Potent, selective and cell-mediated inhibition of human herpesvirus 6 at an early stage of viral replication by the non-nucleoside compound CMV423

Design and Synthesis of 2-Phenylindolizine Acetamides: Molecular Docking, in Vitro Antimicrobial and Anticancer Activity Evaluation

In the present work, we synthesized a small library of 2-phenylindolizine acetamide derivatives 7a-i and studied their biological activity. The synthesis was accomplished starting with easily available starting material phenacyl bromide 1 proceeding through the key intermediate 6-methyl-7-nitro-2-phenylindolizine 4. All the compounds 7a-i were characterized using spectroscopy viz., 1H-NMR, 13C NMR, FTIR, and mass spectrometry. Interestingly, 2-phenylindolizine scaffolds 7c, 7f and 7g revealed a remarkable antibacterial activity against relevant organisms S. aureus, E. coli, S. pneumoniae, P. aeruginosa. The target compounds 7e and 7h showed excellent anticancer activity against Colo-205 and MDA-MB-231 cell lines with IC50 values of 68.62, 62.91, 54.23 and 46.34 μM respectively. Additionally, all the 2-phenylindolizine acetamide derivatives 7a-i were subjected to molecular docking prediction by Autodock 4.2. Compounds 7a, 7f and 7c exhibited very good hydrogen bonding amino acid interactions Asp83 (2.23 Å), Asp83 (2.08 Å), His74 (2.05 Å), His76 (1.71 Å), Ser80 (1.05 Å) with active site of Topoisomerase-IV from S. pneumoniae (4KPE). Further, the compounds 7a-i have revealed acceptable ranges for drug-likeliness properties upon evaluation using SwissADME for ADMET and physiochemical properties.

Visible light-enabled synthesis of phosphorylated indolizine and pyridoindole derivatives via HAT-mediated radical cascade cyclization

A visible light-enabled cascade cyclization strategy is disclosed with concomitant phosphorylation and heterocycle construction. It provides a novel and environmentally benign approach for accessing tetrahydroindolizine-containing phosphonates under metal-free conditions. Mechanistic studies revealed that phosphinoyl radicals were generated from H-phosphonates via a HAT process.

QSER modeling of half-wave oxidation potential of indolizines by theoretical descriptors

Indolizine derivatives hold essential biological functions and have been researched for hypoglycemic, antibacterial, anti-inflammatory, analgesic, and anti-tumor actions. Indolizine scaffold has intrigued conjecture and continuous attention and has become an effective parent system for generating powerful novel medication candidates. This research focused on applying the quantitative structure-electrochemistry relationship (QSER) approach to the half-wave potential (E1/2) for Indolizine derivatives using theoretical molecular descriptors. After calculating the descriptors and splitting the data into both sets, training and prediction. The QSER model was constructed using the Genetic Algorithm/Multiple Linear Regression (GA/MLR) technique, which was used to choose the optimal descriptors for the model. A four-parameter model has been established. Many assessment procedures, including cross-validation, external validation, and Y-scrambling testing, were used to assess the model's performance. Furthermore, the applicability domain (AD) was investigated using the Williams and Insubria graphs to assess the correctness of the established model's predictions. The constructed model exhibits great goodness-of-fit to experimental data, as well as high stability (R²=0.893, Q²LOO= 0.851, Q²LMO=0.843 RMSEtr= 0.052, s= 0.056). Prediction results show a good agreement with the experimental data of E1/2 (R²ext= 0.912, Q²F1= 0.883, Q²F2= 0.883, Q²F3= 0.919, CCCext= 0.942, RMSEext=0.045).

A Route to (Het)arene-Annulated Pyrrolo[1,2-d][1,4]diazepines via the Expanded Intramolecular Paal-Knorr Reaction: Nitro Group and Furan Ring as Equivalents of Amino Group and 1,4-Diketone

A straightforward protocol toward pharmacologically relevant (het)areno[x,y-b]pyrrolo[1,2-d][1,4]diazepines in good to high yields has been described. The designed approach consists of an acid-promoted furan ring opening in easily accessible N-(2-furylethyl)-2-nitroanilines or their heterocyclic analogues followed by the reductive cyclization of the corresponding nitro-1,4-diketones.

A Novel Indolizine Derivative Induces Apoptosis Through the Mitochondria p53 Pathway in HepG2 Cells

Indolizine derivatives are a class of compounds with excellent biological activity. In this study, a series of indolizine derivatives, compound 1 (C1), compound 2 (C2), compound 3 (C3), and compound 4 (C4), were synthesized. 3-(4,5-dimethylthiazole)-2,5-diphenyltetraazolium bromide (MTT) assay was used to evaluate their cytotoxicity against HepG2 (p53-wild), A549, and HeLa cell lines. HepG2 cells apoptosis induced by C3 was determined using Hoechst staining and acridine orange/ethidium bromide staining. Cells’ apoptotic ratio was measured by Annexin V–FITC/PI double staining. Changes in mitochondrial membrane potential and intracellular reactive oxygen species (ROS) in HepG2 cells after C3 treatment were determined. Immunofluorescence staining and Western blot analysis were carried out to detect p53 levels and analyze the apoptosis-associated proteins, respectively. Moreover, the cytotoxic activity of C3 was examined in two other hepatocellular carcinoma (HCC) cell lines with different p53 status including Huh-7 cells (p53-mutant) and Hep3B cells (p53-null). The results indicated that C3 showed stronger inhibition towards HepG2 cells than other cell lines. Fluorescent staining and flow cytometry analysis confirmed that C3 induced apoptosis of HepG2 cells. C3 could also increase intracellular ROS and cause a decrease in the mitochondrial membrane potential. C3 promoted p53 activation and increased p53 accumulation in nuclei. The expression of p53 and Bax was increased with the down-regulation of Bcl-2, which promoted the release of cytochrome c and caspase-3 activation. Collectively, the study demonstrated that C3 caused HepG2 cell apoptosis via the mitochondria p53 pathway. These results inspired us to further develop indolizine derivatives as potential potent inhibitors against liver cancer.

Advances in the Characterization of the T-Cell Response to Human Herpesvirus-6

Human herpesvirus (HHV) 6 is thought to remain clinically latent in most individuals after primary infection and to reactivate to cause disease in persons with severe immunosuppression. In allogeneic hematopoietic stem cell transplant recipients, reactivation of HHV-6 species B is a considerable cause of morbidity and mortality. HHV-6B reactivation is the most frequent cause of infectious meningoencephalitis in this setting and has been associated with a variety of other complications such as graft rejection and acute graft versus host disease. This has inspired efforts to develop HHV-6-targeted immunotherapies. Basic knowledge of HHV-6-specific adaptive immunity is crucial for these endeavors, but remains incomplete. Many studies have focused on specific HHV-6 antigens extrapolated from research on human cytomegalovirus, a genetically related betaherpesvirus. Challenges to the study of HHV-6-specific T-cell immunity include the very low frequency of HHV-6-specific memory T cells in chronically infected humans, the large genome size of HHV-6, and the lack of an animal model. This review will focus on emerging techniques and methodological improvements that are beginning to overcome these barriers. Population-prevalent antigens are now becoming clear for the CD4+ T-cell response, while definition and ranking of CD8+ T-cell antigens and epitopes is at an earlier stage. This review will discuss current knowledge of the T-cell response to HHV-6, new research approaches, and translation to clinical practice.

Effects of Prophylactic Foscarnet on Human Herpesvirus-6 Reactivation and Encephalitis in Cord Blood Transplant Recipients: A Prospective Multicenter Trial with an Historical Control Group

Cord blood transplantation (CBT) is a distinct risk factor for human herpesvirus-6 (HHV-6) reactivation and HHV-6 encephalitis. In a prospective multicenter trial we investigated the effects of prophylactic foscarnet (90 mg/kg i.v. infusion from days 7 to 27 after CBT) on the occurrence of HHV-6 reactivation, HHV-6 encephalitis, and acute graft-versus-host disease (aGVHD) in CBT recipients. Between 2014 and 2016, 57 patients were included in a foscarnet-prophylaxis group. Outcomes were compared with an historical control group who received CBT between 2010 and 2014 (standard-treatment group, n = 63). The cumulative incidence of high-level HHV-6 reactivation, defined as plasma HHV-6 DNA ≥ 10⁴ copies/mL, at 60 days after CBT was significantly lower in the foscarnet-prophylaxis group than in the standard-treatment group (18.3% versus 57.3%, P < .001). Multivariate analysis revealed that myeloablative preconditioning and standard treatment were significant risk factors for high-level HHV-6 reactivation. The cumulative incidence of HHV-6 encephalitis at 60 days after CBT was not different between the groups (foscarnet-prophylaxis group, 12.4%; standard-treatment group, 4.9%; P = .14). The cumulative incidences of grades II to IV and grades III to IV aGVHD at 60 days after CBT were not different between the groups (grades II to IV aGVHD: foscarnet-prophylaxis group, 42.0%; standard-treatment group, 40.5%; P = .96; grades III to IV aGVHD: foscarnet-prophylaxis group, 14.5%; standard-treatment group, 14.5%; P = 1.00). In the setting of this study foscarnet significantly suppressed systemic HHV-6 reactivation in CBT recipients but failed to prevent the development of HHV-6 encephalitis. Suppression of HHV-6 reactivation by foscarnet did not show any effects against the incidence of aGVHD.

Synthesis and crystal structures of three novel benzimidazole/benzoindolizine hybrids

Three benzoindolizine derivatives, 1, 2, and 3, were obtained via 1,3-dipolar cycloaddition. The reaction of 1-(2′-benzimidazolylmethyl)isoquinolinium ylides with dimethyl acetylenedicarboxylate gave a mixture of pyrrolo[2,1-a]isoquinoline-1,2-dicarboxylate (1) and 1,10b-dihydropyrrolo[2,1-a]isoquinoline-1,2-dicarboxylate (2) derivatives containing a benzimidazole moiety. The reaction of this isoquinolinium N-ylide with dimethyl maleate gave an unexpected 2,3-dihydropyrrolo[2,1-a]isoquinoline-1,2-dicarboxylate (3). The structures of all reported compounds have been examined by X-ray crystallography, mass spectrometry, and NMR spectroscopy.

A facile approach for the synthesis of 1,3-di- and 1,2,3-tri-substituted indolizines

A convenient synthesis of 1,3-di- and 1,2,3-tri-substituted indolizines involving the multicomponent reaction of pyridinium salt (or quinolinium salt), olefine acid, and 1,2-dichloroethane has been achieved. The process proceeds smoothly in moderate to high yields.

New indolizines with phenanthroline skeleton: Synthesis, structure, antimycobacterial and anticancer evaluation

We report herein a feasible study concerning the design, synthesis, structure and in vitro antimycobacterial and anticancer activity of two new classes (containing four and five fused rings) of indolizine with phenanthroline skeleton. The preparation is straight and efficient, involving a Huisgen [3+2] dipolar cycloaddition of cycloimmonium ylides to alkynes or alkenes dipolarophiles. The cycloaddition reactions are highly stereo- or regioselective, according with the dipolarophiles nature. The structure of the new compounds was assigned unambiguously, X-ray analysis including. The primary antimycobacterial screening reveals that one of the thirteen tested compounds had a good activity against Mycobacterium tuberculosis H37Rv under aerobic conditions. The antiproliferative evaluation against a NCI 60 human tumor cell line panel, revealed that two indolizine with phenanthroline skeleton exhibit a selective and significant antitumor growth inhibitory activity against Breast Cancer (MCF7 and T-47D) and a slightly moderate activity against some forms of Leukemia, Non-Small Cell Lung Cancer, Renal Cancer and Breast Cancer (MDA-MB-468). The X-ray diffraction study of the indolizines with phenanthroline skeleton prove a flat coplanar structure which, corroborated with their anticancer activity, allow us to suggest that an interaction with DNA (via an intercalation mechanism) would be reasonable.

Laboratory and clinical aspects of human herpesvirus 6 infections

Human herpesvirus 6 (HHV-6) is a widespread betaherpesvirus which is genetically related to human cytomegalovirus (HCMV) and now encompasses two different species: HHV-6A and HHV-6B. HHV-6 exhibits a wide cell tropism in vivo and, like other herpesviruses, induces a lifelong latent infection in humans. As a noticeable difference with respect to other human herpesviruses, genomic HHV-6 DNA is covalently integrated into the subtelomeric region of cell chromosomes (ciHHV-6) in about 1% of the general population. Although it is infrequent, this may be a confounding factor for the diagnosis of active viral infection. The diagnosis of HHV-6 infection is performed by both serologic and direct methods. The most prominent technique is the quantification of viral DNA in blood, other body fluids, and organs by means of real-time PCR. Many active HHV-6 infections, corresponding to primary infections, reactivations, or exogenous reinfections, are asymptomatic. However, the virus may be the cause of serious diseases, particularly in immunocompromised individuals. As emblematic examples of HHV-6 pathogenicity, exanthema subitum, a benign disease of infancy, is associated with primary infection, whereas further virus reactivations can induce severe encephalitis cases, particularly in hematopoietic stem cell transplant recipients. Generally speaking, the formal demonstration of the causative role of HHV-6 in many acute and chronic human diseases is difficult due to the ubiquitous nature of the virus, chronicity of infection, existence of two distinct species, and limitations of current investigational tools. The antiviral compounds ganciclovir, foscarnet, and cidofovir are effective against active HHV-6 infections, but the indications for treatment, as well as the conditions of drug administration, are not formally approved to date. There are still numerous pending questions about HHV-6 which should stimulate future research works on the pathophysiology, diagnosis, and therapy of this remarkable human virus.

The development of new therapies for human herpesvirus 6

Human herpesvirus 6 (HHV-6) infections are typically mild and in rare cases can result in encephalitis. A common theme among all the herpesviruses, however, is the reactivation upon immune suppression. HHV-6 commonly reactivates in transplant recipients. No therapies are approved currently for the treatment of these infections, although small studies and individual case reports have reported intermittent success with drugs such as cidofovir, ganciclovir, and foscarnet. In addition to the current experimental therapies, many other compounds have been reported to inhibit HHV-6 in cell culture with varying degrees of efficacy. Recent advances in the development of new small molecule inhibitors of HHV-6 will be reviewed with regard to their efficacy and spectrum of antiviral activity. The potential for new therapies for HHV-6 infections will also be discussed, and they will likely arise from efforts to develop broad spectrum antiviral therapies for DNA viruses.

Synthesis of Novel Indolizine, Pyrrolo[1,2-A] Quinoline, and 4,5-Dihydrothiophene Derivatives Via Nitrogen Ylides and their Antimicrobial Evaluation

Treatment of 2-(2-bromoacetyl)-3 H-benzo[ f]chromen-3-one with pyridine, quinoline, and 2-methylquinoline afforded the corresponding pyridinium, quinolinium and 2-methylquinolinium bromides. The latter salts underwent [3 + 2] 1,3-dipolar cycloaddition with some electron deficient acetylene and ethylene derivatives to give the corresponding indolizine and pyrrolo[1,2- a]quinoline derivatives. Moreover, 2-(2-bromoacetyl)-3 H-benzo[ f]chromen-3-one reacted with arylidene cyanothioacetamides to afford the corresponding 2-amino-4,5-dihydrothiophene-3-carbonitriles. The synthesised compounds were characterised based on their elemental analysis and spectral data. Antimicrobial activity of some of the synthesised compounds was evaluated.

Indolizine derivatives as HIV-1 VIF-ElonginC interaction inhibitors

Compound 1 (VEC-5) was identified as a potent small-molecular HIV-1 viron infectivity factor inhibitor that targets the viron infectivity factor-ElonginC interaction. A structure-activity relationship study was carried out to develop compounds with improved efficacy against HIV-1 and 49 indolizine derivatives of three categories were designed and synthesized. We found that five compounds exhibited promising anti-HIV-1 activity, and the most active compound 2g had an IC50 value of 11.0 μm. These results provide new information to develop highly potent small-molecule HIV-1 viron infectivity factor inhibitors.

17-allylamino-17-(demethoxy)geldanamycin (17-AAG) is a potent and effective inhibitor of human cytomegalovirus replication in primary fibroblast cells

The 90 % human cytomegalovirus inhibitory concentration of 17-allylamino-17-(demethoxy)geldanamycin (17-AAG) was 0.1 nM and 50 % cytotoxicity required at least a 10 μM concentration. Three molecular targets may explain the antiviral activities of this compound. These are (1) heat shock protein maturation complexes, (2) host cell cycle progression and (3) phosphatidylinositol 3-kinase signaling. However, the data suggested a mechanism of action where 17-AAG blocked immediate-early protein transactivation.

[Human herpesvirus-6 and human herpesvirus-7 (HHV-6, HHV-7)]

human herpesvirus 6 (HHV-6) is the major causative agent of exanthem subitum which is one of popular diseases in infant, and establishes latent infections in adults of more than 90%. Recently, the encephalitis caused by reactivated- HHV-6 has been shown in patients after transplantation. In addition, the relationship HHV-6 and drug-induced hypersensitivity syndrome has also been reported. human herpesvirus 7 (HHV-7) was isolated from the stimulated-peripheral blood lymphocytes of a healthy individual, and also causes exanthema subitum. Both viruses are related viruses which belong to betaherpesvirus subfamily, and replicate and produce progeny viruses in T cells.

Benzimidazole analogs inhibit human herpesvirus 6

Several benzimidazole nucleoside analogs, including 1H-β-D-ribofuranosyl-2-bromo-5,6-dichlorobenzimidazole (BDCRB) and 1H-β-L-ribofuranosyl-2-isopropylamino-5,6-dichlorobenzimidazole (maribavir [MBV]), inhibit the replication of human cytomegalovirus. Neither analog inhibited the related betaherpesvirus human herpesvirus 6 (HHV-6). Additional analogs of these compounds were evaluated against both variants of HHV-6, and two L-analogs of BDCRB had good antiviral activity against HHV-6A, as well as more modest inhibition of HHV-6B replication.

Amberlite-IRA-402 (OH) ion exchange resin mediated synthesis of indolizines, pyrrolo [1,2-a] quinolines and isoquinolines: antibacterial and antifungal evaluation of the products

A number of indolizines and pyrrolo[1,2-a]quinolines/isoquinolines were prepared from phenacyl pyridinium, quinolinium and isoquinolinium salts derived from the reaction of the heterocycles with 2-bromo acetophenone with alkynes and alkenes using amberlite-IRA-402 (OH) ion exchange resin as the base. Antibacterial and antifungal studies were carried out against thirteen bacterial and four fungal strains, which revealed that three derivatives (4a, 4b, 7a) out of fifteen are effective against all the thirteen strains and one derivative, 10, showed dual antibactericidal and antifungal efficacy.

The 6-aminoquinolone WC5 inhibits human cytomegalovirus replication at an early stage by interfering with the transactivating activity of viral immediate-early 2 protein

WC5 is a 6-aminoquinolone that potently inhibits the replication of human cytomegalovirus (HCMV) but has no activity, or significantly less activity, against other herpesviruses. Here we investigated the nature of its specific anti-HCMV activity. Structure-activity relationship studies on a small series of analogues showed that WC5 possesses the most suitable pattern of substitutions around the quinolone scaffold to give potent and selective anti-HCMV activity. Studies performed to identify the possible target of WC5 indicated that it prevents viral DNA synthesis but does not significantly affect DNA polymerase activity. In yield reduction experiments with different multiplicities of infection, the anti-HCMV activity of WC5 appeared to be highly dependent on the viral inoculum, suggesting that WC5 may act at an initial stage of virus replication. Consistently, time-of-addition and time-of-removal studies demonstrated that WC5 affects a phase of the HCMV replicative cycle that precedes viral DNA synthesis. Experiments to monitor the effects of the compound on virus attachment and entry showed that it does not inhibit either process. Evaluation of viral mRNA and protein expression revealed that WC5 targets an event of the HCMV replicative cycle that follows the transcription and translation of immediate-early genes and precedes those of early and late genes. In cell-based assays to test the effects of WC5 on the transactivating activity of the HCMV immediate-early 2 (IE2) protein, WC5 markedly interfered with IE2-mediated transactivation of viral early promoters. Finally, WC5 combined with ganciclovir in checkerboard experiments exhibited highly synergistic activity. These findings suggest that WC5 deserves further investigation as a candidate anti-HCMV drug with a novel mechanism of action.

Effect of (r)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine (H2G) and AZT-lipid-PFA on human herpesvirus-6B infected cells

BACKGROUND

Human herpesvirus-6 (HHV-6) has been associated with a wide spectrum of diseases. (r)-9-[4-Hydroxy-2-(hydroxymethyl)butyl]guanine (H2G) is an acyclic guanosine analogue that is structurally similar to acyclovir and is in clinical development for treatment of herpesvirus infections. H2G has been found to have activity against HSV type 1, HSV type 2, and HHV-6 in lymphoblast cell lines. A new anti-viral duplex drug, 3'-azido-3'-deoxythymidylyl-(5'-->2-O)-3-O-octadecyl-sn-glycerol (AZT-lipid-PFA), linking zidovudine (AZT) and foscarnet (PFA) via a lipophilic octadecylglycerol residue (lipid) also exhibits anti-viral activities against HIV, HSV type 1 and HCMV.

OBJECTIVE

To assess the efficacy of H2G and AZT-lipid-PFA conjugate against HHV-6.

STUDY DESIGN

Drug-associated toxicity and proliferative response were evaluated. We conducted in vitro experiments to determine the efficacy of H2G and an AZT-lipid-PFA conjugate in interfering with expression HHV-6 viral transcript in primary human peripheral blood mononuclear cells (PBMC).

RESULTS

Both H2G and AZT-lipid-PFA were effective at inhibiting expression of HHV-6 gene transcript at comparable concentrations. Additionally, while AZT-lipid-PFA treatment was toxic to cells at concentrations above 5microM, H2G treatment was associated with minimal cytotoxicity.

CONCLUSION

These data suggest the potential application of these anti-viral compounds in controlling HHV-6 infection.

Antiviral activity of diverse classes of broad-acting agents and natural compounds in HHV-6-infected lymphoblasts

BACKGROUND

HHV-6 replication requires complex and poorly understood interactions between viral and cellular factors.

OBJECTIVES

Several natural compounds or broad-acting pharmacological agents were studied in an attempt to discover new targets for anti-HHV-6 therapy.

STUDY DESIGN

The antiviral activity was determined in human T-lymphoblasts, using HHV-6A (GS)-infected HSB-2 cells, HHV-6B (Z29)-infected MOLT-3 cells and HHV- 6B (HST)-infected MT4 cells. Virus replication was measured by CPE and qPCR assay. Foscarnet was included as the reference compound.

RESULTS

Among the 15 natural compounds tested, only 'red marine algae' (an extract rich in sulfated polysaccharides) exhibited strong activity when added during virus adsorption. Among the broad-acting pharmacological agents, chloroquine, artemisinin, hypericin, ribavirin, resveratrol and glycyrrhizic acid were all inactive. Amantadine produced a reproducible inhibition of HHV-6 replication, albeit at relatively high concentrations. Except for lamotrigine, which was moderately active against HHV-6B, several antiepileptic drugs were shown to have no activity. We included several compounds which we previously described as potent HHV-6 inhibitors, i.e., the non-nucleoside inhibitor CMV423 and the acyclic nucleoside phosphonate analogues cidofovir and 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]-3-deazaadenine. The latter compound exhibited remarkable anti-HHV-6 activity.

CONCLUSION

Further optimization of compounds belonging to diverse classes of antiherpetic agents, for their specific action against HHV-6, is warranted.

In search of effective anti-HHV-6 agents

Since HHV-6, like HCMV, is a beta-herpesvirus, anti-HCMV drugs such as (val)ganciclovir, foscarnet and cidofovir may, by extrapolation, be advocated for the treatment of HHV-6 infections. At present, no prime candidate for the treatment of HHV-6 infections has been identified or even proposed, which means that the search for antiviral drugs effective against HHV-6-associated diseases should be encouraged. In essence, this search is going into two directions: nucleoside and non-nucleoside analogues. To the first category belong S2242, an N7-substituted purine acyclic derivative; A-5021, a cyclopropyl nucleoside analogue; cyclopropavir, a methylene cyclopropane analogue; lipophilic ester prodrugs of the acyclic nucleoside phosphonate cidofovir; and various other "old" and "new" acyclic nucleoside phosphonate analogues including those derived from the 2, 4-diaminopyrimidine (DAPy) skeleton. To the non-nucleoside category belong a number of quinoline-3-carboxamide, aryl sulfone, benzimidazole riboside and phenylenediamine sulfonamide derivatives which could be further optimized from a structure-activity relationship (SAR) viewpoint so as to specifically target HHV-6 replication. Also, specific protein kinase inhibitors may be pursued as anti-HHV-6 agents, a representative example being the compound CMV423 which, being inhibitory to (cellular) protein tyrosine kinases, exhibits potent and selective activity against HHV-6.

Main adult herpes virus infections of the CNS

Herpes viruses are widely involved in human infectious diseases, and some are life threatening, such as CNS infections. These manifestations vary according to the type of virus involved and the immune status of the patient. This article will review the clinical manifestations (encephalitis, myelitis, meningitis and postinfectious encephalomyelitis), the diagnostic strategies and the presently used drugs (acyclovir, valacyclovir, ganciclovir, valgancyclovir, foscarnet and cidofovir). The review will also discuss drugs that are currently in the pipeline and that could be used in the future.

Status Presens of Antiviral Drugs And Strategies: Part I: DNA Viruses and Retroviruses

More than 40 compounds have been formally licensed for clinical use as antiviral drugs, and half of these are used for the treatment of HIV infections. The others have been approved for the therapy of herpesvirus (HSV, VZV, CMV), hepadnavirus (HBV), hepacivirus (HCV) and myxovirus (influenza, RSV) infections. New compounds are in clinical development or under preclinical evaluation, and, again, half of these are targeting HIV infections. Yet, quite a number of important viral pathogens (i.e. HPV, HCV, hemorrhagic fever viruses) remain in need of effective and/or improved antiviral therapies.

Viruses and Viral Diseases

More than 40 compounds have been formally licensed for clinical use as antiviral drugs, and half of these are used for the treatment of human immunodeficiency virus (HIV) infections. The others have been approved for the therapy of herpesvirus (herpes simplex virus (HSV), varicella-zoster virus (VZV), cytomegalovirus (CMV)), hepadnavirus (hepatitis B virus (HBV)), hepacivirus (hepatitis C virus (HCV)), and myxovirus (influenza, respiratory synctural virus (RSV)) infections. New compounds are in clinical development or under preclinical evaluation, and, again, half of these target HIV infections. Yet, quite a number of important viral pathogens (i.e., human papilloma virus (HPV), HCV, hemorrhagic fever viruses) remain in need of effective and/or improved antiviral therapies.

Efficacy of antiviral compounds in human herpesvirus-6-infected glial cells

The beta-herpesvirus human herpesvirus-6 (HHV-6) is becoming increasingly recognized as an important pathogen in immunocompromised patients, particularly in post bone marrow transplant (BMT). Reactivation of latent HHV-6 resulting in encephalitis has been reported in BMT and stem cell transplant (SCT) patients. The development of HHV-6 encephalitis can be a fatal complication, the frequency of which is increasing likely due to improved diagnosis with quantitative polymerase chain reaction (PCR) of cerebrospinal fluid. There are currently no antiviral compounds approved for HHV-6, nor have any controlled clinical trials been conducted. The frequency and severity of HHV-6 encephalitis in both immunocompetent and immunocompromised patients necessitates studies on the usefulness of currently available anti-viral compounds. The authors compared the antiviral efficacy of four drugs currently used for cytomegalovirus (CMV) infection, a beta-herpesvirus sharing homology with HHV-6. In HHV-6A- and HHV-6B-infected T cells, acyclovir, ganciclovir, foscarnet, and cidofovir exhibited antiviral activity consistent with that published in other studies. In HHV-6-infected human astrocytes (U251), however, only foscarnet and cidofovir exhibited antiviral activity and this effect was restricted to infection with HHV-6 variant A. In pathological brain sections from patients with neurological disorders such as multiple sclerosis and epilepsy, HHV-6 has been localized to glial cells. Determination of antiviral activity in human glial fibrillary acidic protein (GFAP)-positive astrocytes of currently used antiviral compounds is essential for potential treatment of HHV-6 and neurological disorders. Our data highlight the necessity for further study of antiviral compound in HHV-6-infected glial cells as well as the development of more selective compounds for HHV-6.

Biological and clinical advances in human herpesvirus-6 and -7 research

Since its isolation more than 20 years ago, human herpesvirus (HHV)-6 has been considered an opportunistic pathogen whose infection and/or reactivation is associated with diseases such as roseola, organ transplant anomalies and central nervous system disorders. The lack of relevant animal models, standardized diagnostic reagents and specific anti-HHV-6 drugs has impaired our ability to prove a causal relationship between the presence of this virus and the development of many diseases. Unless such models and reagents are developed and clinical trials performed, speculations on the role for this virus in various pathologies will continue to grow. In this review, recent biological, clinical and epidemiological research advances in the HHV-6 field as well as that of its closest relative, HHV-7, will be presented. Additionally, priority research areas that will help move the field forward are discussed.

Antiviral properties of new arylsulfone derivatives with activity against human betaherpesviruses

Based on our previous experience with arylsulfone derivatives displaying antiherpetic activity, we synthesized several analogues in which the sulfonyl group is part of a bicyclic structure. The benzene-fused derivative 2H-3-(4-chlorophenyl)-3,4-dihydro-1,4-benzo-thiazine-2-carbonitrile 1,1-dioxide and its thiophene-fused analogue were shown to have favorable activity and selectivity against the betaherpesviruses human cytomegalovirus (HCMV) and human herpesvirus 6 (HHV-6) and 7 (HHV-7). The benzene-fused derivative retained its anti-HCMV activity when evaluated against virus strains resistant to foscarnet, ganciclovir, and/or cidofovir. The compound conferred >or=95% inhibition of viral DNA synthesis in HHV-6-infected cells. RT-PCR analysis of immediate-early, early and late gene products revealed that this arylsulfone compound acts at a step preceding late gene expression, and coinciding with the inhibition exerted by foscarnet. No inhibitory effect was seen in an enzyme assay for DNA elongation catalyzed by the HCMV or HHV-6 DNA polymerase catalytic subunit. The arylsulfone derivatives had no effect on the functional interaction between the catalytic subunit of HCMV DNA polymerase and its accessory protein, nor did they disrupt the physical interaction between the two proteins. We conclude that these arylsulfone derivatives represent new betaherpesvirus inhibitors with a novel mode of action that results in indirect inhibition of viral DNA synthesis.

Recent highlights in the development of new antiviral drugs

Twenty antiviral drugs, that is about half of those that are currently approved, are formally licensed for clinical use in the treatment of human immunodeficiency virus infections (acquired immune deficiency syndrome). The others are used in the treatment of herpesvirus (e.g. herpes simplex virus, varicella zoster virus and cytomegalo virus), hepatitis B virus, hepatitis C virus or influenza virus infections. Recent endeavours have focussed on the development of improved antiviral therapies for virus infections that have already proved amenable to antiviral drug treatment, as well as for virus infections for which, at present, no antiviral drugs have been formally approved (i.e. human papilloma viruses, adenoviruses, human herpesvirus type 6, poxviruses, severe acute respiratory syndrome coronavirus and hemorrhagic fever viruses).