Potent inhibition of Epstein-Barr virus by phosphorothioate oligodeoxynucleotides without sequence specification

Toll-like receptor 9 ligand D-type oligodeoxynucleotide D35 as a broad inhibitor for influenza A virus replication that is associated with suppression of neuraminidase activity

The most effective drugs available to treat influenza are neuraminidase (NA) inhibitors, which provide important additional measures for the control of influenza virus infections. However, since the emergence of NA inhibitor-resistant viruses may compromise the clinical utility of this class of anti-influenza agents, it is very important to develop new anti-influenza agents which target a different region in NA responsible for its sensitivity from that for NA inhibitors and could be used to treat NA inhibitors-resistant isolates. The oligodeoxynucleotide D35, multimerized and aggregated, suppressed replication of influenza A viruses except A/WSN/33 (WSN). The suppressive viral replication by D35 depended on G-terad and multimer formation. The range of the suppressive viral replication at the late stage, including virus assembly and release from infected cells, was much larger than that at the initial stage, viral attachment and entry. D35 suppressed NA activity of influenza A viruses. Furthermore, replacing the NA gene of A/Puerto Rico/8/34 (PR8), in which viral replication was inhibited by D35 at the late stage, with the NA gene from WSN, in which viral replication was not inhibited, eliminated the D35-dependent suppression. D35 showed an additive anti-influenza effect with oseltamivir. It was also effective in vivo. These results suggest that the influenza virus NA mainly contributse to the D35-suppressible virus release from infected cells at the late stage. In addition, because administration of D35 into the virus-infected mice suppressed viral replication and weight loss, clinical application of D35 could be considered.

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The oligodeoxynucleotide D35 suppressed replication of some influenza A viruses.

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D35 inhibits viral replication at the late step which is dependent on NA activity.

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Antiviral mechanism by D35 is different from that by oseltamivir.

Oligonucleotides designed to inhibit TLR9 block Herpes simplex virus type 1 infection at multiple steps

Herpes simplex virus type 1 (HSV-1) is an important human pathogen which requires activation of nuclear factor-kappa B (NFκB) during its replication cycle. The persistent nature of HSV-1 infection, and the emergence of drug-resistant strains, highlights the importance of research to develop new antiviral agents. Toll-like receptors (TLRs) play a prominent role during the early antiviral response by recognizing viral nucleic acid and gene products, activating NFκB, and stimulating the production of inflammatory cytokines. We demonstrate a significant effect on HSV-1 replication in ARPE-19 and Vero cells when oligonucleotides designed to inhibit TLR9 are added 2h prior to infection. A greater than 90% reduction in the yield of infectious virus was achieved at oligonucleotide concentrations of 10-20 μM. TLR9 inhibitory oligonucleotides prevented expression of essential immediate early herpes gene products as determined by immunofluorescence microscopy and Western blotting. TLR9 oligonucleotides also interfered with viral attachment and entry. A TLR9 inhibitory oligonucleotide containing five adjacent guanosine residues (G-ODN) exhibited virucidal activity and inhibited HSV-1 replication when added post-infection. The antiviral effect of the TLR9 inhibitory oligonucleotides did not depend on the presence of TLR9 protein, suggesting a mechanism of inhibition that is not TLR9 specific. TLR9 inhibitory oligonucleotides also reduced NFκB activity in nuclear extracts. Studies using these TLR inhibitors in the context of viral infection should be interpreted with caution.

A deneddylase encoded by Epstein-Barr virus promotes viral DNA replication by regulating the activity of cullin-RING ligases

The large tegument proteins of herpesviruses encode conserved cysteine proteases of unknown function. Here we show that BPLF1, the Epstein-Barr-virus-encoded member of this protease family, is a deneddylase that regulates virus production by modulating the activity of cullin-RING ligases (CRLs). BPLF1 hydrolyses NEDD8 conjugates in vitro, acts as a deneddylase in vivo, binds to cullins and stabilizes CRL substrates. Expression of BPLF1 alone or in the context of the productive virus cycle induces accumulation of the licensing factor CDT1 and deregulates S-phase DNA synthesis. Inhibition of BPLF1 during the productive virus cycle prevents cellular DNA re-replication and inhibits virus replication. Viral DNA synthesis is restored by overexpression of CDT1. Homologues encoded by other herpesviruses share the deneddylase activity. Thus, these enzymes are likely to have a key function in the virus life cycle by inducing a replication-permissive S-phase-like cellular environment.

Real-time quantitative PCR for assessment of antiviral drug effects against Epstein-Barr virus replication and EBV late mRNA expression

This study assesses the ability of quantitative real-time PCR to measure the effects of virus DNA polymerase inhibitors on EBV DNA and late mRNAs syntheses in EBV-producing cell lines. In-house real-time quantitative PCRs were used to measure EBV DNA (thymidine kinase) and mRNAs (BLLF1 gene/gp350/220, BVRF2 gene/protease) in P3HR-1 and B95-8 cells induced for EBV production by PMA and exposed to ganciclovir, cidofovir and foscarnet. The calculated 50% effective concentrations (EC(50)) for viral DNA replication inhibition in P3HR-1 cells after 7 days of drug exposure were 0.28+/-0.06, 0.29+/-0.01 and 13.6+/-0.17 microg/mL for ganciclovir, cidofovir and foscarnet, respectively. The EC(50) for B95-8 cells were 0.44+/-0.02, 0.70+/-0.06 and 46.8+/-0.5 microg/mL, respectively. The quantitation of the late viral mRNAs showed a decrease of 79-89% in the mRNA amount after 4 days of antiviral treatment. Nevertheless, a substantial amount of mRNA still remained detectable after drug exposure. The real-time PCR is an improvement in the attempt to simplify EBV DNA-quantitation for antiviral assays. The quantitation of late mRNA does not appear as more informative than DNA quantitation for the assessment of the DNA polymerase inhibitor activity, but it may be useful to assess the antiviral activity of drugs acting by another mechanism.

Modulation of adenovirus infection in vitro by antisense oligodeoxynucleotides

OBJECTIVE

Antisense oligodeoxynucleotides (ODNs) may represent a novel, airway directed approach to the treatment of adenovirus infection of the lung, for which no specific therapy exists. This study assessed the efficacy of antisense ODNs in modulating adenovirus infection in vitro.

METHODOLOGY

A biological assay, which quantified viral plaque formation by wild type adenovirus 5 in a lung epithelial cell line (A549), was used to evaluate the inhibitory effect of a number of antisense ODNs targeted to the early (E) 1 A and protein IX genes of adenovirus 5. Antisense ODNs (20-21mers, phosphorothioate end-protected) were designed to straddle the initiation of translation (AUG) codon of the mRNA of the targeted gene.

RESULTS

There was a consistent and significant (P < 0.005) reduction in viral plaque formation in those cells treated with an E1A antisense ODN, compared with the nonsense control ODN. Neither the addition of a cationic lipid (Lipofectamine), nor increasing the concentration of ODN from 1 micro mol to 15 micro mol enhanced the original inhibitory effect observed with the E1A antisense ODN.

CONCLUSIONS

An antisense ODN targeted to the E1A gene can specifically inhibit adenovirus 5 infection in vitro, suggesting a potential therapeutic role for antisense ODNs in adenovirus infection of the lung.

Anti-Epstein-Barr virus (EBV) activity of beta-L-5-iododioxolane uracil is dependent on EBV thymidine kinase

beta-L-5-Iododioxolane uracil was shown to have potent anti-Epstein-Barr virus (EBV) activity (50% effective concentration = 0.03 microM) with low cytotoxicity (50% cytotoxic concentration = 1,000 microM). It exerts its antiviral activity by suppressing replicative EBV DNA and viral protein synthesis. This compound is phosphorylated in cells where the EBV is replicating but not in cells where the EBV is latent. EBV-specific thymidine kinase could phosphorylate beta-L-5-iododioxolane uracil to the monophosphate metabolite. The K(m) of beta-L-5-iododioxolane uracil with EBV thymidine kinase was estimated to be 5.5 microM, which is similar to that obtained with thymidine but about fivefold higher than that obtained with 2' fluoro-5-methyl-beta-L-arabinofuranosyl uracil, the first L-nucleoside analogue discovered to have anti-EBV activity. The relative V(max) is seven times higher than that of thymidine. The anti-EBV activity of beta-L-5-iododioxolane uracil and its intracellular phosphorylation could be inhibited by 5'-ethynylthymidine, a potent EBV thymidine kinase inhibitor. The present study suggests that beta-L-5-iododioxolane uracil exerts its action after phosphorylation; therefore, EBV thymidine kinase is critical for the antiviral action of this drug.

Value of long-term administration of acyclovir and similar agents for protecting against AIDS-related lymphoma: case-control and historical cohort studies

Acyclovir or similar agents with activity against Epstein-Barr virus (EBV) theoretically may prevent non-Hodgkin's lymphoma (NHL) in AIDS. A case-control study of 29 patients with AIDS-related NHL and 58 matched control subjects assessed the frequency with which daily acyclovir (>/=800 mg/d) or similar agents were used for > or =1 year. In a historical cohort of 304 patients with AIDS for > or =2 years, the prevalence of NHL was assessed among 3 groups of patients: those who received long-term treatment with high-dose acyclovir (or similar agents) or low-dose or intermittent acyclovir; those treated with ganciclovir/foscarnet for <1 year; and those who had not previously been treated with acyclovir, ganciclovir, or foscarnet. In the case-control study, 22 patients (72.4%) with NHL never received acyclovir or similar drugs versus 19 control subjects (32.8%; P=. 002); 2 patients (6.9%) with NHL received acyclovir (> or =800 mg/d) for > or =1 year versus 27 (46.6%) of control subjects (P=.0001). In the cohort study, 6 (6.8%) of 88 patients who received acyclovir (> or =800 mg/d) for > or =1 year developed NHL versus 15 (15.5%) of 97 patients who received intermittent or lower-dose acyclovir and 30 (25.2%) of 119 patients who never received these agents (P=.002). Long-term administration (>1 year) of high-dose acyclovir or similar agents with anti-EBV activity may prevent NHL in patients with AIDS. A prospective, randomized study is warranted to confirm these results.

Gene therapy for infectious diseases

Gene therapy is being investigated as an alternative treatment for a wide range of infectious diseases that are not amenable to standard clinical management. Approaches to gene therapy for infectious diseases can be divided into three broad categories: (i) gene therapies based on nucleic acid moieties, including antisense DNA or RNA, RNA decoys, and catalytic RNA moieties (ribozymes); (ii) protein approaches such as transdominant negative proteins and single-chain antibodies; and (iii) immunotherapeutic approaches involving genetic vaccines or pathogen-specific lymphocytes. It is further possible that combinations of the aforementioned approaches will be used simultaneously to inhibit multiple stages of the life cycle of the infectious agent.

Inhibition of respiratory syncytial virus replication by antisense oligodeoxyribonucleotides

Oligodeoxyribonucleotides targeted against respiratory syncytial virus (RSV) genomic RNA inhibited RSV replication in cell culture by an apparent antisense mechanism. HEp-2 cells were infected with RSV strain A2 and incubated in the presence of oligonucleotides. Virus replication was measured by enzyme-linked immunosorbent assay (ELISA), virus yield assay, or production of specific RSV mRNAs. Using ELISA, 50% effective concentration (EC50) values were about 0.5-1 microM for an antisense oligonucleotide targeted to the start of the NS2 gene. All oligonucleotides inhibited virus antigen production as measured by ELISA. In all assays, this antisense oligonucleotide was more potent than: (1) a control oligonucleotide containing the reverse sequence; (2) oligonucleotides targeted at RSV mRNA; (3) a random sequence oligonucleotide; and (4) ribavirin. Reverse transcriptase polymerase chain reaction (PT-PCR) showed sequence specific depletion of the genomic RNA target following treatment of cells with the antisense oligonucleotide. Specific cleavage of the genomic target RNA has been detected at the antisense oligonucleotide binding site, suggesting that cellular Rnase H participates in the reaction. These results indicate that antisense oligonucleotides targeted against RSV genomic RNA can effectively inhibit RSV replication and may have therapeutic value.

Antisense inhibition of virus infections

This chapter summarizes the new approaches to identify novel antiviral drug targets and to develop novel antiviral strategies. The chapter also reviews genetic pharmacology as it relates to antiviral antisense research and drug development. Antisense oligonucleotides are selective compounds by virtue of their interaction with specific segments of RNA. For potential antivirals, identification of appropriate target RNA sequences for antisense oligonucleotides is performed at two levels: the optimal gene within the virus, and the optimal sequence within the RNA. The importance of these oligonucleotide modifications in designing effective drugs is just now being evaluated, both in animal model systems and in the clinic. The first generation of widely used antisense oligonucleotides has been the phosphorothioate (PS) compounds and a body of data on biodistribution, pharmacokinetics, and metabolism in animals and in humans is now available. Since the identification and sequencing of human immunodeficiency virus (HIV), there has been a strong interest in identifying a potent oligonucleotide inhibitor that would have the potential for development as a therapy for acquired immunodeficiency syndrome (AIDS). Numerous phosphorothioate oligonucleotides, with no apparent antisense sequence specificity, can have an anti-herpes simplex virus (HSV) effect. Oligonucleotides can be effective anti-influenza agents in cell culture assays. Hepatitis B virus (HBV) X protein that is a transactivator has been also reported to be targeted successfully by antisense oligonucleotides in vivo. Several of picornaviruses have been targets for antisense oligonucleotide inhibition, and the studies demonstrate the versatility of the antisense approach. However, the fact that oligonucleotides may contribute numerous mechanisms toward the antiviral activity, in addition to the antisense mechanism, may in some cases be an asset in the pursuit of clinically useful antiviral drugs.

Inhibition of Epstein-Barr virus replication by a novel L-nucleoside, 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil

A novel L-nucleoside analog, 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU), was found to be a potent and selective inhibitor of Epstein-Barr virus (EBV) replication. The decrease in the amount of viral production was concentration dependent with a 90% inhibitory concentration of approximately 5 muM. Upon removal of the drug from treated cells, virus production resumed in 21 days. Metabolism studies indicated that L-FMAU could be converted to its mono-,di- and triphosphate metabolites in both EBV producing and non-producing cells than in EBV non-producing cells. The mechanism of selectivity of L-FMAU against EBV producing cells. However, the amount of L-FMAU nucleotides formed was three times larger in EBV producing cells than in EBV non-producing cells. The mechanism of selectivity of L-FMAU against EBV does not appear to be due solely to the preferential phosphorylation of L-FMAU in EBV producing cells. The triphosphate of L-FMAU could not be utilized as a substrate by EBV DNA polymerase or the human DNA polymerases alpha, beta, gamma, or delta. Therefore, the incorporation of L-FMAU residues into viral DNA may not be the mechanism of antiviral activity. This compound appears to have a mechanism of action different from that of any other antiherpes virus nucleoside analogs. In addition, L-FMAU has very low cytotoxicity with 50% inhibition of cell growth occurring at a concentration of 1mM. Given the potent inhibitory activity of this compound against EBV and its inability to be incorporated into cellular DNA, L-FMAU analogs should be explored as a new class of anti-EBV agents.

Antisense oligodeoxynucleotides against the BZLF1 transcript inhibit induction of productive Epstein-Barr virus replication

Expression of the Epstein-Barr virus (EBV) BZLF1 gene product, ZEBRA, in latently infected cells is sufficient to induce the viral lytic cycle. The use of oligodeoxynucleotides complementary to the BZLF1 transcript was studied to inhibit this induction of productive viral replication. For this purpose, we employed oligodeoxynucleotides complementary to the translation initiation codons and their flanking sequences. Incubation of Akata cells with the 25-mer phosphodiester (PO)- or phosphorothioate (PS)-antisense oligodeoxynucleotides for 3 h before stimulation with anti-immunoglobulin G antibodies (anti-IgG) partially inhibited the anti-IgG-mediated induction of ZEBRA synthesis. Both the PO- and PS-antisense oligodeoxynucleotide treatments also suppressed the productive EBV replication (as measured by linear DNA production) in a dose-dependent manner, with much greater efficiency than did PO and PS-oligodeoxynucleotides with sense, reverse or random sequences of the same length. Another 20-mer antisense oligodeoxynucleotide complementary to sequences downstream of the translation initiation codons showed a similar inhibitory effect on EBV replication. However, the inhibition was considerably lower when the cells were treated with oligodeoxynucleotides complementary to sequences upstream of the start codons. These results indicate that BZLF1 antisense oligodeoxynucleotides inhibit the viral activation in a sequence-specific fashion. In the virus-producer cell line P3HR-1, the same PS-antisense oligodeoxynucleotides also partially suppressed the spontaneous viral replication after 6-10 days, substantially more than the PS-random oligodeoxynucleotides. Inhibition of BZLF1 appears to be sufficient to suppress the induction of EBV replication.

Randomised trial of ganciclovir and acyclovir in the treatment of herpes simplex dendritic keratitis: a multicentre study

AIMS

This study was designed to assess the relative efficacy of topical ganciclovir 0.15% gel and acyclovir 3% ointment in the treatment of herpes simplex dendritic keratitis.

METHODS

Both treatment modalities were administered on a five times daily basis to patients suffering from herpes simplex keratitis. Patients were assigned randomly to one of the two treatment groups for the purpose of the trial. They were then examined on days 2, 7, 10, and 14 to assess the rate of healing of the dendritic ulceration.

RESULTS

There was no statistically significant difference detected in the rate of healing between the two treatment groups over the course of the trial.

CONCLUSIONS

Review of the relative efficacy of topical ganciclovir and acyclovir in the treatment of herpes simplex dendritic keratitis showed that both treatment modalities were equally effective in their ability to heal the viral induced corneal ulceration. There were no significant side effects or adverse effects reported for either treatment modality.

Use of 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil as a novel antiviral agent for hepatitis B virus and Epstein-Barr virus

A novel anti-hepatitis B virus (anti-HBV) agent, 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU), was synthesized and found to be a potent anti-HBV and anti-Epstein-Barr virus agent. Its in vitro potency was evaluated in 2.2.15 and H1 cells for anti-HBV and anti-Epstein-Barr virus activities, respectively. In vitro cytotoxicity in MT2, CEM, 2.2.15, and H1 cells was also assessed, and the results indicated high antiviral selectivities of L-FMAU in these cells.

Characterization of sublines of Epstein-Barr virus producing HR-1 cells and its implication in virus propagation in culture

To understand the mechanism regulating the EBV replication cycle, several sublines were obtained from HR-1 cells by the limiting dilution method. Based on their biochemical and molecular characteristics, these sublines can be categorized into two classes: the high EBV-DNA containing (H) subline and low EBV-DNA containing (L) subline. The amount of EBV proteins, such as EBV polymerases, EBV DNase, EAD, ZEBRA, MA, and VCA, was much higher in H sublines than in L sublines. Only 20% of cells in the H subline express those proteins. In addition to regular EBV DNA restriction enzyme fragments, additional DNA restriction enzyme fragments, as detected by different EBV DNA fragment probes, were found to be present in H sublines but not in L sublines. No BamH1 W-Z DNA fragment rearrangement, which was the primary reason for ZEBRA expression in a high EBV-DNA containing subline, Clone 5, was found in H sublines. When L sublines were treated with 12-0-tetradecanoylphorbol-13-acetate and sodium butyrate, EBV-specific proteins, including ZEBRA protein, could be induced in cells, but no virus could be detected in the medium. Thus, the lack of EBV production by L sublines is more than the simple lack of expression of ZEBRA protein. L sublines are susceptible to EBV infection and are capable of producing EBV after infection. The importance of the presence of L cells in the H subline for the propagation of EBV in culture is suggested.

Gene inhibition using antisense oligodeoxynucleotides

Antisense oligodeoxynucleotides (ODNs) have great promise as agents for the specific manipulation of gene expression. Until recently, nonspecific effects of ODNs often confounded the interpretation of antisense studies. Improvements in ODN chemistry and cellular delivery techniques now allow for more potent and specific gene inhibition. This review critically evaluates recent progress in the development of antisense ODNs.

Molecular therapeutic strategies in hepatitis B virus infection

Chronic infection with the hepatitis B virus is a major health problem worldwide. The only established therapy is interferon-alpha, with an efficacy of only 30-40% in highly selected patients. Nucleoside analogues do not show a significant clinical benefit. Molecular therapeutic strategies aimed at blocking gene expression include antisense DNA/RNA and ribozymes acting at the posttranscriptional level and triple helix formation blocking at the transcriptional level. In vitro, antisense oligodeoxynucleotides inhibit viral replication and gene expression in human hepatoma cell lines. In vivo, an antisense oligodeoxynucleotide directed against the 5'-region of the pre-S gene of the duck hepatitis B virus inhibited viral replication and gene expression in ducks. In vitro, ribozymes accurately cleave HBV substrate RNA. Triple helix formation is another very promising molecular approach. Results in hepadnaviral infection are not yet available, however.