Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.1.21 (thymidine kinase)
7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Varicella zoster virus (VZV) is responsible for a primary infection (varicella) and, upon reactivation, zoster, which in immunocompromised patients, may both lead to life-threatening disseminated disease. There is a great need for antiviral compounds that are effective inhibitors of VZV replication and for rapid and accurate methods for evaluating viral sensitivity to candidate anti-VZV drugs. With the monoclonal antibody (mAb) (VL8), which is directed against the gpI of VZV, and using the fluorescence-activated cell sorter (FACS) we could readily demonstrate expression of the VZV gpI antigen at 3-4 days after VZV infection. (E)-5-(2-Bromovinyl)-2'-deoxyuridine (BVDU), (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) and (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMC) were shown to be potent inhibitors of VZV replication by this assay. HPMPA and HPMPC were also active against thymidine kinase-deficient (TK-) VZV whereas BVDU was not. The flow cytometric method based on the use of mAb VL8 may be of considerable help for the early diagnosis of VZV infection and evaluation of viral sensitivity to antiviral drugs.
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PMID:Flow cytometric method for the detection of gpI antigens of varicella zoster virus and evaluation of anti-VZV agents. 132 72

A previously healthy 5-year-old boy developed cerebral vasculopathy, presenting as two episodes of acute hemiparesis 3 and 9 months, respectively, after a primary varicella infection (chickenpox). This association has not been reported before, to our knowledge, although cerebral vasculopathy is a well-known complication of herpes zoster ophthalmicus. The diagnosis was based on the presence of oligoclonal varicella-specific IgG in the cerebrospinal fluid and angiographic findings. Clinical and angiographic follow-up, and serial thymidine kinase activity levels in the cerebrospinal fluid suggested a self-limiting course of the virus-induced vasculopathy. Varicella zoster virus seems to be another potential causative agent to be considered in acute childhood hemiplegia.
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PMID:Cerebral vasculopathy associated with primary varicella infection. 195 9

Four patients with human immunodeficiency virus (HIV) infection who received chronic oral acyclovir therapy for suppression of recurrent varicella zoster or herpes simplex virus infection developed persistent disseminated hyperkeratotic papules that failed to heal with intravenous or high-dose oral acyclovir therapy. Varicella zoster virus, resistant to acyclovir in vitro, was isolated from skin lesions of all four patients. Three patients were adults in whom the acquired immunodeficiency syndrome (AIDS) had been diagnosed 12 to 20 months before isolation of acyclovir-resistant varicella zoster virus. The fourth patient was a perinatally HIV-infected child who developed primary varicella infection at age 7 years when profoundly immunosuppressed (absolute CD4+ lymphocyte count less than 50 cells/microL). Mean antiviral susceptibilities (ED50 values) of the four clinical isolates compared with the ED50 values of the reference strain Oka were 85 compared with 3.3 mumol/L for acyclovir, 1.4 compared with 0.8 mumol/L for vidarabine, and 123 compared with 117 mumol/L for foscarnet. When assayed by [125I]-dC plaque autoradiography, 90% to 100% of the viral isolate populations had altered or no measurable thymidine kinase function. Acyclovir-resistant varicella zoster virus infection may complicate long-term oral acyclovir administration in patients with AIDS and may be associated with the appearance of atypical hyperkeratotic papules.
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PMID:Acyclovir-resistant varicella zoster virus infection after chronic oral acyclovir therapy in patients with the acquired immunodeficiency syndrome (AIDS). 229 95

Varicella zoster virus (VZV) is recognized as one of the major viral pathogens reactivated in patients with the acquired immune deficiency syndrome (AIDS). We report the case of meningoradiculoneuritis in an AIDS patient,associated with the isolation in the cerebrospinal fluid (CSF) of a thymidine kinase (TK)-deficient, acyclovir (ACV)-resistant strain of VZV. Although the virus was sensitive in vitro to phosphonoformate (PFA), the patient did not improve during PFA therapy and finally died. Several VZV strains isolated from this patient (including two isolates from the patient's CSF) were analyzed for their TK activity and subsequently the viral TK gene was sequenced showing a major deletion leading to a truncated protein. Their susceptibility to several antiviral agents including ACV, PFA, (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU), 9-beta-D-arabinofuranosyladenine (vidarabine), (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine (HPMPC), and (S)-9-(3-hydroxy-2-phosphonyl-methoxypropyl)adenine (HPMPA) was evaluated. All the virus strains isolated from this patient remained sensitive to HPMPA and HPMPC, pointing to the potential usefulness of these acyclic nucleoside phosphonates for the treatment of ACV-resistant VZV infections in immunocompromised patients.
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PMID:Meningoradiculoneuritis due to acyclovir-resistant varicella zoster virus in an acquired immune deficiency syndrome patient. 804 24

Replication-defective retroviral vectors were created that contained chimeric genes composed of either the albumin (ALB) or the alpha-fetoprotein (AFP) transcriptional regulatory sequences linked to the coding domain of the thymidine kinase gene from Varicella zoster virus (VZV TK). These viruses were used to infect the human hepatoblastoma cell line, HepG2. Subsequent to infection, the infected cells were single-cell cloned. The level of expression of VZV TK from the chimeric genes correlated with the level of endogenous expression of ALB or AFP in most clones, indicating that the transcription of the chimeric VZV TK gene is controlled in a similar manner to the endogenous ALB or AFP genes, and that sites of viral integration are less important to overall gene expression. Most importantly, as the expression of the endogenous ALB gene was modified, so was expression of VZV TK from the ALB/VZV TK chimeric gene. This demonstrates that retroviruses can deliver a chimeric gene containing tissue-specific transcriptional regulatory sequences that can respond to endogenous cell regulatory signals resulting in regulated gene expression.
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PMID:Regulated expression of artificial chimeric genes contained in retroviral vectors: implications for virus-directed enzyme prodrug therapy (VDEPT) and other gene therapy applications. 886 54

To investigate the potential of the thymidine kinase gene from Varicella zoster virus (VZVtk) to act as a suicide gene, VZVtk was transferred via a dicistronic retroviral construct into MCF7, T-47D and MDA-MB-435 human breast cancer cells. The cytotoxicity of antiviral drugs was then evaluated in vitro on the wild-type and transduced cells. Acyclovir and ganciclovir did not show any selective toxicity for the modified cells. In contrast, (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) was extremely toxic for the VZVtk expressing cells, with IC50 values of 0.6 microM, 0.1 microM and 0.06 microM for MCF7, T-47D and MDA-MB-435 cells, respectively. The selectivity index of BVDU (ie the IC50 value ratio of the wild-type to the VZVtk cells) was 400 for MCF7, 750 for T-47D and 2000 for MDA-MB-435 cells. To test the system in vivo, VZVtk carrying MDA-MB-435 cells were inoculated subcutaneously into nude mice. An intraperitoneal treatment with BVDU administered at the emergence of the tumors, led to a prolonged arrest of the tumor growth and a reduced tumor mass. This effect was BVDU dose-dependent. No bystander effect of BVDU killing could be demonstrated in vitro on mixed populations of VZVtk positive and negative MDA-MB-435 cells. However, an important bystander effect was observed in identical experiments performed on 9L rat gliosarcoma cells infected with the VZVtk-carrying vector. These results demonstrate the efficiency of VZVtk as a suicide gene when BVDU is used as prodrug. The bystander effect measured in vitro, depends however on the tumoral cell type used.
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PMID:Potential of Varicella zoster virus thymidine kinase as a suicide gene in breast cancer cells. 923 Oct 72

Varicella zoster virus (VZV), a member of the herpesvirus family, is responsible for both primary (varicella, chickenpox) as well as reactivation (zoster, shingles) infections. In immunocompetent patients, the course of varicella is generally benign. For varicella zoster, post-herpetic neuralgia is the most common complication. In immunocompromised patients (particularly those with AIDS), transplant recipients and cancer patients, VZV infections can be life-threatening. For these patients and also for immunocompetent patients at risk such as pregnant women or premature infants, the current treatment of choice is based on either intravenous or oral aciclovir (acyclovir). The low oral bioavailability of aciclovir, as well as the emergence of drug-resistant virus strains, have stimulated efforts towards the development of new compounds for the treatment of individuals with VZV infections. Among these new compounds, penciclovir, its oral prodrug form famciclovir and the oral pro-drug form of aciclovir (valaciclovir), rank among the most promising. As with aciclovir itself, all of these drugs are dependent on the virus-encoded thymidine kinase (TK) for their intracellular activation (phosphorylation), and, upon conversion to their triphosphate form, they act as inhibitors/alternative substrate of the viral DNA polymerase. Therefore, cross-resistance to these drugs may be expected for those virus mutants that are TK-deficient and thus resistant to aciclovir. Other classes of nucleoside analogues dependent for their phosphorylation on the viral TK that have been pursued for the treatment of VZV infections include sorivudine, brivudine, fialuridine, fiacitabine and netivudine. Among oxetanocins, which are partially dependent on viral TK, lobucavir is now under clinical evaluation. Foscarnet, which does not require any previous metabolism to interact with the viral DNA polymerase, is used in the clinic when TK-deficient VZV mutants emerge during aciclovir treatment. TK-deficient mutants are also sensitive to the acyclic nucleoside phosphonates (i.e. [s]-1-[3-hydroxy-2-phosphonylmethoxypropyl]cytosine; HPMPC); these agents do not depend on the virus-encoded TK for their phosphorylation but depend on cellular enzymes for conversion to their diphosphoryl derivatives which then inhibit viral DNA synthesis. Vaccination for VZV has now come of age. It is recommended for healthy children, patients with leukaemia, and patients receiving immunosuppressive therapy or those with chronic diseases. The protection induced by the vaccine seems, to some extent, to include zoster and associated neuralgia. Passive immuniatin based on specific immunoglobulins does not effectively prevent VZV infection and is therefore restricted to high risk individuals (i.e. immunocompromised children and pregnant women).
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PMID:Current pharmacological approaches to the therapy of varicella zoster virus infections: a guide to treatment. 1018 60

The inhibitory effects of (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) and its arabinosyl derivative (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil (BVaraU) on the growth of both MDA-MB-435 human breast carcinoma and 9L rat gliosarcoma cells expressing the thymidine kinase (tk)-encoding gene of the Varicella zoster virus (VZV) or the Herpes simplex virus (HSV) were evaluated. In vitro, BVDU and BVaraU effectively killed both cell types expressing VZVtk, with 50% inhibitory concentration values ranging from 0.06 to 0.4 microM, whereas ganciclovir (GCV) lacked activity. On HSVtk+ cells, BVDU had high cytotoxic activity, with 50% inhibitory concentration values that were similar to those of GCV, whereas BVaraU was inactive. In vivo, BVDU applied intraperitoneally caused a 50% tumor growth inhibition in nude mice inoculated subcutaneously with VZVtk+ as well as HSVtk+ mammary tumor cells. In mice and at variance with the in vitro results, BVaraU had very little activity against the VZVtk+ mammary cells; GCV had the highest activity on the HSVtk+ cells, resulting in a 50% eradication of the tumors. With the 9L rat gliosarcoma model, the VZVtk/BVDU system completely failed to inhibit the development of VZVtk+ glioma tumors induced subcutaneously in syngeneic rats, although BVDU had a similar 45-minute half-life in both rats and mice. Factors other than degradation of the prodrug and related to the mode of action of these analogs are possibly involved in the observed discrepancies between the in vitro and in vivo results.
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PMID:Comparative in vitro and in vivo cytotoxic activity of (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) and its arabinosyl derivative, (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil (BVaraU), against tumor cells expressing either the Varicella zoster or the Herpes simplex virus thymidine kinase. 1077 Jun 29

To investigate the factors influencing the bystander effect--a key element in the efficacy of suicide gene therapy against cancer--we compared the effect triggered by four extremely efficient gene/prodrug combinations, i.e., VZVtk/BVDU, the thymidine kinase of Varicella zoster virus associated with (E)-5-(2-bromovinyl)-2'-deoxyuridine; VZVtk/BVaraU, the same enzyme associated with (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil; HSVtk/BVDU, the association of the Herpes simplex virus thymidine kinase with BVDU; and the classical HSVtk/GCV (ganciclovir) paradigm. The cells used, the human MDA-MB-435 breast cancer, and the rat 9L glioblastoma lines were equally sensitive in vitro to these four associations. In both cell types, the combinations involving pyrimidine analogues (BVDU, BVaraU) displayed a smaller bystander killing than the combination involving the purine analogue (GCV). In addition, the bystander effect induced by all the tk/prodrug systems was reduced in MDA-MB-435 cells in comparison to 9L cells; albeit, the viral kinases were produced at a higher level in the breast cancer cells. All systems induced apoptotic death in the two cell types, but the MDA-MB-435 cells, deprived of connexin 43, were noncommunicating in striking contrast with the 9L cells. That functional gap junctions have to be increased in order to improve the breast cancer cell response to suicide gene therapy was demonstrated by transducing the Cx43 gene: this modification enhanced the bystander effect associated in vitro with GCV treatment and, by itself, decreased the tumorigenicity of the untreated cells. However, the noncommunicating MDA-MB-435 cells triggered a significant bystander effect both in vitro and in vivo with the HSVtk/GCV system, showing that communication through gap junctions is not the only mechanism involved.
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PMID:The role of cellular- and prodrug-associated factors in the bystander effect induced by the Varicella zoster and Herpes simplex viral thymidine kinases in suicide gene therapy. 1112 88

Herpes virus thymidine kinases are responsible for the activation of nucleoside antiviral drugs including (E)-5-(2-bromovinyl)-2'-deoxyuridine. Such viral thymidine kinases (tk), beside having a broader substrate specificity compared with host cell enzymes, also show significant variation in nucleoside phosphorylation among themselves. We have determined the crystal structure of Varicella zoster virus (VZV, human herpes virus 3) thymidine kinase complexed with (E)-5-(2-bromovinyl)-2'-deoxyuridine 5'-monophosphate and ADP. Differences in the conformation of a loop region (residues 55-61) and the position of two alpha-helices at the subunit interface of VZV-tk compared with the herpes simplex virus type 1 (human herpes virus 1) enzyme give rise to changes in the positioning of residues such as tyrosine 66 and glutamine 90, which hydrogen bond to the substrate in the active site. Such changes in combination with the substitution in VZV-tk of two phenylalanine residues (in place of a tyrosine and methionine), which sandwich the substrate pyrimidine ring, cause an alteration in the positioning of the base. The interaction of the (E)-5-(2-bromovinyl)-2'-deoxyuridine deoxyribose ring with the protein is altered by substitution of tyrosine 21 and phenylalanine 139 (analagous to herpes simplex virus type 1 histidine 58 and tyrosine 172), which may explain some of the differences in nucleoside sugar selectivity between both enzymes. The altered active site architecture may also account for the differences in the substrate activity of ganciclovir for the two thymidine kinases. These data should be of use in the design of novel antiherpes and antitumor drugs.
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PMID:Crystal structure of varicella zoster virus thymidine kinase. 1268 43


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