Serial detection of Epstein-Barr virus DNA in sera and peripheral blood leukocyte samples of pediatric renal allograft recipients with persistent mononucleosis-like symptoms defines patients at risk to develop post-transplant lymphoproliferative disease

Chronic Epstein-Barr viral load carriage after pediatric organ transplantation

Epstein-Barr virus (EBV) infection and EBV-associated post-transplant lymphoproliferative disorder (EBV/PTLD) is one of the most devastating complications occurring in pediatric solid organ transplant (SOT) recipients. Observations of SOT recipients undergoing serial EBV monitoring to inform reduction of immune suppression to prevent EBV-/PTLD has identified patients who maintain chronic high EBV load (CHL) in their blood. The CHL carrier state has been seen more commonly in pediatric compared to adult transplant recipients. Some but not all CHL may progress to EBV/PTLD. However, little is known regarding the biology of this CHL carrier state and the optimal clinical approach to CHL has not been established. This review summarizes the current knowledge and evidence of chronic high EBV load and introduces commonly adopted approaches from experts in this field.

Long-lasting chronic high load carriage of Epstein-Barr virus is more common in young pediatric renal transplant recipients

BACKGROUND

Epstein-Barr virus (EBV) infections can induce post-transplant lymphoproliferative disorder (PTLD). A chronic high load (CHL), as indicated by long-term high EBV DNA levels after transplantation, has been associated with an enhanced risk of PTLD. We aimed to evaluate incidence, time of occurrence, risk factors, and outcome of EBV CHL carrier state after pediatric renal transplantation.

METHODS

A retrospective study of 58 children aged 1-17 years (median 10), who underwent renal transplantation between January 2004 and June 2017 at a single medical center. EBV IgG antibodies in serum were analyzed before and yearly after transplantation. EBV DNA in whole blood were analyzed weekly for the first 3 months post-transplant, monthly up to 1 year and then at least once yearly. CHL was defined as EBV DNA ≥ 4.2 log₁₀ Geq/ml in > 50% of the samples during ≥ 6 months.

RESULTS

At transplantation, 31 (53%) patients lacked EBV IgG and 25 (81%) of them developed primary EBV infection post-transplant. Of the 27 seropositive patients, 20 (74%) experienced reactivation of EBV. Altogether, 14 (24%) children developed CHL, starting at a median of 69 days post-transplant and lasting for a median time of 2.3 years (range 0.5-6.5), despite reduction of immunosuppression. Patients with CHL were younger and 11/14 were EBV seronegative at transplantation. No child developed PTLD during median clinical follow-up of 7.8 years (range 0.7-13).

CONCLUSIONS

CHL was frequent, long lasting, and occurred mainly in young transplant recipients. The absence of PTLD suggests that monitoring of EBV DNA to guide immunosuppression was effective.

Pediatric renal transplantation: A retrospective single-center study on epidemiology and morbidity due to EBV

Pediatric R-Tx patients are at high risk of developing EBV primary infection. Although high DNA replication is a risk factor for PTLD, some patients develop PTLD with low viral load. In this retrospective single-center study including all pediatric patients having received R-Tx (2003-2012 period), we aimed to identify risk factors for uncontrolled reactions to EBV (defined as the presence of a viral load >10 000 copies/mL or PTLD). A Cox proportional hazard model was performed. A total of 117 patients underwent R-Tx at a mean age of 9.7 ± 5.3 years, 46 of them being seronegative for EBV at the time of R-Tx. During follow-up, 54 patients displayed positive EBV viral load, 22 of whom presenting with primary infection. An uncontrolled reaction to EBV was observed in 24 patients, whilst 4 patients developed PTLD. Univariate and multivariate analyses suggested the following risk factors for an uncontrolled reaction: age below 5 years, graft from a deceased donor, ≥5 HLA mismatches, EBV-seronegative status at the time of R-Tx, and a secondary post-Tx loss of anti-EBNA. Monitoring anti-EBNA after R-Tx may contribute to the early identification of patients at risk for uncontrolled reaction.

Risk factors and long-term outcomes of pediatric liver transplant recipients with chronic high Epstein-Barr virus loads

BACKGROUND

Serial monitoring of Epstein-Barr virus (EBV) reveals that certain pediatric liver transplant (LT) recipients exhibit high EBV loads for long periods. We investigated the incidence and risk factors of chronic high EBV (CHEBV) loads (continuous EBV DNA >10 000 IU/mL of whole blood for ≥6 months) and long-term outcomes.

METHODS

This single center, retrospective observational study investigated pediatric LT recipients who survived ≥6 months. We quantitated EBV DNA weekly during hospitalization and subsequently every 4 or 6 weeks at the outpatient clinic. Tacrolimus was maintained at a low trough level (<3 ng/mL, EBV DNA load >5000 IU/mL).

RESULTS

Thirty-one of 77 LT recipients developed CHEBV. Univariate analysis revealed that age <2 years and body weight <10 kg upon LT, operation time <700 minutes, warm ischemia time (WIT) >35 minutes, graft-to-recipient weight ratio (GRWR) >2.7%, and preoperative EBV seronegativity were significantly associated with the development of CHEBV loads. Multivariate analysis identified significant associations of CHEBV with WIT >35 minutes, GRWR >2.7%, and preoperative seronegative. None of the recipients developed post-transplantation lymphoproliferative disorder. Survival rates of patients with and without CHEBV loads were not significantly different.

CONCLUSIONS

A significant number of pediatric LT recipients developed CHEBV loads. Long WIT, high GRWR, and preoperative EBV seronegativity were significantly associated with the development of CHEBV loads. Although the long-term outcomes of patients with or without CHEBV loads were not significantly different, further studies of more subjects are warranted.

Impact of Desensitization on Antiviral Immunity in HLA-Sensitized Kidney Transplant Recipients

Viral infections represent significant morbidity and mortality factors in kidney transplant recipients, with CMV, EBV, and BKV infections being most common. Desensitization (DES) with IVIg and rituximab with/without plasma exchange followed by kidney transplantation with alemtuzumab induction increased successful transplant rates in HLA-sensitized patients but may represent an increased risk for viral infections due to severe lymphocyte depletion. Here, we report on the posttransplant viral infection status in 372 DES versus 538 non-DES patients. CMV and EBV viremia were significantly lower in DES patients, while BKV viremia was similar. This trend was observed primarily in CMV sero(-), EBV sero(+), and sero(-) patients. No patient developed PTLD. The incidence of BKAN, allograft, and patient survival was similar in both groups. These viral infections were not associated with subsequent allograft rejection which occurred within 6 months after the infection. Conclusions. The IVIg + rituximab desensitization combined with alemtuzumab induction with triple immunosuppression maintenance does not increase the risk for CMV, EBV, and BKV infections. Possible factors include, in addition to posttransplant antiviral prophylaxis and PCR monitoring, presence of memory T cells and antibodies specific to CMV and likely EBV, NK cell-mediated ADCC despite lymphocyte depletion, elimination of EBV and CMV reservoirs by rituximab and alemtuzumab, and use of IVIg with antiviral properties.

520-d Isolation and confinement simulating a flight to Mars reveals heightened immune responses and alterations of leukocyte phenotype

During interplanetary exploration, chronic stress caused by long term isolation and confinement in the spacecraft is one of the major concerns of physical and psychological health of space travelers. And for human on Earth, more and more people live in an isolated condition, which has become a common social problem in modern western society. Collective evidences have indicated prolonged chronic stress could bring big influence to human immune function, which may lead to a variety of health problems. However, to what extent long-term isolation can affect the immune system still remains largely unknow. A simulated 520-d Mars mission provided an extraordinary chance to study the effect of prolonged isolation. Six healthy males participated in this mission and their active neuroendocrine and immune conditions were studied with saliva and blood samples from all participants on chosen time points during the isolation period. As a typical neuroendocrine parameter, stress hormone cortisol was measured in the morning saliva samples. Immune phenotype changes were monitored through peripheral leukocyte phenotype analysis. Using an ex vivo viral infection simulation assay we assessed the immune response changes characterized by the ability to produce representative endogenous pro-inflammatory cytokines. The results of this study revealed elevated cortisol levels, increased lymphocyte amount and heightened immune responses, suggesting that prolonged isolation acting as chronic stressors are able to trigger leukocyte phenotype changes and poorly controlled immune responses.

Effective and long-term control of EBV PTLD after transfer of peptide-selected T cells

Posttransplantation lymphoproliferative disease (PTLD) associated with Epstein-Barr virus (EBV) is a life-threatening complication after allogeneic hematopoietic stem cell transplantation. PTLD is efficiently prevented by adoptive transfer of EBV-specific T cells from the donor. To make EBV-specific T cells available in urgent clinical situations, we developed a rapid protocol for their isolation by overnight stimulation of donor blood cells with peptides derived from 11 EBV antigens, interferon-gamma surface capture, and immunomagnetic separation. Six patients with PTLD received 1 transfusion of EBV-specific T cells. No response was seen in 3 patients who had late-stage disease with multiorgan dysfunction at the time of T-cell transfer. In 3 patients who received T cells at an earlier stage of disease, we observed complete and stable remission of PTLD. Two patients have remained free from EBV-associated disease for more than 2 years. CD8(+) T cells specific for EBV early antigens rapidly expanded after T-cell transfer, temporarily constituted greater than 20% of all peripheral blood lymphocytes, and were maintained throughout the observation period. Thus, a rapid and sustained reconstitution of a protective EBV-specific T-cell memory occurred after the infusion of small numbers of directly isolated EBV-specific T cells.

Significance of Epstein-Barr virus (EBV) load and Interleukin-10 in post-transplant lymphoproliferative disorders

The complex relationship between EBV, IL-10 and lymphomagenesis has been widely investigated and several studies have highlighted the diagnostic value of EBV DNA copies and serum IL-10, that may be considered as tumor markers. Notwithstanding the great number of data published in the last few years on the behavior of EBV DNA copies in the peripheral blood of transplanted patients, a threshold value significant for impending or overt post-transplant lymphoproliferative disorder (PTLD) has not yet been defined. Too many factors, both technical and clinicopathological, may affect the results of clinical studies, making their comparison difficult. On the contrary, although the role of IL-10 in PTLDs has been well documented, a sufficient number of studies exploring sensitivity and specificity of serum IL-10 measurement is lacking. The aim of this review is to summarise data on EBV load quantification and serum IL-10 detection in transplanted patients, providing clinicians with wide and useful information in order to improve bedside management of transplanted patients with regard to PTLDs occurrence and treatment.

Clinical significance of peripheral blood Epstein-Barr viral load monitoring using polymerase chain reaction in renal transplant recipients

PTLD is a complication of EBV infection. We examined the efficacy of EBV-PCR monitoring to detect early replication in an attempt to prevent EBV-associated PTLD. Blood EBV levels in 156 renal transplant recipients (58 children) from three institutions over nine yr were retrospectively analyzed. Patients who were asymptomatic and at high risk for PTLD were monitored for EBV infection by PCR or serology followed by PCR at the time of EBV seropositivity. More children than adults had positive EBV-PCR (12/58 vs. 2/98, p < 0.001). Adults remained asymptomatic and viremia resolved post-therapy. 3/12 EBV-PCR positive children developed PTLD (3/12 children vs. 0/2 adults, p = NS). Two out of three with PTLD were initially monitored by serology, and later by PCR. PTLD resolved post-therapy in all three patients. The remaining 9/12 EBV-PCR positive children stayed asymptomatic. None of the children and adults with negative EBV-PCR developed PTLD. EBV-PCR monitoring in high-risk renal transplant recipients, especially in children, may allow early diagnosis and intervention, and therefore may help in preventing EBV-associated PTLD.

Epstein-Barr virus DNA load and seroconversion in pediatric renal transplantation with tacrolimus immunosuppression

EBV infection is one of major complications arising in pediatric patients who have undergone renal transplantation. A strong correlation between the grade of immunosuppression and the development of PTLD, one of the most severe EBV-associated diseases, has been recognized. In this study, we monitored the serologic profile in conjunction with peripheral blood EBV-DNA load of 32 children who underwent renal transplantation with tacrolimus as an immunosuppressant. Six patients were EBV-seronegative (EBV-) before the transplantation, and the mean DNA load in the EBV- group was significantly higher than that in the EBV-seropositive (EBV+) group. Seroconversion occurred in five of these patients in a mean period of 22 weeks after the transplantation. The EBV-DNA load in the EBV+ group was maintained at a low level for a year, whereas it increased rapidly to over 1 x 10(5) copies/mL in two patients in the EBV- group three to seven months after the transplantation, which corresponds to the timing of seroconversion, and one of them developed PTLD. These observations suggest that the close monitoring of the EBV-DNA load, along with longitudinal observation of seroconversion, is essential in pediatric renal transplantation, particularly for younger children who are more likely to be EVB-.

Avoiding steroids in pediatric renal transplantation: long-term experience from a single centre

We report our experience in pediatric renal transplantation avoiding steroids whenever possible. Immunosuppression consisted of an initial induction with antithymocyte globulin followed by maintenance therapy with a calcineurin inhibitor and MMF. Steroids were only given to selected patients because of the primary disease, recurrence, rejection, or PTLD. Thirty-four transplants grafted into 32 recipients between 1995 and 2005 were followed for a median of 3.5 yr (range 1-9.8). All patients survived. Graft rejection occurred in 10 cases during the first year post-transplantation and graft survival at one, five, and seven yr was 97, 88 and 88%, respectively. Steroids were given to half of the patients (n = 16); in nine cases due to rejection. Only four patients (13%) were continuously on steroids. Calculated GFR at one to five yr post-transplant were 73, 74, 68, 64, and 70 mL/min/1.73 m(2). Unfortunately PTLD occurred in three patients, but all survived with functioning grafts. Accordingly, our findings indicate that steroid avoidance in pediatric renal transplantation is possible with good results with respect to acute graft rejection as well as long-term graft survival.

Epstein-Barr viremia levels after pediatric liver transplantation as measured by real-time polymerase chain reaction

Effective immunosuppression has improved the results following liver transplantation, but also increased the risk for opportunistic infections. Epstein-Barr virus (EBV) infection in transplant patients can cause various symptoms including the life-threatening premalignant condition, post-transplantation lymphoproliferative disorder (PTLD). Serum specimens from 24 consecutive children (mean 7.6 specimens/patient), who had undergone liver transplantation in Göteborg from January 1995 to May 2002, were analyzed retrospectively for EBV DNA by real-time TaqMan polymerase chain reaction (PCR). The results were related to clinical picture, immunosuppression, graft rejection and infections with other agents. Eleven patients (46%) developed primary EBV infection at a mean time of 4.8 months after transplantation, and six (25%) reactivated EBV infection at a mean of 4.0 months after transplantation. Four of the 11 patients with primary infection had symptomatic EBV infection: two had PTLD and two hepatitis. One patient in the group with reactivated infection developed PTLD. EBV DNA levels were significantly higher in the group with primary symptomatic infection compared with the patients with primary asymptomatic infection (mean 65 500 copies/mL; range 14 200-194 300 vs. 3700 copies/mL; range 100-9780). In patients with symptomatic infection EBV DNA levels did not differ between PTLD and hepatitis patients. The data suggest that quantitative analysis of EBV DNA in serum by real-time PCR is useful for identification of EBV-related disease.

Induction of pre-transplant Epstein-Barr virus (EBV) infection by donor blood transfusion in EBV-seronegative recipients may reduce risk of post-transplant lymphoproliferative disease in adolescent renal transplant patients: report of two cases

BACKGROUND

Post-transplant lymphoproliferative disease (PTLD) is a life-threatening complication following organ transplantation. The greatest risk is seen in Epstein-Barr virus (EBV)-seronegative patients receiving allografts from EBV-seropositive donors. We demonstrate a new approach of pre-transplant prophylaxis of EBV-related PTLD, suggesting that, prior to living-related renal transplantation, blood transfusion from an EBV-seropositive donor to an EBV-seronegative recipient could induce primary EBV infection in the recipient, developing EBV immunity and decreasing risk of PTLD.

METHODS

Recipients underwent weekly donor-specific blood transfusion (3 x 100 mL) before transplantation. EBV-mRNA expression, viral load, serological tests, and clinical signs of EBV infection were assessed following blood transfusion.

RESULTS

We explored a new approach in 2 young EBV-seronegative renal allograft recipients. Both patients developed primary EBV infection following blood transfusion before transplantation and showed symptom-free seroconversion post-transplantation without persistent EBV activation. There were no signs of PTLD during 5-year follow-up.

CONCLUSIONS

A new effective and inexpensive approach is suggested for development of EBV immunity and probably for prophylaxis of EBV-associated PTLD.

Infectious risk in pediatric organ transplant recipients: is it increased with the new immunosuppressive agents?

The risk of infection in pediatric organ transplant recipients is determined by several factors, including age, the types of organ transplanted and the immunosuppressive treatment which has dramatically changed over the past 10 yr. Little information has been reported regarding the infectious complications related to the current immunosuppressive protocols used in these children. This paper reviews (i) the immunosuppressive agents, focusing on their mechanisms of action and on the new regimens, (ii) the infections related to excessive immunosuppression and also anti-infectious properties or infectious adverse reactions associated with specific immunosuppressive agents. With the new immunosuppressive protocols, the advances in immunologic monitoring, microbiological diagnosis, anti-infectious prophylactic and preemptive treatments, strategies to minimize the risk of infection related to the immunosuppressive therapy are proposed.

Detection of EBV-DNA in serum samples of an immunosuppressed child during a three years follow-up: association of clinical and PCR data with active infection

Twenty-four whole blood and serum samples were drawn from an eight year-old heart transplant child during a 36 months follow-up. EBV serology was positive for VCA-IgM and IgG, and negative for EBNA-IgG at the age of five years old when the child presented with signs and symptoms suggestive of acute infectious mononucleosis. After 14 months, serological parameters were: positive VCA-IgG, EBNA-IgG and negative VCA-IgM. This serological pattern has been maintained since then even during episodes suggestive of EBV reactivation. PCR amplified a specific DNA fragment from the EBV gp220 (detection limit of 100 viral copies). All twenty-four whole blood samples yielded positive results by PCR, while 12 out of 24 serum samples were positive. We aimed at analyzing whether detection of EBV-DNA in serum samples by PCR was associated with overt disease as stated by the need of antiviral treatment and hospitalization. Statistical analysis showed agreement between the two parameters evidenced by the Kappa test (value 0.750; p < 0.001). We concluded that detection of EBV-DNA in serum samples of immunosuppressed patients might be used as a laboratory marker of active EBV disease when a Real-Time PCR or another quantitative method is not available.

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.

Lymphoplasmacytic hyperplasia (possibly pre-PTLD) has varied expression and appearance in intestinal transplant recipients receiving Campath immunosuppression

Posttransplant lymphoproliferative disorders (PTLD) are a frequent complication in bowel transplant recipients. Histological changes in PTLD range from expansile lymphoplasmacytic (LP) hyperplasia to frank lymphoma. Small bowel allograft biopsies obtained in the first 250 days posttransplant were retrospectively graded after patients had received induction immunosuppression with either anti-CD52 (Campath) or anti-CD25 (Zenapax) monoclonal antibodies. The biopsies were analyzed with respect to the onset intensity of lymphoplasmacytic infiltrates and presence of in situ EBV hybridization (EBER) positivity. We observed that lymphoplasmacytic infiltrates were a frequent change in all bowel transplant patients over the examined period. Campath-treated patients developed earlier LP infiltrates of mild to moderate intensity between day 1 and 100 posttransplant, thereafter decreasing to mild. No EBER positivity was detected in this group. Zenapax-treated patients presented with LP infiltrates later of mild to moderate intensity through day 100 posttransplant. However, more persistent and intense LP infiltrates was observed after day 101 in this group, including a case of lymphoma and two cases of EBER positivity. We conclude that Campath immunosuppression results in an earlier appearance of LP lesions that are generally less intense than those evident with Zenapax. We attribute these findings to the more profound immunodeficiency and cell targeting following Campath treatment.

Effect of combined T- and B-cell depletion of allogeneic HLA-mismatched bone marrow graft on the magnitude and kinetics of Epstein-Barr virus load in the peripheral blood of bone marrow transplant recipients

Recipients of T-cell-depleted bone marrow (BM) transplants (BMT) frequently develop Epstein-Barr virus (EBV)-associated post-transplant lymphoproliferative disease (PTLD) preceded by a rapid and prominent increase of EBV load in the peripheral blood. The level of this increase positively correlates with the incidence of PTLD. Using a semiquantitative PCR assay we compared the blood levels of EBV-DNA in patients transplanted with either T-cell or T- and B-cell-depleted human leukocyte antigen (HLA)-mismatched BM grafts. Combined T- and B-cell depletion correlated with significantly lower maximal levels of EBV load, which were reached with slower kinetics. These data indicate that B-cell depletion of BM can be used for prophylaxis of PTLD in BM transplant recipients and can affect the long-term balance between EBV and its host.

Virologic Diagnosis, Viral Monitoring, and Treatment of Epstein-Barr Virus Infectious Mononucleosis

Epstein-Barr virus (EBV) is the cause of infectious mononucleosis and is associated with severe infections in immunocompromised patients. EBV is also causally linked with several human malignancies. The heterophile antibody test and EBV-specific antibody tests remain the principal means of diagnosis of initial infection in otherwise healthy patients. Enzyme-linked immunosorbent assays have replaced the traditional immunofluorescence assays for EBV-specific antibodies. Several newer molecular diagnostic tests have become available that facilitate accurate monitoring of infection. The role of these tests for patients with uncomplicated infectious mononucleosis is limited, although these tests are being increasingly used to monitor the state and level of EBV replication for severe infections and among immunocompromised patients. Antiviral therapy has a limited, short-term effect on oropharyngeal shedding but has proven ineffective for the clinical manifestations of infectious mononucleosis. Patients with selected complications frequently benefit from short-term corticosteroid therapy.

The post-transplant lymphoproliferative disorder-a literature review

The Epstein-Barr virus (EBV)-induced post-transplant lymphoproliferative disorder (PTLD) affects 1%-10% of all paediatric renal transplant recipients. This is a heterogeneous group of conditions characterised by EBV-driven proliferation of B-lymphocytes in the face of impaired T-cell immune surveillance. The risk factors predisposing to PTLD are becoming better understood, but its pathogenesis and myriad of clinical and histological features remain poorly defined. While new treatment modalities are being tried with variable success, regular EBV surveillance and carefully monitored reduction of immunosuppression remain the mainstay of treatment. In this review, we have presented the current knowledge of this increasingly common complication in renal transplant recipients.

Monitoring and modulation of Epstein-Barr virus loads in pediatric transplant patients

A major risk faced by bone-marrow and solid organ transplant patients is the development of post-transplant lymphoproliferative disease or post-transplant lymphoma (PTLD). In pediatric transplantation, PTLD onset is often associated with a rapid rise in Epstein-Barr virus (EBV) load in peripheral blood mononuclear cells (PBMC). We have analyzed EBV viral loads in PBMC over time using real-time quantitative PCR in 56 patients, 19 of which have been followed for more than 1 year. In nine patients; eight bone marrow (BMT) and one kidney transplant, PTLD was associated with a rapid rise in viral load, exceeding 1 x 10(5) EBV genomes/microg of PBMC-derived DNA. Four of these patients exceeded 1 x 10(6) EBV genomes/microg PBMC DNA. All patients with viral loads exceeding 1 x 10(5) EBV genomes/microg PBMC DNA were clearly at high risk for transplant-associated mortality, with only six of nine surviving. Importantly, only one of these deaths was directly attributable to EBV. A second elevated state of EBV load, defined as exceeding 2 x 10(4) EBV genomes/microg PBMC, was seen in a total of 12 BMT, kidney, heart, and liver transplant patients. These patients did not appear to be at immediate lethal risk for PTLD and one EBV-attributable death was found in this group as well. Thirty-four transplant patients whose EBV viral load oscillated from undetectable to 10 000 EBV genomes/microg PBMC DNA are reported as well. The threshold for normal EBV viral load based on our combined experience with viral load analysis is defined as 1 x 10(4) EBV genomes/microg PBMC DNA. The ability to rapidly analyze EBV load allows rapid changes in viral load, such as those that occur with PTLD onset, and the impact of anti-CD20 antibody therapy to be rapidly detected.