB from S. latiuscula was further examined in BALB/c mice that were cutaneously infected with HSV-1 strain 7401H. Three daily oral administrations of the MeOH extract and TDB significantly delayed the appearance of score 2 skin lesions (local vesicles) and limited the development of further score 6 (mild zosteriform) lesions in infected mice without toxicity compared with controls. In addition, TDB suppressed virus yields in the brain and skin. Therefore TDB should be a promising anti HSV agent.     

Potent cationic inhibitors of West Nile virus NS2B/NS3 protease with serum stability, cell permeability and antiviral activity

West Nile virus (WNV) has spread rapidly around the globe, efficiently crossing species from migrating birds into humans and other mammals. The viral protease NS2B-NS3 is important for WNV replication and recognizes dibasic substrate sequences common to other flaviviral proteases but different from most mammalian proteases. Potent inhibitors of WNV protease with antiviral activity have been elusive to date. We report the smallest and most potent inhibitors known for this enzyme, cationic tripeptides with nonpeptidic caps at the N-terminus and aldehyde at the C-terminus. One of these, compound 3 ( Ki = 9 nM) is stable in serum (>90% intact after 3 h, 37 degrees C), cell permeable, and shows antiviral activity (IC 50 1.6 microM) without cytotoxicity (IC 50 >400 microM), thereby validating the approach of inhibiting WNV protease to suppress WNV replication.     

Virucidal activity of a beta-triketone-rich essential oil of Leptospermum scoparium (manuka oil) against HSV-1 and HSV-2 in cell culture

The inhibitory activity of manuka oil against Herpes simplex virus type 1 (HSV-1) and Herpes simplex virus type 2 (HSV-2) was tested in vitro on RC-37 cells (monkey kidney cells) using a plaque reduction assay. In order to determine the mode of antiviral action of the essential oil, manuka oil was added at different times to the cells or viruses during the infection cycle. Both HSV types were significantly inhibited when the viruses were pretreated with manuka oil 1 h prior to cell infection. At non-cytotoxic concentrations of the essential oil, plaque formation was significantly reduced by 99.5 % and 98.9 % for HSV-1 and HSV-2, respectively. The 50 % inhibitory concentration (IC (50)) of manuka oil for virus plaque formation was determined at 0.0001 % v/v ( = 0.96 microg/mL) and 0.00006 % v/v ( = 0.58 microg/mL) for HSV-1 and HSV-2, respectively. On the other hand, pretreatment of host cells with the essential oil before viral infection did not affect plaque formation. After virus penetration into the host cells only replication of HSV-1 particle was significantly inhibited to about 41 % by manuka oil. Flavesone and leptospermone, two characteristic ss-triketones of manuka oil, inhibited the virulence of HSV-1 in the same manner as the essential oil itself. When added at non-cytotoxic concentrations to the virus 1 h prior to cell infection, plaque formation was reduced by 99.1 % and 79.7 % for flavesone and leptospermone, respectively.     

Phenoxazine derivatives inactivate human cytomegalovirus, herpes simplex virus-1, and herpes simplex virus-2 in vitro.

We examined whether phenoxazine derivatives, 2-amino-4,4alpha-dihydro-4alpha-7-dimethyl-3H-phenoxazine-3-one (Phx-1), 3-amino-1,4alpha-dihydro-4alpha-8-dimethyl-2H-phenoxazine-2-one (Phx-2), and 2-amino-phenoxazine-3-one (Phx-3) may have antiviral activity against herpes family viruses: human cytomegalovirus (HCMV), herpes simplex virus type 1 (HSV-1), and herpes simplex virus type 2 (HSV-2). The antiviral activity was evaluated by the selectivity index (SI), which is the ratio of 50% cytotoxic concentration (CC(50)) and 50% antiviral concentration (IC(50)). Among these phenoxazines, Phx-2 exerted strong antiviral activity to HCMV with the SI of 200, while Phx-1 and Phx-3 exerted no marked anti-HCMV activity. Phx-2 also showed moderate inhibition of HSV-1 and HSV-2, with the SI of 6.7 and 17, respectively. In the time-of-addition experiments, inhibitory effect of Phx-2 against HCMV was active even when applied to cells at 100 h after HCMV infection, while ganciclovir (GCV) showed potent inhibition when applied to cells before 42-h post-infection, but its inhibitory effects disappeared thereafter. Attachment and penetration of HCMV was not affected by the presence of Phx-2. When HCMV was pretreated with Phx-2, concentration-dependent virucidal action was observed, suggesting that Phx-2 inactivates HCMV directly. From these data, it was found that Phx-2 might have a different anti-HCMV target from GCV.     

Antiviral effect of aqueous extracts from species of the Lamiaceae family against Herpes simplex virus type 1 and type 2 in vitro

Aqueous extracts from species of the Lamiaceae family were examined for their antiviral activity against Herpes simplex virus (HSV). Extracts from lemon balm (Melissa officinalis), peppermint (Mentha x piperita), prunella (Prunella vulgaris), rosemary (Rosmarinus officinalis), sage (Salvia officinalis) and thyme (Thymus vulgaris) were screened. Their inhibitory activity against Herpes simplex virus type 1 (HSV-1), type 2 (HSV-2) and an acyclovir-resistant strain of HSV-1 (ACV (res)) was tested in vitro on RC-37 cells in a plaque reduction assay. The 50% inhibitory concentrations (IC (50)) of the extracts for HSV plaque formation were determined in dose-response studies. All test compounds showed a high antiviral activity against HSV-1, HSV-2 and ACV (res). In order to identify the mode of antiviral action, the extracts were added to the cells or viruses at different stages of infection. Both types of Herpes virus including ACV (res) were considerably neutralized after treatment with the extracts prior to infection. At maximum non-cytotoxic concentrations of the extracts, plaque formation was significantly reduced by > 90% for HSV-1 and HSV-2 and > 85% for ACV (res). In time-response studies over a period of 2 hours, a clearly time-dependent activity was demonstrated. These results indicate that the extracts affect HSV before adsorption, but have no effect on the intracellular virus replication. Therefore, the extracts exert their antiviral effect on free HSV and offer a chance to use them for topical therapeutic application against recurrent HERPES infections.     

Evaluation of the antiviral drug susceptibility of influenza viruses in Italy from 2004/05 to 2009/10 epidemics and from the recent 2009 pandemic

Antiviral monitoring of influenza viruses circulating in Italy has been carried out since 2007 by the National Influenza Centre (NIC), using both phenotypic and sequence-based assays. Here, we report results of the susceptibility evaluation to neuraminidase (NA) inhibitors (NAIs, zanamivir and oseltamivir) and adamantanes of nearly 300 influenza type A and B seasonal viruses isolated in Italy during six recent seasons, together with over 30 pandemic (H1N1) 2009 virus strains. The present work is the first such study conducted in Italy, aimed to develop national data on antiviral drug profile and to establish a nationwide surveillance programme on antiviral susceptibility. Sequencing of the NA gene was undertaken either to confirm the phenotypic findings or to identify any NA change, in potentially resistant viruses (outliers), which might be associated with reduced susceptibility to NAIs. The 50% inhibitory concentration values (IC(50)s) showed slightly different sensitivities of the seasonal Italian isolates to the two NAI drugs, depending on the specific NA subtype. We found mean zanamivir IC(50)s of 0.74, 1.33 and 7 nM, and oseltamivir IC(50)s of 0.67, 2.34 and 30.1 nM for the N2, N1 and B NAs, respectively. The pandemic (H1N1) 2009 viruses showed IC(50)values overall comparable to the seasonal N1 viruses from previous years, showing mean zanamivir IC(50)s of 1.02 nM and mean oseltamivir IC(50)s of 2.82 nM. Oseltamivir resistance was found in a total of 19 seasonal N1viruses of 2007/2008 and 2008/2009, and in three pandemic (H1N1) 2009 strains. A gradual increase of resistance to adamantanes was observed among the N2 viruses isolated in recent seasons; no resistant viruses were found among the seasonal N1 strains, whereas all the pandemic (H1N1) 2009 isolates analysed were resistant to the M2 blockers.     

Antiviral effects of 28-deacetylsendanin on herpes simplex virus-1 replication.

The compound purified from the fruit of Melia azedarach exerted an antiviral effect on herpes simplex virus-1 (HSV-1) in Vero cells. It was identified as 28-deacetylsendanin (28-DAS). The 50% inhibitory concentration (IC50) of 28-DAS was 1.46 microg/ml without cytotoxicity at 400 microg/ml on Vero cells. Electron microscopy showed that low electron-dense cores of newly synthesized nucleocapsids remained in swollen nuclei and no extracellular virus particles were observed at 15 h p.i. Consistent with this result, it was confirmed by a plaque assay that few infectious progeny viruses were released from the 28-DAS-treated virus-infected cells at 24 h p.i. Intracellular viruses in 28-DAS-treated virus-infected cells were 23% of untreated and infected cells. The synthesis of thymidine kinase (TK) was reduced by 28-DAS at early stage. In conclusion, 28-DAS inhibited the replication of HSV-1, reduced the synthesis of HSV-1 TK, and led to the formation of defective nucleocapsids.     

Activity of two synthetic amphiphilic peptides and magainin-2 against herpes simplex virus types 1 and 2

The in vitro antiviral activity of two amphiphilic synthetic peptides, modelin-1 (mod-1) and modelin-5 (mod-5), and of the natural antibacterial peptide magainin-2 (mag-2) against herpes simplex viruses type 1 (HSV-1) and 2 (HSV-2) were evaluated. The peptides were incubated with the virus, i.e. direct inactivation, and their effects examined by means of plaque reduction assay and/or reduction in virus yield. Only mod- displayed a strong antiviral effect against HSV-1 and HSV-2, with 50% effective dose (ED₅₀) values of 4.6 and 4.1 μg/mL, respectively. Mag-2, mod-5 and a mixture of both had no significant inhibitory effect. Addition of mod-1 up to a concentration of 100μg/mL to the culture medium had no significant cytotoxic effect on host vero cells, as measured by the trypan blue-exclusion method. It showed, however, considerable hemolytic activity against human red blood cells. Experiments including acyclovir (ACV) as a reference viral inhibitor indicated that the mode of action of mod-1 is different from that of ACV. In contrast to ACV, the peptide inactivates the virus following a very short incubation before vero cell infection, suggesting some kind of direct interaction of the peptide with the viral envelope, rather than inhibition of viral DNA replication or gene expression. Our results suggest that mod-1 may be an effective topical antiviral agent against herpes viruses.     

The effect of thymidine on the antibacterial and antiviral activity of zidovudine.

The effect of thymidine and deoxyadenosine on the antiviral and antibacterial effect of zidovudine was studied in human immunodeficiency virus type 1 (HIV-1) Escherichia coli and Salmonella typhimurium. In quantitative assays, 10 micrograms mL-1 thymidine was shown to increase the 50% inhibitory concentration (IC50) of zidovudine for HIV-1 by approximately 100-fold and to reduce zidovudine (1 microM)-induced protection of C8166 cells from 2.04 to 0.18 log syncytial-forming units. Thymidine also antagonized the antibacterial effect of zidovudine for two E. coli and three S. typhimurium species in a dose-dependent manner; 10 micrograms mL-1 of thymidine increased the minimum inhibitory concentration of zidovudine for E. coli strains by 10-40-fold and for S. typhimurium strains by three-fold. Deoxyadenosine reduced the minimum inhibitory concentration of zidovudine against all five bacterial strains but had no effect on the IC50 of zidovudine for HIV-1, nor did it significantly reverse the antagonism of the antibacterial and antiviral activity of thymidine. The induction of the SOS response in E. coli was reversed in a dose-dependent manner by thymidine while the presence of deoxyadenosine increased induction of the SOS response by zidovudine at suboptimal concentrations.     

Oligomeric proanthocyanidins from Rumex acetosa L. inhibit the attachment of herpes simplex virus type-1

The polyphenole-enriched acetone-water extract R2 from the aerial parts of Rumex acetosa L. containing high amounts of oligomeric and polymeric proanthocyanidins and flavonoids was tested for antiviral activity. R2 exhibited strong antiviral activity against herpes simplex virus type-1 (HSV-1) while the replication of adenovirus 3 was not affected. By plaque reduction test and MTT assay on Vero cells, the HSV-1-specific inhibitory concentration (IC(50)) and cytotoxic concentration (CC(50)) were determined. R2 exibited an IC(50) of 0.8 μg/mL and a selectivity index (SI) (ratio of IC(50) to CC(50)) of approximately 100 when added to the virus inoculum for 1h at 37°C prior to infection. The antiviral activity was due to the presence of flavan-3-ols and oligomeric proanthocyanidins in the extract. Structure-activity analyses indicated that flavan-3-ols and proanthocyanidins with galloylation at position O-3 are highly potent compounds (SI>40), while ungalloylated compounds did not exhibit antiviral effects (SI<1). R2 and a major proanthocyanidin from R2, epicatechin-3-O-gallate-(4β→8)-epicatechin-3-O-gallate abolished virus entry into the host cell by blocking attachment to the cell surface. When added after attachment at a concentration of ≥ 12.5 μg/mL, R2 inhibited also penetration of HSV-1 into the host cell. R2 and epicatechin-3-O-gallate-(4β→8)-epicatechin-3-O-gallate were shown to directly interact with viral particles leading to the oligomerisation of envelope proteins as demonstrated for the essential viral glycoprotein gD. Using raft cultures with three-dimensional organotypic human skin equivalents it was shown that treatment of cultures with R2 after infection with HSV-1 resulted in a reduced viral spread.     

鱼腥草不同溶剂提取物的抗病毒活性研究

目的 研究鱼腥草不同溶剂提取物体外抗手足口病毒（enterovirus type 71,EV71）、单纯疱疹病毒1型（herpes simplex virus type 1,HSV-1）、呼吸道合胞病毒（respiratory syncytial virus,RSV）、柯萨奇病毒B3型（coxsackie virus type B3,CV-B3）、柯萨奇病毒B5型（coxsackie virus type B5,CV-B5）的活性。方法 采用细胞体外培养技术,建立不同病毒感染模型,用鱼腥草不同溶剂提取物进行治疗,通过细胞融合病变观察法以及MTT比色法检测得到治疗指数（therapeutic index,TI）,以此判定其体外抗病毒活性。结果 体外抗病毒试验结果证明,鱼腥草不同溶剂提取物对HSV-1、EV71抗病毒作用较强,对RSV、CV-B3、CV-B5的效果甚微或无明显作用。鱼腥草醇提物中黄酮类成分含量较高,抗病毒活性相对较高;30%,50%,75%乙醇提取物以及水提醇沉处理沉淀物对HSV-1的TI值分别是81.68,67.23,41.91,32.61,均高于阳性对照阿昔洛韦TI值23.43,显示鱼腥草水醇提取物抗HSV-1的活性较强;75%,50%,30%乙醇提取物对EV71的TI值分别是19.58,20.13,18.84,效果较为显著。结论 研究证实鱼腥草提取物对HSV-1、EV71的抗病毒活性较高,可一定程度为临床应用鱼腥草治疗这2种病毒感染引发的疾病提供参考依据。     

In vitro antiviral activity of marine sponges collected off Brazilian coast

This paper describes the in vitro antiviral evaluation of 27 different marine sponges (Porifera) collected off Brazilian coastline in the search for novel drug leads. With these sponges aqueous and organic extracts were prepared and tested for anti-herpetic (HSV-1, KOS strain), anti-adenovirus (human AdV serotype 5) and anti-rotavirus (simian RV SA11) activities. The evaluation of the cytotoxicity and potential antiviral activity of these extracts were performed by using MTT assay. Results were expressed as 50% cytotoxicity (CC50) and 50% effective (EC50) concentrations, respectively, in order to calculate the selectivity indices (SI=CC50/EC50) of each extract. From the 40 sponge extracts tested, 17 extracts showed antiviral action in different degrees. The results concerning the antiviral activity were obtained by using three different strategies: (1) simultaneous assay, when sponge extracts were added to the cells at the same time of the viruses; (2) pre treatment assay, when sponge extracts were added to the cells 15 h prior to the viruses infection; and (3) post treatment assay, when the viruses were added to the cells and remained during 2 h prior to the addition of sponge extracts. The antiviral assays with HSV-1/KOS and AdV-5 showed more promising results when the pre treatment test was employed. In relation to the RV-SA11 virus, only the simultaneous assay showed antiviral activity. The extracts presenting the most promising results were the aqueous extracts of Cliona sp., Agelas sp.2, Tethya sp., Axinella aff corrugata, Polymastia janeirensis and Protosuberites sp., and these extracts deserve special attention in further studies.