Rapid diagnosis of varicella-zoster virus infection by detection of viral deoxythymidine kinase in serum and vesicle fluid

Recognition and treatment of shingles

Varicella zoster virus (VZV) is responsible for a primary infection (varicella) followed by a latency, eventually resulting in herpes zoster (shingles). The replication cycle of VZV is normally interrupted after varicella. Consequently, VZV remains dormant in the organism. Reactivation occurs after viraemia, and the development of tissue alterations (skin and viscera) depends on the immunological status of the patient. Diagnosis of herpes zoster relies on clinical recognition and cytological and histological evaluations combined with immunohistochemistry and molecular biology techniques. Treatment of herpes zoster primarily relies upon antiviral drugs and incidentally on immunomodulating agents, specific immunoglobulins, antimicrobial agents, antiviral enzymes and corticosteroids. Drugs with a clinically relevant activity against varicella zoster virus infections include aciclovir, adenosine monophosphate, bromodeoxyuridine, desciclovir, fiacitabine, idoxuridine, interferon-alpha and vidarabine. Among them, aciclovir appears to be a first-line agent. Its efficacy has been well established by many clinical studies. Promising drugs for the future include famciclovir, penciclovir, valaciclovir and other molecules currently under investigation. Recent and promising improvements in antiviral drug development may increase patient compliance, cost-benefit ratios and therapeutic efficacy.

Thymidine kinase: a tumor marker with prognostic value for non-Hodgkin's lymphoma and a broad range of potential clinical applications

Thymidine kinase (TK) is a cellular enzyme which is involved in a "salvage pathway" of DNA synthesis. It is activated in the G1/S phase of the cell cycle, and its activity has been shown to correlate with the proliferative activity of tumor cells. Additionally, certain viruses are able to induce cellular TK production and activity. Clinical studies have reported elevated serum TK levels in a variety of neoplasias. The majority of these studies concerned hematologic malignancies. TK seems to be a useful marker in non-Hodgkin's lymphoma, where it correlates with clinical staging and provides significant prognostic information on (progression-free) survival. Preliminary results in acute myeloid leukemia indicate that pretreatment serum TK values may predict the response to the first induction chemotherapy. Moreover, serum TK appears to have some clinical value in such solid tumors as prostate cancer, breast cancer, and small-cell lung cancer, whereas it is not a reliable marker of non-small-cell lung cancer and brain tumors.

Neuron specific enolase (NSE) and thymidine kinase (TK) as markers in biological fluids of brain tumor patients

We studied the activity of two enzymes NSE and TK in the biological fluids of 104 patients with nervous system diseases, who fell into 4 groups. 20 subjects out of 35 in the tumor group had glial tumors. We fixed a cut-off value of NSE and TK activity at the 95th percentile of the control group, both in serum and in CSF. The aim of our investigation was to assess the reliability of TK and NSE assays in separating brain tumors from other neurological diseases. In our patients, most of the TK activity above the cut-off value was found in the tumor group. Serum TK seems to be a useful marker for following up cerebral tumors after surgery, but NSE is less useful for this purpose.

Molecular forms in human serum of enzymes synthesizing DNA precursors and DNA

Both thymidine kinase (TK) and DNA polymerase (DNAp) are present in measurable amounts in human serum. Even though the use of TK as a clinical marker is rapidly increasing there has been no attempt to characterize the serum TK in a wider extent, i.e.; with respect to Mw or other biochemical parameters. Therefore sera with high TK or DNAp activities derived from patients with cytomegalovirus (CMV) infection, B12-deficiency and leukaemia were fractionated by gel exclusion chromatography. The TK activity eluted as two peaks, one major TK activity with an apparent molecular weight (Mw) or 730 kD and one minor TK activity corresponding to a Mw of 58 kD. The amount of TK activity at 58 kD varied between 7 and 23% of total activity, depending on the serum fractionated. The DNAp activity in sera from patients with malignant disease and B12 deficiency eluted as a single peak corresponding to a Mw of 240 kD. A DNAp with a different Mw (greater than 1000 kD) was recovered from 1 of 3 investigated immunosuppressed patients with CMV infection. A similar pattern of enzyme forms was observed when sera were separated by glycerol gradient centrifugation. The effect of high salt and various reaction solution components on the enzymes were studied. The only condition found that affected the molecular forms of TK was the state of reduction. Incubation of sera with high concentrations of dithioerythritol (DTE) (400 mM) prior to separation transferred all serum TK to the 58 kD form, it also converted most of the serum DNAp from the 240 kD form to a smaller form (56 kD) without affecting the total recovery of enzymatic activity. The reaction product from both TK forms was exclusively monophosphate and none of the TK forms could efficiently utilize cytidine triphosphate as phosphate donor. The substrate kinetics of the small serum TK fraction was identical with those of an enzyme with similar size purified from proliferating HeLa cells, indicating that both serum TK activities are forms of TK 1, the proliferation associated cellular isozyme.

Antibodies against varicella-zoster virus and herpes simplex virus deoxythymidine kinase in heterologous infections

Antibody responses to varicella-zoster virus (VZV) deoxythymidine kinase (dTK) and herpes simplex virus (HSV) dTK in homologous and heterologous infections were studied. Antibodies blocking the enzymatic activity of VZV-dTK appeared late after varicella and decreased more or less in parallel with the decreasing complement fixing [CF] titre. In herpes zoster, on the other hand, antibodies to VZV-dTK appeared soon after infection. Antibodies against HSV dTKs appeared long after primary infection, but they were subsequently present in all other HSV-CF positive sera. In recurrent HSV, all acute sera were already HSV-dTK antibody positive, and three of nine persons showed an increase in titer between their acute and convalescent sera. Blocking antibodies to VZV-dTK appeared rapidly in specimens from three of 18 individuals positive by an immunofluorescence VZV-immunity test during HSV infection, whereas all other specimens remained devoid of blocking antibodies against VZV-dTK. A rise in antibody titre against HSV-dTK during VZV infections was observed in serum specimens from three of 13 HSV-CF positive patients, whereas an antibody response against HSV-dTK was not found in HSV-CF negative individuals in connection with VZV infections. The relevance of the sporadic increase in the titres of antibodies against heterologous viral dTKs is discussed.

Varicella zoster virus deoxythymidine kinase is present in serum before the onset of varicella

A sensitive enzyme assay with 125I-iododeoxyuridine as substrate and cytidine triphosphate as phosphate donor was used for the direct detection of varicella zoster virus (VZV) deoxythymidine kinase (TK) in human serum. Sera sampled during the incubation period of varicella from 2 patients, a 42-year-old man and his 11-year-old son, have been analysed for TK activity. A simultaneous increase in cellular and VZV TK activity, starting 5 to 3 days before the onset of clinical varicella, was observed.

An optimized thymidylate kinase assay, based on enzymatically synthesized 5-[125I]iododeoxyuridine monophosphate and its application to an immunological study of herpes simplex virus thymidine-thymidylate kinases

The biological synthesis and purification of 5-[125I]iododeoxyuridine monophosphate (IdUMP) are described. The specificity of IdUMP as substrate in the thymidylate monophosphate kinase (TMPK) assay is demonstrated, and a 100-fold gain in sensitivity as compared to the conventional TMPK assay is shown. TMPK measurements of isozymes derived from herpes simplex virus (HSV)-infected cells, uninfected cells, and tumor biopsies were performed. The results showed a significant difference in dependence of phosphate donor concentration present for TMPK activity from HSV-infected cells compared to the corresponding activity from uninfected cells, while only a minor difference in pH optima was observed for these enzyme activities. The increased sensitivity made it possible to detect and quantify HSV TMPK-blocking antibodies (ab) present in human sera. Sera from HSV ab-positive individuals were found to block the two HSV TMPKs to varying degrees and with different specificities. The immunological relationship between the TMPK and thymidine kinase (TK) induced by HSV-1 and HSV-2, respectively, was studied by comparing the capacities of different sera to block the two enzymatic activities. The results showed that the capacity to block HSV-1 TK and TMPK was proportional for all of the sera studied, while sera that preferentially blocked only the HSV-2 TMPK or HSV-2 TK were found. It was concluded that the HSV-2 TMPK and TK activities are less related than the corresponding activities for HSV-1 and that the HSV-2 enzyme activities are mediated by different catalytic sites.

Serum deoxythymidine kinase correlates with peripheral lymphocyte thymidine uptake in chronic lymphocytic leukemia

The serum thymidine kinase (S-TK) and proliferative activity of the leukemic cells were determined in 27 untreated patients with chronic lymphocytic leukemia (CLL). A significant positive correlation between S-TK and proliferation expressed as a proliferative index (PI) was found (r = 0.70, p less than 0.001). Additionally, PI (r = 0.59, p less than 0.01) and S-TK (r = 0.47, p less than 0.05) correlated to peripheral blood lymphocyte count. When different variables and combinations of variables were studied in order to define their capacity for discriminating between progressive and indolent CLL, S-TK activity and PI proved to be powerful indications. In longitudinal studies, both S-TK and PI paralleled disease activity. A model where a combination of S-TK and PI gives information of the degree of localized disease is proposed.

Inhibiting effect of (RS)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine on varicella-zoster virus replication in cell culture

The activity and mode of action of the new nucleoside analog (RS)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine (2HM-HBG) against varicella-zoster virus (VZV) were determined. In cell culture, replication of different strains of VZV was inhibited to 50% by 0.4 to 0.7 microM 2HM-HBG, while 685 microM was required to inhibit 50% of the DNA synthesis in uninfected human lung fibroblasts. A thymidine kinase-negative VZV strain was not inhibited by 100 microM 2HM-HBG. Inhibition of VZV replication was not reversible after 7 to 14 days of incubation, depending on the multiplicity of VZV. 2HM-HBG was shown to be selectively phosphorylated by purified VZV thymidine kinase, with an inhibition constant of 32.5 microM. The antiviral activity of 2HM-HBG in cell culture was decreased by the addition of deoxythymidine and deoxycytidine but not by other ribo- or deoxyribonucleosides.

Serum deoxythymidine kinase in small cell carcinoma of the lung. Relation to clinical features, prognosis, and other biochemical markers

Thymidine kinase (s-TK), lactate dehydrogenase (LDH), and carcinoembryonic antigen (CEA) were determined in pretreatment serum from 125 patients with small cell carcinoma of the lung. The distribution of marker levels into three ranges, when including all patients were as follows: s-TK less than 5 units 49%, 5-less than 10 units 25%, greater than or equal to 10 units 26%; LDH less than 6.7 mukat 31%, 6.7-less than 13.4 mukat 48%, greater than or equal to 13.4 mukat 21%; CEA less than 7.5 micrograms/l 51%, 7.5-less than 15 micrograms/l 25%, greater than or equal to 15 micrograms/l 24%. The percentages of patients with limited and with extensive disease within each range were s-TK less than 5 82/18, 5-less than 10 29/71, greater than or equal to 10 9/91; LDH less than 6.7 76/24, 6.7-less than 13.4 51/49, greater than or equal to 13.4 21/79; CEA less than 7.5 70/30, 7.5-less than 15 39/61, greater than or equal to 15 23/77. Analyses in relation to metastases present showed that patients with skeletal and bone marrow metastases had significantly higher s-TK and LDH than those without, while this was not the case for CEA. A strong correlation between s-TK and LDH level, a weaker correlation between CEA and s-TK, and no correlation between CEA and LDH level, was found. Both the level of s-TK and LDH correlated to the patients' performance, as defined by the Karnofsky index. These correlations were mainly confined to the patients with extensive disease. Analyses of the prognostic capacity of variables showed that s-TK, stage, and Karnofsky index could divide the patients into groups with highly significant difference in survival time, while LDH and CEA were of less value. Longitudinal studies showed that the serum markers mirrored the disease activity, with the exception that highly increased s-TK was found during remission induction for some patients. It was concluded that the expression of pathologic levels for the serum markers were dependent on different biological parameters. Of the serum markers, only s-TK was judged useful for estimation of disease spread and prognosis of the individual patient.

Acyclic guanosine analogs as substrates for varicella-zoster virus thymidine kinase

This study was performed to obtain information on the enzymatic background to the antiviral activity of acyclic guanosine analogs. Five acyclic guanosine analogs, the (R)- and (S)-enantiomers of 9-(3,4-dihydroxybutyl)guanine, 9-(4-hydroxybutyl)guanine, 9-[(2-hydroxyethoxy)methyl]guanine, and 9-[[2-hydroxy-1-(hydroxymethyl)ethoxy]methyl]guanine, were compared in enzyme kinetic experiments using purified varicella-zoster virus and human placenta mitochondrial thymidine kinase (TK). All analogs showed competitive patterns of inhibition in the phosphorylation of thymidine by varicella-zoster virus TK, but only low affinities and phosphorylation rates were observed. No affinity for the mitochondrial TK was observed for any of the analogs.

Evaluation of serum deoxythymidine kinase as a marker in multiple myeloma

A recently developed deoxythymidine kinase assay utilizing 125I-iododeoxyuridine as substrate was used in an investigation of sera from 122 untreated patients with multiple myeloma. Most patients had slightly elevated or normal serum deoxythymidine kinase activity (S-TK), although in some patients values increased by more than forty-fold were found. S-TK correlated with the haemoglobin level but did not correlate with sex, age, erythrocyte sedimentation rate, nor with the serum concentrations of creatinine, beta 2-micro-globulin, Ca or M-component. The distribution of S-TK values in IgG, IgA and pure Bence-Jones myeloma did not differ significantly. Patients with IgG and IgA myeloma excreting light-chain immunoglobulin in the urine had significantly higher S-TK than non-excreters. There was a significant correlation between S-TK values and tumour cell mass as determined by clinical staging. A high pretreatment S-TK (greater than 5.1 units) also distinguished a group of patients with a significantly shorter survival time. Patients with no response to initial therapy had significantly higher S-TK values than those who did respond. In longitudinal studies of 11 patients, S-TK was found to increase when the disease became more aggressive. The possibility of diagnosing disease progression at an early stage by an elevation of S-TK is discussed.

Serum deoxythymidine kinase gives prognostic information in chronic lymphocytic leukemia

A recently developed deoxythymidine kinase assay, utilizing iodine-125-iodo-deoxyuridine as substrate and capable of detecting enzyme activity in serum from healthy humans, was used in an investigation of sera from 55 untreated patients with chronic lymphocytic leukemia (CLL). When confined to the study, the patients were classified as having progressive or indolent disease and according to Rai stage. The results showed a significant correlation between serum deoxythymidine kinase activity (S-TK) and disease status, i.e., higher values were found in patients with progressive disease, compared to those with indolent disease. S-TK also correlated with Rai stage. S-TK values of more than 40 times the normal value were found in some patients. All patients with S-TK greater than 8.4 units had a disease that was or became progressive during the observation period. Within the patient group with indolent disease two groups that differed with regard to prognosis could be distinguished according to their initial S-TK values. In longitudinal studies of 18 patients with indolent disease, S-TK was found to exceed 8.4 units only on one occasion during an observation period of up to 68 months. In patients with indolent disease, a transition to progressive disease was parallelled by an increase in S-TK. Studies of S-TK levels in 18 patients receiving treatment showed that S-TK decreased during successful therapy. S-TK was also found to increase when the disease was reactivated. From these results it is concluded that S-TK could be used as a prognostic marker for the individual CLL patient. Furthermore, S-TK seems to be useful for longitudinal follow-up studies of disease status, both in indolent disease and in progressive disease during treatment.

Application of an in vitro assay for serum thymidine kinase: results on viral disease and malignancies in humans

An improved method for the detection of deoxythymidine kinase (TK) in human sera is reported. The method which utilizes 125I-iododeoxyuridine (IdUrd) as a substrate was used to measure TK in sera from patients with different diseases. Sera collected during the acute stage of infectious mononucleosis were found to contain elevated levels of TK, in most cases 10-40 times the normal value. The serum TK activity disappeared gradually and reached a normal level within 4 weeks. Sera from patients with other viral infections contained in most cases normal serum TK levels except in connection with measles, rubella, varicella, herpes simplex virus and cytomegalovirus infections. Additional studies revealed that sera from patients with different types of advanced lymphomas, acute leukemias, chronic granulocytic leukemia and lung cancer of the small-cell type with metastases, contained high TK levels which fluctuated in parallel with alterations in activity of the disease. The TK activity in sera from patients with both mononucleosis and tumor disease was characterized by electrophoresis and by its ability to utilize cytidine triphosphate as the phosphate donor. The results showed that the serum TK has the same properties as the human cytosolar TKI, except in connection with varicella.

Serum thymidine kinase in vitamin B12 deficiency

In DNA synthesis deoxythymidine kinase (TK) catalyses the conversion of deoxythymidine to deoxythymidine monophosphate (dTMP) via the 'salvage pathway'. Serum deoxythymidine kinase (S-TK) was measured in this study in 75 patients with vitamin B12 deficiency by a new, very sensitive method, using 125I-deoxyuridine as substrate. Elevated S-TK levels were found in those patients who had developed haemolysis and anaemia and the more advanced the disease the higher the S-TK value. Thus there was a highly significant correlation between S-TK, haemoglobin level and lactic dehydrogenase activity. These findings are consistent with the theory that elevated levels of S-TK are due to release from unstable proliferating tissue.