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

Whole Blood versus Plasma Samples-How Does the Type of Specimen Collected for Testing Affect the Monitoring of Cytomegalovirus Viremia?

Viral infections, or their reactivations, are one of the most important groups of transplantation complications that can occur among recipients of both hematopoietic cells and solid organ transplants. They are the most commonly caused by cytomegalovirus (CMV). Currently, the use of whole blood or plasma samples is recommended for CMV viral load monitoring. The aim of the study was to assess and compare the level of CMV DNA, depending on the type of clinical material—whole blood or plasma fraction derived from the same patient. The studies were carried out on 156 whole blood samples in which the presence of CMV genetic material was confirmed and the corresponding plasma samples from the same rounds of sampling. CMV DNA was not present in 59 (37.8%) of plasma samples compared to whole blood-positive counterparts. Of the samples positive in both types of clinical specimen, 77 (79.4%) had higher viral DNA levels in the whole blood samples. There were statistically significant differences in the detected CMV DNA load in the whole blood compared to plasma fraction counterparts (p < 0.001). The detected CMV DNA value is usually higher in whole blood compared to plasma samples of the same patient. Due to the variability in CMV viral load depending on the clinical material used for a particular patient, one type of specimen should be always used consequently for CMV viremia monitoring.

Risk Factors Analysis for Human Cytomegalovirus Viremia in Donor+/Recipient+ Hematopoietic Stem Cell Transplantation

OBJECTIVE

To assess the rate of, and risk factors for, human cytomegalovirus viremia (HCMV) in donor+/recipient+ (HCMV serostatus matched) hematopoietic stem-cell transplantation (HSCT) recipients.

METHODS

HCMV DNA from 144 donor+/recipient+ HSCT recipients was examined by quantitative polymerase chain reaction (qPCR).

RESULTS

The cumulative incidence of HCMV viremia was 69.4% (100/144) during the 48 weeks after HSCT. In a multivariate analysis, acute graft-versus-host disease (aGVHD) was discovered to be a risk factor for the occurrence of HCMV viremia (P = .006). The cumulative incidence of HCMV viremia and increasing DNA loads were significantly associated with aGVHD occurrence (P = .001 for each). The occurrence of late-term HCMV viremia was associated with aGVHD (P = .001) and a higher DNA load during the first 12 weeks after HSCT (P = .04).

CONCLUSIONS

aGVHD is a risk factor for HCMV viremia. Recipients with aGVHD who have a high HCMV DNA load should be strictly monitored to prevent HCMV activation.

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.

Fungal and viral infections after allogeneic hematopoietic transplantation from unrelated donors in adults: improving outcomes over time

Umbilical cord blood (CB) is increasingly used as an alternative source of stem cells in adult unrelated transplantation. Although registry studies report similar overall outcomes in comparison with BM/PB, comparative studies focusing on severe infections and infection-RM (IRM) with a long follow-up are scarce. A total of 434 consecutive unrelated transplants (1997-2009) were retrospectively analyzed to compare overall outcomes, incidence and risk factors of severe viral and invasive fungal infections in CB (n=65) vs BM/PB recipients (n=369). The 5-year OS was 38 vs 43%, respectively (P=0.2). CB transplantation (CBT) was associated with a higher risk of invasive aspergillosis (100-days-cumulative incidence 16 vs 6%, P=0.04) and CMV infection without differences in RM. No statistically significant differences were found regarding NRM (NRM of 38% in CB vs 37% in BM/PB at 1 year) nor IRM (30% in CB vs 27% in BM/PB at 1 year). In the overall population, NRM and IRM improved in more recent years. In adults who receive a single CBT, the risk of severe infections is increased when compared with unrelated BM/PB recipients, but mortality from infections is similar, leading to similar NRM and survival.

Human cytomegalovirus detection by real-time PCR and pp65-antigen test in hematopoietic stem cell transplant recipients: a challenge in low and middle-income countries

AIM

Cytomegalovirus (CMV) infection is one of the most common complications in patients submitted to hematopoietic stem cell transplant (HSCT). Pre-emptive therapy has been indicated in patients with laboratory evidence of CMV replication. The aims of this study were to compare real-time PCR or pp65 antigen assay methodologies to detect CMV replication in HSCT patients, define a viral load threshold for initiation of pre-emptive therapy, and assess the feasibility of its implementation in hospitals of countries with low and middle income.

MATERIAL AND METHODS

Human CMV detection by real-time PCR and pp65 antigen assay was carried out in blood and plasma samples of HSCT patients collected weekly during 3 months. Pre-emptive therapy was based on CMV antigenemia results.

RESULTS

Twenty-one patients were monitored with a total of 227 samples collected; 13 (62%) patients were children. A poor correlation was observed between qualitative results, though quantitative results showed statistically significant difference, with higher viral loads detected in patients with positive antigenemia. Compared to a positive antigenemia, a cutoff value of 1067·5 copies/ml, 3·03 log10/ml, for viral load was obtained with 100% sensitivity and 71% specificity.

CONCLUSION

CMV real-time PCR in whole blood was suitable for monitoring HSCT patients. However, its high cost is a limiting factor, and it could be used to monitor selected patients, those with prolonged leukopenia and underweight children, and subsequently switched to pp65 antigen test. Further studies involving larger numbers of patients should be performed to confirm this statement.

Detection of human cytomegalovirus DNA in various blood components after liver transplantation

The quantification of human cytomegalovirus (HCMV DNA) by real-time PCR is currently a primary option for laboratory diagnosis of HCMV infection. However, the optimal sample material remains controversial due to the use of different PCR assays. To explore the best blood component for HCMV DNA surveillance after liver transplantation, whole blood (WB), serum (SE), and plasma (PL) specimens were collected simultaneously from targeted patients and examined for HCMV DNA using one commercially available assay. The HCMV DNA-positive rate with WB (16.67%) was higher than that with either SE or PL (8.33%, both P<0.01). Quantitative DNA levels in WB were of greater magnitude than those in SE (WB-SE mean log-transformed difference, 0.99; 95%CI=0.74-1.25; P<0.0001) and PL (WB-PL mean log-transformed difference, 1.37; 95%CI=1.07-1.66; P<0.0001). Dynamic monitoring revealed that HCMV DNA in WB was positive sooner and had higher values for a longer period of time during therapy. With earlier positive detection, higher sensitivity, and yield of greater viral loads, WB compared favorably to SE or PL and hence is recommended as the superior material for HCMV DNA surveillance after liver transplantation. In addition, infant recipients require more intensive monitoring and prophylactic care because of their higher susceptibility to primary HCMV infection.

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.

Diagnosis and monitoring of cytomegalovirus infection by the quantification of viral load in dried blood spots samples

Cytomegalovirus (CMV) represents the major infectious cause of birth defects, as well as an important pathogen for immune-compromised individuals. Several studies described the use of dried blood spots (DBS) for the detection of CMV DNA for late diagnosis of congenital CMV infection in cases of strong clinical suspicion. In the article under evaluation, Limaye et al. perform for the first time the quantification of CMV in pairs of finger-stick DBS and plasma samples collected from transplant patients. The work concluded that finger-stick DBS could be an alternative sample type for quantification of CMV load that correlates well with plasma levels. Prospective trials to evaluate the use of DBS for monitoring CMV load in transplant recipients will be required.

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.

The role of the clinical microbiology laboratory in solid organ transplantation programs

Infections remain a major complication of solid organ transplantation. For this reason, the clinical microbiology laboratory plays a key role in the success of transplant programs, which must have the support of a qualified laboratory, both technically and professionally. Transplant programs strongly condition the structure and functionality of microbiology laboratories, but at the same time, benefit greatly from the knowledge generated from these programs. The laboratory must make a special effort to implement rapid methods that can respond to the broad spectrum of potential pathogens in solid organ transplant patients. The integration of microbiologists in multidisciplinary teams is highly recommended, as only then can they obtain the highest quality and efficiency in the diagnostic process. This article provides an updated review of the techniques to be used once transplantation has occurred. The role of the microbiologist is also crucial in the pretransplant period, as good microbiological candidate evaluation at this time strongly conditions the success of the transplantation program.

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.

Human cytomegalovirus and kidney transplantation: a clinician's update

Infection with human cytomegalovirus (CMV) is an important cause of morbidity and mortality in kidney transplant recipients. CMV disease is diagnosed based on the detection of viral replication by phosphoprotein 65 antigenemia or CMV DNA polymerase chain reaction in combination with typical signs and symptoms. Risk factors include CMV-seronegative recipients receiving a CMV-seropositive transplant, older donor age, exposure to cyclosporine and/or antilymphocyte antibody, rejection episodes, and impaired transplant function. Current preventive strategies in kidney transplant recipients include pre-emptive therapy with valganciclovir or intravenous ganciclovir and universal prophylaxis with valacyclovir, valganciclovir, or ganciclovir for 3-6 months after kidney transplantation and for 1-3 months after treatment with antilymphocyte antibody. Established disease should be treated using either intravenous ganciclovir or oral valganciclovir until CMV replication can no longer be detected. In addition to direct effects, CMV infection also induces a wide range of indirect effects, such as decreased transplant and recipient survival and susceptibility to rejection and opportunistic infections. In this review, we highlight the most relevant topics on CMV and kidney transplantation based on current evidence and guidelines.

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.

CMV plasma DNAemia and risk of cancer among HIV-infected patients: a case-control study nested in the ANRS CO3 Aquitaine Cohort, France, 2002-2007

BACKGROUND

CMV reactivation, which enhances immune senescence, could be associated with a higher risk of cancer.

OBJECTIVES

We compared the prevalence of positive CMV DNAemia in HIV-infected patients with and without cancer.

STUDY DESIGN

This case-control study, nested in the ANRS-CO3 Aquitaine Cohort, included patients with a first diagnosis of cancer (2002-2007) as cases. Two controls were matched per case. Cancer risk was estimated using conditional logistic regression models, an Odds Ratio (OR) of 2 could be detected with 80% power. The variables considered were: ≥ 1 positive CMV DNAemia, CD4+ and CD8+ counts, HIV plasma load. Plasma CMV DNA was retrospectively quantified within the 3-year period preceding the endpoint.

RESULTS

The 143 cases (93 non-AIDS-related and 50 AIDS-related cancers) and 284 controls had a median age of 47 years (IQR: 41-56). At the time of diagnosis or censorship, for cases and controls, median values were respectively, for CD4+ count: 327 cells/mm(3) (IQR: 164-514) and 416 (IQR: 275-582), and for HIV plasma load: 2.6 log(10)copies/mL (IQR: 1.7-4.7) and 1.7 log(10)copies/mL (IQR: 1.7-3.3). We performed 2056 CMV PCR; 14 cases (9.8% [95% CI: 4.9-14.7]) and 19 controls (6.7% [CI: 3.8-9.6]) presented ≥ 1 positive PCR. CMV DNAemia was not associated with the risk of cancer (unadjusted and adjusted p-values=0.19 and 0.54, respectively). HIV load >500 copies/mL was independently associated with a higher risk of cancer (OR=2.02; p=0.002; 95% CI: 1.29-3.17).

CONCLUSION

This large case-control study did not show any differential exposure to positive CMV plasma DNAemia between cancer cases and controls.

The effect of cytomegalovirus antigenemia titer on the efficacy of preemptive therapy for the prevention of cytomegalovirus disease after kidney transplantation

There is some controversy regarding the exact cytomegalovirus (CMV) antigenemia titer that should be used as a guideline for preemptive anti-CMV therapy. We performed 634 consecutive kidney transplantations between January 2000 and June 2007. Preemptive therapy employed intravenous gancyclovir treatment when the CMV antigenemia titer was >or=50/4x10(5) leukocytes after kidney transplantation. The 634 recipients were allocated into 2 groups according to the peak CMV antegenemia: group A, CMV antigenemia titer<50/4x10(5) (n=550); and group B, >or=50/40x10(5) (n=84). Among the 634 recipients, 264 were positive for CMV antigenemia, and 61 developed symptomatic CMV infections. The incidence of symptomatic CMV infections in group B was significantly higher than in group A. Two cases in both groups developed tissue-proven CMV disease: group A CMV colitis and CMV nephritis, and group B, 2 cases of CMV colitis. Graft and patient survival rates in groups A and B at 5 years posttransplantation were not different. The authors concluded that a CMV antigenemia titer of >or=50/4x10(5) leukocytes can be considered an appropriate guideline for preemptive anti-CMV therapy.

Surveillance of active human cytomegalovirus infection in hematopoietic stem cell transplantation (HLA sibling identical donor): search for optimal cutoff value by real-time PCR

BACKGROUND

Human cytomegalovirus (CMV) infection still causes significant morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Therefore, it is extremely important to diagnosis and monitor active CMV infection in HSCT patients, defining the CMV DNA levels of virus replication that warrant intervention with antiviral agents in order to accurately prevent CMV disease and further related complications.

METHODS

During the first 150 days after allogeneic HSTC, thirty patients were monitored weekly for active CMV infection by pp65 antigenemia, nested-PCR and real-time PCR assays. Receiver operating characteristic (ROC) plot analysis was performed to determine a threshold value of the CMV DNA load by real-time PCR.

RESULTS

Using ROC curves, the optimal cutoff value by real-time PCR was 418.4 copies/104 PBL (sensitivity, 71.4%; specificity, 89.7%). Twenty seven (90%) of the 30 analyzed patients had active CMV infection and two (6.7%) developed CMV disease. Eleven (40.7%) of these 27 patients had acute GVHD, 18 (66.7%) had opportunistic infection, 5 (18.5%) had chronic rejection and 11 (40.7%) died - one died of CMV disease associated with GVHD and bacterial infection.

CONCLUSIONS

The low incidence of CMV disease in HSCT recipients in our study attests to the efficacy of CMV surveillance based on clinical routine assay. The quantification of CMV DNA load using real-time PCR appears to be applicable to the clinical practice and an optimal cutoff value for guiding timely preemptive therapy should be clinically validated in future studies.

[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.

Cellular normalization of viral DNA loads on whole blood improves the clinical management of cytomegalovirus or Epstein Barr virus infections in the setting of pre-emptive therapy

Two quantitative duplex real-time PCR assays were developed for co-amplification of human albumin and cytomegalovirus (CMV) or Epstein Barr virus (EBV) genes after automated extraction on whole blood, and compared two units for expressing viral DNA loads (copies per ml of blood or per 10(6) peripheral blood leukocytes (PBLs)) on 1,138 positive samples. Both PCRs were characterized by high sensitivity, reproducibility, and linear range. Automated extraction by a MagNA Pure LC Instrument was shown to be more efficient when peripheral blood cell count was inferior to 5 x 10(9) PBLs/L. Albumin co-amplification allows the detection of PCR inhibitors and normalization of viral load according to the number of cells calculated in the sample. The two ways of expressing viral load results were highly correlated, but quantitative differences varied in relation to variations of blood cell count. As these two viruses are highly cell associated, viral loads can be underestimated in patients with leucopenia. In the setting of pre-emptive strategies during CMV infection, the units in which results are expressed can influence clinical management, as illustrated in this article.

Quantification of adenovirus DNA in unrelated donor hematopoietic stem cell transplant recipients

BACKGROUND

Adenovirus (AdV) infection is a life threatening condition in immunosuppressed patients. Quantitative AdV assays can improve the clinical management of these patients.

OBJECTIVES

To evaluate quantitative measurement of AdV DNA with PCR in blood from hematopoietic stem cell transplant (HSCT) recipients.

STUDY DESIGN

Quantitative PCR was used to measure viral DNA levels of AdV in consecutive blood samples from 40 HSCT recipients (27 adults and 13 children) during a 1-year post-engraftment period. All patients received grafts from unrelated donors and were given anti-T-cell antibodies in the conditioning regimen.

RESULTS

In the group of 40 patients, six (15%) had detectable AdV DNA in blood for different lengths of time. None of these six patients suffered from severe graft-versus-host disease. In three of the patients a high AdV viral load (>10,000 copies/mL) was detected, one of whom also had high viral load of EBV and CMV and one of EBV only. These three patients died within 2 months after detection of ADV viremia. A low AdV viral load (<500 copies/mL) was detected in three surviving patients and they did not have concomitant high viral load of neither CMV nor EBV.

CONCLUSIONS

AdV viremia was present in 15% of the HSCT recipients and a high AdV viral load was associated with fatal outcome. Screening for AdV DNA with quantitative PCR in blood may be of clinical importance in allogeneic HSCT recipients in order to prevent severe clinical virological complications.

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.

Prediction of cytomegalovirus (CMV) plasma load from evaluation of CMV whole-blood load in samples from renal transplant recipients

In a prospective cohort of 82 renal transplant recipients, we evaluated the capacity of the cytomegalovirus (CMV) load in whole blood (WB) to predict the plasma CMV load, aiming to identify active CMV infections by using WB samples only and to deduce a WB threshold. Using quantitative real-time PCR, a total of 1,474 WB samples were assayed, of which 279 were positive for CMV, and 140 out of the 276 paired plasma samples tested positive. Thirty (36.6%) patients presented with at least one positive plasma PCR result, and 21 infection episodes (19 patients) required curative treatment (median follow-up time, 12 months). When the plasma CMV load was >500 copies/ml (n = 70), more than 94% (95% confidence interval, 86.0%, 98.4%) of WB samples had >500 copies/ml. Two prediction models were built: log(10) plasma viral load (VL) was calculated as -0.3777 + 0.9342 x log(10) WB VL and as -0.3777 + 0.8563 x log(10) WB VL for patients with and without treatment, respectively. In the validation sample (578 routine samples), 77.2% of the observed and expected plasma viral loads were concordant (95% confidence intervals, 73.5 and 80.5%). According to the model, the plasma viral load was >500 copies/ml when the WB load was >3,170 or >4,000 copies/ml in patients with or without treatment, respectively. WB seems to be an appropriate candidate for routine CMV monitoring of transplant recipients by using a single assay.

Monitoring of human cytomegalovirus infection in immunosuppressed patients using real-time PCR on whole blood

BACKGROUND

Quantitative monitoring of human cytomegalovirus (HCMV) is currently used in the follow-up of immunosuppressed patients.

OBJECTIVE

To investigate whether real-time PCR quantification (QPCR) of HCMV DNA could replace pp65 antigenemia.

STUDY DESIGN

We compared HCMV QPCR on whole blood (WB) and on plasma with a pp65-antigenemia assay on 192 samples. Afterwards, we tested 1310 samples from 308 immunosuppressed patients both by antigenemia assay and QPCR on WB.

RESULTS

The first study comparison showed that QPCR results on WB and plasma were significantly correlated with antigenemia. QPCR on WB was more sensitive than QPCR on plasma or antigenemia, detecting 31 and 49 additional positive samples, respectively. During the second comparison, QPCR on WB and antigenemia were again correlated (r=0.70; p<0.0001), but QPCR detected 244 additional positive samples. HCMV DNA was detected earlier than pp65 antigen (median difference: 14 days; range: 7-30). One, 5, 10, 50 and 100 pp65-positive cells/200,000 leukocytes corresponded to 439, 1531, 2623, 9150 and 15,671 HCMV DNA copies/mL of WB, respectively, but this equivalence differed according to the sub-group of patients considered.

CONCLUSION

QPCR on WB is the most sensitive method for the monitoring of HCMV infection in immunosuppressed patients.

Quantitative real-time polymerase chain reaction for evaluating DNAemia due to cytomegalovirus, Epstein-Barr virus, and BK virus in solid-organ transplant recipients

Testing for cytomegalovirus-, Epstein-Barr virus-, and BK virus-specific gene targets in specimens from solid-organ transplant recipients for DNA by quantitative real-time polymerase chain reaction has been implemented in many diagnostic facilities. This technology provides rapid, accurate, and reproducible results for early detection, monitoring, and medical management of patients with these infections. Because these assays are becoming commonly used in clinical practice, the technical variables associated with specimen processing (e.g., nucleic acid extraction, gene target, and result reporting), amplification, and unique patient characteristics (e.g., age, sex, underlying diseases, immune status, and immunosuppressive regimens received) are factors that may influence the understanding and interpretation of test results. We emphasize the need for standardization of existing variables through parallel comparative and proficiency testing, uniform units for expressing results, to provide for clinical correlation with the results of these molecular assays.

Variability of UL18, UL40, UL111a and US3 immunomodulatory genes among human cytomegalovirus clinical isolates from renal transplant recipients

BACKGROUND

Variability of human cytomegalovirus (HCMV) genes counteracting immune responses is poorly investigated in non-cultured clinical strains.

OBJECTIVES

In HCMV-infected renal graft recipients, we aimed to (i) investigate the variability of four HCMV immunomodulatory genes, without any culture-related viral selection, (ii) provide evolutionary sequence data, and (iii) study co-existing HCMV variants and their evolution.

STUDY DESIGN

UL18, UL40, UL111a and US3 were sequenced in 31 blood samples from 17 patients (8 with sequential samples). Cloning of UL40 PCR products was performed in one donor-positive/recipient-positive (D+/R+) patient's samples.

RESULTS

Each patient harboured a unique strain (combination of four genes), however single identical genes were demonstrated among various patients, suggesting recombination events. Sequencing showed in D+/R- recipients, either complete gene stability (four patients) or significant variability (one patient); in three D+/R+ patients, multiple gene variations, possibly linked to super- or co-infections. Cloning evidenced different variants at each time point with an increasing variability over time, illustrating possibly viral reactivations and the subsequent evolution of the variants mixture.

CONCLUSION

A noticeable HCMV natural polymorphism was shown, with different evolutive patterns. Moreover, we described the co-evolution of variants mixtures in one patient. Consequences on HCMV infection and graft function deserve further studying.

Patients at high risk for CMV infection and disease show delayed CD8+ T-cell immune recovery after allogeneic stem cell transplantation

Human cytomegalovirus (CMV) is a major cause of death after transplantation. The frequency of pp65-specific T cells was examined in 38 HLA-A2+ stem cell recipients during the first year after transplantation. Patients were divided into four groups based on donor/recipient serostatus: d+/r+ (n=17), d+/r- (n=7), d-/r+ (n=9) and d-/r- (n=5). Peripheral blood mononuclear cells were stimulated with the CMVpp65 peptide NLVPMVATV, and the specific T-cell frequency was assessed by interferon gamma (IFN-gamma) ELISPOT assay. Responding T cells were characterized by flow cytometry revealing a terminal differentiated effector phenotype. Surveillance of CMV infection was carried out by real-time polymerase chain reaction (n=26) or immunofluorescence (n=12). Infection was present in 7/9 d-/r+ high-risk patients, and CMV disease occurred exclusively in this group with delayed or absent virus-specific T-cell recovery. In contrast, 16/24 intermediate-risk patients showed CMV-specific T cells. Our data suggest that CMV infection and disease rates are elevated in high-risk patients with delayed CMV-specific T-cell immune reconstitution and lower in those with early recovery of T-cell immunity. We recommend preferring CMV seropositive donors for CMV seropositive recipients, as this should lead to durable CMV-specific T-cell responses soon after transplantation with consecutive protection from CMV disease.

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 x 10(4) copies/ml) than in asymptomatic (185copies/ml) patients (p = 0.001). The estimated cut-off value of CMV DNA for CMV symptoms/disease was > or =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.