Molecular methods for cytomegalovirus surveillance in bone marrow transplant recipients

Lung Infections

A review of pulmonary infections of all types with diagnostic and morphological features.

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.

Late-onset cytomegalovirus (CMV) in lung transplant recipients: can CMV serostatus guide the duration of prophylaxis?

Evidence supports the use of 12 months of cytomegalovirus prophylaxis in all at-risk lung transplants; whether cytomegalovirus serostatus can be used to further optimize this duration remains to be determined. The purpose of this retrospective study was to determine if cytomegalovirus serostatus of both donor and recipient were associated with late-onset cytomegalovirus. The primary outcome was the proportion of lung transplants that developed cytomegalovirus infection or disease during the 180-day period following 6 months of prophylaxis in each at-risk serotype. Two hundred forty-four consecutive lung transplants were evaluated, 131 were included. The proportion of recipients with cytomegalovirus differed significantly between serotypes (20 of 41 [48.8%] D+/R- vs. 19 of 56 [33.9%] D+/R+ vs. 2 of 34 [5.9%] D-/R+; p < 0.001). In a multivariate model, older age (odds ratio [OR], 1.05, 95% confidence interval [CI] 1.004-1.099; p = 0.03) and D+/R- serostatus (OR, 3.83; 95% CI 1.674-8.770; p = 0.002) were associated with cytomegalovirus. Among R+ lung transplants, D- serostatus was associated with the absence of cytomegalovirus (OR, 0.12; 95% CI 0.0263-0.563; p = 0.007). These findings suggest that in the valganciclovir era, cytomegalovirus serostatus of both donor and recipient may identify lung transplants at heightened risk for late-onset cytomegalovirus.

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.

Monitoring human cytomegalovirus infection with nested PCR: comparison of positive rates in plasma and leukocytes and with quantitative PCR

BACKGROUND

Human cytomegalovirus (HCMV) infection poses a significant health threat to immunocompromised individuals. Here we performed this study to set up a highly sensitive nested PCR method applicable for detecting HCMV infection in high-risk individuals. In this work, 106 blood specimens from 66 patients with potential HCMV infection were obtained. Total DNA was extracted separately from plasma and peripheral blood leukocytes (PBL) of each sample. HCMV DNA was detected in parallel by nested PCR and quantitative real-time PCR (qRT-PCR), and the results were compared.

RESULTS

Serial dilution test revealed that the detection limit of nested PCR was 180 copies/ml. The nested PCR showed a higher positive rate than qRT-PCR (34.9% vs. 12.3%, p < 0.001). The positive rate of nested PCR based on PBL DNA was significantly higher than that based on plasma DNA (34.9% vs. 18.9%, p = 0.002). Of the 14 patients with serial samples, 11 were positive for HCMV DNA in PBL while only 7 were positive in plasma. Moreover, for each patient, nested PCR using PBL DNA also detected more positive samples than that using plasma DNA.

CONCLUSION

Combined use of nested PCR with PBL DNA is highly sensitive in defining HCMV infection. This assay is particularly useful in the case of quantification not essential.

Incidence and predictive factors for cytomegalovirus infection in renal transplant recipients

BACKGROUND

Cytomegalovirus (CMV) infection is a common cause of morbidity, graft loss, and mortality among kidney recipients due to its direct and indirect influences on organs and systems, namely, immunomodulation, which favors the appearance of opportunistic infections, vasculopathy, and decreased graft and patient survival. In Mexico the dimensions of this infection are unknown in kidney transplant recipients. We evaluated the incidence and predictive factors for CMV infection among renal transplant recipients of the Mexican Institute of Social Security in Guadalajara.

METHODS

This prospective cohort analysis of patients >or=16 years of age of both genders, included transplantations from May 2006 to July 2007. Two hundred twenty-five patients were followed over 6 months to evaluate CMV infection or disease. We evaluated demographic, clinical, and paraclinical aspects, such as total lymphocyte count and quantitative CMV polymerase chain reactions (PCR).

RESULTS

The overall incidence of CMV infection was 17.8%. CMV infections were associated with lymphopenia (relative risk [RR] 14.75; confidence interval [CI] 95%, 3.46-62.77), serostatus D+/R- (RR 5.53; CI 95%, 2.18-14.05), and fever (RR 4.57; CI 95%, 1.50-13.95). Receiver-operating characteristic (ROC) curves for lymphopenia versus PCR showed a sensitivity of 27% and a specificity of 98%.

CONCLUSION

In our study, lymphopenia, serostatus D+/R-, and fever were good predictors of CMV infections among renal transplant recipients.

Comparison of quantitative cytomegalovirus real-time PCR in whole blood and pp65 antigenemia assay: clinical utility of CMV real-time PCR in hematopoietic stem cell transplant recipients

Successful preemptive therapy for cytomegalovirus (CMV) infection in transplant patients depends on the availability of sensitive, specific, and timely diagnostic tests for CMV infection. Although the pp65 antigenemia assay has been widely used for this purpose, real-time quantification of CMV DNA has recently been recognized as an alternative diagnostic approach. However, the guidelines for antiviral therapy based on real-time quantitative polymerase chain reaction (RQ-PCR) have yet to be established. From November 2004 to March 2005, a total of 555 whole blood samples from 131 hematopoietic stem cell transplant (HSCT) recipients were prospectively collected. RQ-PCR was conducted using an Artus CMV LC PCR kit (QIAGEN). Both qualitative and quantitative correlations were drawn between the two methods. Exposure to the antiviral agent influenced the results of the two assays. Additionally, the discrepancy was observed at low levels of antigenemia and CMV DNA load. Via ROC curve analysis, the tentative cutoff value for preemptive therapy was determined to be approximately 2x10(4) copies/mL (sensitivity, 80.0%; specificity, 50.0%) in the high risk patients, and approximately 3x10(4) copies/mL (sensitivity, 90.0%; specificity, 70.0%) in the patients at low risk for CMV disease. Further study to validate the optimal cutoff value for the initiation of preemptive therapy is currently underway.

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.

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/200000 polymorphonuclear leukocytes was 5.26log(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 0.77log(10), 0.04log(10), 0.77log(10) and 0.97log(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.

Analysis of cytomegalovirus (CMV) viremia using the pp65 antigenemia assay, the amplicor CMV test, and a semi-quantitative polymerase chain reaction test after allogeneic marrow transplantation

A pp65 antigenemia assay for polymorphonuclear leukocytes (PMNLs) (CINAkit Rapid Antigenemia), and a qualitative polymerase chain reaction (PCR) test for plasma 'PCR-P qual' (Amplicor cytomegalovirus [CMV] test) were performed for 126 samples (blood and plasma) obtained from 18 bone marrow transplant patients, over a 9-month surveillance period. Among those samples, 92 were assayed with a semi-quantitative PCR test for PMNLs 'PCR-L quant.' The number of samples with a positive CMV test for antigenemia and PCR-P qual assays was 20.63% and 12.7%, respectively, whereas the PCR-L quant assay was positive in 48 of the 92 samples assayed (52.17%). The rates of concordance of the results of PCR-P qual and antigenemia, PCR-P qual and PCR-L quant, antigenemia and PCR-L quant were 92%, 65.2% and 66.8%, respectively. The analysis of the results for the 92 specimens tested by all 3 methods showed a rate of concordance of 63% among all methods. Good agreement (kappa=0.72) was found only between pp65 Ag and PCR-P qual assays. Clinical disease correlates with an antigenemia high viral load. Three patients had CMV disease despite preemptive therapy, and all of them had graft-versus-host-disease (GVHD). PMNLs-based assays are more efficient in monitoring CMV reactivation, but for high-risk patients with GVHD, more sensitive assays (real-time PCR) must be done.

Valganciclovir is safe and effective as pre-emptive therapy for CMV infection in allogeneic hematopoietic stem cell transplantation

Despite significant advances in prevention and therapy, cytomegalovirus (CMV) infection continues to be an important cause of morbidity and mortality in the hematopoietic stem cell transplant (HSCT) recipient. The standard drug for pre-emptive therapy is intravenous ganciclovir (GCV). Valganciclovir (VGC), the oral pro-drug of GCV, has excellent bioavailability and is ideal for oral therapy. Since March 2002, VGC was adopted in our center for outpatient pre-emptive therapy in all patients undergoing allogeneic HSCT. Fifty-two allogeneic HSCT recipients were followed weekly via Digene hybrid capture assay. Patients with a positive assay were treated with VGC 900 mg p.o. b.i.d. x 14 days followed by 900 mg p.o. QD until at least 7 days after a negative test. Eighteen patients (14 sib, four MUD) had 30 episodes of CMV DNA detection treated with oral VGC. Median duration of therapy was 21 days (range 10-21 days). The rate of response was 93% (28/30) as confirmed by a negative assay within 14 days. No significant toxicity was encountered. Two patients failed oral VGC. One case of CMV enteritis was diagnosed in a patient with acute GVHD. Pre-emptive therapy of CMV infection with oral VGC is safe and effective in allogeneic HSCT recipients.

Evaluation of pulmonary infiltrates in patients after stem cell transplantation

Hematopoietic stem cell transplantation is potentially curative therapy that has become the standard of care for many hematologic malignancies. Pulmonary complications occur in about 50% of stem cell transplant recipients and no other organ dysfunction has a higher mortality. Unfortunately the diagnosis of these infiltrates is hampered by the poor yield from routine studies and this patient population is rarely able to tolerate more risky procedures that will obtain tissue for microscopy and culture. A bronchoalveolar lavage (BAL) is usually insufficient to make a diagnosis of invasive fungal, significant bacterial, or pathogenic viral infections in patients that will still benefit from a change in therapy. In this review we discuss the infectious etiologies of pulmonary infiltrates post hematopoietic stem cell transplant, the non-infectious causes of infiltrates such as diffuse alveolar hemorrhage, engraftment syndrome, and idiopathic pneumonia syndrome, and the yield of newer diagnostic procedures ranging from peripheral blood galactomannan to cytomegalovirus antigenemia, and report on new technologies that promise more accurate and timely diagnoses of these infiltrates.

Treatment of multidrug-resistant cytomegalovirus retinitis with systemically administered leflunomide

Multiresistant cytomegalovirus (CMV) infection is increasingly recognized in solid organ transplant recipients. Leflunomide is a novel drug with both immunosuppressive and anti-CMV properties. Herein we report a case of a renal transplant recipient treated with leflunomide for multiresistant CMV retinitis, and provide correlation between serum and vitreous levels of leflunomide. She had stabilization of her retinitis and measurable levels of drug in her vitreous fluid and serum. These initial findings suggest that leflunomide may be useful in the treatment of CMV disease, including retinitis in patients after solid organ transplantation.

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.

A follow up study of cytomegalovirus infection in a group of Turkish renal transplant recipients using molecular assays

The clinical value of an in-house cytomegalovirus nested polymerase chain reaction (CMV-PCR) and a commercial molecular assay hybrid capture CMV DNA assay (HCA) was evaluated in monitoring a group of renal transplant patients for six months follow up. In this study, the sensitivity, specificity, positive predictive value, and negative predictive value of nested CMV DNA PCR assay and HCA at the beginning of the study were 70, 42.9, 46.7, 66.7, and 60, 78.6, 66.7, and 73.3% respectively. After six months, they were 80, 66.7, 80, 66.7 for CMV PCR and 73.3, 88.9, 91.7, 66.7% for HCA respectively. These results indicate that in monitoring and predicting CMV infections in renal transplant recipients, not only qualitative but also quantitative assays must be used together in order to decide the preemptive strategies.

Following universal prophylaxis with intravenous ganciclovir and cytomegalovirus immune globulin, valganciclovir is safe and effective for prevention of CMV infection following lung transplantation

We prospectively determined the safety and efficacy of valganciclovir for prevention of cytomegalovirus (CMV) in at-risk (donor positive/recipient negative [D+/R-] or R+) lung transplant recipients. We also determined the length of prophylaxis required to significantly decrease both CMV infection and disease. Consecutive lung transplant recipients surviving >30 days (n = 90) received combination prophylaxis with intravenous (i.v.) ganciclovir (GCV) 5 mg/kg/day and cytomegalovirus immune globulin (CMV-IVIG) followed by valganciclovir (450 mg twice-daily) to complete 180, 270 or 365 days of prophylaxis. This group was compared to a historical group (n = 140) who received high-dose oral acyclovir following i.v. GCV and CMV-IVIG. CMV disease was significantly lower in patients receiving valganciclovir compared to acyclovir (2.2% vs. 20%; p < 0.0001). Freedom from CMV infection and disease was significantly greater (p < 0.02) in patients receiving 180, 270 or 365 days of prophylaxis (90%, 95% and 90%, respectively) compared to those receiving 100-179 days (64%) or < 100 days (59%). No patient receiving valganciclovir died during the study. Following prophylaxis with i.v. GCV and CMV-IVIG, valganciclovir is safe and effective for prevention of CMV infection and disease in at-risk lung transplant recipients. The required length of prophylaxis was at least 180 days.