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

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.

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.

Genetic variability of cytomegalovirus glycoprotein O in hematopoietic stem cell transplant recipients

Genetic variation of cytomegalovirus (CMV) strains can correlate with their pathogenicity for immunocompromised patients. Glycoprotein O (gO), together with glycoprotein L and glycoprotein H, mediate the fusion of the viral envelope with the cell membrane and promotes virus penetration, envelopment, and release. The variability of gO might play a role in CMV cell tropism. The goal was a retrospective analysis of gO variability in a cohort of hematopoietic stem cell transplant (HSCT) recipients to determine the distribution of gO genotypes and to investigate their impact on clinical outcome and manifestation of CMV infection.

METHODS

In archived blood samples from 51 adult allogeneic HSCT recipients with active CMV infection, gO was analyzed by sequencing the N-terminal domain of the UL74 gene using the dye deoxy termination method.

RESULTS

The gO1 and gO2 clades were most common (39% and 20%, respectively, and gO3 was associated with higher risk of symptomatic infection (P = 0.026 in multivariant analysis). Despite being associated with higher antigenemia levels (P = 0.02), gO4 had the best survival and lower rate of CMV recurrence. No significant differences were found in clinical manifestation and outcome of CMV disease between patients with various gO clades. Because CMV strains sharing an identical gO sequence differed in glycoprotein B genotypes, sequencing the N-terminal part of the gO gene does not seem to be optimal for the identification of strains.

CONCLUSIONS

gO genotyping may contribute to the biological characterization of CMV strains in HSCT recipients.

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.

Prevalence of human cytomegalovirus co-infection in patients with chronic viral hepatitis B and C: a comparison of clinical and histological aspects

BACKGROUND

Human cytomegalovirus (HCMV) is a common pathogen of severe disease in patients with impaired immune functions. Reactivation of HCMV in immunocompetent host is usually asymptomatic, but may deteriorate the prognosis of patient with chronic illness.

OBJECTIVES

This study was conducted to detect HCMV infection in patients with chronic hepatitis B virus (HBV) and chronic hepatitis C virus (HCV) infections and to point out the effects of HCMV-HBV and HCMV-HCV co-infections on liver histology.

STUDY DESIGN

Expression of HCMV DNA was determined in liver tissue biopsies by real-time quantitative polymerase chain reaction (qPCR) method. There were 44 chronic HBV, and 25 chronic HCV patients within the study group. Control group consisted of 36 patients with hepatologic malignancies.

RESULTS

HCMV infection was demonstrated in 52.3% of chronic HBV, and 36% of chronic HCV patients. Although alanine aminotransferase (ALT) levels of HCMV-infected HBV patients were decreased slightly, they were increased in HCV patients. Histologic activity scores (necroinflammation and fibrosis) of HCMV-positive patients were higher than that of HCMV-negatives in both HBV and HCV groups. Intrahepatic HBV DNA or HCV RNA loads of the corresponding study groups were decreased in HCMV-infected patients.

CONCLUSION

We conclude that HCMV infection is common in chronic HBV and HCV patients, who can be regarded as patients at high risk for HCMV disease. Though the histological changes were more marked in liver, replication of HBV and HCV were inhibited in HCMV-positive cases.

[Infections in immunosuppressed patients]

Molecular biology techniques represent a major advance in the microbiologic diagnosis of infectious diseases, since these methods are able to detect etiological microorganisms with high sensitivity. Moreover, these procedures can also establish prognostic and therapeutic efficacy markers with a sufficiently short turnaround time for the results to have a real impact on the clinical management of immunosuppressed patients. However, these techniques still have substantial limitations that should be solved in the near future: lack of standardization, inter- and intra-assay variability, the difficulty of comparing results among different laboratories and low positive predictive value, due to their high sensitivity, leading to problems in the interpretation of results. The present article reviews the usefulness of molecular biology techniques in the diagnosis and clinical management of infectious diseases caused by human cytomegalovirus, Epstein-Barr virus, human herpes viruses 6 and 7, JC and BK viruses, Toxoplasma gondii and Pneumocystis jiroveci in immunosuppressed patients.

Incidence, risk factors, and outcome of cytomegalovirus infection and disease in patients receiving prophylaxis with oral valganciclovir or intravenous ganciclovir after umbilical cord blood transplantation

There is no information on the efficacy and safety of anticytomegalovirus (CMV) prophylaxis with intravenous ganciclovir or oral valganciclovir after unrelated cord-blood transplantation (UCBT). This issue was addressed in 151 adults (117 CMV-seropositive) undergoing UCBT at a single institution. The first 38 CMV-seropositive recipients were assigned to receive prophylactic ganciclovir, and the next 79 were given valganciclovir after engraftment. The cumulative incidence (CI) of CMV infection and disease was similar in patients receiving valganciclovir or ganciclovir (59% versus 55%, P = .59; and 9% versus 18%, P = .33, respectively). The toxicity profile and CI of nonrelapse mortality (CMV) and infection-related mortality did not differ between drugs. Patients receiving valganciclovir required fewer visits to the day hospital (P = .04). The CI of CMV infection and disease in 34 CMV-seronegative recipients was 12% and 6%, indicating that tight CMV monitoring is mandatory in this subset. The recipient's CMV serostatus, acute and extensive chronic graft-versus-host disease (aGVHD, cGVHD) were the main risk factors for CMV infection, and aGVHD for CMV disease. This study suggests that prophylaxis with oral valganciclovir is as safe and effective as intravenous ganciclovir for preventing CMV infection and disease after UCBT, but valganciclovir reduces the use of hospital resources.

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.

Laboratory diagnosis of cytomegalovirus infection and disease in immunocompromised patients

PURPOSE OF REVIEW

To review new developments in PCR technology as they apply to detecting cytomegalovirus viremia and pneumonia, recent advances in detecting CMV resistance to antivirals and assays of specific CMV lymphocyte function.

RECENT FINDINGS

This review summarizes the attempts to use real time PCR for cytomegalovirus deoxyribonucleic acidemia and to compare it to conventional PCR and antigenemia, it also reviews the use of quantitative PCR on bronchoalveolar lavage to assist in the diagnosis of CMV pneumonia. Phenotypic assays of susceptibility in tissue culture are much too slow to assist clinical decisions, taking weeks for completion. Genotypic assays may be performed directly on clinical samples such as blood, and cerebrospinal fluid and can be done by sequencing in a very few days.Finally, assays of lymphocytic functional responsiveness to cytomegalovirus can be used to identify transplant recipients at continuing risk for cytomegalovirus disease.

SUMMARY

Assays for CMV DNA or antigen in blood are superior to culture for documenting viremia and pneumonia. Genotypic assays have largely replaced phenotypic assays for CMV resistance to antivirals. Lymphocyte responses to CMV antigen(s) may identify patients at risk for CMV disease.

Pulmonary dysfunction in pediatric hematopoietic stem cell transplant patients: overview, diagnostic considerations, and infectious complications

Pulmonary complications are among the most common and serious sequelae seen in hematopoietic stem cell transplantation (HSCT) recipients. This two-part review addresses the incidence and impact of pulmonary complications in pediatric HSCT patients. In this first part we review the available data for the use of diagnostic modalities in this population, including flexible bronchoscopy with bronchoalveolar lavage (BAL) and open lung biopsy (OLB). We also review the many infectious pulmonary complications that may occur in pediatric HSCT recipients, utilizing the traditional chronologic divisions of neutropenic phase (0-30 days following HSCT), early phase (30-100 days), and late phase (>100 days).

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.

Clinical Utility of Autopsy after Hematopoietic Stem Cell Transplantation

Autopsy is the gold standard for establishing the cause of death. We present results of the largest retrospective review of complete autopsies of subjects after hematopoietic stem cell transplantation to better define the role of the autopsy in discovering a missed diagnosis. We reviewed the medical chart and autopsy records of 111 patients who had undergone hematopoietic stem cell transplantation from July 1986 to June 2003 from a single center. We compared the cause of death as charted by the clinical team with data obtained from postmortem chart review and autopsy reports. Of 29 (26%) cases when the premortem and postmortem major diagnoses did not agree, only 4 (4%) autopsy records provided data that might have led to the initiation of new treatments, and none of these diagnoses would be missed today with more sensitive and specific diagnostics and improved supportive care. Although autopsies after transplantation can be important educational, research, and epidemiologic tools and provide an emotional benefit to patient's families, in our series they rarely provided missed diagnoses that would alter the management of subsequent patients. Improvements in noninvasive tests for relapse or occult infections may further erode the role of autopsies in discovering missed diagnoses.