Quantitation Of Cytomegalovirus DNA Research Articles

Detection of Cytomegalovirus (CMV) DNA in EDTA Whole-Blood Samples: Evaluation of the Quantitative artus CMV LightCycler PCR Kit in Conjunction with Automated Sample Preparation

Whole blood has been found to be a reliable matrix for the detection and quantitation of cytomegalovirus (CMV) DNA. In this study, the performance of the artus CMV LightCycler (LC) PCR kit in conjunction with automated sample preparation on a BioRobot EZ1 workstation was evaluated. The accuracy, linearity, analytical sensitivity, and inter- and intra-assay variations were determined. A total of 102 clinical EDTA whole-blood samples were investigated, and results were compared with those obtained with the in vitro diagnostics (IVD)/Conformité Européene (CE)-labeled CMV HHV6,7,8 R-gene quantification kit. When the accuracy of the new kit was tested, seven of eight results were found to be within +/-0.5 log(10) unit of the expected panel results. Determination of linearity resulted in a quasilinear curve over more than 5 log units. The lower limit of detection of the assay was determined to be 139 copies/ml in EDTA whole blood. The interassay variation ranged from 15 to 58%, and the intra-assay variation ranged from 7 to 35%. When clinical samples were tested and the results were compared with those of the routinely used IVD/CE-labeled assay, 53 samples tested positive and 13 samples tested negative by both of the assays. One sample was found to be positive with the artus CMV LC PCR kit only, and 35 samples tested positive with the routinely used assay only. The majority of discrepant results were found with low-titer samples. In conclusion, use of the artus CMV LC PCR kit in conjunction with automated sample preparation on the BioRobot EZ1 workstation may be suitable for the detection and quantitation of CMV DNA in EDTA whole blood in the routine low-throughput laboratory; however, low-positive results may be missed by this assay.

Multicentric evaluation of a new commercial cytomegalovirus real-time PCR quantitation assay

Automated real-time PCR systems have become the most common method in the quantitation of viral load during cytomegalovirus (CMV) infection in immuno-compromised patients. In order to evaluate a new commercially available CMV real-time PCR assay (CMV R-gene™, Argene, France), a pp65 antigenemia assay and four different “in-house” real-time PCR assays were compared to the CMV R-gene™ for the detection and the quantitation of CMV load in 506 specimens of whole blood from transplant patients in four French hospital laboratories. The CMV R-gene™ was more sensitive than the pp65 antigenemia: there were 18% antigenemia-negative versus CMV R-gene™-positive samples. A significant correlation was found between DNA quantitation by CMV R-gene™ and the number of positive cells detected by the pp65 antigenemia test (Spearman's rank test, r = 0.63, p < 0.0001). A CMV DNA load equivalent to 50 pp65-positive cells/200 000 polymorphonuclear leukocytes was 5.26 log 10 copies/mL of whole blood. When the CMV R-gene™ kit was compared to the four other “in-house” real-time PCR assays, there were few discordant results (6.7% total for the four laboratories), all detected with a weak positive CMV DNA viral load. Spearman's coefficients showed a good ( r = 0.82 for laboratory 1, r = 0.66 for laboratory 3) to excellent ( r = 0.99 for laboratory 2, r = 0.94 for laboratory 4) correlation between CMV R-gene™ and the four real-time “in-house” PCR assays. However, the results of CMV DNA viral load generated by CMV R-gene™ test were constantly higher than those generated by three out of four “in-house” PCR assays. This mean variation in CMV DNA viral load measured by CMV R-gene™ and “in-house” PCRs was of 0.77 log 10, 0.04 log 10, 0.77 log 10 and 0.97 log 10, for laboratories 1, 2, 3 and 4, respectively. We concluded that there was variability between results of different real-time PCR assays for CMV DNA quantitation. This observation emphasized the need of a standardised commercial assay to allow an “inter-laboratory” comparison of results. Our study showed that CMV R-gene™ is an accurate, efficient, reliable and versatile tool for rapid diagnosis and monitoring of CMV disease in transplantation recipients.

Detection and Monitoring of Cytomegalovirus Infection in Renal Transplant Patients by Quantitative Real-Time PCR

Objectives: To establish a sensitive and specific real-time PCR for quantitation of cytomegalovirus (CMV) DNA in clinical specimens.Subjects and Methods: In a prospective study, CMV DNA was quantified in blood samples of 255 kidney recipients with and without CMV-related symptoms between the years 2000 and 2005 in Kuwait. In a selected group of patients, the effect of anti-CMV chemotherapy was monitored by quantitative real-time PCR (qRT-PCR). Results: The established qRT-PCR assay had a sensitivity to detect 30 CMV DNA copies. CMV DNA was detected in 54/255 (24%) patients; of these, 17 (31.5%) were asymptomatic, and 37 patients (68.5%) had symptomatic CMV infection. Sequential blood specimens were collected from all CMV-positive patients and tested by CMV pp65 antigenemia and qRT-PCR assays. There was a moderate positive correlation between the two assays (Pearson’s correlation = 0.52). The median CMV viral load measured by qRT-PCR was higher in symptomatic (6.5 × 10⁴ copies/ml) than in asymptomatic (185copies/ml) patients (p = 0.001). The estimated cut-off value of CMV DNA for CMV symptoms/disease was ≧800 copies/ml of blood. Testing of sequential samples from patients treated with symptomatic CMV infection showed that the viral load was significantly reduced after 3 weeks of anti-CMV chemotherapy (p = 0.001). Conclusion: The reported qRT-PCR is a sensitive method for quantitation of CMV DNA in the blood of kidney recipients and can be useful in monitoring the efficacy of anti-CMV therapy.

Real-time ed end-point Polymerase Chain Reaction per la quantizzazione del DNA di Citomegalovirus: confronto tra metodi e con il test per l’antigene pp65

Quantitave Polymerase Chain Reaction (PCR) for Cytomegalovirus (CMV) DNA provides highly sensitive and specific data for detecting CMV as well as monitoring the infection and determining the appropriate antiviral strategy.To determine the clinical application of a recently introduced real-time (RT) PCR assay for CMV DNA quantitation in peripheral blood leukocytes (PBLs) and defining its correlation with the commercial quantitative end-point (EP) PCR method COBAS AMPLICOR CMV Monitor and pp65 antigen test. Sequential PBL samples (n=158) from 32 liver transplanted patients with CMV asymptomatic infection and positive for CMV DNA by EP-PCR were retrospectively analysed with RT-PCR and studied according to pp65 antigen levels. A good correlation was found between RT-PCR and pp65 antigen test (r=0.691) and between the two PCR assays (r=0.761). RT-PCR data were significantly higher in pre-emptive treated patients (those with &gt;20 pp65+positive cells, median value: 3.8 log10 copies/500,000 PBLs) than in not-treated ones (2.9 logs).According to pp65 levels of 0, 1-10, 11-20, 21-50, 51-100 and &gt;100 positive cells/200,000 PBLs, median CMV DNA load by RT-PCR was 2.6, 3.0, 3.6, 4.0. 4.2 and 4.8, log10 copies/ 500,000 PBLs, respectively (EP-PCR CMV DNA levels: 2. 8, 2.9, 3.8, 3.7, 3.9 and 4.0 logs). For samples with &gt;20 pp65+cells, that is above the level at which pre-emptive therapy was started, RT-PCR values were significantly higher than in groups with less than 20 pp65+cells, whereas EP-PCR values did not significantly differ and showed a slower progression rate. Dilutions of DNA from CMV AD169 strain were used to probe RT-PCR reproducibility (between and intra-assay variability &lt; 2%) and sensitivity (100% detection rate at 10 copies/reaction, 28.5% with EP-PCR). A significant improvement is coming from the introduction of RT-PCR to the study of CMV DNA dynamics in differently CMV infected patients due to a more reliable quantitation of CMV DNA for moderate and high DNA level compared to EP-PCR with better sensitivity and specificity. RTPCR gives more precise informations on viral load kinetics for evaluating the infection progress and assessing antiviral response, significantly simplifying and accelerating the process of producing a reliable quantification of CMV DNA for clinical purposes.

Whole blood real-time quantitative PCR for cytomegalovirus infection follow-up in transplant recipients

Background Cytomegalovirus (CMV) remains a major opportunistic agent among transplant recipients. While detection of CMV pp65-lower matrix protein (pp65Ag) is still widely used for monitoring CMV infection, real-time PCR assays have been recently developed for routine quantitation of CMV DNA. However, correlations are lacking between results of pp65Ag and quantitative PCR assays and there is no consensus yet as to the more appropriate blood compartment (whole blood (WB), leukocytes, plasma) to be tested with PCR assays. Objectives The aims of the study were to determine, in a population of transplant recipients: (i) the correlation between pp65Ag and CMV quantitative real-time PCR in our setting and (ii) the utility of plasma CMV DNA quantitation in comparison to WB quantitation. Methods In 170 blood samples (from 61 solid organ or bone marrow transplant recipients) with pp65Ag results, CMV quantitation was performed in WB and plasma using an in-house real-time quantitative PCR. Results Real-time PCR and pp65Ag results in WB were correlated: thresholds of 10 and 50(+) cells/200,000 cells were equivalent to 3.3 log 10 copies/mL (2000 copies/mL) and 3.8 log 10 copies/mL (6300 copies/mL), respectively. When WB viral load was ≥3.6 log 10 copies/mL, the risk to have a negative plasma CMV DNA result was ≤2.5%. Conclusions For the routine exploration of a single compartment, whole blood would represent a suitable compromise: easy processing for a sensitive assay. The 3.6 log 10 copies/mL threshold, which could help in identifying active CMV infection, deserves further evaluation.

Comparison of quantitative competitive polymerase chain reaction–enzyme-linked immunosorbent assay with LightCycler-based polymerase chain reaction for measuring cytomegalovirus DNA in patients after hematopoietic stem cell transplantation

Development of highly sensitive quantitative assays for cytomegalovirus (CMV) DNA detection is crucial for identification of immunodeficient patients at high risk of CMV disease. We designed 2 internally controlled competitive quantitative assays, enzyme-linked immunosorbent assay (ELISA)-based and real-time polymerase chain reaction (PCR) tests, using amplification of the same segment of the CMV genome. The aim of this study was to compare sensitivity, specificity, and laboratory performance characteristics of these assays. In both assays, a 159-bp segment of UL83 gene was amplified. External and internal controls were constructed by cloning the amplification product and heterogenous DNA segment flanked by target sequences for CMV-derived primers into bacterial plasmids, respectively. Real-time PCR was performed on LightCycler (Roche Diagnostics, Mannheim, Germany), and amplicons were detected using fluorescence resonance energy transfer probes. Alternatively, PCR products were labeled by digoxigenin, hybridized to immobilized probes, and detected by ELISA. The assays were tested on genomic DNA isolated from laboratory strains of CMV, QCMD control panel, and CMV DNA-positive peripheral blood DNA samples from hematopoietic stem cell transplant recipients, previously characterized by pp65 antigenemia and qualitative nested PCR. Real-time and ELISA-based PCR assays showed a linear course of 1–10 8 and 10–10 5 copies of CMV DNA per reaction, respectively. When compared with ELISA-based PCR, real-time PCR showed superiority in inter- and intra-assay reproducibility. Both assays were highly specific in detecting CMV DNA. No difference in amplification efficiency of internal or external standards and wild-type CMV DNA was found. The assays exhibited 83% concordance in CMV DNA detection from clinical samples, all discrepant samples having low CMV DNA copy numbers. There was a good correlation between viral DNA loads measured by the 2 assays. Statistically significant correlation was observed between the numbers of CMV DNA copies and pp65-positive leukocytes in the samples tested. Both variants of competitive PCR are adequately sensitive to be used for CMV DNA quantitation in clinical samples. LightCycler PCR, having superior performance characteristics and being less time-consuming, seems to be more suitable for routine diagnosis.

Quantitation of cytomegalovirus DNA by real-time polymerase chain reaction in peripheral blood specimens of patients with solid organ transplants: Comparison with end-point PCR and pp65 antigen test

The polymerase chain reaction (PCR) for cytomegalovirus (CMV) DNA quantitation provides sensitive and specific data for detecting CMV as well as monitoring the infection and determining the appropriate antiviral strategy. A recently introduced real-time PCR assay for CMV DNA quantitation was applied on 158 peripheral blood leukocytes (PBLs) from 32 liver-transplanted patients with CMV asymptomatic infection and correlated with a commercial quantitative end-point PCR (COBAS AMPLICOR CMV Monitor) and CMV pp65 antigenemia. A good correlation was found between real-time PCR and pp65 antigen test (r2 = 0.691) and the two PCR assays (r2 = 0.761). Real-time PCR data were higher in pre-emptive treated patients (>20 pp65 + positive cells, median CMV DNA value: 3.8 log(10) copies/500,000 PBLs) than in not-treated ones (2.9 logs). According to pp65 levels of 0, 1-10, 11-20, 21-50, 51-100, and >100 positive cells/200,000 PBLs, median CMV DNA by real-time PCR was 2.6, 3.0, 3.6, 4.0, 4.2, and 4.8 logs, respectively, (CMV DNA levels by COBAS AMPLICOR: 2.8, 2.9, 3.8, 3.7, 3.9, and 4.0 logs). For samples with >20 pp65 + cells, real-time PCR gave significantly higher values than in groups with <20 pp65 + cells, whereas the COBAS AMPLICOR results showed a slower progression rate. Dilutions of CMV AD169 strain were used to probe real-time PCR reproducibility (between and intra-assay variability <2%) and sensitivity (100% detection rate at 10 copies/reaction, 28.5% with end-point PCR). In conclusion, real-time PCR significantly improves the study of CMV DNA dynamics due to a more reliable quantitation of CMV DNA for moderate and high DNA level compared to end-point PCR with better sensitivity and specificity. Real-time PCR provides more precise information for evaluating infection progress and assessing antiviral response, simplifying and accelerating the process of producing a reliable quantitation of CMV DNA for clinical purposes.

Association of cytomegalovirus DNA concentration in epithelial lining fluid and symptomatic cytomegalovirus infection in lung transplant recipients.

The authors have investigated the effectiveness of virus detection from bronchoalveolar lavage (BAL) samples for the identification of symptomatic cytomegalovirus (CMV) infection in lung transplant recipients. Thus, 275 BAL samples taken from 105 lung transplant recipients during follow-up were analyzed by quantitative polymerase chain reaction (PCR) and virus isolation. Quantitative PCR detected virus in all 24 BAL samples taken at onset of symptomatic disease, and virus culture in only 7 samples (29.2%). Twenty-three of 251 BAL samples (9.2%) were positive by PCR, although they were obtained in an asymptomatic phase. Quantitation of CMV DNA from BAL allowed no discrimination between symptomatic and asymptomatic infection in individual cases. However, when the urea dilution method was used to recalculate the CMV DNA concentration for the epithelial lining fluid (ELF) diluted in the BAL, a CMV DNA level of more than 10 copies/mL ELF was clearly associated with symptomatic disease. The CMV DNA level in ELF may be a marker for symptomatic CMV infection.

Assessment of removal of human cytomegalovirus from blood components by leukocyte depletion filters using real-time quantitative PCR

AbstractTo assess removal of cytomegalovirus (CMV) by leukocyte depletion (LD) filters, we developed a spiking model of latent virus using peripheral blood mononuclear cells (PBMCs) infected by coculture with CMV-infected human fibroblasts. Infected PBMCs were purified by dual magnetic column selection and then spiked into whole blood units or buffy coat pools prior to LD by filtration. CMV load and fibroblast contamination were assessed using quantitative CMV DNA real-time PCR and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) of mRNA encoding the fibroblast-specific splice variant of prolyl-4-hydroxylase, respectively. After correcting for fibroblast-associated CMV, the mean CMV load was reduced in whole blood by LD from 7.42 × 102 to 1.13 copies per microliter (2.8110log reduction) and from 3.8 × 102 to 4.77 copies per microliter (1.910log reduction) in platelets. These results suggest that LD by filtration reduces viral burden but does not completely remove CMV from blood components. (Blood. 2004;103:1137-1139)

A real-time TaqMan PCR for routine quantitation of cytomegalovirus DNA in crude leukocyte lysates from stem cell transplant patients

A real-time TaqMan PCR based on the cytomegalovirus (CMV) polymerase ( pol) gene was developed for quantitation of CMV DNA in crude peripheral blood leukocyte (PBL) lysate from stem cell transplantation (SCT) patients. The dynamic range of the assay was between 10 and 4×10 6 copies. Both intra- and inter-assay variability were well within ±0.25 log 10 S.D. Thus, a pooled PBL sample that was used as positive control in 57 consecutive TaqMan PCR runs over 7 months showed a stable CMV quantity (4.12±0.13, log 10 mean±S.D.). The sensitivity of the pol TaqMan PCR was validated by parallel analysis of 177 PBL samples with a nested PCR. The use of crude PBL lysate as PCR input did not cause PCR inhibition. We demonstrated further the clinical utility of the newly developed TaqMan PCR by monitoring changes in CMV levels in eight patients receiving antiviral therapy. This TaqMan PCR was highly sensitive, reproducible, and stable and has served a useful tool for monitoring CMV DNA levels in large number of clinical samples in a routine diagnostic setting for over 1 year.

Comparative Quantitation of Cytomegalovirus (CMV) DNA in Solid Organ Transplant Recipients with CMV Infection by Using Two High-Throughput Automated Systems

Cytomegalovirus (CMV) DNA quantitation in clinical specimens is progressively becoming a cornerstone in the diagnosis and management of CMV infection in the immunocompromised host. We evaluated two automated and reproducible PCR tests, the LightCycler (Roche Molecular Biochemicals, Indianapolis, Ind.) and the COBAS AMPLICOR CMV Monitor (Roche Diagnostics, Pleasanton, Calif.), for the detection of CMV DNA in blood samples from transplant recipients with CMV infection as determined by shell vial culture. Following a log transformation analysis, the mean CMV DNA in plasma (PL), whole blood (WB), peripheral blood leukocytes (PBL), and peripheral blood mononuclear cells (PBMC) using the LightCycler was 6.79 copies per ml, 7.23 copies per ml, 6.38 copies per 2 x 10(6) cells, and 6.27 copies per 2 x 10(6) cells, respectively. This compares to 7.86 copies per ml, 8.37 copies per ml, 7.59 copies per 2 x 10(6) cells, and 7.44 copies per 2 x 10(6) cells, respectively, using COBAS AMPLICOR CMV Monitor. While higher CMV DNA levels were observed for the various blood compartments analyzed using COBAS AMPLICOR CMV Monitor, a high degree of correlation was evident between the two automated systems (jackknife correlation r = PL 0.77 [95% confidence interval (CI); 0.64, 0.90], WB 0.77 [95% CI; 0.62, 0.92], PBL 0.77 [95% CI; 0.67, 0.88], and PBMC 0.81 [95% CI; 0.72, 0.89], all P < 0.001). Therefore, we conclude that either automated diagnostic system is accurate for CMV DNA quantitation.

Longitudinal Analysis of Plasma Cytomegalovirus DNA in a Child with Crohn's Disease and Cytomegalovirus Gastroenteritis

Longitudinal Analysis of Plasma Cytomegalovirus DNA in a Child with Crohn's Disease and Cytomegalovirus Gastroenteritis

Single tube competitive PCR for quantitation of CMV DNA in the blood of HIV+ and solid organ transplant patients

Cytomegalovirus (CMV) infection is a major cause of morbidity and mortality in transplant and HIV-infected patients. However, CMV can also cause asymptomatic infection. An elevated blood viral load as assessed by various methods appears to be a predictor for symptomatic infections, and can be used to identify patients at the highest risk of developing CMV disease. We developed a single tube competitive quantitative PCR assay for CMV DNA, using as a competitor a plasmid carrying the target sequence for amplification with an internal deletion. The analysis of data from repeated extractions and amplifications of samples showed that the coefficient of variation of the assay was typically less than 20%. Clinical samples from 14 HIV-infected and 13 solid organ transplant patients were analyzed. Widely varying CMV DNA levels were found in leukocytes, with a positive correlation with the measure of infectivity in the leukocytes by quantitative culture on fibroblasts. The highest CMV DNA content in leukocytes was found in two patients with presumptive CMV disease. In HIV patients, the amount of DNA in leukocytes was much larger than in solid organ transplant recipients, when standardized for infectivity. Although based on a very limited number of patients, this observation probably points to a difference in the biology of CMV infection in these two categories of susceptible individuals. CMV DNA was also found in the plasma of some of the patients with a high CMV DNA leukocyte load. The present test should be useful for identifying patients at high risk of developing CMV disease, for monitoring therapeutic efficacy of antiviral regimens and to improve the understanding the pathogenesis of CMV infection.

Patterns of viremia in liver transplant recipients with symptomatic cytomegalovirus infection.

Cytomegalovirus (CMV) titer in blood seems to be the principal determinant of clinical symptoms in immunosuppressed patients. We have developed an assay for quantitation of CMV DNA in serum. The assay requires the coamplification by polymerase chain reaction (PCR) of extracted serum DNA with 1000 molecules of mutated internal standard DNA, and then an ELISA detection system. We examined 133 paired buffy coats and sera from 15 patients with symptomatic infection. Sera were examined by quantitative PCR, and buffy coats were examined by qualitative PCR (with a detection threshold of approximately 40 copies per 150,000 cells). Serum viral titers peaked during the seventh week after transplant (median day 40, range 26-58) at about the time of symptom onset. Mean viral titer measured during the seventh week was 1.2 x 10(5) copies per milliliter of serum (standard error 6.5 x 10(4). Buffy-coat PCR results were generally concordant with results of serum PCR (overall concordance 103/133=77.4%). Serum CMV titer fell, as symptoms resolved with reduction of immunosuppression and specific antiviral therapy. High titers and poor response to antiviral therapy were observed in the context of excessive immunosuppression and bacterial sepsis. Measurement of serum CMV titer may be useful for the management of immunosuppressed transplant recipients, and provides a tool for the better understanding of factors that enhance or inhibit viral replication.

Quantitation of cytomegalovirus DNA and characterization of viral gene expression in bronchoalveolar cells of infected patients with and without pneumonitis.

Cytomegalovirus (CMV) is often present in bronchoalveolar lavage (BAL) fluid of immunosuppressed patients without CMV pneumonitis. The amount of viral DNA within BAL cells of patients with definite CMV pneumonitis and of viral shedders was quantitated by polymerase chain reaction (PCR) and the extent of CMV gene expression within BAL cells was defined by reverse transcription - PCR. No viral DNA was detected in 6 viral shedders, and 12 had low copy numbers (mean, 72 copies/10(5) BAL cells; median, 20) compared with numbers in pneumonitis patients (267,580 and 57,000, respectively). When CMV intranuclear inclusions were absent within BAL cells of patients with pneumonitis, copy numbers (mean, 9362; median, 7110) were still significantly higher than among shedders. Expression of viral glycoprotein H mRNA was detected in BAL cells of all 11 pneumonitis patients tested but in 0 of 18 viral shedders. Thus, high-grade infection and viral replication within BAL cells are integral features of CMV pneumonitis but not viral shedding.

Detection of ganciclovir resistance mutations quantitation of cytomegalovirus (CMV) DNA in leukocytes of patients with fatal disseminated CMV disease.

Cytomegalovirus (CMV) UL97 mutations associated with ganciclovir resistance at codons 460, 594, and 595 were detected by polymerase chain reaction (PCR) followed by restriction enzyme analysis in CMV blood isolates and directly in polymorphonuclear leukocyte (PMNL) DNA extracts of 4 subjects who died of progressive disseminated CMV disease due to ganciclovir-resistant CMV strains. The CMV DNA load was also serially determined in leukocyte fractions of these patients using a quantitative-competitive PCR assay. There was excellent concordance between specific UL97 mutations in blood culture isolates and those detected in PMNL fractions for all patients. Emergence of such UL97 mutations during ganciclovir therapy was associated with an increasing CMV DNA burden in leukocytes of the 2 patients with AIDS but not in the 2 subjects with chronic lymphocytic leukemia. Rapid molecular strategies, including detection of common CMV UL97 mutations and CMV DNA quantitation, can be used directly in leukocytes of immunocompromised subjects with CMV disease to monitor antiviral therapy.

Level of Cytomegalovirus (CMV) DNA in Cerebrospinal Fluid of Subjects with AIDS and CMV Infection of the Central Nervous System

The objective of this study was to correlate cytomegalovirus (CMV) DNA levels in the cerebrospinal fluid (CSF) of subjects with AIDS with clinical and pathologic findings attributable to CMV infection of the central nervous system (CNS). CMV polymerase chain reaction (PCR) was done on serial dilutions of CSF samples from 24 AIDS patients with autopsy-proven CNS disorders. CMV DNA was detected in CSF from 12 of 13 subjects with evidence of CMV infection of the brain or spinal cord but in none of 11 subjects without autopsy evidence of CMV CNS infection. Subjects whose CSF contained > 10(3) CMV DNA molecules/8 microL of CSF had severe CMV CNS disease (e.g., ventriculoencephalitis). PCR appears to be more useful than clinical and neuroradiologic findings for documenting CMV infection of the CNS in patients with AIDS. Quantitation of CMV DNA in CSF shows promise for evaluation of the extent of involvement.

Quantitation of human cytomegalovirus DNA in leukocytes by end-point titration and duplex polymerase chain reaction

The presence of human cytomegalovirus (CMV) DNA and cellular DNA in leukocytes was detected by duplex polymerase chain reaction (PCR) and quantitated by end-point titration. Two different duplex PCR methods were used to co-amplify CMV DNA and a 536 bp fragment of globin DNA. MIE-globin PCR amplified a 435 bp fragment of the major immediate early (MIE) gene of CMV DNA whereas the LA-globin PCR amplified a 200 bp fragment of the late antigen (LA) gene of CMV DNA. PCR products were separated by electrophoresis in 3% agarose gels and detected by ethidium bromide staining. Amplification of globin DNA was included in the PCR as a positive control to monitor the accuracy and reproducibility of the PCR assay and to provide a reference point for CMV DNA levels. End-point titration PCR using known amounts of recombinant CMV DNA and human placental DNA showed that the end-point titres of the amplified CMV DNA correlated directly with the amount of CMV DNA in the sample. The limit of detection of MIE-globin and LA-globin PCR was 1 ng for placental DNA, and 10 fg (1000 copies) for CMV-MIE DNA and 1 fg (100 copies) for CMV-LA DNA, respectively. The amount of CMV DNA was quantitated in leukocytic lysates of 16 immunocompromised patients, who were tested for the presence of CMV in blood by cell culture, and of four normal controls. The blood concentration of CMV DNA, calculated as the number of copies of CMV DNA per μg of leukocyte DNA, varied between 10 4 and 10 7 in the seven bloods that were CMV-cell-culture-positive, and between 10 2 and 10 4 in the blood of five patients that were CMV-cell-culture-negative. CMV DNA was undetected by PCR in the blood of another eight CMV-negative cases. This study shows that end-point titration and duplex PCR can be used as a simple and rapid method to quantitate CMV DNA in blood of patients that are either CMV-positive or CMV-negative by cell culture. Quantitation of CMV DNA in blood by end-point titration PCR has potential to differentiate between asymptomatic CMV infection and symptomatic CMV disease, and to monitor viral load during viral therapy.

Quantitation of cytomegalovirus DNA in lung tissue of bone marrow transplant recipients

Five bone marrow transplant recipients who died of respiratory failure were retrospectively analyzed with polymerase chain reaction (PCR) assay for pulmonary cytomegalovirus (CMV) infection. Two patients had CMV interstitial pneumonitis according to the virus isolation and the histologic and immunofluorescent examinations of the lungs, while the other three patients had non-CMV diseases (ie, idiopathic interstitial pneumonitis, pulmonary aspergillosis, or Streptococcus mitis septicemia). Cytomegalovirus DNA was amplified from the postmortem lung tissue with PCR. The PCR assay showed apparent PCR signals specific to CMV DNA in the two patients with CMV pneumonitis. In contrast, CMV DNA was hardly detectable or undetectable in the three patients without CMV disease. With quantitative PCR assay the initial CMV copy number in the lung tissue of the two patients with CMV pneumonitis was more than 10 4 copies/μg DNA and was over 1,000-fold more than that of the three patients without CMV pneumonitis. These results show that quantitative PCR assay could be useful as a diagnostic measure for pulmonary CMV infection.

Quantitation of cytomegalovirus DNA by blot hybridization in blood leukocytes of viremic patients

We describe a technique for quantitation of viral DNA in blood leukocytes during viremic infection with human cytomegalovirus (CMV). Using a cloned subgenomic DNA probe and a blot hybridization assay, small amounts of viral DNA within samples of leukocyte DNA could be quantitated reproducibly using a videodensitometer. Critical components of the assay were: (1) a direct relationship between optical density and known amounts of viral DNA diluted in cellular DNA as positive standard samples and, (2) determination of the proper duration of autoradiographic exposure. The technique was sufficiently sensitive to detect 10 picograms of CMV DNA in the presence of microgram quantities of host cell DNA. In addition, samples containing minute amounts of CMV DNA could reliably be distinguished from samples that were negative. We have used the technique to characterize the pathogenesis of CMV viremia and to monitor the effects of antiviral chemotherapy. This procedure could easily be applied to pathogenetic studies of a variety of other infectious agents.