Persistent increased Epstein-Barr virus loads after solid organ transplantation: truth and consequences?

Chronic high Epstein-Barr viral load carriage in pediatric small bowel transplant recipients

The development of EBV infection and PTLD is normally associated with a high EBV load in peripheral blood. Often, children undergoing primary or reactivation of EBV infection subsequent to ITx will have chronically elevated EBV loads. To better understand this phenomenon and its consequences, we retrospectively reviewed the records of children who underwent ITx (either isolated or part of multivisceral transplantation) at our center from 1992 to 2007, to identify chronic high EBV load carriers in this population. CHL state was defined as the presence of high load for >50% of samples for greater than or equal to six months following either asymptomatic infection or complete clinical resolution of EBV disease/PTLD. Thirty-five CHL carriers were identified from our patient population. Pretransplant serologies were available on 34 of these patients: 17 were EBV negative and 17 seropositive; one had unknown EBV serostatus prior to transplant. Seven of the 17 seronegative patients developed their CHL carrier state at the time of their primary EBV infection. Thirteen of the 35 (37%) HLC patients developed EBV disease after meeting the definition of high-load carrier states. EBV-related diseases developing in CHL carriers included EBV adenitis (n=1), EBV enteritis (n=7), PTLD (n=4), and EBV+ spindle cell tumor (n=1). Disease was seen in 7/17 of the seronegative (one PTLD) and 6/17 of the seropositive patients (three PTLD). Thirteen of 35 patients (37%) resolved their CHL state without apparent sequelae while nine remain asymptomatic CHL carriers. Three children have had more than one episode of CHL. These data provide important information about the outcome of chronic EBV high-load carriage in pediatric intestinal transplant recipients.

Posttransplant lymphoproliferative diseases

The risk of developing cancer after solid organ transplantation (SOT) is about 5- to 10-fold greater than that of the general population. The cumulative risk of cancer rises to more than 50% at 20 years after transplant and increases with age, and so children receiving transplants are at high risk of developing a malignancy. Posttransplant lymphoproliferative disease (PTLD) is the most common cancer observed in children following SOT, accounting for half of all such malignancies. PTLD is a heterogeneous group of disorders with a wide spectrum of pathologic and clinical manifestations and is a major contributor to long-term morbidity and mortality in this population. Among children, most cases are associated with Epstein-Barr virus infection. This article reviews the pathology, immunobiology, epidemiology, and clinical aspects of PTLD, underscoring the need for ongoing systematic study of complex biologic and therapeutic questions.

The impact of EBV load on T-cell immunity in pediatric thoracic transplant recipients

BACKGROUND

Immunologic monitoring of pediatric transplant (Tx) recipients, who are at increased risk of Epstein-Barr virus (EBV)-driven posttransplant lymphoproliferative disease, is an important goal in clinical transplantation. Here, we investigated the impact of EBV load on T-cell immunity from pediatric Tx recipients, using clinically applicable tests for improved assessment of T-cell immune competence.

METHODS

Thirty-five asymptomatic pediatric thoracic Tx patients were categorized into three groups according to their EBV load levels as follows: undetectable viral load (UVL), chronic low viral load (LVL) and chronic high viral load (HVL). Global and EBV-specific T-cell immunity were assessed by ATP release using Cylex Immuknow and T Cell Memory assays.

RESULTS

UVL patients exhibited normal ATP release to Concanavalin A (ConA) and phytohemagglutinin (PHA; 190+/-86 ng/mL, 328+/-163 ng/mL) and detectable EBV-specific (37+/-34 ng/mL) ATP responses. LVL patients displayed significantly stronger responses to ConA (373+/-174 ng/mL), PHA (498+/-196 ng/mL) and EBV (152+/-179 ng/mL), when compared with UVL or to HVL patients (ConA 185+/-114 ng/mL, PHA 318+/-173 ng/mL, and EBV 33+/-42 ng/mL). Moreover, HVL patients displayed significant inverse correlation between CD4+ T-cell ATP levels and EBV loads.

CONCLUSIONS

Evaluation of global and EBV-specific T-cell immunity provides a rapid assessment of patients' immune competence. It is still unclear whether selective oversuppressed ATP release by CD4+ T cells reflects HVL patients at risk of posttransplant lymphoproliferative disease. Further longitudinal studies will determine the importance of Immuknow test in identifying asymptomatic HVL patients vulnerable to EBV complications.

Chronic high Epstein-Barr viral load carriage in pediatric liver transplant recipients

Development of EBV disease and PTLD is usually accompanied by the detection of a high EBV load in peripheral blood. However, many children undergoing primary EBV infection following LTx will maintain chronically elevated EBV loads in the absence of clinical symptoms. To better understand this phenomenon, we retrospectively reviewed the records of children undergoing LTx at our center from 1997 to 2007 to identify chronic high EBV load carriers in this population. A CHL state was defined by the presence of a high load for >50% of samples for greater than or equal to six months following either asymptomatic or complete clinical resolution of EBV disease/PTLD. A total of 35 CHL carriers were identified. Pretransplant serologies were available for 29 of the 35; 22/29 (76%) were EBV negative prior to LTx; eight of these 22 developed their CHL state at the time of their primary EBV infection. Fourteen of the 35 had EBV disease (n = 7) or PTLD (n = 7) prior to development of the CHL state. Only one of 35 CHL carriers developed PTLD or lymphoma while they were a high load carrier. In all, 23/35 resolved their CHL state without apparent sequelae while 11 children continue to be asymptomatic high load carriers. These data provide important information about the outcome of chronic EBV high load carriage in pediatric liver transplant recipients.

Efficacy and safety of valganciclovir in liver-transplanted children infected with Epstein-Barr virus

Epstein-Barr virus (EBV) infection after liver transplantation (LT) is associated with increased risk of posttransplant lymphoproliferative disorder (PTLD). Lowering immunosuppression is the current method to prevent PTLD in LT children with a high viral load. The aim of this study was to assess the efficacy and safety of valganciclovir (VGCV) in children with EBV infection after LT. Forty-seven children showing detectable EBV-DNA (72% asymptomatic) were treated with VGCV (520 mg/sqm twice daily) with no immunosuppression decrease (except in 4 cases). VGCV treatment started 17 months (median) after the onset of EBV infection. A 30-day treatment applied to 26 patients led to undetectable EBV-DNA in 11/32 courses (34.3%), with 82% relapsing. A long VGCV treatment (median: 8 months) achieved undetectable EBV-DNA in 20/42 (47.6%), 60% of whom maintained response off therapy. There were no new PTLD cases. Symptoms worsened in 1 (2.1%) in whom PTLD was suspected but not confirmed in liver and jejunum biopsies. Factors associated with achievement of undetectable EBV-DNA were a longer time from LT and a lower rate of intervening infections in comparison with nonresponders. The safety profile for VGCV was excellent. Graft rejection occurred in 6%. In conclusion, in 47 LT children with a sustained increased EBV load treated with VGCV and unchanged immunosuppression, PTLD was suspected in 1 child (2.1%). A viral load decrease could be achieved as EBV-DNA was undetectable in 47% of patients under prolonged treatment.

Chronic high Epstein-Barr viral load state and risk for late-onset posttransplant lymphoproliferative disease/lymphoma in children

Increased use of serial EBV-PCR monitoring after pediatric transplantation has led to the identification of asymptomatic patients who carry very high viral loads over prolonged periods. The significance of this high-load state is unknown. We speculated that this state may identify patients at high risk for development of late PTLD/lymphoma. We reviewed data on 71 pediatric heart recipients who had serial viral load monitoring since 1997. Chronic high-load state was defined as the presence of >16,000 genome copies/mL whole blood on > or =50% of samples over at least 6 months. Among 20 high-load carriers (eight following prior PTLD, seven with prior symptomatic EBV infection, five without previous EBV disease), 9 (45%) developed late-onset PTLD 2.5-8.4 years posttransplant (including with four Burkitt's lymphoma). Among 51 controls with low (n = 39) or absent (n = 12) loads, only 2 (4%; p < 0.001 absent/low vs. high load) developed late PTLD/lymphoma. By multivariable analysis, high-load carrier state (OR = 12.4, 95% CI 2.1-74.4) and prior history of PTLD (OR = 10.7, 95% CI 1.9-60.6) independently predicted late PTLD. A chronic high EBV-load state is not benign and is a predictor of de novo or recurrent PTLD.