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

Comparative analyses of DNA extraction methods for whole blood quantification of HCMV DNAemia in patients with hematological diseases: false negative cases in manual method

Human cytomegalovirus (HCMV) DNA quantitation in whole blood (WB) by real-time or quantitative polymerase chain reaction (qPCR) is a highly sensitive and reproducible diagnostic procedure for monitoring HCMV DNAemia (DNAemia is the detection of DNA in samples of plasma, whole blood, isolated peripheral blood leukocytes or in buffy-coat specimens) in patients. We provided a comparative analysis of HCMV DNA extraction performance by two different techniques, one performed by an automated extractor and the other by a manual method. We observed that the automated extraction method allowed HCMV DNA detection in the presence of weak viremia while no differences are observed when the viral load is greater. Therefore, automated DNA extraction is a suitable and recommended protocol not only for early detection of HCMV infection but also for more accurate monitoring of HCMV DNAemia during post-therapy follow-up.

Cytomegalovirus Viral Load in Transplanted Patients Using the NeuMoDx™ (Qiagen) Automated System: A 1-Month Experience Feedback

Cytomegalovirus (CMV) reactivations represent a significant morbidity and mortality problem in transplant patients. Reliable and rapid measurement of CMV viral load is a key issue for optimal patient management. We report here the evaluation of NeuMoDx™ (Qiagen) in a routine hospital setting (University Hospitals of Marseille, France) in comparison with our classical reference technique R-GENE. During one month, 719 CMV viral loads from 507 patients were measured in parallel in both techniques. Using the ROC (receiver operating characteristic) curve and our biological experience we suggest that values <52 IU/mL (geometric mean) correspond to negative samples, values >140 IU/mL (Fowlkes–Mallows index) correspond to quantifiable positive results and values ranging from 52 to 140 IU/mL represent non-quantifiable positive results. Follow-up of 15 transplant patients who developed CMV reactivation during the study showed that NeuMoDx™ provided higher viral load measurement during the first two weeks of follow-up for three patients. These important intra-individual variations resulted in a significant median increase considering the whole data set (6.7 points of difference expressed as a percentage of the initial viral load). However, no difference between the two techniques was noticeable after two weeks of treatment. Subsequent to this first study we conclude that NeuMoDx™, used with optimized logistics and an adapted threshold, allows a rapid CMV viral load measurement and that its use does not lead to any difference in patient management compared to the reference technique R-GENE^®.

An Isothermal, Multiplex Amplification Assay for Detection and Genotyping of Human Papillomaviruses in Formalin-Fixed, Paraffin-Embedded Tissues

Rapid and accurate identification of human papillomavirus (HPV) is important for both clinical management and population screening. Analytic validation of Atila AmpFire Multiplex HPV assays on formalin-fixed, paraffin-embedded (FFPE) cervix/vulva and oropharynx diagnostic tissue samples was performed. The AmpFire assay incorporates a novel isothermal multiplex amplification coupled with real-time fluorescent detection to detect and genotype 15 high-risk (HR) HPV genotypes. Limits of detection determined by plasmids cloned with HPV genotype-specific sequences were 2 copies/reaction for HPV16, HPV18, and some HR HPV genotypes, and 20 copies/reaction for the remaining HR HPV genotypes. The performance of the AmpFire assays in clinical samples was evaluated using 214 FFPE specimens. The AmpFire assay failed in one clinical specimen for an invalid rate of 0.5%. The AmpFire assay detected HPV in clinical samples with positive percent agreements of 100.0% for HPV16, 100.0% for HPV18, and 94.7% for non-16/18 HR HPV, and 100% negative percent agreements for HPV16, HPV18, and non-16/18 HR HPV. Qualitative detection agreement was obtained in the reproducibility study. In summary, the Atila AmpFire HPV assay demonstrated excellent analytic sensitivity and specificity for detection and genotyping of 15 HR HPV genotypes. Assay parameters of simple specimen processing, small sample size requirement, rapid turnaround time, and being near instrument-free render it well suited for HPV detection and genotyping in FFPE specimens.

Cytomegalovirus

Cytomegalovirus (CMV), the largest of the herpesviruses, causes a wide range of clinical syndromes, from asymptomatic infection to severe disease in immunocompromised hosts. Laboratory methods for diagnosis include molecular testing, antigenemia, culture, serology, and histopathology. Treatment of CMV infection and disease is indicated in selected immunocompromised hosts, and preventive approaches are indicated in high-risk groups. This chapter reviews the epidemiology, clinical aspects, and the laboratory diagnosis and management of CMV in immunocompromised hosts.

An update on the management and prevention of cytomegalovirus infection following allogeneic hematopoietic stem cell transplantation

ABSTRACT 

A significant progress has been made in deciphering critical aspects of the biology and immunology of CMV infection in the allogeneic stem cell transplantation setting. Genetic traits predisposing to active CMV infection and CMV end-organ disease have begun to be delineated. Reliable molecular assays for CMV DNA load quantitation in body fluids have been developed. Elucidation of immune mechanisms affording control of CMV infection will help to improve the management of active CMV infection. Finally, the advent of new CMV-specific antivirals and promising vaccine prototypes as well as the development of fine procedures for large-scale ex vivo generation of functional CMV-specific T cells for adoptive T cell transfer therapies will certainly minimize the negative impact of CMV on survival in these patients.

Multicenter comparison of laboratory performance in cytomegalovirus and Epstein-Barr virus viral load testing using international standards

BACKGROUND

Infections with cytomegalovirus (CMV) and Epstein-Barr virus (EBV) remain important in solid organ transplantation. Quantitative viral nucleic acid testing is a major advance to patient management. These assays are limited by a lack of standardization, resulting in viral load measurements that differ among clinical laboratories. The variability in viral load measurements makes interpretation of multicenter clinical trials data difficult. This study compares the current practices in CMV and EBV viral load testing at four large transplant centers participating in multicenter Clinical Trials in Organ Transplantation and the Clinical Trials in Organ Transplantation in Children (CTOT and CTOTC).

METHODS

Viral load testing was performed on well-defined viral preparations according to standard operating procedures at each site.

RESULTS

Among centers, CMV viral load testing was accurate compared to WHO International Standards and within acceptable variation for this testing method. Epstein-Barr virus viral load data were more variable and less accurate despite the use of international standards.

CONCLUSIONS

These data suggest that comparison of CMV, but not EBV, viral load measurements at these sites is possible using current assays and control standards. Standardization of these assays is facilitated using the WHO International Standards and will allow comparison of viral load results among transplant centers. Assay standardization must be performed prior to initiation of multicenter trials.

Favorable impact of natural killer cell reconstitution on chronic graft-versus-host disease and cytomegalovirus reactivation after allogeneic hematopoietic stem cell transplantation

Natural killer cells are the first lymphocyte subset to reconstitute, and play a major role in early immunity after allogeneic hematopoietic stem cell transplantation. Cells expressing the activating receptor NKG2C seem crucial in the resolution of cytomegalovirus episodes, even in the absence of T cells. We prospectively investigated natural killer-cell reconstitution in a cohort of 439 adult recipients who underwent non-T-cell-depleted allogeneic hematopoietic stem cell transplantation between 2005 and 2012. Freshly collected blood samples were analyzed 3, 6, 12 and 24 months after transplantation. Data were studied with respect to conditioning regimen, source of stem cells, underlying disease, occurrence of graft-versus-host disease, and profiles of cytomegalovirus reactivation. In multivariate analysis we found that the absolute numbers of CD56(bright) natural killer cells at month 3 were significantly higher after myeloablative conditioning than after reduced intensity conditioning. Acute graft-versus-host disease impaired reconstitution of total and CD56(dim) natural killer cells at month 3. In contrast, high natural killer cell count at month 3 was associated with a lower incidence of chronic graft-versus-host disease, independently of a previous episode of acute graft-versus-host disease and stem cell source. NKG2C(+)CD56(dim) and total natural killer cell counts at month 3 were lower in patients with reactivation of cytomegalovirus between month 0 and month 3, but expanded greatly afterwards. These cells were also less numerous in patients who experienced later cytomegalovirus reactivation between month 3 and month 6. Our results advocate a direct role of NKG2C-expressing natural killer cells in the early control of cytomegalovirus reactivation after allogeneic hematopoietic stem cell transplantation.

Assessment of the efficacy and safety of pre-emptive anti-cytomegalovirus (CMV) therapy in HIV-infected patients with CMV viraemia

A number of studies have demonstrated that cytomegalovirus (CMV) viraemia is a strong predictor for CMV end-organ disease (EOD) and death in HIV-infected patients. We assess the efficacy and safety of pre-emptive anti-CMV therapy (PACT) for preventing these events. We performed a retrospective study of all HIV-infected patients seen in our institution who had detectable CMV viraemia in 2007. Seventy-one patients with advanced HIV disease (median CD4 cell count = 61 cells/mm3) were studied. Sixteen patients received PACT (mainly valganciclovir). Patients who received PACT had lower CD4 cell counts and higher blood CMV DNA levels. The cumulative incidence of CMV EOD and death at one year was 44% and 21% in patients with and without PACT, respectively ( p = 0.013). Both PACT and high blood CMV DNA levels were significantly associated with CMV EOD and death in unadjusted analysis. In adjusted analyses, only blood CMV DNA levels remained significantly associated with the risk of CMV EOD and death, whereas PACT was associated with a non-significant trend towards reduced CMV EOD or death (hazard ratio: 0.25, p = 0.13). Five patients with PACT experienced severe drug-related adverse events. In conclusion, the use of PACT in HIV-infected patients with CMV viraemia could improve outcome but is associated with significant toxicity.

Clinical utility of viral load in management of cytomegalovirus infection after solid organ transplantation

The negative impact of cytomegalovirus (CMV) infection on transplant outcomes warrants efforts toward improving its prevention, diagnosis, and treatment. During the last 2 decades, significant breakthroughs in diagnostic virology have facilitated remarkable improvements in CMV disease management. During this period, CMV nucleic acid amplification testing (NAT) evolved to become one of the most commonly performed tests in clinical virology laboratories. NAT provides a means for rapid and sensitive diagnosis of CMV infection in transplant recipients. Viral quantification also introduced several principles of CMV disease management. Specifically, viral load has been utilized (i) for prognostication of CMV disease, (ii) to guide preemptive therapy, (iii) to assess the efficacy of antiviral treatment, (iv) to guide the duration of treatment, and (v) to indicate the risk of clinical relapse or antiviral drug resistance. However, there remain important limitations that require further optimization, including the interassay variability in viral load reporting, which has limited the generation of standardized viral load thresholds for various clinical indications. The recent introduction of an international reference standard should advance the major goal of uniform viral load reporting and interpretation. However, it has also become apparent that other aspects of NAT should be standardized, including sample selection, nucleic acid extraction, amplification, detection, and calibration, among others. This review article synthesizes the vast amount of information on CMV NAT and provides a timely review of the clinical utility of viral load testing in the management of CMV in solid organ transplant recipients. Current limitations are highlighted, and avenues for further research are suggested to optimize the clinical application of NAT in the management of CMV after transplantation.

Quantification of cytomegalovirus viral load

Cytomegalovirus (CMV), a member of the Herpesviridae family, is worldwide distributed. After the primary infection, CMV induces a latent infection with possible reactivation(s). It is responsible for severe to life-threatening diseases in immunocompromised patients and in foetuses and newborns of infected mothers. For monitoring CMV load, classical techniques based on rapid culture or pp65 antigenemia are progressively replaced by quantitative nuclear acid tests (QNAT), easier to implement and standardize. A large variety of QNAT are available from laboratory-developed assays to fully-automated commercial tests. The indications of CMV quantification include CMV infection during pregnancy and in newborns, and viral surveillance of grafted and non-grafted immunocompromised patients, patients with bowel inflammatory diseases and those hospitalised in intensive care unit. A close cooperation between virologists and clinicians is essential for optimizing the benefit of CMV DNA monitoring.

Time profile of viral DNA in aqueous humor samples of patients treated for varicella-zoster virus acute retinal necrosis by use of quantitative real-time PCR

The objective of this study was to evaluate the kinetics of varicella-zoster virus (VZV) loads using quantitative PCR (qPCR) in patients treated for acute retinal necrosis (ARN). Six patients (52 ± 13 years old) with ARN syndrome were consecutively studied. Aqueous humor (AH) was sampled from both eyes of all patients for qPCR evaluation. The patients were treated with intravenous acyclovir and intravitreal injections of antiviral drugs. The mean follow-up time was 17.6 ± 16.4 months. Main outcome measures were the numbers of viral genome copies in the AH, assessed using real-time qPCR with hydrolysis probe technology with a threshold of detection of 200 copies/ml. Two main portions of the viral load curves were observed for each patient: a plateau phase (27.8 ± 24.9 days) and a decrease in the number of viral genome copies. The mean baseline viral load was 3.4 × 10(7) ± 4.45 × 10(7) copies/ml (6 × 10(6) to 1.2 × 10(8) copies/ml). The viral load decreased according to a logarithmic model, with a 50% reduction obtained in 3 ± 0.7 days. There was a significant viral load (>102 copies/ml) at 50 days after the onset of treatment, despite antiviral drugs. qPCR use demonstrated reproducible VZV DNA kinetics with a two-phase evolution: a plateau followed by a logarithmic decrease. These data suggest that high-dosage antiviral therapy administered for the conventional 10-day duration is insufficient for most patients. This series of patients responded with a similar decrease in viral load once treatment was initiated, and the data from these patients may be used to predict the responses of future patients.

[Large diversity of routine methods used for monitoring human cytomegalovirus infections in France]

Monitoring cytomegalovirus circulating viral load is an important parameter of the follow-up in immunocompromised patients. It can be measured either by DNAemia or by pp65 antigenemia. The French national reference center for cytomegaloviruses organized an investigation of practice in 37 teacher hospital virology laboratories to assess the situation in France in 2010.

METHODS

A questionnaire was sent to collect following information: method used in routine for monitoring of circulating viral load of CMV, assay used, sample matrix and extraction method.

RESULTS

Thirty-six over thirty-seven laboratories filled the questionnaire. Among these, 67% used the quantitative PCR in routine, 11% antigenemia and 22% antigenemia or quantitative PCR; 87% of the laboratories use whole blood for quantitative PCR, whereas 10% and 3% use plasma and leukocytes respectively. Among the laboratories using DNAemia, 100% used real-time PCR assays, 91% use an automated extraction and 9% a manual extraction.

CONCLUSION

Thus in France, measurement of DNAemia by real-time PCR is a tool, which gradually replaces the antigenemia for the monitoring of cytomegalovirus infection among immunocompromised patients. The very great diversity of the methods used justifies the installation of a national quality control on total blood, matrix used by 87% of the laboratories.

Quantification of cytomegalovirus DNA by a fully automated real-time PCR for early diagnosis and monitoring of active viral infection in solid organ transplant recipients

BACKGROUND

Quantification of cytomegalovirus (CMV) DNA by real-time PCR is currently considered an alternative diagnostic approach for the evaluation of active infection in transplant patients. The pp65 antigenemia assay has been used as reference test for monitoring active CMV infection and guiding preemptive therapy in transplant recipients. However, this assay suffers from some limitations: need for immediate processing of the samples, labour-intensive process, lack of standardization and subjective result interpretation.

OBJECTIVES

The aim of this study was to evaluate the performance of a new commercially available real-time PCR assay coupled with a fully automated DNA extraction system (COBAS Ampliprep/COBAS Taqman CMV Test, Roche Diagnostics) for the detection of CMV-DNA in plasma comparing it with pp65 antigenemia assay for monitoring active CMV infection in solid organ transplant recipients (SOTRs).

STUDY DESIGN

A total of 266 consecutive samples from 45 SOTRs were monitored with pp65 antigenemia and in parallel with CMV-DNA quantitation by real-time PCR assay.

RESULTS

Fifty-eight samples resulted PCR-positive, 163 negative and for 45 samples the CMV-DNA values obtained were below the lower limit of quantification (<150 copies/ml); pp65 antigen was detected in 47 samples and resulted negative in 219 specimens. Concordance between the two evaluations was 76.7%; also a good correlation was observed (r=0.718). Considering the existing treatment criteria based on pp65 antigenemia evaluation corresponding to pp65 levels≥20 positive cells/200,000, preemptive therapy was administered to four asymptomatically infected patients. The corresponding cut-off value of CMV-DNA load calculated for discrimination between self-clearing infections and those requiring therapy was 2500 copies/ml (or 2275 IU/ml).

CONCLUSION

The fully automated real-time PCR from Roche provided specific and sensitive results and represented a rapid and simple assay for the evaluation and monitoring of CMV infection in SOTRs. Further studies are required to validate the threshold level for the initiation of preemptive therapy.

Comparison of real-time PCR quantitative analysis of the cytomegalovirus DNA level using LightCycler 2.0 and LightCycler 480 instruments

Cytomegalovirus infection is a frequent complication after transplantation. It is commonly believed that the level of CMV viraemia, usually measured with real-time PCR, is directly correlated with the risk of developing a serious cytomegaloviral disease.

OBJECTIVES

The aim was the comparison of results obtained with a commercial test for the quantitative diagnostics of CMV infections, using LightCycler 2.0 and LightCycler 480 real-time PCR systems.

STUDY DESIGNS

Study comprised 97 samples of nucleic acids isolated from serum, in which the CMV DNA was detected during routine tests. Measurement in both analysers was performed simultaneously for paired serum samples. Comparison and of the results obtained with two types of thermocyclers included regression analysis, Spearman correlation, Friedman test and Bland-Altman analysis (p<0.05).

RESULTS

CMV DNA was detected in all samples with use of both thermocyclers. Correlation coefficient of results obtained with both analysers was 0.94. According to Friedman and Bland-Altman tests' results, there were significant differences in measurements between instruments (p<0.001 and p=0.017, respectively). Difference of median values was 0.137 log(10)CMV viral load/ml, and difference of mean values was 0.215 log(10)CMV viral load/ml. Clear threshold of fluorescence crossing point of 1.4-1.8 cycles in advantage of LightCycler 480 was an apparent difference between both analysers.

CONCLUSIONS

There was good overall correlation between both analysers, as detected shift in both median and mean values was close to intra-assay variability declared by its producer. Observed differences were probably due to different fluorescence excitation and detection systems used in both instruments.

Comparison of a UL111a real-time PCR and pp65 antigenemia for the detection of cytomegalovirus

Surveillance of cytomegalovirus (CMV) replication in transplant patients is crucial for the success of transplantation. To compare a CMV pp65 antigenemia (pp65Ag) and a quantitative real-time PCR targeting the CMV-UL111a (UL111aPCR), all whole blood samples taken between July 2008 and October 2009 were identified which had been analyzed prospectively by both assays in parallel. Discordant results were re-analyzed using a published CMV duplex PCR targeting regions UL55 and UL123exon4. Of 720 samples from 81 transplant patients, CMV replication was detected in 244 specimens (34%) by the UL111aPCR (median, 1,019 geq/ml), compared to 113 (16%) detected by the pp65Ag (median, 2/250,000 leukocytes). Concordant UL111aPCR/pp65Ag results were obtained in 561 (78%) samples, being positive in 99 (14%), and negative in 462 (64%). As a rule of thumb, 1 pp65Ag-positive cell per 250,000 leukocytes corresponded to 1,000 geq/ml CMV DNA of whole blood. Discordant results were found in 159 samples (22%), being UL111aPCR-positive/pp65Ag-negative in 145 (91%; median, 650 geq/ml), or UL111aPCR-negative/pp65Ag-positive in 14 (9%; median, 1/250,000 cells). Using the duplex PCR targeting the CMV UL55 and the UL123-exon4 genes, 131 of 139 (94%) discordant UL111aPCR-positives (median UL111aPCR, 639 geq/ml; median UL55PCR, 715 geq/ml; median UL123PCR, 1,103 geq/ml) were confirmed. Of 14 discordant pp65Ag-positives, duplex PCR was also negative in 8, and of low copy number in 6. Thus, CMV UL111aPCR provides more sensitive quantitation of CMV replication than pp65Ag, however, discordant results can occur at very low viral loads.

Comparative evaluation of three automated systems for DNA extraction in conjunction with three commercially available real-time PCR assays for quantitation of plasma Cytomegalovirus DNAemia in allogeneic stem cell transplant recipients

Limited data are available on the performance of different automated extraction platforms and commercially available quantitative real-time PCR (QRT-PCR) methods for the quantitation of cytomegalovirus (CMV) DNA in plasma. We compared the performance characteristics of the Abbott mSample preparation system DNA kit on the m24 SP instrument (Abbott), the High Pure viral nucleic acid kit on the COBAS AmpliPrep system (Roche), and the EZ1 Virus 2.0 kit on the BioRobot EZ1 extraction platform (Qiagen) coupled with the Abbott CMV PCR kit, the LightCycler CMV Quant kit (Roche), and the Q-CMV complete kit (Nanogen), for both plasma specimens from allogeneic stem cell transplant (Allo-SCT) recipients (n = 42) and the OptiQuant CMV DNA panel (AcroMetrix). The EZ1 system displayed the highest extraction efficiency over a wide range of CMV plasma DNA loads, followed by the m24 and the AmpliPrep methods. The Nanogen PCR assay yielded higher mean CMV plasma DNA values than the Abbott and the Roche PCR assays, regardless of the platform used for DNA extraction. Overall, the effects of the extraction method and the QRT-PCR used on CMV plasma DNA load measurements were less pronounced for specimens with high CMV DNA content (>10,000 copies/ml). The performance characteristics of the extraction methods and QRT-PCR assays evaluated herein for clinical samples were extensible at cell-based standards from AcroMetrix. In conclusion, different automated systems are not equally efficient for CMV DNA extraction from plasma specimens, and the plasma CMV DNA loads measured by commercially available QRT-PCRs can differ significantly. The above findings should be taken into consideration for the establishment of cutoff values for the initiation or cessation of preemptive antiviral therapies and for the interpretation of data from clinical studies in the Allo-SCT setting.

Molecular detection of herpesviruses

In routine molecular diagnostics, detection of herpesviruses has made a major impact. Infection with herpesviruses is indicated by demonstrating the presence of the virus in selected specimens. Rapid and reliable detection of herpesvirus DNA helps to decrease the lethality as well as the sequelae of herpesvirus infection in patients at risk. This chapter discusses specimen types and both laboratory-developed and commercially available assays useful for molecular detection of herpesviruses. To meet the need for reliable laboratory results, it is advisable to employ maximum automated and standardized kits based on reagents and standards of reproducible high quality. In the routine diagnostic laboratory, introduction of IVD/CE and/or FDA-labeled tests is preferred.

Real-time electrochemical monitoring of the polymerase chain reaction by mediated redox catalysis

We described the proof-of-principle of a nonoptical real-time PCR that uses cyclic voltammetry for indirectly monitoring the amplified DNA product generated in the PCR reaction solution after each PCR cycle. To enable indirect measurement of the amplicon produced throughout PCR, we monitor electrochemically the progressive consumption (i.e., the decrease of concentration) of free electroactive deoxynucleoside triphosphates (dNTPs) used for DNA synthesis. This is accomplished by exploiting the fast catalytic oxidation of native deoxyguanosine triphosphate (dGTP) or its unnatural analogue 7-deaza-dGTP by the one-electron redox catalysts Ru(bpy)(3)(3+) (with bpy = 2,2'-bipyridine) or Os(bpy)(3)(3+) generated at an electrode. To demonstrate the feasibility of the method, a disposable array of eight miniaturized self-contained electrochemical cells (working volume of 50 microL) has been developed and implemented in a classical programmable thermal cycler and then tested with the PCR amplification of two illustrated examples of real-world biological target DNA sequences (i.e., a relatively long 2300-bp sequence from the bacterial genome of multidrug-resistant Achromobacter xylosoxidans and a shorter 283-bp target from the human cytomegalovirus). Although the method works with both mediator/base couples, the catalytic peak current responses recorded with the Ru(bpy)(3)(3+)/dGTP couple under real-time PCR conditions are significantly affected by a continuous current drift and interference with the background solvent discharge, thus leading to poorly reproducible data. Much more reproducible and reliable results are finally obtained with the Os(bpy)(3)(3+)/7-deaza-dGTP, a result that is attributed to the much lower anodic potential at which the catalytic oxidation of 7-deaza-dGTP by Os(bpy)(3)(3+) is detected. Under these conditions, an exponential decrease of the catalytic signal as a function of the number of PCR cycles is obtained, allowing definition of a cycle threshold value (C(t)) that correlates inversely with the initial amount of target DNA. A semilogarithmic plot of C(t) with the initial copy number of target DNA gives a standard linear curve similar to that obtained with fluorescent-based real-time PCR. Although the detection limit (10(3) molecules of target DNA in 50 microL) and sensitivity of the electrochemical method is not as high as conventional optical-based real-time PCR, the methodology described here offers many of the advantages of real-time PCR, such as a high dynamic range (over 8-log(10)) and speed, high amplification efficiency (close to 2), and the elimination of post-PCR processing. The method also has the advantage of being very simple, just requiring the use of low-cost single-use electrodes and the addition of a minute amount of redox catalyst into the PCR mixture. Moreover, compared to the other recently developed electrochemical real-time PCR based on solid-phase amplification, the present approach does not require electrode functionalization by a DNA probe. Finally, on account of the relative insensitivity of electrochemical methods to downscaling, the detection scheme is quite promising for use in miniaturized devices and in the development of point-of-care diagnosis applications.

[Comparison between the LightCycler CMV Quant Kit (Roche Diagnostics) with a standardized in-house Taqman assay for cytomegalovirus blood viral load quantification]

The broad use of cytomegalovirus (CMV) viral load quantification in blood to follow immunosuppressed patients need standardized assays. Choice of whole blood allows follow-up for several viruses and simplifies pretreatment and storage of samples.

METHODS

We therefore evaluated the LightCycler CMV Quant Kit (Roche Diagnostics) assay on whole blood after a manual extraction (High Pure viral nucleic acid kit, Roche Diagnostics), using as a reference an in-house Taqman assay (LC1UL83) which has been validated in various clinical situations. A panel obtained by serial dilutions of a virion stock in CMV whole blood, a commercial plasma quality control (VQC, Argène, France) crude or diluted in whole blood, infected cells extracts and 46 clinical samples from transplanted patients were tested simultaneously by both techniques.

RESULTS

For plasma quality controls, both PCR assays are correlated VQC (R(2)=0.93). On whole blood or infected cells dilutions, correlation shows an overestimation by the LC1UL83 assay (mean 1.2 log copies/ml) over 3 log though R(2)=0.94. Results with CMV Quant Kit are closer to expected values. Results on clinical samples are close to quality controls with a lower variation of quantification (0.76 log copies/ml).

CONCLUSION

CMV Quant Kit performs well when compared with a clinically validated PCR. Quality control results showed discrepancies between plasma and whole blood, demonstrating the need for whole blood standardized panels to compare the methods. This underlines the need to follow a patient with the same technique during his follow-up.

[Evaluation of cytomegalovirus quantification in blood by the R-gene real-time PCR test]

AIM OF THE STUDY

Diagnosing the presence of cytomegalovirus (CMV) in the blood of immunodepressed patients is often done by quantitative polymerase chain reaction (Q-PCR) even though the reference method remains the antigenemia pp65 (Ag-pp65) test.

OBJECTIVES

To define the predictive value of the Q-PCR in the diagnosis of CMV disease and assess treatment efficacy using the CMV R-gene test. To compare the Q-PCR results and feasibility with those of the Ag-pp65 test.

PATIENTS AND METHODS

The Q-PCR was performed in 34 whole blood samples (frozen at -80 degrees C until use) from five patients diagnosed with CMV disease, defined as the presence of clinical signs and Ag-pp65 in the nuclei of more than two cells. After extraction, viral DNA was quantified in each sample using the Q-PCR CMV R-gene kit according to the manufacturer's instructions. Immediately after blood was drawn, the Ag-pp65 test had been performed in 32 samples using CINAkit (Argene).

RESULTS

The 16 samples positive by the Ag-pp65 test were also positive by PCR; six samples negative by the Ag-pp65 test were positive by PCR; and the remaining 10 samples were negative by both techniques. During treatment, the two markers' kinetics were similar.

CONCLUSION

The CMV R-gene test has a predictive value as good as that of the Ag-pp65 test but is fast and easier to use. A prospective study with a greater number of patients is needed to define the prediction threshold for CMV disease.

Comparative evaluation of a commercially available automated system for extraction of viral DNA from whole blood: application to monitoring of epstein-barr virus and cytomegalovirus load

The NucliSENS easyMAG automated system was compared to the column-based Qiagen method for Epstein-Barr virus (EBV) or cytomegalovirus (CMV) DNA extraction from whole blood before viral load determination using the corresponding R-gene amplification kits. Both extraction techniques exhibited a total agreement of 81.3% for EBV and 87.2% for CMV.

Herpesviruses in abscesses and cellulitis of endodontic origin

Acute apical abscesses and cellulitis are severe endodontic diseases caused by opportunistic bacteria with possible coinfection with latent herpesviruses. The objectives of this study are to identify herpesviruses, including human cytomegalovirus (HCMV), Epstein-Barr virus (EBV), herpes simplex virus-1 (HSV-1), and Varicella zoster virus (VZV) in patients (n = 31) presenting with acute apical abscesses and cellulitis of endodontic origin. Primary and nested polymerase chain reaction (PCR) was conducted using virus-specific primers and DNA isolated from cell-free abscess fluid. From patients exhibiting concurrent spontaneous pain (n = 28), nine abscesses contained HCMV, two abscesses contained EBV, one abscess contained HSV-1, and no abscesses contained VZV. Control PCR using genomic or recombinant templates showed detection limits to a single genomic copy of HCMV, 100 genomic copies for EBV, and 1 to 10 copies for HSV-1 with no cross-amplification between herpesviral DNA targets. Nested PCR was required for detection of herpesviral DNA in the abscess specimens, indicating that these viruses were present in low copy number. Filtration of abscess specimens and virus transfer experiments using human fibroblastic MRC-5 cells confirmed the presence of HCMV particles in several abscess specimens. We conclude that herpesviruses are present but not required for the development of acute apical abscesses and cellulitis of endodontic origin.

Monitoring of human cytomegalovirus infection in bone marrow and liver transplant recipients by antigenaemia assay and enzyme-linked immunosorbent assay

Human cytomegalovirus (HCMV) infection is a common complication in transplant recipients. Sensitive, specific and timely diagnostic tests for the detection of HCMV infection remain essential for successful therapy. The results of three tests to detect HCMV in bone marrow and liver transplant recipients were compared: a pp65 antigenaemia assay, an immediate-early (IE) antigenaemia assay and an anti-HCMV immunoglobulin M (IgM) antibody enzyme-linked immunosorbent assay (ELISA). Of 1344 samples, 911 (67.8%) and 917 (68.2%) samples were positive for pp65 and IE, respectively. The coincidence level was 85.1%. There was no statistical difference after transplantation to the first positive detection of HCMV (mean first checkout time) between the pp65 and IE antigenaemia assays. Moreover, the levels of HCMV detected by the pp65 and IE antigenaemia assays were significantly correlated. The HCMV-positivity rate as detected by the anti-HCMV IgM ELISA was 11.1%, which was significantly different from the IE and pp65 antigenaemia assays. We suggest that the IE antigenaemia assay could replace the pp65 antigenaemia assay for monitoring active HCMV infection and early detection of HCMV infection.

Quantification of DNA in plasma by an automated real-time PCR assay (cytomegalovirus PCR kit) for surveillance of active cytomegalovirus infection and guidance of preemptive therapy for allogeneic hematopoietic stem cell transplant recipients

The performance of a plasma real-time PCR (cytomegalovirus [CMV] PCR kit; Abbott Diagnostics) was compared with that of the antigenemia assay for the surveillance of active CMV infection in 42 allogeneic hematopoietic stem cell transplantation (Allo-SCT) recipients. A total of 1,156 samples were analyzed by the two assays. Concordance between the two assays was 82.2%. Plasma DNA levels correlated with the number of pp65-positive cells, particularly prior to the initiation of preemptive therapy. Fifty-seven episodes of active CMV infection were detected in 37 patients: 18 were defined solely by the PCR assay and four were defined on the basis of the antigenemia assay. Either a cutoff of 288 CMV DNA copies/ml or a 2.42-log(10) increase of DNAemia levels between two consecutive PCR positive samples was an optimal value to discriminate between patients requiring preemptive therapy and those not requiring therapy on the basis of the antigenemia results. The real-time PCR assay allowed an earlier diagnosis of active CMV infection and was a more reliable marker of successful clearance of CMV from the blood. Analysis of the kinetics of DNAemia levels at a median of 7 days posttreatment allowed the prediction of the response to CMV therapy. Two patients developed CMV colitis. The PCR assay tested positive both before the onset of symptoms and during the disease period. The plasma real-time PCR from Abbott is more suitable than the antigenemia assay for monitoring active CMV infection in Allo-SCT recipients and may be used for guiding preemptive therapy in this clinical setting.

Human cytomegalovirus and Epstein-Barr virus in apical and marginal periodontitis: a role in pathology?

Periodontitis is presumably caused by bacterial infection, but it has been shown recently that affected tissue often contains human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV). The present study was initiated to evaluate the role of these viruses in the pathogenesis of periodontitis. HCMV and EBV were quantified in 40 apical and 25 marginal periodontitis samples using real time PCR. In situ hybridization or immunohistochemistry was carried out on apical samples to detect viral presence within cells. A possible association with relevant bacteria was examined. Of the apical periodontitis samples, 50% contained EBV, while none contained HCMV. Of the marginal periodontitis samples, 40% were positive for EBV and 12% for HCMV. With one exception, however, the amount of virus was close to the detection limits. EBV was only detected in 1 out of 15 healthy periodontium samples. Immunohistochemistry and in situ hybridization were all negative. Significant associations were found between periodontal EBV and the presence of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis. Although there was an obvious association of the virus with clinical samples, it seems unlikely that these viruses play a major role in the pathogenesis of periodontitis of the average patient. Their presence may reflect that the clinical samples contain more blood or saliva compared to controls, or an accumulation of lymphoid cells harboring virus in the inflamed tissue.

A Decline in Hepatitis B virus Surface Antigen (HBsAg) Predicts Clearance, but does not Correlate with Quantitative HBeAg or HBV DNA Levels

Background

The elimination of hepatitis B virus surface antigen (HBsAg) is the final goal of hepatitis B treatment, but is rarely achieved. As quantitative assays for HBsAg recently became available, we have investigated whether quantitative HBsAg measurements can substitute for hepatitis B virus (HBV) DNA quantification in treatment monitoring.

Methods

Within this study, 23 liver transplant patients and 18 heart transplant recipients were retrospectively analysed. Patients had been treated with famciclovir and/or lamivudine, in addition some had also received adefovir in cases of lamivudine resistance. Quantitative HBsAg and hepatitis B virus e antigen (HBeAg) levels were determined with the ArchitectTM assay. HBV DNA levels were determined with different assays available at given time points.

Results

We did not find a significant correlation between either HBsAg or HBeAg and HBV DNA levels – both in treated and untreated patients. More importantly, there was no significant concordance between an increase or decrease of HBsAg or HBeAg with HBV DNA. However, the curve and decline of quantitative HBsAg enabled prediction of eventual viral clearance. Eight patients showed a 2 log10 drop of HBsAg levels and eight patients demonstrated a reduction of HBsAg levels below 100 IU/ml; five patients fulfilled both criteria. Three of those five cleared HBsAg and became positive for antibodies against HBsAg.

Conclusions

Quantitative HBsAg and HBeAg cannot substitute for HBV DNA quantification during the assessment of antiviral therapy; however, the decline of HBsAg does predict eventual HBsAg clearance. A 2 log10 drop to below 100 IU/ml is associated with a high likelihood of HBsAg clearance.