Toward standardization of Epstein-Barr virus DNA load monitoring: unfractionated whole blood as preferred clinical specimen

Long-term follow-up of Epstein-Barr virus viremia in pediatric recipients of renal transplants

The common observation of Epstein-Barr virus (EBV) viremia in pediatric recipients of renal transplants and the occurrence of an EBV-related pulmonary leiomyoma prompted us to intensify the follow-up of EBV infections from 1995 to October 2000. Follow-up included serology and detection of viral DNA in blood using a semi-quantitative nested polymerase chain reaction (PCR) and later a real-time PCR with higher sensitivity. The aim of this study was the early detection of primary infections or reactivations. We obtained 250 samples from 32 patients. EBV DNA detection was consistently negative in 14 patients. There were 5 patients that were considered at risk for post-transplant lymphoproliferative disease, as they were EBV seronegative and were given a kidney from a positive donor. Of these, 4 had at least one episode of high-level EBV viremia. During these episodes, an absence of noticeable symptoms that could be related to EBV was noted for all but 1 patient. This child presented with severe neutropenia 1 month after grafting and, 28 months later, several nodules of pulmonary leiomyoma, which were found to be EBV related. Four episodes of high-level viremia were observed before the discovery of the leiomyoma. Viral DNA detection is important for the follow-up of such patients that are especially at risk of serious complications of EBV infections.

Dynamic EBV gene loads in renal, hepatic, and cardiothoracic transplant recipients as determined by real-time PCR light cycler

BACKGROUND

Epstein-Barr virus (EBV) is recognised as one of the causative agents for most cases of post-transplant lymphoproliferative disease (PTLD). Elevated levels of EBV DNA are known to be associated with the onset of PTLD, but little information is available regarding how EBV loads change with time in asymptomatic transplant recipients following transplantation. Our aims were to study the trend of EBV loads in renal (RTx), hepatic, and cardiothoracic transplant recipients and to compare their EBV loads with other healthy and patient controls.

METHODS

A prospective study was performed using a real-time TaqMan polymerase chain reaction technique to measure EBV DNA loads from three types of organ transplant recipients and haemodialysis patients (HD). Their results were then compared with those from the healthy controls (HC); monospot test negative (MN-) and infectious mononucleosis positive (IM+) patients; patients who were previously treated for PTLD (pPTLD); those who were currently diagnosed to have PTLD (PTLD+); and patients who had a stable renal, hepatic, or cardiothoracic graft for more than a year.

RESULTS

Post-transplant EBV loads were significantly higher than the pre-transplant levels. Asymptomatic transplant recipients were differentiated from the PTLD+group at 600 genome copies of EBV/mug DNA, and from IM+group at 100 genome copies. Both HC and MN- groups had significantly lower EBV loads than the three transplant groups. The dynamic change of EBV loads in RTx was greater in the first post-transplant month when compared with the HD group. All transplant recipients had transient rises of EBV loads whereas EBV load continued to rise in one suspected PTLD patient.

CONCLUSIONS

Asymptomatic transplant recipients had higher baseline post-transplant EBV levels than the non-transplant and MN- groups. The rising post-transplant EBV load in these transplant recipients did not seem to be sustained for longer than 2 weeks. However, in a PTLD+patient the rising EBV load continued over a period of 4 weeks. Hence, the dynamic pattern of EBV loads is more important than absolute EBV DNA measurements alone in identifying those who might go on to develop PTLD.

Role of cytomegalovirus, Epstein-Barr virus, and human herpes virus-8 in benign lymphoepithelial cysts of the parotid gland

OBJECTIVE

To provide background and evaluate the role of herpesviruses in benign lymphoepithelial cysts (BLC) of the parotid gland.

STUDY DESIGN

Case series derived from review of pathology specimens.

METHODS

Radiolabeled polymerase chain reaction (PCR) analysis was used to detect for the presence of cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpes virus 8 (HHV-8) DNA sequences in 14 paraffin embedded specimens and 1 freshly aspirated BLC specimen. Thirteen normal parotid tissue specimens obtained from paraffin embedded blocks were used as a control group.

RESULTS

CMV was detected with nearly equal frequency between the two groups (23% of normal vs. 20% in BLC). HHV-8 was found in 13% of the BLC group and in none of the normal group (P =.4841). There was significant difference in EBV detection between the normal (0%) and the BLC (33%) groups (P =.0437).

CONCLUSION

CMV and HHV-8 does not appear to be associated with BLCs. Although EBV is found more frequently in BLC than in normal parotid controls, further studies are needed to elucidate the role of this virus in BLC pathogenesis.

Assessment of automated DNA extraction coupled with real-time PCR for measuring Epstein-Barr virus load in whole blood, peripheral mononuclear cells and plasma

BACKGROUND

Epstein-Barr virus (EBV) DNA load monitoring in blood has been shown to be essential for the diagnosis of EBV-associated diseases. However, the methods currently used to assess EBV DNA load are often time-consuming and require prior blood separation.

OBJECTIVES

The aim of this study was to evaluate the relative diagnostic value of EBV DNA load monitoring in whole blood, peripheral blood mononuclear cells (PBMCs) and plasma after automated DNA extraction using the MagNA Pure extractor followed by LightCycler real-time quantitative PCR (LC-PCR).

STUDY DESIGN

First, EBV DNA load was assessed retrospectively after automated or manual extraction on 104 PBMC specimens. Second, EBV DNA load was determined prospectively with the automated extraction procedure in the whole blood, PBMCs and plasma of 100 samples from patients with EBV-related diseases (group 1, n = 20), HIV-seropositive individuals (group 2, n = 66), and healthy EBV carriers (group 3, n = 14).

RESULTS

A good correlation was observed between automated and manual extraction on 104 PBMC specimens (r = 0.956; P < 0.0001). In the prospective study, 67 samples were positive in both whole blood and PBMCs, with a good correlation between EBV DNA loads in whole blood and PBMCs (r = 0.936; P < 0.0001). Only 18/100 samples were positive in plasma. Higher viral loads were regularly observed in the three blood compartments from group 1 than from groups 2 and 3.

CONCLUSION

This study demonstrated that an automated extraction of EBV DNA is easier to perform in whole blood or plasma than in PBMCs and facilitates the standardisation of EBV DNA measurement by real-time quantitative PCR. The quantitative detection of EBV DNA load in whole blood appeared more sensitive than in plasma for infectious mononucleosis in immunocompetent patients, probably because of a rapid loss of plasmatic EBV DNA. In transplant patients, EBV DNA load monitoring in whole blood and in plasma turned out to be equivalent in terms of feasibility and accuracy for the early diagnosis of post-transplant lymphoproliferative diseases (PTLDs).

Solid phase DNA amplification: a simple Monte Carlo Lattice model

Recently, a new way to amplify DNA, called solid phase amplification (SPA), has been introduced. SPA differs from the traditional polymerase chain reaction (PCR) in the use of surface-bound instead of freely-diffusing primers to amplify DNA. This limits the amplification to two-dimensional surfaces and therefore allows the easy parallelization of DNA amplification in a single system. Furthermore, SPA could provide an alternate route to DNA target implantation on DNA chips for genomic studies. Standard PCR processes are usually characterized (at least initially) by an exponential growth and a broad population distribution, and they are well described by the theory of branching processes, wherein a generating function can be used to obtain the probability distribution function for the population of offspring. This theoretical approach is not appropriate for SPA because it cannot properly take into account the many-body (steric) and geometric effects in a quenched two-dimensional environment. In this article, we propose a simple Lattice Monte Carlo technique to model SPA. We study the growth, stability, and morphology of isolated DNA colonies under various conditions. Our results indicate that, in most cases, SPA is characterized by a geometric growth and a rather sharp size distribution. Various non-ideal effects are studied, and we demonstrate that such effects do not generally change the nature of the process, except in extreme cases.

Viral participation in cellular and microenvironmental transformation and amplification towards malignancy in AIDS patients

HIV-1 infection would initially predispose to neoplastic transformation in terms of a progressive lymphocytic proliferation followed by the onset of an immunodeficiency state. Both virion genomic integration and also active host cell proliferation would perhaps participate in the establishment of an often multifocal primary CNS lymphoma of AIDS type. Repeated opportunistic infections in AIDS patients tend to especially involve the central nervous system to also carry an increased risk of neoplastic transformation of the reactive B lymphocytes reaching the brain. A microenvironmental set of circumstances in patients with AIDS would predispose to non-Hodgkin's lymphoma largely in terms of an HIV-1 infection that progresses concurrently with evolving cell replication, immunodeficiency, and repeated opportunistic infections as caused by several different potential pathogens. Epstein-Barr virus infection in particular appears closely related to Hodgkin's disease that develops in some AIDS patients. A viral role in the development of lymphomas and of Kaposi sarcoma in HIV-infected individuals would account for neoplastic aggressiveness and for a particular predilection for primary CNS lymphoma. Such a role perhaps implicates viral integration within the genome of host cells that are actively proliferating or else infected by multiple viral pathogens such as EBV, HIV-1, CMV, and Herpes virus.

The Effect of Valacyclovir Treatment on Natural Killer Cells of Infertile Women

PROBLEM

The aim of this study was to investigate the effect of valacyclovir treatment on natural killer (NK) cell concentration in the peripheral blood of infertile women.

METHOD OF STUDY

Peripheral blood NK cell concentration of 104 non-pregnant women with a history of infertility was determined by flow cytometry. The controls were 14 fertile non-pregnant women. A cohort of 42 out of 104 women--whose NK cell levels were 175/microL or higher--was prospectively studied for the presence of HSV-1, 2, VZV, cytomegalovirus, HHV-6, HHV-7 and HHV-8 DNA in the peripheral blood and was orally administered valacyclovir (open label study).

RESULTS

Herpes virus DNA was detected in 64.3% of the 42 women examined. Prior to valacyclovir treatment mean NK cell concentration in herpes-negative group was statistically higher from control group but lower from herpes positive group (P = 0.0007, ANOVA). Following valacyclovir treatment the mean NK cell concentration was statistically decreased in all studied women (P = 0.000453), in herpes-negative (P = 0.01622) and in herpes positive group (P = 0.0056). Sufficient decrease was observed in 31 (73.8%) of 42 women who received the drug.

CONCLUSIONS

Valacyclovir treatment is associated with a decrease of NK cell levels in most of the women with a history of infertility.

Measurement of Epstein-Barr virus DNA loads in whole blood and plasma by TaqMan PCR and in peripheral blood lymphocytes by competitive PCR

Epstein-Barr virus (EBV) DNA load values were measured in samples of whole blood (n = 60) and plasma (n = 59) by TaqMan PCR and in samples of peripheral blood lymphocytes (PBLs) (n = 60) by competitive PCR (cPCR). The samples were obtained from 44 transplant recipients. The whole-blood and PBL loads correlated highly (r(2) > 0.900), whereas the plasma and PBL loads correlated poorly (r(2) = 0.512). Testing of whole blood by TaqMan PCR is an acceptable alternative to testing of PBLs by cPCR for quantifying EBV DNA load.

Viral load in Epstein-Barr virus-associated hemophagocytic syndrome

The viral load in peripheral blood from patients with Epstein-Barr virus (EBV)-associated hemophagocytic syndrome was measured by real-time quantitative PCR and compared with that in infectious mononucleosis. Patients with EBV-associated hemophagocytic syndrome generally had larger viral burdens, although it was difficult to differentiate EBV-associated hemophagocytic syndrome from infectious mononucleosis simply by viral load. The difference in viral load seemed to be clearer in peripheral blood mononuclear cells than in plasma.

Case report: Kinetics of Epstein-Barr virus load in a bone marrow transplant patient with no sign of lymphoproliferative disease

The kinetics of Epstein-Barr virus (EBV) load was measured in peripheral blood mononuclear cells of a severely immunocompromised allogeneic bone marrow recipient child, in conditions not associated with lymphoproliferative disease. The viral doubling time was 46.4 hr. The study permitted monitoring EBV clearance from blood, when the anti-rejection therapy was interrupted. Likely, this is the first accurate kinetic assessment of EBV load increasing phase in a clinical context marked by the absence of an overt post-transplant lymphoproliferative disease. According to these data gamma-herpesviruses behave like beta-herpesviruses in being capable of rapid growth.

Comparison of quantitative competitive PCR with LightCycler-based PCR for measuring Epstein-Barr virus DNA load in clinical specimens

The aim of this study was to develop a LightCycler-based real-time PCR assay for monitoring the Epstein-Barr virus (EBV) DNA load in unfractionated whole blood. This assay was compared with quantitative competitive PCR (Q-PCR) for EBV. The LightCycler-based assay was highly sensitive and reproducible when quantifying plasmid DNA in either the presence or absence of healthy donor blood DNA. Amplifying plasmid DNA in DNA backgrounds from different donors slightly increased the variation of quantification, indicating that clinical specimen DNA has an influence on quantification. In most transplant recipients, a good correlation was observed between EBV DNA load dynamics determined by LightCycler and Q-PCR in follow-up samples, although the correlation between absolute values of EBV DNA loads was weak and occasional samples were false negative in the LightCycler assay. In 253 cross-sectional blood samples from patients with Burkitt's lymphoma, infectious mononucleosis, or human immunodeficiency virus infection, a weak but significant correlation between the two methods was found (r(2) = 0.37, P < 0.001). Our results indicate that the clinical specimen DNA background may influence the absolute values of EBV DNA load in LightCycler analyses but that this effect is rare. LightCycler PCR is very well suited for monitoring of EBV DNA load dynamics, and its diagnostic value is comparable to that of Q-PCR. To avoid false negativity or underestimation of viral load, future internal calibration of the LightCycler is recommended. This would also enhance EBV load assay standardization and interinstitute comparisons.

Molecular diagnosis of viral infections in renal transplant recipients

PURPOSE OF REVIEW

To discuss biological and methodological aspects of virus infection monitoring in the renal transplant setting.

RECENT FINDINGS

New insights on the molecular pathogenesis of acute and persistent virus infections and rapid developments in real-time monitoring techniques are changing the current diagnostic routine. Accurate risk-assessment prior to transplantation and quantitative monitoring of parameters that reflect virus activity in the post-transplant period, including genome load fluctuations and aberrant viral mRNA or protein expression, provide early signs of undesired viral behaviour and allow pre-emptive therapeutic intervention. As opposed to prophylactic administration of antiviral drugs, a pre-emptive approach is more selective and will allow for antiviral immune responses to build, which may have a long-term beneficial effect. In addition, these virus-monitoring techniques allow for on-line assessment of therapeutic efficacy and rapid identification of emerging resistant strains. The combination of virus-monitoring techniques with rapid assessment of host immune responses using FACS and ELISPOT techniques, will improve overall patient management and long-term survival.

SUMMARY

Viral infections continue to be a significant complication in the transplant setting. Diagnostic monitoring allows timely and accurate therapeutic intervention. Knowledge of pathogenic mechanisms leading to disease is important for clinical decision making as well as for the selection of appropriate molecular parameters discriminating normal and disease-related activity of human pathogenic viruses. The increasing availability of effective antiviral drugs permits pre-emptive intervention that strongly depends on accurate viral monitoring procedures.

Epstein-Barr virus DNA in body fluids

Advances in polymerase chain reaction technology have greatly simplified the ability to detect and monitor Epstein-Barr virus DNA copy number in a variety of settings. An initial focus on cell-associated viruses by many investigators has shown some interesting results regarding the dynamics of Epstein-Barr virus infection. Several findings are unexpected. A relation between HIV load or CD4 T-cell counts and Epstein-Barr virus copy number is not seen. Furthermore, highly active antiretroviral treatment therapy in HIV patients that results in a rise of CD4 T cells may sometimes be associated with a rise in cell-associated Epstein-Barr virus load. Detection of Epstein-Barr virus in spinal fluid is useful in the diagnosis of primary central nervous system lymphoma, and monitoring of Epstein-Barr virus DNA copy number in spinal fluid may be useful in assessing response. Cell-free DNA in serum or plasma is emerging as a useful diagnostic tool in several settings. Fetal DNA can be detected in maternal serum or plasma. Tumor DNA can be detected in serum or plasma in association with a variety of cancers. Epstein-Barr virus DNA in serum or plasma has been found in infectious mononucleosis, nasopharyngeal carcinoma, posttransplant lymphoma, and nasal lymphoma. In each of these malignancies, its detection or quantification has been shown to be of prognostic significance. The utility of Epstein-Barr virus DNA detection and quantification in the serum or plasma of patients with HIV malignancies has yet to be determined but holds great promise.

High Epstein-Barr virus (EBV) DNA loads in HIV-infected patients: correlation with antiretroviral therapy and quantitative EBV serology

OBJECTIVE

To study Epstein-Barr virus (EBV) DNA loads in peripheral blood of HIV carriers to determine base-line values and diagnostic relevance of viral load in relation to quantitative serology; to compare EBV presence in parallel plasma and unfractionated whole blood samples; and to correlate EBV DNA load to HIV, CD4 T-cell counts and HAART.

DESIGN

One-hundred and nine random patients receiving highly active antiretroviral therapy (HAART) during 1999 and 99 patients on anti-HIV monotherapy during 1993-1996 were included.

METHODS

EBV DNA load was determined by quantitative competitive PCR. EBV serology was determined by immunoblot profile and quantitative enzyme-linked immunosorbent assay for responses against VCA-p18 and EBNA-1.

RESULTS

Twenty-two out of 109 patients receiving HAART and 28 out of 99 of patients on anti-HIV monotherapy showed elevated EBV DNA loads in whole blood (> 2000 copies/ml), without elevated loads in parallel plasma. EBV DNA load distribution did not differ between the two groups (P = 0.78) and did not correlate with HIV or CD4 T-cell count. In three patients with high EBV DNA loads EBV RNA was virtually absent. Patients with high EBV DNA loads (3610-89 400 copies/ml) had higher anti-VCA-p18 IgG levels than patients with undetectable EBV DNA (P < 0.0001) but lower anti-EBNA-1 IgG levels (P = 0.005).

CONCLUSION

Absolute values of EBV DNA load may have poor diagnostic value for defining HIV patients at risk for developing EBV-associated disease. Elevated EBV DNA loads are cell-associated and are not influenced by HAART. Increased anti-p18-VCA and decreased anti-EBNA-1 IgG levels in patients with high EBV loads indicate impaired latency control and increased lytic replication suggesting disturbed overall immunosurveillance against EBV.

Role of Epstein-Barr virus DNA load monitoring in prevention and early detection of post-transplant lymphoproliferative disease

Posttransplant lymphoproliferative disease (PTLD) is a severe and life-threatening complication after stem cell or solid-organ transplantation, virtually always associated with presence of Epstein-Barr virus (EBV) in the proliferating cells. PTLD is probably caused by the iatrogenically impaired T-cell response allowing outgrowth of EBV-positive B-cells. Quantitative EBV DNA load monitoring is a minimally invasive technique increasingly recognized as a valuable tool in posttransplant patient management. In this review, we focus on the clinical utility of EBV DNA load monitoring in the peripheral blood of transplant recipients using PCR and we discuss the currently most-widely used techniques and their value and limitations in predicting and diagnosing PTLD. Options for EBV DNA load-guided pre-emptive therapy and application of monitoring EBV DNA load dynamics in the prediction of clinical response after therapy are described. Origins of elevated EBV DNA loads in immunosuppressed patients and recent insights in the EBV life cycle in the immuncompromised host are discussed. Finally, a standardization of methodology, clinical specimen type, and cut-off values is proposed. This is essential for comparisons between different institutes and more adequate patient management.

Evaluation of use of Epstein-Barr viral load in patients after allogeneic stem cell transplantation to diagnose and monitor posttransplant lymphoproliferative disease

Epstein-Barr virus (EBV)-induced posttransplant lymphoproliferative disease (PTLD) continues to be a serious complication following transplantation. The aim of the present study was to evaluate the EBV load as a parameter for the prediction and monitoring of PTLD. The EBV load was analyzed by a quantitative competitive PCR with 417 whole-blood samples of 59 patients after allogeneic stem cell transplantation (SCT). The EBV load was positive for all 9 patients with PTLD and for 17 patients without PTLD. The viral loads of patients with manifest PTLD differed from the loads of those without PTLD (median loads, 1.4 x 10(6) versus 4 x 10(4) copies/microg of DNA; P < 0.0001). A threshold value of 10(5) copies/microg of DNA showed the best diagnostic efficacy (sensitivity, 87%; specificity, 91%). However, in patients with less than three major risk factors for PTLD, the positive predictive value of this threshold was rather low. One week prior to the manifestation of PTLD, the EBV load was as low in patients who developed PTLD as in patients without disease (median, 2.2 x 10(4) copies/microg of DNA; P was not significant). EBV DNA tested positive first at 20 to 71 days prior to the clinical manifestation of PTLD and occurred with the same delay after transplantation regardless of disease (median delay, 52 versus 63 days; P was not significant). EBV DNA was detected earlier in patients with primary infections than in those with reactivations (33 versus 79 days; P = 0.01), but the peak levels were similar in the two groups. EBV primary infection or EBV reactivation is frequent in patients after allogeneic SCT but results in PTLD only in a subgroup of patients. Although evaluation of the EBV load has limitations, the EBV load represents a valuable parameter to guide therapy.

Diagnostic testing in Epstein-Barr virus infection

Laboratory diagnosis of Epstein-Barr virus (EBV) infection is improving with the development of new technologies. Quantification of the virus by real-time polymerase chain reaction (PCR) and evaluation of EBV-specific T cells, especially by tetrameric human leukocyte antigens, are noteworthy candidates for monitoring procedures in clinical laboratories involved in the management of transplant recipients. Standardization of PCR is essential for improving the quality of these monitoring procedures.