Natural product honokiol exhibits antiviral effects against Micropterus salmoides rhabdovirus (MSRV) both in vitro and in vivo

Micropterus salmoides rhabdovirus (MSRV) is a formidable pathogen, presenting a grave menace to juvenile largemouth bass. This viral infection frequently leads to epidemic outbreaks, resulting in substantial economic losses within the aquaculture industry. Unfortunately, at present, there are no commercially available vaccines or pharmaceutical treatments to combat this threat. In order to address the urgent need for therapeutic strategy to resist MSRV infection, the antiviral activity of natural product honokiol against MSRV was explored in this study. Firstly, cellular morphology was directly observed in an inverted microscope when treated with honokiol after MSRV infection. The results clarified that honokiol significantly lessened cytopathic effect (CPE) induced by MSRV and protected the integrity of GCO cells. Furthermore, the viral nucleic acid expression (G gene) was detected by reverse transcription real-time quantitative PCR (RT-qPCR) and the results indicated that honokiol significantly decreased the viral loads of MSRV in a concentration-dependent manner, and honokiol showed a high antiviral activity with IC50 of 2.92 μM. Besides, honokiol significantly decreased the viral titre and suppressed apoptosis caused by MSRV. Mechanistically, honokiol primarily inhibited the initial replication of MSRV and discharge of progeny virus to exert anti-MSRV activity. More importantly, in vivo experiments suggested that honokiol (40 mg/kg) expressed a fine antiviral activity against MSRV when administrated with intraperitoneal injection, which led to a notable 40% improvement in the survival rate among infected largemouth bass. In addition, it also resulted in significant reduction in the viral nucleic acid expression within liver, spleen and kidney at 2, 4 and 6 days following infection. What is more, 100 mg/kg honokiol with oral administration also showed certain antiviral efficacy in MSRV-infected largemouth bass via improving the survival rate by 10.0%, and decreasing significantly the viral nucleic acid expression in liver, spleen and kidney of largemouth bass on day 2. In summary, natural product honokiol is a good candidate to resist MSRV infection and has promising application prospects in aquaculture.

Generation of Recombinant Snakehead Rhabdovirus (SHRV) Expressing Artificial MicroRNA Targeting Spring Viremia of Carp Virus (SVCV) P Gene and In Vivo Therapeutic Use Against SVCV Infection

Spring viremia of carp virus (SVCV) is a highly lethal virus in common carp (Cyprinus carpio) and other cyprinid fish species. The aim of the present study was to develop an in vivo therapeutic measure against SVCV using artificial microRNA (AmiRNA) targeting the SVCV P gene transcript. Three candidates of AmiRNAs (AmiR-P1, -P2, and -P3) were selected, and their ability to downregulate SVCV P gene transcript was analyzed by both synthesized AmiRNA mimics and AmiRNA-expressing vector system, in which AmiR-P3 showed the strongest inhibitory activity among the three candidates. To overcome in vivo limitation of miRNA mimics or plasmid-based miRNA expression systems, we rescued recombinant snakehead rhabdoviruses (SHRVs) expressing SVCV P gene-targeting AmiRNA (rSHRV-AmiR-P3) or control AmiRNA (rSHRV-AmiR-C) using reverse genetic technology. The successful expression of AmiR-P3 and AmiR-C in cells infected with the rescued viruses was verified by quantitative PCR. To evaluate the availability of rSHRV-AmiR-P3 for in vivo control of SVCV, zebrafish (Danio rerio) were (i) infected with either rSHRV-AmiR-C or rSHRV-AmiR-P3 followed by SVCV infection or (ii) infected with SVCV followed by either rSHRV-AmiR-C or rSHRV-AmiR-P3 infection. Fish infected with rSHRVs before and after SVCV infection showed significantly higher survival rates than fish infected with SVCV alone. There was no significant difference in survival rates between groups of fish infected with rSHRV-AmiR-C and rSHRV-AmiR-P3 before SVCV infection; however, fish infected with SVCV followed by infection with rSHRV-AmiR-P3 showed significantly higher survival rates than fish infected with rSHRV-AmiR-C. These results suggest that rSHRV-AmiR-P3 has therapeutic potential against SVCV in fish when administered after SVCV infection, and rSHRVs expressing artificial microRNAs targeting SVCV transcripts could be used as a tool to control SVCV infection in fish for a therapeutic purpose.

mAb therapy controls CNS-resident lyssavirus infection via a CD4 T cell-dependent mechanism

Infections with rabies virus (RABV) and related lyssaviruses are uniformly fatal once virus accesses the central nervous system (CNS) and causes disease signs. Current immunotherapies are thus focused on the early, pre-symptomatic stage of disease, with the goal of peripheral neutralization of virus to prevent CNS infection. Here, we evaluated the therapeutic efficacy of F11, an anti-lyssavirus human monoclonal antibody (mAb), on established lyssavirus infections. We show that a single dose of F11 limits viral load in the brain and reverses disease signs following infection with a lethal dose of lyssavirus, even when administered after initiation of robust virus replication in the CNS. Importantly, we found that F11-dependent neutralization is not sufficient to protect animals from mortality, and a CD4 T cell-dependent adaptive immune response is required for successful control of infection. F11 significantly changes the spectrum of leukocyte populations in the brain, and the FcRγ-binding function of F11 contributes to therapeutic efficacy. Thus, mAb therapy can drive potent neutralization-independent T cell-mediated effects, even against an established CNS infection by a lethal neurotropic virus.

How modular protein nanoparticles may expand the ability of subunit anti-viral vaccines: The spring viremia carp virus (SVCV) case

Spring viremia of carp (SVC) remains as a vaccine orphan disease mostly affecting juvenile specimens. Young fish are especially difficult to vaccinate and oral administration of vaccine combined with food would be the election system to minimise stress and the vaccination costs associated to injection. However, administration of prophylactics with food pellets faces off several drawbacks mainly related with vaccine degradation and weak protection correlates of oral vaccines. Here we present a platform based on recombinant proteins (subunit vaccines) manufactured as highly resistant nanostructured materials, and providing excellent levels of protection against SVC virus in a preliminary i.p injection challenge. The G3 domain of SVCV glycoprotein G was overexpressed in E. coli together with IFNγ and the modular protein was purified from bacterial aggregates (inclusion bodies) as highly organised nanostructured biomaterial (nanopellets, NP). These SVCV-IFN^NP were taken up by zebrafish cells leading to the enhanced expression of different antiviral and IFN markers (e.g vig1, mx, lmp2 or ifngr1 among others) in zebrafish liver cells (ZFL). To monitor if SVCV^NP and SVCV-IFN^NP can be taken up by intestinal epithelia and can induce antiviral response we performed experiments with SVCV^NP and SVCV-IFN^NP in 3 days post fertilization (dpf) zebrafish larvae. Both, SVCV^NP and SVCV-IFN^NP were taken up and accumulated in the intestine without signs of toxicity. The antiviral response in larvae showed a different induction pattern: SVCV-IFN^NP did not induce an antiviral response while SVCV^NP showed a good antiviral induction. Interestingly ZF4, an embryonic derived cell line, showed an antiviral response like ZFL cells, although the lmp2 and ifngr1 (markers of the IFNγ response) were not overexpressed. Experiments with adult zebrafish indicated an excellent level of protection against a SVCV model infection where SVCV-IFN^NP vaccinated fish reached 20% cumulative mortality while control fish reached over 80% cumulative mortality.

Antiviral effects of natural small molecules on aquatic rhabdovirus by interfering with early viral replication

Spring viremia of carp virus (SVCV) is globally widespread and poses a serious threat to aquatic ecology and aquaculture due to its broad host range. To develop effective agents to control SVCV infection, we selected 16 naturally active small molecules to assess their anti-SVCV activity. Notably, dihydroartemisinin (DHA) (100 µmol/L) and (S, S)-(+)-tetrandrine (TET) (16 µmol/L) exhibited high antiviral effects in epithelioma papulosum cyprinid (EPC) cells, with inhibitory rates of 70.11% and 73.54%, respectively. The possible antiviral mechanisms were determined as follows: 1. Pre-incubation with DHA and TET decreased viral particle infectivity in fish cells, suggesting that horizontal transmission of SVCV in the aquatic environment was disrupted; 2. Although neither had an effect on viral adhesion, TET (but not DHA) interfered with SVCV entry into host cells (>80%), suggesting that TET may have an antiviral function in early viral replication. For in vivo study, both agents enhanced the survival rate of SVCV-infected zebrafish by 53.3%, significantly decreased viral load, and modulated the expression of antiviral-related genes, indicating that DHA and TET may stimulate the host innate immune response to prevent viral infection. Overall, our findings indicated that DHA and TET had positive effects on suppressing SVCV infection by affecting early-stage viral replication, thus holding great potential as immunostimulants to reduce the risk of aquatic rhabdovirus disease outbreaks.

Nano-bubble hydrogen water: an effective therapeutic agent against inflammation related disease caused by viral infection in zebrafish model

Since the anti-inflammatory effect of hydrogen has been widely known, it was supposed that hydrogen could suppress tissue damage by inhibiting virus-related inflammatory reactions. However, hydrogen is slightly soluble in water, which leads to poor effect of oral hydrogen-rich water therapy. In this study, the nano-bubble hydrogen water (nano-HW) (about 0.7 ​ppm) was prepared and its therapeutic effect against viral infection was investigated by utilizing spring viraemia of carp virus (SVCV)-infected zebrafish as model. Three-month-old zebrafish were divided into nano-HW treatment–treated group and aquaculture water treated group (control group). The results revealed that the cumulative mortality rate of SVCV-infected zebrafish was reduced by 40% after treatment with nano-bubble hydrogen water, and qRT-PCR results showed that SVCV replication was significantly inhibited. Histopathological examination staining showed that SVCV infection caused tissue damage was greatly alleviated after treatment with nano-bubble hydrogen water. Futhermore, SVCV infection caused reactive oxygen species (ROS) accumulation was significantly reduced upon nano-HW treatment. The level of proinflammatory cytokines IL-1β, IL-8, and TNF-α was remarkably reduced in the nano-HW-treated group in vivo and in vitro. Taken together, our data demonstrated for the first time that nano-HW could inhibit the inflammatory response caused by viral infection in zebrafish, which suggests that nano-HW can be applied to antiviral research，and provides a novel therapeutic strategy for virus-caused inflammation related disease.

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Nano-HW treatment reduces the mortality of SVCV-infected zebrafish.

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Nano-HW alleviates the inflammatory response caused by SVCV infection.

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Nano-HW inhibits SVCV replication.

Red elemental selenium (Se0 ) improves the immunoactivities of EPC cells, crucian carp and zebrafish against spring viraemia of carp virus

Selenium, as an essential trace element, interferes through selenoproteins in many physiological processes of plants and mammals. Its antiviral activity has recently attracted much attention because selenium improves the antiviral capacity of animal cells against a few viruses relevant to human diseases. In this study, the red elemental selenium was purified from the fermentative culture of Herbaspirillum camelliae WT00C and then used to culture epithelioma papulosum cyprinid (EPC) cells or feed crucian carp and zebrafish. Finally, its antiviral effects were investigated at the cell level and living fishes after spring viraemia of carp virus infection. At the cell level, 5, 10 and 20 μg ml^-1 red elemental selenium significantly induced the expression of interferon (IFN) and ISG15 genes in EPC cells. The viral TCID₅₀ (50% tissue culture infective dose) values in the EPC cells incubated with 5, 10 and 20 μg ml^-1 red elemental selenium were significantly less than those of the control. More expression of IFN and ISG15 genes and less TCID₅₀ values indicate that red elemental selenium indeed improves the antiviral capability of EPC cells. In the crucian carp fed with the food containing 5 and 10 μg g^-1 red elemental selenium, IFN expressions showed 13- and 39-fold increases at the 16th day of post-injection, and its expression was dependent on selenium concentrations. Meanwhile, no fish death occurred in all the experimental groups. In the zebrafish fed with the red worm containing 5 μg g^-1 red elemental selenium, IFN and Mx expressions and survival rate were significantly higher than those of the control. The results of this study show that red elemental selenium indeed improves the antiviral activity of fish. The antiviral effects of selenium mainly come from its immune regulation through its incorporation into selenoproteins. The optimum level of selenium contributes to improving fish immunity, whereas excess selenium causes excessive immune and inflammatory responses.

Virucidal effects of various agents-including protease-against koi herpesvirus and viral haemorrhagic septicaemia virus

In a search for alternative, environmentally friendly and effective disinfecting agents, a commercially available protease-Neutrase^® -was tested in this work for inactivation of koi herpesvirus (KHV) and of viral haemorrhagic septicaemia virus (VHSV). For comparison, the stability of these viral pathogens in similar configurations at various pH values and concentrations of peracetic acid or quicklime, typically used for disinfection, was tested. Therefore, virus suspensions were incubated with various concentrations of different agents for 24 hr and the titre of the remaining infectious particles was determined by virus titration. Furthermore, the treatment of both viruses, with the agents at concentrations that were previously appointed as effective, was also examined in the presence of solid material (quartz sand). All procedures investigated in this study, including the protease treatment, were able to reduce the titre of KHV and VHSV below the detection limit of the titration. Although further studies are necessary, this is the first report of the application of a protease for the inactivation of the selected fish pathogens, demonstrating the great potential of the latter for disinfection.

Ursolic acid from Prunella vulgaris L. efficiently inhibits IHNV infection in vitro and in vivo

Infectious hematopoietic necrosis virus (IHNV) is a fish viral pathogen that causes severe disease and huge economic losses in the salmonid aquaculture industry. However, anti-IHNV drugs currently are scarce. For the purpose of seeking out anti-IHNV drugs, the anti-IHNV activities of 32 medicinal plants were investigated by using epithelioma papulosum cyprini (EPC) cells. Among these plants, Prunella vulgaris L. (PVL) showed the strongest inhibition on IHNV replication with an inhibitory percentage of 99.3% at the concentration 100 mg/L. Further studies demonstrated that ursolic acid (UA), a major constituent of PVL, also showed a highly effective anti-IHNV activity. The half-maximal inhibitory concentration (IC50) at 72 h of UA on IHNV was 8.0 μM. Besides, UA could significantly decrease cytopathic effect (CPE) and the viral titer induced by IHNV in EPC cells. More importantly, UA also showed a strong anti-IHNV activity in vivo, as indicated by increasing the survival rate of rainbow trout and inhibiting viral gene expression. Intraperitoneal injection of UA increased the relative percentage of survival of rainbow trout by 18.9% and inhibited IHNV glycoprotein mRNA expression by > 90.0% in the spleen at the 1st-day post-infection. Altogether, UA was expected to be a therapeutic agent against IHNV infection in aquaculture.

Antivirals for human use against rabies and prospects for their future application

Rabies is probably the deadliest and most severe encephalitis known to humankind. Caused by any lyssavirus, it is recognised as a disease of the poor, the less fortunate and the young. No other known infectious disease can cause 100% mortality, and rabies and the clinical manifestations which precede a death from the disease are often described as excruciating. Animals are not spared this deadly illness either, essentially every mammal can be infected with the virus, resulting in the development of lethal encephalitis. However, rabies is also one of the few infectious diseases that can be prevented through vaccination. Yet, its mortality figures are on the increase. Only a small number of patients have been reported to have survived rabies once infection has been established; a survival based on pre-/post-exposure prophylaxis, natural induction following infection or experimentation and the intuition of attending physicians, while available antivirals have previously been used without success. Therefore, the need for novel and innovative interventions is urgent. In this paper, the authors summarise past failures in treating the disease and highlight future hopes in the field of rabies treatment.

Antiviral effect of 7-(4-benzimidazole-butoxy)-coumarin on rhabdoviral clearance via Nrf2 activation regulated by PKCα/β phosphorylation

Coumarin forms an elite class of naturally occurring compounds that possess promising antiviral therapeutic perspectives. In the previous study, we designed and synthesized a coumarin derivative, 7-(4-benzimidazole-butoxy)-coumarin (BBC), to evaluate its antiviral activity on spring viraemia of carp virus (SVCV). In this study, our results show that BBC does not affect viral adhesion and delivery from endosomes to the cytosol, indicating BBC has no inhibitory activity in the early stage of viral infection. Further data are determined that BBC significantly declines SVCV-infected apoptosis and recovers caspase-3/8/9 activity. To reveal the pathway that affects Nrf2 translocation by BBC, we examine changes in protein kinase C (PKC) in EPC cells treated with BBC. We observe that BBC results in a higher phosphorylation of PKCα/β that is involved in the activation of erythroid 2-related factor 2 (Nrf2) phosphorylation to favor Nrf2 translocation to nucleus at 24 and 48 h. In addition, the results show that BBC also up-regulates both antiviral responses, heme oxygenase-1 (HO-1) expression and cellular IFN response. Overall, this mechanism of action provides a new therapeutic target for the treatment of SVCV infection, and these results suggest that treatment with BBC is effective in reducing SVCV infection and differently regulates SVCV-induced undesirable conditions.

β-glucan administration induces metabolic changes and differential survival rates after bacterial or viral infection in turbot (Scophthalmus maximus)

The innate immune response is able to ward off pathogens and remember previous infections using different mechanisms; this kind of immune reaction has been called "trained immunity". Changes in cellular metabolism (aerobic glycolysis) have been observed during training with some immunostimulants like β-glucans or during viral and bacterial infections. We hypothesize that β-glucans can induce metabolic changes used by the host to fight pathogens. Accordingly, we evaluated changes in metabolic parameters in turbot that could affect their survival after a previous intraperitoneal treatment with β-glucans and subsequent administration of Viral Hemorrhagic Septicemia Virus (VHSV) or bacteria (Aeromonas salmonicida subsp. salmonicida). The results obtained support that β-glucans, VHSV and A. salmonicida induce changes in lactate, glucose and ATP levels in plasma, head kidney and liver and in the mRNA expression of enzymes related to glucose and fatty acid metabolism in head kidney. Additionally, the metabolic changes induced by β-glucans are beneficial for VHSV replication, but they are harmful to A. salmonicida, resulting in reduced mortality. β-glucans appear to have great therapeutic potential and can induce trained immunity against bacterial disease but not against viral disease, which seems to take advantage of β-glucan metabolic alterations.

Synthesis and antiviral activity of a new coumarin derivative against spring viraemia of carp virus

Coumarin as a lead structure have received a considerable attention in the last three decades for the discovery of antiviral agents. Our previous study indicated that imidazole coumarins possessed antiviral activities against SVCV. Based on the structure-activity relationship in that study, a new imidazole coumarin derivative, 7-(4-benzimidazole-butoxy)-coumarin (BBC), was designed, synthesized and its anti-SVCV activity was evaluated. By comparing inhibitory concentration at half-maximal activity (IC₅₀), we found that BBC (IC₅₀ = 0.56 mg/L) possessed a higher antiviral activity than those imidazole coumarins in our previous study. Besides, BBC can significantly inhibit cell death and reduce cellular morphological damage induced by SVCV. Our further data indicated that intraperitoneal injection of BBC increased the survival rate of zebrafish by 17.5%, decreased viral titer in fish body and inhibited SVCV glycoprotein expression in kidney and spleen. In uninfected zebrafish, the expression levels of ifnγ, ifnφ1, ifnφ2 and rig1 genes were up-regulated after BBC treatment, which indicated that BBC could activate interferon response. In addition, data of the antioxidant enzymes activities and results of the antioxidant enzymes-related genes expressions suggested BBC could reduce SVCV-induced oxidative damage in infected zebrafish. Altogether, BBC is expected to be a therapeutic agent against SVCV infection in the field of aquaculture.

A new coumarin derivative plays a role in rhabdoviral clearance by interfering glycoprotein function during the early stage of viral infection

Coumarin forms an elite class of naturally occurring compounds that possess promising antiviral therapeutic perspectives. In this study, a coumarin derivative 7-[6-(2-methylimidazole) hexyloxy] coumarin (D5) was designed and synthesized to evaluate antiviral activity on a rhabdovirus, spring viraemia of carp virus (SVCV). Our results demonstrated that D5 had a robust antiviral activity with >90% inhibitory rate of SVCV expression in the host cells. And D5 significantly reduced viral-induced apoptosis and recovered virus-activated caspase-3/8/9 activities. Further data determined that SVCV could alter the cytoskeletal structure of EPC cells, characterized by a circumferential ring of microtubules and a disrupted microfilament organization, whereas cytoskeleton structure in D5-treated cells kept the normal morphology. Mechanistically speaking, D5 could interfere with SVCV replication inside or outside of cells through two different approaches. Before the process of virus entry into EPC cells, D5 had an impact on SVCV glycoprotein structure so as to disrupt viral binding to the cell surface or translocation to the cytosol. Another strategy for D5 to against SVCV was that D5 significantly suppressed SVCV-activated autophagy, which was beneficial for the host cells to restrict SVCV viral replication, accompanied by a higher phosphorylation of Akt-mTOR. In summary, our results revealed that D5 was effective in weakening SVCV infection and regulating SVCV-induced undesirable conditions, and this compound provided new therapeutic implications for the treatment of rhabdoviruses.

Nitrosporeusine analogue ameliorates Chandipura virus induced inflammatory response in CNS via NFκb inactivation in microglia

Chandipura Virus (CHPV), a negative-stranded RNA virus belonging to the Rhabdoviridae family, has been previously reported to bring neuronal apoptosis by activating several factors leading to neurodegeneration. Following virus infection of the central nervous system, microglia, the ontogenetic and functional equivalents of macrophages in somatic tissues gets activated and starts secreting chemokines, thereby recruiting peripheral leukocytes into the brain parenchyma. In the present study, we have systemically examined the effect of CHPV on microglia and the activation of cellular signalling pathways leading to chemokine expression upon CHPV infection. Protein and mRNA expression profiles of chemokine genes revealed that CHPV infection strongly induces the expression of CXC chemokine ligand 10 (CXCL10) and CC chemokine ligand 5 (CCL5) in microglia. CHPV infection triggered the activation of signalling pathways mediated by mitogen-activated protein kinases, including p38, JNK 1 and 2, and nuclear factor κB (NF-kappaB). CHPV-induced expression of CXCL10 and CCL5 was achieved by the activation of p38 and NF-kappaB pathways. Considering the important role of inflammation in neurodegeneration, we have targeted NF-kappaB using a newly synthesised natural product nitrosporeusine analogue and showed incapability of microglial supernatant of inducing apoptosis in neurons after treatment.

Z-FA-FMK demonstrates differential inhibition of aquatic orthoreovirus (PRV), aquareovirus (CSRV), and rhabdovirus (IHNV) replication

Benzyloxycarbonyl-phenylalanyl-alanyl-fluoromethyl ketone (Z-FA-FMK) is a protease inhibitor that has been shown to strongly inhibit mammalian orthoreovirus replication. Here we explore the ability of Z-FA-FMK to inhibit three important yet genetically discrete aquatic fish viruses: chum salmon aquareovirus (CSRV), piscine orthoreovirus (PRV), and the rhabdovirus infectious hematopoietic necrosis virus (IHNV). Z-FA-FMK significantly attenuated CSRV in vitro transcription and infectious yield following low-dose (2-20μM) exposure, yet a relatively high dose (200μM) was required to completely block CSRV replication. For PRV and IHNV, no significant attenuation of in vitro viral transcription was observed following low-dose (2-20μM) exposure; and although high dose (200μM) exposure significantly attenuated both PRV and IHNV transcription, neither was completely inhibited. These transcriptional results were similarly reflected in IHNV infectious titre observed at 7days post exposure. PRV titre is currently undeterminable in vitro; however, in vivo intra-peritoneal injection of PRV into juvenile Atlantic salmon (Salmo salar) in conjunction with 1.5mg/kg Z-FA-FMK did not affect PRV replication as measured by blood associated viral transcripts at 14days post challenge. These results indicate that aquatic ortho- and aqua-reoviruses appear to possess resilience to Z-FA-FMK relative to mammalian orthoreoviruses and suggest that environmental parameters or alternative mechanisms for viral replication may affect the efficacy of Z-FA-FMK as an antireoviral compound. Further, as Z-FA-FMK has been shown to irreversibly inhibit cysteine proteases such as cathepsins B and L in vitro at concentrations of ≤100μM, continued replication of IHNV (and possibly PRV) at 200μM Z-FA-FMK suggests that replication of these viruses can occur in a cathepsin-independent manner whereas CSRV likely requires cathepsins or similar cysteine proteases for successful replication.

Virus inhibition induced by polyvalent nanoparticles of different sizes

The development of antiviral agents is one of the major challenges in medical science. So far, small monovalent molecular drugs that inhibit the late steps in the viral replication cycle, i.e., virus budding, have not worked well which emphasizes the need for alternative approaches. Polyvalently presented viral receptors, however, show potential as good inhibitors of virus-cell binding, which is the first step in the viral infection cycle. By gradually increasing the size of ligand functionalized gold nanoparticles, up to virus-like dimensions, we are now able to quantify the polyvalent enhancement of virus-cell binding inhibition and to identify varying mechanisms of virus inhibition with different efficacies: by employing a new binding assay we found that surface area-normalized polysulfated gold nanoparticles of diameters equal to and larger than the virus diameter (>50 nm) more efficiently inhibit the binding of vesicular stomatitis virus (VSV) to cells than smaller particles. On a per particle basis, larger sized gold nanoparticles were surprisingly shown to inhibit the viral infection up to two orders of magnitude more efficiently than smaller particles, which suggests different mechanisms of virus inhibition. Based on complementary electron microscopic data, we noticed that larger gold nanoparticles act as efficient cross-linkers between virions, whereas smaller gold nanoparticles decorate the surface of individual virus particles. Our systematic study accentuates the need for the design of biodegradable, virus-sized inhibitors capitalizing on polyvalent binding.

[Antiviral activity of 2,3-secotriterpenic hydrazones of lupane and 19beta,28-epoxy-18alpha-oleanane type]

Novel hydrazones of lupane and 19beta,28-epoxy-18alpha-oleanane type have been synthesized via interaction of 2,3-secotriterpenic aldehydonitriles with substituted hydrazines. As a result of investigation of 2,3-secotriterpenic hydrazones antiviral activity to the strain "Indiana" of vesicular stomatitis virus on two models of mammal's line cell infection, acetylhydrazone 1-cyano-2,3-seco-19beta,28-epoxy-18alpha-olean-3-al has been found to have a high prophylactic activity 0.00016 microg/ml to vesicular stomatitis virus and to inhibit a virus reproduction in primarily infected cells in 0.21 microg/ml concentration.

Cloning and characterization of a novel feline IFN-omega

The interferons (IFNs) are a large family of multifunctional secreted protein involved in antiviral defense, cell growth regulation, and immune activation. The human IFNs are used worldwide as antiviral drugs. Here, we present cDNAs encoding 13 novel feline IFN-omega (FeIFN-omega) subtypes that share 95%-99% amino acid sequence identity. FeIFN-omega2 and FeIFN-omega4 have seven additional amino acids at position 109 that are not present in other subtypes. Sequence identity of the present FeIFN proteins encoded by the 13 subtypes is approximately 57% compared with human IFN-omega (HuIFN-omega). All 13 FeIFN-omega subtypes were expressed in Escherichia coli using a periplasmic expression system. The antiviral activity of each product was evaluated in vitro. In addition, subtype FeIFN-omega2 was cytoplasm expressed in E. coli and secretion expressed in Pichia pastoris. The purified mature recombinant protein demonstrated significant antiviral activity on both homologous and heterologous animal cells in vitro.

VSV replication in neurons is inhibited by type I IFN at multiple stages of infection

Vesicular stomatitis virus (VSV) is a rhabdovirus which causes acute encephalitis in mice after intranasal infection. Because type I interferon (IFN) has been shown to be a potent inhibitor of VSV, we investigated the role of type I IFN in viral replication in neurons in culture. Pre-treatment of NB41A3 neuroblastoma cells or primary neuron cultures with IFN-beta or IFN-alpha strongly inhibits virus replication, with 1000-fold inhibition of infectious virus release occurring at 7 h post-infection, and maximum inhibition of 14,000-fold occurring at 14 h. Type I IFN inhibited both viral protein and RNA synthesis, but not enough to account for the inhibition of infectious virus yield. The influenza virus protein NS1 binds dsRNA and antagonizes induction of PKR activity, an IFN-inducible antiviral protein which phosphorylates and inactivates the elongation factor eIF-2alpha, resulting in cessation of translation. In NS1-expressing neuroblastoma cells, VSV replication was inhibited by IFN-beta as well as in control NB41A3 cells, and eIF-2alpha phosphorylation was blocked, suggesting that PKR activity was not involved in inhibition of viral protein synthesis. Similarly, inhibition of VSV by IFN-beta was not affected by addition of inhibitors of nitric oxide synthase, indicating that IFN-beta activity is not mediated by nitric oxide or superoxide. This contrasts with the essential role of NOS-1 in inhibition of VSV replication when neurons are treated with IFN-gamma. Analysis of cell culture supernatants revealed suppression of release of VSV particles from both NB41A3 cells and primary neurons treated with IFN. The inhibition of virion release closely matched the overall suppression of infectious VSV particle release, suggesting that type I IFN plays a role in inhibition of VSV assembly.

Influence of methisoprinol on the replication of rhabdoviruses isolated from carp (Cyprinus carpio) and catfish (Ictalurus melas): in vitro study

Rhabdoviruses constitute one of the most pathogenic viruses isolated from rainbow trout and carp culture. Several viruses were also isolated from other species of fish. These viruses are mostly associated with epizootics and heavy losses. Spring viraemia of carp virus (SVCV) and pike fry rhabdovirus (PFRV) have been the most extensively studied, due to their significant economic impact. Significant progress has been made towards controlling the major bacterial fish diseases using vaccines, but this approach has not yet been successful in preventing viral diseases in fish culture. However, for an effective therapeutic approach, specific drugs should be developed to selectively inhibit virus replication and/or stimulate antiviral protection. In this investigation we examined the in vitro influence of methisoprinol on the SVCV and virus isolated from catfish (Ictalurus melas) replication by measuring their RNA synthesis. The viruses were propagated in EPC cells and cell cultures containing methisoprinol were followed by infection with SVCV or catfish rhabdovirus suspension containing 10(7) TCID50/ml. Methisoprinol (Polfa, Poland) at concentrations of 0, 100, 200, 300, 400 and 500 microg/ml of medium (Glasgow MEM) was used in this study. The results of this study show the strong inhibition of incorporation (cpm) of [3H]-uridine into SVCV and catfish rhabdovirus RNA in cell culture exposed to methisoprinol at various concentrations. The highest percent of inhibition of viral RNA at 72 h after infection with two rhabdoviruses were observed in doses of 400 and 500 microg/ml of methisoprinol in medium. The results of this in vitro study showed that methisoprinol inhibits the rhabdoviruses isolated from carp and catfish.

Selective inhibition of COX-2 is beneficial to mice infected intranasally with VSV

Cyclooxygenase (COX) is the key enzyme for prostaglandin (PG) synthesis. PGs are mediators of many critical physiological and inflammatory responses. There are two isoforms, COX-1 and COX-2, both of which are constitutively expressed in the central nervous system (CNS). Studies have shown that COX-1 and COX-2 are involved in physiological and pathological conditions of the brain. However, little is known about the role(s) of COX in the host defense system against a viral infection in the CNS. In this report, we used Vesicular Stomatitis Virus (VSV) induced acute encephalitis to distinguish between the contribution(s) of the two isoforms. COX-2 activity was inhibited with a COX-2 selective drug, celecoxib (Celebrex), and COX-1 was antagonized with SC560. We found that inhibition of COX-2 led to decreased viral titers, while COX-1 antagonism did not have the same effect at day 1 post infection. 5-lipooxygenase (5-LO) expression and neutrophil recruitment in the CNS were increased in celecoxib-inhibited mice. Furthermore, mice treated with celecoxib expressed more Nitric Oxide Synthase-1 (NOS-1), a crucial component of the innate immune system in the restriction of VSV propagation. The expression of type 1 cytokines, IFN-gamma and IL-12, were also increased in celecoxib-treated mice.

The role of interleukin-18 in vesicular stomatitis virus infection of the CNS

Intranasal application of vesicular stomatitis virus (VSV) results in the initial infection of the olfactory receptor neurons and a rapid progression of the virus through the mouse central nervous system (CNS). Interleukin-18 (IL-18) is an 18.3-kd cytokine that induces interferon gamma (IFN-gamma) production in mice. IL-18 is synthesized as an inactive precursor that is cleaved and activated by caspase-1/interleukin-1beta converting enzyme (ICE). IL-18 shares several biological properties with IL-12, including the ability to induce IFN-gamma production in T lymphocytes and natural killer (NK) cells. In the CNS, microglia and astrocytes produce IL-18 and IL-12. We have previously shown that IL-12 promotes recovery from VSV encephalitis. This led us to examine the potential role of IL-18 in the pathogenesis of VSV encephalitis. We show that both IL-18 and caspase-1 mRNA are consistently present in the CNS of mice. The addition of exogenous IL-18 to cell cultures does not affect the production of VSV, and addition of exogenous IL-18 at the time of infection does not alter the morbidity or mortality of BALB/c mice. In vitro studies with neutralizing monoclonal antibody to IL-18 had no effect. From these results we conclude that in this system and under the experimental conditions used, unlike IL-12 and IFN-gamma, IL-18 does not play a significant role in the host response to VSV infection.

Neuronal expression of NOS-1 is required for host recovery from viral encephalitis

The role of nitric oxide synthase (NOS) in host defense and clearance of vesicular stomatitis virus (VSV) from the central nervous system (CNS) was examined. NOS-1, NOS-2, and NOS-3 knockout mice were infected with VSV and were treated with either IL-12 or medium. IL-12 treatment resulted in substantially decreased VSV titers in wildtype and NOS-3 knockout mice, but had a marginal effect in the NOS-1 and NOS-2 knockout mice. NOS-1 expression in neurons was associated with survival from VSV infection. The data indicate that the enzyme activity is local, since NOS-2 expression in microglia and inflammatory macrophages and NOS-3 expression in astrocytes, endothelial cells, and ependymal cells did not compensate.

Interleukin-12 promotes recovery from viral encephalitis

Infusion of interleukin-12 (IL-12) enhances recovery from lethal experimental vesicular stomatitis virus (VSV) infection of the central nervous system (CNS). Interleukin-12 treatment resulted in: 1) increased survival frequency; 2) faster recovery from weight loss; 3) substantially decreased VSV titers in brain homogenates and diminished immunohistochemical detection of VSV antigens in tissue sections; 4) earlier and increased CNS expression of types 1, 2, and 3 nitric oxide synthase (NOS) and both major histocompatibility complex (MHC) class I and class II antigens; 5) earlier and increased blood and CNS levels of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). These results suggest that IL-12 enhances recovery from VSV infection of the CNS.

Partial inhibition of vesicular stomatitis virus by the interferon-induced human 9-27 protein

To determine whether the interferon-induced 9-27 protein of human cells contributes to the antiviral state, we expressed the 9-27 cDNA under the control of a constitutive promoter and assayed transfected cells for enhanced virus resistance. The intracellular distribution of 9-27 resembled that of cytoskeleton-associated proteins. Analysis at the single-cell level by indirect immunofluorescence revealed that mouse cells expressing 9-27 were less permissive for vesicular stomatitis virus than control cells not expressing 9-27. No significant inhibition of influenza virus was observed. When tested in parallel, 9-27 was found to have less powerful antiviral activity toward vesicular stomatitis virus than the interferon-induced MxA protein. Thus, 9-27 joins the family of interferon-induced proteins with intrinsic antiviral activity.

Modulation of alpha-interferon's antiviral and clinical effects by aspirin, acetaminophen, and prednisone in healthy volunteers

The magnitude and duration of the antiviral and clinical effect of alpha-interferon was measured in healthy volunteers. A single 3 million unit intramuscular dose of interferon was given either alone (controls) or after 72 h of concomitant medications. These medications included either aspirin (650 mg every 4 h), acetaminophen (650 mg every 4 h), or prednisone (40 mg per day). Peripheral blood mononuclear cells were assayed for resistance to vesicular stomatitis virus infection and induction of 2'-5'-oligoadenylate synthetase activity as evidence of interferon's antiviral effect. Co-administration of acetaminophen increased both antiviral parameters by more than 70% (P < 0.05) and reduced symptoms after interferon dosing, compared to controls. Aspirin and prednisone did not demonstrate any significant differences from controls in antiviral effect. As a group, acetaminophen, aspirin, and prednisone reduced the clinical symptoms by 47% compared to controls (P = 0.03) after interferon dosing, although individual drug comparisons failed to reach statistical significance. Independent of treatment group, the changes in antiviral markers after interferon dosing correlated closely with each other (r = 0.72, P < 0.001), but neither correlated with symptoms or fever (r < 0.30, P > 0.05). Acetaminophen enhances the antiviral effects of a single intramuscular dose of alpha-interferon, considering the parameters measured in these healthy volunteers.