anti-EBV Activity Research Articles

Ocrelizumab Alters Cytotoxic Lymphocyte Function While Reducing EBV-Specific CD8+ T-Cell Proliferation in Patients With Multiple Sclerosis.

The role of B cells in the pathogenic events leading to relapsing multiple sclerosis (R-MS) has only been recently elucidated. A pivotal step in defining this role has been provided by therapeutic efficacy of anti-CD20 monoclonal antibodies. Indeed, treatment with anti-CD20 can also alter number and function of other immune cells not directly expressing CD20 on their cell surface, whose activities can contribute to unknown aspects influencing therapeutic efficacy. We examined the phenotype and function of cytotoxic lymphocytes and Epstein-Barr virus (EBV)-specific immune responses in people with R-MS before and after ocrelizumab treatment. In this prospective study, we collected blood samples from people with R-MS (n = 41) before and 6 and 12 months after initiating ocrelizumab to assess the immune phenotype and the indirect impact on cytotoxic functions of CD8+ T and NK cells. In addition, we evaluated the specific anti-EBV proliferative responses of both CD8+ T and NK lymphocytes as surrogate markers of anti-EBV activity. We observed that while ocrelizumab depleted circulating B cells, it also reduced the expression of activation and migratory markers on both CD8+ T and NK cells as well as their in vitro cytotoxic activity. A comparable pattern in the modulation of immune molecules by ocrelizumab was observed in cytotoxic cells even when patients with R-MS were divided into groups based on their prior disease-modifying treatment. These effects were accompanied by a significant and selective reduction of CD8+ T-cell proliferation in response to EBV antigenic peptides. Taken together, our findings suggest that ocrelizumab-while depleting B cells-affects the cytotoxic function of CD8+ and NK cells, whose reduced cross-activity against myelin antigens might also contribute to its therapeutic efficacy during MS.

SUMOylation of the m6A reader YTHDF2 by PIAS1 promotes viral RNA decay to restrict EBV replication.

YTH N6-methyladenosine RNA-binding protein F2 (YTHDF2) is a member of the YTH protein family that binds to N6-methyladenosine (m6A)-modified RNA, regulating RNA stability and restricting viral replication, including Epstein-Barr virus (EBV). PIAS1 is an E3 small ubiquitin-like modifier (SUMO) ligase known as an EBV restriction factor, but its role in YTHDF2 SUMOylation remains unclear. In this study, we investigated the functional regulation of YTHDF2 by PIAS1. We found that PIAS1 promotes the SUMOylation of YTHDF2 at three specific lysine residues (K281, K571, and K572). Importantly, PIAS1 synergizes with wild-type YTHDF2, but not a SUMOylation-deficient mutant, to limit EBV lytic replication. Mechanistically, YTHDF2 lacking SUMOylation exhibits reduced binding to EBV transcripts, leading to increased viral mRNA stability. Furthermore, PIAS1 mediates SUMOylation of YTHDF2's paralogs, YTHDF1 and YTHDF3, to restrict EBV replication. These results collectively uncover a unique mechanism whereby YTHDF family proteins control EBV replication through PIAS1-mediated SUMOylation, highlighting the significance of SUMOylation in regulating viral mRNA stability and EBV replication.IMPORTANCEm6A RNA modification pathway plays important roles in diverse cellular processes and viral life cycle. Here, we investigated the relationship between PIAS1 and the m6A reader protein YTHDF2, which is involved in regulating RNA stability by binding to m6A-modified RNA. We found that both the N-terminal and C-terminal regions of YTHDF2 interact with PIAS1. We showed that PIAS1 promotes the SUMOylation of YTHDF2 at three specific lysine residues. We also demonstrated that PIAS1 enhances the anti-EBV activity of YTHDF2. We further revealed that PIAS1 mediates the SUMOylation of other YTHDF family members, namely, YTHDF1 and YTHDF3, to limit EBV replication. These findings together illuminate an important regulatory mechanism of YTHDF proteins in controlling viral RNA decay and EBV replication through PIAS1-mediated SUMOylation.

Screening and identification of emodin as an EBV DNase inhibitor to prevent its biological functions

BackgroundThe Epstein-Barr virus (EBV) is a prevalent oncovirus associated with a variety of human illnesses. BGLF5, an EBV DNase with alkaline nuclease (AN) activity, plays important roles in the viral life cycle and progression of human malignancies and has been suggested as a possible diagnostic marker and target for cancer therapy. Methods used conventionally for the detection of AN activity, radioactivity-based nuclease activity assay and DNA digestion detection by gel electrophoresis, are not suitable for screening AN inhibitors; the former approach is unsafe, and the latter is complicated. In the present study, a fluorescence-based nuclease activity assay was used to screen several natural compounds and identify an EBV DNase inhibitor.ResultsFluorescence-based nuclease activity assays, in which the DNA substrate is labelled with PicoGreen dye, are cheaper, safer, and easier to perform. Herein, the results of the fluorescence-based nuclease activity assay were consistent with the results of the two conventional methods. In addition, the PicoGreen-labelling method was applied for the biochemical characterisation of viral nucleases. Using this approach, we explored EBV DNase inhibitors. After several rounds of screening, emodin, an anthraquinone derivative, was found to possess significant anti-EBV DNase activity. We verified the efficacy of emodin using the conventional DNA-cleavage assay. Furthermore, using comet assay and micronucleus formation detection, we confirmed that emodin can inhibit DNase-induced DNA damage and genomic instability. Additionally, emodin treatment inhibited EBV production.ConclusionsUsing a PicoGreen-mediated nuclease activity assay, we successfully demonstrated that emodin has the potential to inhibit EBV DNase nuclease activity. Emodin also inhibits EBV DNase-related biological functions, suggesting that it is a potential inhibitor of EBV DNase.

PIAS1 potentiates the anti-EBV activity of SAMHD1 through SUMOylation

BackgroundSterile alpha motif and HD domain 1 (SAMHD1) is a deoxynucleotide triphosphohydrolase (dNTPase) that restricts the infection of a variety of RNA and DNA viruses, including herpesviruses. The anti-viral function of SAMHD1 is associated with its dNTPase activity, which is regulated by several post-translational modifications, including phosphorylation, acetylation and ubiquitination. Our recent studies also demonstrated that the E3 SUMO ligase PIAS1 functions as an Epstein-Barr virus (EBV) restriction factor. However, whether SAMHD1 is regulated by PIAS1 to restrict EBV replication remains unknown.ResultsIn this study, we showed that PIAS1 interacts with SAMHD1 and promotes its SUMOylation. We identified three lysine residues (K469, K595 and K622) located on the surface of SAMHD1 as the major SUMOylation sites. We demonstrated that phosphorylated SAMHD1 can be SUMOylated by PIAS1 and SUMOylated SAMHD1 can also be phosphorylated by viral protein kinases. We showed that SUMOylation-deficient SAMHD1 loses its anti-EBV activity. Furthermore, we demonstrated that SAMHD1 is associated with EBV genome in a PIAS1-dependent manner.ConclusionOur study reveals that PIAS1 synergizes with SAMHD1 to inhibit EBV lytic replication through protein–protein interaction and SUMOylation.

Bioactive constituents of Lindernia crustacea and its anti-EBV effect via Rta expression inhibition in the viral lytic cycle.

Lindernia crustacea (L.) F.Muell. (Scrophulariaceae) was selected for phytochemical investigation owing to its traditional use against human herpes virus infection and its anti-Epstein-Barr virus (EBV) effect. The present study focused on the phytochemical investigation of L. crustacea including the isolation and structure determination of its biologically active compounds. Compounds with anti-EBV effects were also investigated. The EtOH extract of L. crustacea was subsequently partitioned using different solvents. The EtOAc fraction was subjected to several chromatographic methods to obtain pure compounds. The structures of all isolates were established by spectroscopic analysis and compared with previously reported physical data. The anti-EBV effect was evaluated in an EBV-containing Burkitt's lymphoma cell line (P3HR1) to study the expression of EBV lytic proteins. Thirty-three compounds, including one diterpene (1), four anthraquinones (2-5), two ionones (6 and 7), fourteen phenylpropanoid glycosides (8-21), five flavonoids (22-26), one lignan glycoside (27), one phenethyl alcohol glycoside (28), one phenylpropene glycoside (29), one glucosyl glycerol derivative (30), one furanone (31), and two cinnamic acid derivatives (32 and 33), were isolated from the ethanolic extract of the plant. All isolated compounds were obtained for the first time from Lindernia sp. The evaluation of the anti-EBV activity of L. crustacea crude extract, partitioned fractions, and constituents was performed for the first time. Phytol (1), aloe-emodin (2), byzantionoside B (7), a mixture of trans-martynoside (8) and cis-martynoside (9), a mixture of trans-isomartynoside (10) and cis-isomartynoside (11), luteolin-7-O-β-D-glucopyranoside (24), and apigenin-7-O-[β-D-apiofuranosyl (1→6)-β-D-glucopyranoside] (25) exhibited significant inhibitory effects on the EBV lytic cycle at 20μg/mL in the immunoblot analysis. On the other hand, (6R,7E,9R)-3-oxo-α-ionol-β-D-glucopyranoside (6) and a mixture of trans-dolichandroside A (12) and cis-dolichandroside A (13) showed moderate anti-EBV activity at 20μg/mL. L. crustacea and its active isolates could be developed as potential candidates against EBV. Our findings provide scientific evidence for the traditional use of L. crustacea for its antiviral effects.

Emodin Inhibits EBV Reactivation and Represses NPC Tumorigenesis.

Nasopharyngeal carcinoma (NPC) is a unique malignancy derived from the epithelium of the nasopharynx. Despite great advances in the development of radiotherapy and chemotherapy, relapse and metastasis in NPC patients remain major causes of mortality. Evidence accumulated over recent years indicates that Epstein-Barr virus (EBV) lytic replication plays an important role in the pathogenesis of NPC and inhibition of EBV reactivation is now being considered as a goal for the therapy of EBV-associated cancers. With this in mind, a panel of dietary compounds was screened and emodin was found to have potential anti-EBV activity. Through Western blotting, immunofluorescence, and flow cytometric analysis, we show that emodin inhibits the expression of EBV lytic proteins and blocks virion production in EBV- positive epithelial cell lines. In investigating the underlying mechanism, reporter assays indicated that emodin represses Zta promoter (Zp) and Rta promoter (Rp) activities, triggered by various inducers. Mapping of the Zp construct reveals that the SP1 binding region is important for emodin-triggered repression and emodin is shown to be able to inhibit SP1 expression, suggesting that it likely inhibits EBV reactivation by suppression of SP1 expression. Moreover, we also show that emodin inhibits the tumorigenic properties induced by repeated EBV reactivation, including micronucleus formation, cell proliferation, migration, and matrigel invasiveness. Emodin administration also represses the tumor growth in mice which is induced by EBV activation. Taken together, our results provide a potential chemopreventive agent in restricting EBV reactivation and NPC recurrence.

Novel Therapeutics for Epstein⁻Barr Virus.

Epstein–Barr virus (EBV) is a human γ-herpesvirus that infects up to 95% of the adult population. Primary EBV infection usually occurs during childhood and is generally asymptomatic, though the virus can cause infectious mononucleosis in 35–50% of the cases when infection occurs later in life. EBV infects mainly B-cells and epithelial cells, establishing latency in resting memory B-cells and possibly also in epithelial cells. EBV is recognized as an oncogenic virus but in immunocompetent hosts, EBV reactivation is controlled by the immune response preventing transformation in vivo. Under immunosuppression, regardless of the cause, the immune system can lose control of EBV replication, which may result in the appearance of neoplasms. The primary malignancies related to EBV are B-cell lymphomas and nasopharyngeal carcinoma, which reflects the primary cell targets of viral infection in vivo. Although a number of antivirals were proven to inhibit EBV replication in vitro, they had limited success in the clinic and to date no antiviral drug has been approved for the treatment of EBV infections. We review here the antiviral drugs that have been evaluated in the clinic to treat EBV infections and discuss novel molecules with anti-EBV activity under investigation as well as new strategies to treat EBV-related diseases.

Antiviral and apoptosis modulating potential of fluorinated derivatives of uracil

The Epstein-Barr virus (EBV) is the first virus that has been classified as a human oncology virus. The ability of EBV to immortalize the cells of the human body is the highest among all known transforming viruses. Fluorine-containing nucleoside analogs represent a significant class of the chemotherapeutics widely used in the treatment for a lot of diseases. They have been playing a major role in treating tumor and virus either as selective inhibitors of enzymes for cancer or viral replication or as nucleic acid chain terminators which interrupt the replication of cancer cells or a virus.Aim. The purpose of this study was to analyze the potential antiviral and apoptosis modulating activity of fluorinated derivatives of uracil by using in silico and in vitro methods.Materials and methods. Two analogs (compound G26 and G27) on the base of 5-(p-tolilsulfonil)-6(polyfluoroalkyl)uracil were used in the study. The studies were conducted on cultures of Raji (latent infected EBV) and B95-8 (chronically producing virus) B-lymphoma cells. Trypan blue assay, MTT-method, neutral red uptake assay, PCR, flow cytometry, and web-servers PASS, PharmMapper were used.Results. According to PASS prediction, all compounds may possess the antiviral activity and anticancer activity. The in vitro study let to reveal the low level of cytotoxicity of these uracil derivatives. Anti-EBV activity was observed for all compounds and EC50 values were 75 and 65 µg/ml. Using PharmMapper, it has been shown that the targets are enzymes necessary for the replication of viral DNA (protease, kinase) and proteins that provide an apoptotic cascade (MAPK, cytochrome). For compound G27, several peaks on the histogram were observed, which may be evidence of changes in the cell cycle of lymphoblastoid cultures.Conclusions. In this way, the results of the present research shown an antiviral and apoptosis modulating activity of derivatives based on uracil. The data assumed by in silico methods can be used to model the relationship between the structure and activity of substance and predict possible targets of studied chemical compounds. These results can be applied to the further creation of new high-level antiviral agents

Potential Antiviral Lignans from the Roots of Saururus chinensis with Activity against Epstein–Barr Virus Lytic Replication

Epstein-Barr virus (EBV) is a member of the γ-herpes virus subfamily and has been implicated in the pathogenesis of several human malignancies. Bioassay-guided fractionation was conducted on an EtOAc-soluble extract of the roots of Saururus chinensis and monitored using an EBV lytic replication assay. This led to the isolation of 19 new (1-19) and nine known (20-28) lignans. The absolute configurations of the new lignans were established by Mosher's ester, ECD, and computational methods. Eight lignans, including three sesquineolignans (19, 23, and 24) and five dineolignans (3, 4, 26, 27, and 28), exhibited inhibitory effects toward EBV lytic replication with EC50 values from 1.09 to 7.55 μM and SI values from 3.3 to 116.4. In particular, manassantin B (27) exhibited the most promising inhibition, with an EC50 of 1.72 μM, low cytotoxicity, CC50 > 200 μM, and SI > 116.4. This is the first study demonstrating that lignans possess anti-EBV lytic replication activity.

148 The effect of natalizumab and interferon-β on urinary free light chains and anti-EBV nuclear antigen-1 antibodies in relapsing remitting multiple sclerosis

BackgroundEpstein-Barr Virus (EBV) has been associated with multiple sclerosis (MS), but its role in disease pathogenesis has yet to be confirmed. B cells are also implicated in MS, and urinary...

Synthesis and Biological Activity of the Nucleoside Analogs Based on Polyfluoroalkyl-Substituted 1,2,3-Triazoles

This paper offers the results of a synthesis and study of cytotoxicity and the anti-Epstein-Barr virus (EBV) activity of new 2-deoxy-2-chloro-pyranosyl derivatives of 4-tosyl-5-trifluoromethyl-1,2,3-triazole obtained via the addition reaction of the corresponding 2-N-chlorotriazole to the double bond of 3,4,6-tri-O-acetyl-D-glucal. Nucleoside mimetics, derivatives of 4-tosyl-5-polyfluoroalkyl-1,2,3-triazoles containing fragments of 3-chloro-tetrahydrofuran, 3-chloro-tetrahydropyran, tetrahydropyran, dihydrofuran, dihydropyran, or acyclic substituents, were also studied. Evaluation of cytotoxicity (trypan blue and MTT methods) and anti-EBV activity (polymerase chain reaction (PCR) method) showed high selectivity indices for the compounds 4a, 4b, 5b, 6, and 8. A total of 15 novel compounds were examined in this study.

Investigation of Anti-EBV Activity of Ganciclovir in Combination with Antiflogistics

Investigation of Anti-EBV Activity of Ganciclovir in Combination with Antiflogistics

Anti-EBV Activity of Hemocyanin Isolated from Helix Lucorum

henotype. To better characterize the activity of ODE-MPMPA eplicon rebound and compound uptake studies were performed. Methods: Huh-7.5.1 cells stably expressing the BM4-5 FEO eplicon (1b) were seeded in 96 well plates (2500 cells/well) and xposed to ODE-MPMPA at the EC50 (1.5 M) and EC90 (8 M). fter 48h compound was removed and replaced with complete edia. Luciferase expressionwasdeterminedand replication levels xpressed as a percentage of control wells. Cellular uptake studies ere performed in Huh7 cells with 8 M 14C-labeled MPMPA and DE-MPMPA. Results: Replications levels at 48hwere 52% and 8% at the EC50 nd EC90, respectively. At 96h after compound removal replication evels had declined further (23% and 2%). At one week replication emained suppressed (57% and 2%). After exposure to 8 M drug, ntracellular concentrations of radiolabeled MPMPA at 2, 4 and 4h were 43, 46 and 54pmol/106 cells compared with 330, 970 nd 3340pmol/106 cells for ODE-MPMPA. At 2, 4 and 24h, cellular evels of ODE-MPMPA were 8-, 21and 62-fold higher than those bserved with 8 M MPMPA. Conclusions: ODE-MPMPA displays potent and prolonged uppression of HCV replicon replication after a single expoure. Prolonged elevated intracellular concentrations of drug and etabolites lead to the delayed rebound on removal. High intraellular levels combined with the high fitness cost and/or low old-change of resistant mutants contribute to the high resistance arrier. Studies to determine the intracellular concentrations of the ctive metabolite (MPMPApp) are underway.

A reporter system for Epstein-Barr virus (EBV) lytic replication: Anti-EBV activity of the broad anti-herpesviral drug artesunate

Epstein-Barr virus (EBV) is associated with severe human diseases. Therapies with conventional anti-herpesviral drugs are mostly ineffective so that novel drugs are urgently needed. As cell culture-based evaluation systems are required, a GFP (green fluorescent protein) reporter system was generated, which was conceived for an easy quantitation of lytic EBV replication and the analysis of EBV drug sensitivity. A reporter construct was generated on the basis of an EBV plasmid mini-replicon which enabled an episomal maintenance and selection of stably transfected Raji and 293T cell clones. Controlled by the viral lytic origin of DNA replication (oriLyt), this reporter construct could be activated through experimental EBV infection or through chemically stimulated reactivation from EBV latency. Using this system, the sensitivity of EBV to the broad-spectrum anti-herpesviral drug artesunate could be demonstrated: (i) artesunate inhibits EBV in the low micromolar range, (ii) two different strains of EBV are equally artesunate-sensitive, (iii) inhibition is detectable similarly in EBV-infected epithelial cells or lymphocytes, and (iv) the mode of antiviral action is based on a block of viral immediate early protein synthesis. The data demonstrate the usefulness of this reporter system for the quantitation of EBV replication and for determining EBV drug sensitivity.

Susceptibility in vitro of Epstein-Barr Virus to myristoylated-peptide

The anti-Epstein-Barr Virus (EBV) myristoylated-peptide (M.W. 916.2Da) is a natural product isolated from Heliothis virescens insect larval hemolymph (blood) that essentially has no cytotoxicity against human foreskin fibroblast cells. A (3 methyl only) version (M.W. 902.2 Da) of the structure was synthesized and tested for in vitro anti-EBV activity and cytotoxicity. The N-terminal end is lipophilic and used to get the compound across the cell membrane. The C-terminal end with its ring-shaped structures is likely used to inhibit DNA synthesis. The synthetic compound inhibited DNA synthesis/replication of EBV in Akata cells (B-lymphocyte from Burkitt's lymphoma patient) in in vitro tissue culture. A DNA hybridization assay for anti-EBV activity using the Akata B-cell and two cytotoxicity assays using human foreskin fibroblast cells were done with the synthetic peptide. Effective concentration (EC90) at 20 microM inhibited viral replication by 90%. The EBV, known as Human Herpesvirus-4 (HHV-4) of the Herpesviridae family, has been described as a cancer-promoting double-stranded DNA virus that may also be involved in autoimmune disease. There are no antiviral drugs in clinical use for diseases caused by the EBV.

Simultaneous determination of acyclovir, ganciclovir, and (R)‐9‐[4‐hydroxy‐2‐(hydroxymethyl)butyl]guanine in human plasma using high‐performance liquid chromatography

Acyclovir, ganciclovir and (R)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine are active in vitro against the Epstein-Barr virus (EBV) but their in vivo anti-EBV activity is not well understood. We developed a novel, sensitive high-performance liquid chromatography assay with ultraviolet detection for measuring acyclovir, ganciclovir and (R)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine in human plasma to identify quantitative relationships between in vitro anti-EBV activity and therapeutic response. Characteristics of the assay include a low plasma volume (200 microL), perchloric acid protein precipitation, use of penciclovir as the internal standard, run times less than 8 min and a 50 ng/mL lower limit of quantification. The within- and between-assay variability is 0.7-4.8 and 1.0-7.9%, respectively. Accuracy for all three drugs ranges from 89.5 to 106.4% for four quality controls (50, 100, 1000 and 10,000 ng/mL). This assay supports pharmacokinetic and pharmacodynamic studies of candidate anti-EBV drugs in children and adults with EBV infections.

Antiviral activity of cyclosaligenyl prodrugs of the nucleoside analogue bromovinyldeoxyuridine against herpes viruses

A series of 42 lipophilic bromovinyldeoxyuridine monophosphates (BVDUMPs) are presented as potential prodrugs of the antiviral agent (E)-5-(2-bromovinyl)-2′-deoxyuridine (BVDU). The 5′- cycloSal-masking group technique has been applied to this cyclic nucleoside analogue to achieve delivery of the monophosphate of BVDU inside the target cells. The new substances have been tested for their antiviral activity against herpes simplex virus types 1 and 2 (HSV-1 and -2), thymidine kinase-deficient (TK −) HSV-1, varicella-zoster virus (VZV), human cytomegalovirus (HCMV) and Epstein–Barr virus (EBV). The XTT-based tetrazolium reduction assay EZ4U (for HSV), the plaque inhibition test (for VZV and HCMV) and a DNA hybridisation assay (for EBV) were used to assess antiviral activity. The results indicate that cycloSal-BVDUMP triesters proved to be potent and selective inhibitors of HSV-1 comparable with aciclovir. VZV replication was inhibited by very low concentrations, and two substances had a slightly better anti-VZV activity than the parent compound BVDU. No antiviral effect could be demonstrated against TK −-HSV-1, HSV-2 and HCMV, most likely owing to the lack of phosphorylation to BVDU diphosphate. Most remarkably, several cycloSal-BVDUMP triesters yielded promising anti-EBV activity whereas the parent compound BVDU was entirely inactive.

CycloSal-Pronucleotides of Brivudine Monophosphate - Highly Active Antiviral Agents

CycloSal-BVDUMP triesters 32-34 5-[(E)-2-bromovinyl]-2-deoxyuridine (BVDU 2) have been studied with regard to their potential anti-EBV activity. In addition to the 3-unmodified cycloSal-BVDUMP triesters 32a-f, the 3- hydroxyl function has been esterified with different aliphatic carboxylic acids (33a-g) and α-amino acids having natural and non-natural Cα-configuration (34a-m). In addition to the synthesis of these compounds, different physicochemical properties will be reported, i.e. lipophilicity and hydrolysis behaviour. It could be shown that BVDUMP and not 3,5- cyclic BVDUMP was delivered from most of the compounds by chemical hydrolysis in phosphate buffers at pH 6.8 and 7.3 as well as P3HR-1 cell extracts. Finally, the compounds were tested for their anti-EBV activity. As a result, the prototype compounds and particularly triesters 32c,d exhibited pronounced anti-EBV activity making these compounds promising candidates for further development. However, the 3-ester derivatives were devoid of any antiviral activity, while the 3-aminoacyl derivatives showed an antiviral activity, in dependence of the amino acid and the Cα- configuration. In addition, all cycloSal-BVDU phosphotriesters proved to be potent and selective inhibitors of herpes simplex virus type 1 replication. Several pronucleotide concepts will be briefly summarised but the cycloSal-pronucleotide system described in more detail is the only approach that showed an improvement in antiviral activity of the nucleoside analogue BVDU.

CycloSal-BVDUMP pronucleotides: how to convert an antiviral-inactive nucleoside analogue into a bioactive compound against EBV.

Novel cycloSal-BVDUMP triesters 2-4 5-[(E)-2-bromovinyl]-2'-deoxyuridine (BVDU, 1) have been studied with regard to their potential anti-EBV activity. In addition to the 3'-unmodified cycloSal-BVDUMP triesters 2a-f, the 3'-hydroxyl function has been esterified with different aliphatic carboxylic acids (3a-g) and alpha-amino acids having natural and nonnatural Calpha-configuration (4a-m). In addition to the synthesis of these compounds, different physicochemical properties of the new derivatives will be reported, i.e., lipophilicity and hydrolysis behavior. It could be proven that the monophosphate BVDUMP and not 3',5'-cyclic BVDUMP was delivered from most of the compounds by chemical hydrolysis in phosphate buffers at pH 6.8 and 7.3 as well as P3HR-1 cell extracts. Finally, the new compounds were tested for their anti-EBV activity. As a result, the prototype compounds and particularly triesters 2c,d exhibited pronounced anti-EBV activity making these compounds promising candidates for further development. However, the 3'-ester derivatives were devoid of any antiviral activity while the 3'-aminoacyl derivatives showed an antiviral activity dependent upon the amino acid and the Calpha-configuration

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.