Prospective longitudinal analysis of quantitative Epstein-Barr virus polymerase chain reaction in pediatric liver transplant recipients

The Role of Antiviral Prophylaxis for the Prevention of Epstein-Barr Virus-Associated Posttransplant Lymphoproliferative Disease in Solid Organ Transplant Recipients: A Systematic Review

The role of antiviral prophylaxis for the prevention of posttransplant lymphoproliferative disease (PTLD) remains controversial for solid organ transplantation (SOT) recipients who are seronegative for Epstein-Barr virus (EBV) but who received organs from seropositive donors. We performed a systematic review and meta-analysis to address this issue. Two independent assessors extracted data from studies after determining patient eligibility and completing quality assessments. Overall, 31 studies were identified and included in the quantitative synthesis. Nine studies were included in the direct comparisons (total 2366 participants), and 22 were included in the indirect analysis. There was no significant difference in the rate of EBV-associated PTLD in SOT recipients among those who received prophylaxis (acyclovir, valacyclovir, ganciclovir, valganciclovir) compared with those who did not receive prophylaxis (nine studies; risk ratio 0.95, 95% confidence interval 0.58-1.54). No significant differences were noted across all types of organ transplants, age groups, or antiviral use as prophylaxis or preemptive therapy. There was no significant heterogeneity in the effect of antiviral prophylaxis on the incidence of PTLD. In conclusion, the use of antiviral prophylaxis in high-risk EBV-naive patients has no effect on the incidence of PTLD in SOT recipients.

Therapeutic options in post-transplant lymphoproliferative disorders

Post-transplantation lymphoproliferative disorders (PTLD) are the second most frequent malignancies after solid organ transplantation and cover a wide spectrum ranging from polyclonal early lesions to monomorphic lymphoma. Available treatment modalities include immunosuppression reduction, immunotherapy with anti-B-cell monoclonal antibodies, chemotherapy, antiviral therapy, cytotoxic T-cell therapy as well as surgery and irradiation. Owing to the small number of cases and the heterogeneity of PTLD, current treatment strategies are mostly based on case reports and small, often retrospective studies. Moreover, many studies on the treatment of PTLD have involved a combination of different treatment options, complicating the evaluation of individual treatment components. However, there has been significant progress over the last few years. Three prospective phase II trials on the efficacy of rituximab monotherapy have shown significant complete remission rates without any relevant toxicity. A prospective, multicenter, international phase II trial evaluating sequential treatment with rituximab and CHOP-based chemotherapy (cyclophosphamide, doxorubicin, vincristine, prednisone) is ongoing and preliminary results have been promising. Cytotoxic T-cell therapy targeting Epstein-Barr virus (EBV)-infected B cells has shown low toxicity and high efficacy in a phase II trial and will be a future therapeutic option at specialized centers. Here, we review the currently available data on the different treatment modalities with a focus on PTLD following solid organ transplantation in adult patients.

Post-transplant lymphoproliferative disorder following renal transplantation: a single-center experience over 40 years

OBJECTIVES

To investigate post-transplant lymphoproliferative disorder (PTLD) following renal transplantation at our institution.

METHODS

Medical records of 631 patients who underwent renal transplantation at Osaka University Hospital between March 1965 and December 2008 were reviewed.

RESULTS

PTLD following renal transplantation was detected in 10 patients (five men, five women; mean age at transplantation, 38.5 years). Mean duration from renal transplantation to the onset of PTLD was 7.1 years (range, 5 months to 18 years, 9 months). Mean duration of observation was 3.9 years from the onset of PTLD. Immunosuppressant therapy comprised multidrug combination therapy, including cyclosporine in six patients and tacrolimus in four patients. In addition to a reduction in the immunosuppressant dose, which was performed in all patients, PTLD was treated with surgery in seven patients, radiotherapy in two patients, rituximab in five patients, and cytotoxic chemotherapy in four patients. A complete remission in eight patients and progressive disease in two were observed. At last follow up, seven patients were alive and five patients had functioning grafts.

CONCLUSIONS

The incidence of PTLD following renal transplantation at our institution is 1.6% with onset occurring more than 5 years after transplantation in five patients. Consequently, with long-term renal graft survival now feasible, attention must be paid to detecting late-onset PTLD.

Avoiding pitfalls: what an endoscopist should know in liver transplantation--part II

Over the last decade the number of patients undergoing transplantation has increased. At the same time, effective peri- and postoperative care and better surgical techniques have resulted in greater numbers of recipients achieving long-term survival. Identification and effective management in the form of adequate treatment is essential, since any delay in diagnosis or treatment may result in graft loss or serious threat to patient's life. Various aspects of endoscopic findings that can be commonly encountered among liver transplant recipients are discussed herein. Topics include: persistent and/or recurrent esophageal varices, reflux, Candida or cytomegalovirus (CMV) esophagitis, esophageal neoplasms, posttransplant peptic ulcer, biliary complications, posttransplant lymphoproliferative disorder (PTLD), Kaposi's sarcoma, CMV colitis and inflammatory bowel disease, colonic neoplasms, Clostridium difficile infection, and graft versus host disease (GVHD).

Increased Ig-null B lymphocytes in the peripheral blood of pediatric solid organ transplant recipients with elevated Epstein-Barr viral loads

In this study, the characteristics of Ig-null B cells in high viral load carriers were examined by four-color flow cytometry. The frequency of Ig-null B cells in patients with high, low or undetectable virus loads was found that while patients with a high load had more Ig-null cells, these cells were also present in the low and undetectable load groups. As Ig-null cells from patients with no viral load were EBV-negative, EBV infection was not absolutely required for the generation or survival of Ig-null cells. Ig-null cells were CD19(+), sIg(-), CD5(-), CD10(-), CD27(-), CD23(-), CD38(-), and CD69(-) with variable surface expression of CD20 and CD40. Ig-null cells did not have a proliferating cell phenotype (Ki67(-)) and a high proportion were HLA class I(-) and class II(-). Virus copy number in CD19(+) Ig-null cell populations may be much higher than in CD19(+) Ig(+) cell populations. EBV infected Ig-null cells were common in blood specimens from pediatric solid organ transplant recipients and infected Ig-null cells may pose potential problems for immunotherapies that target infected B cells directly.

B lymphocytes and Epstein-Barr virus: the lesson of post-transplant lymphoproliferative disorders

Epstein-Barr virus (EBV) is a ubiquitous human gamma-herpes virus that establishes a life-long asymptomatic infection in immunocompetent hosts by colonizing memory B lymphocytes and hijacking cellular signaling pathways that regulate antigen-dependent B-cell activation and differentiation. In patients with solid organ or hematopoietic stem cell transplantation, the defect in EBV-specific immune responses may allow the outgrowth of EBV-carrying B lymphocytes that may give rise to a spectrum of different clinico-pathologic entities encompassed by the term post-transplantation lymphoproliferative disorders (PTLD). EBV-driven immortalization of B-cells is mediated by the cooperative activity of viral proteins that derange critical cellular pathways controlling growth and/or survival of B lymphocytes. Full transformation of infected B-cells is achieved by the contribution of poorly defined additional co-factors, including microenvironmental stimuli, genetic and epigenetic alterations. The quantification of circulating EBV DNA and EBV-specific T cells are valuable tools in the clinical monitoring of EBV-associated PTLD. The recent advances in elucidation of the mechanisms underlying EBV-induced growth transformation will be instrumental in guiding the design of novel approaches for the treatment of these often life-threatening lymphoproliferative disorders.

Post-transplantation lymphoproliferative disorders localizing to the gastrointestinal tract after liver transplantation: report of five pediatric cases

Post-transplantation lymphoproliferative disorder (PTLD) is a life-threatening complication of organ transplantation. PTLD can occur in every kind of organ transplantation. From July 1992 to July 2004, five patients were diagnosed at our transplantation center with PTLD after pediatric liver transplantation. During this period, there were 52 pediatric patients (<18 yr) receiving an orthotopic liver transplantation (OLT) at our center. All five patients had transmural gastrointestinal (GI) PTLD, which occurred mostly in the stomach and duodenum. Epstein-Barr virus (EBV) in situ was demonstrated in each case. EBV viral load was noted to be an important risk factor. Treatment included dose reduction of immunosuppressants and anti-CD20 antibody infusion. Chemotherapy, including cyclophosphamide, doxorubicin, vincristine, and prednisolone, was given to three patients. Four patients have survived more than 10 months until now after treatment. The one who was unresponsive to chemotherapy and anti-CD20 antibody had diffuse metastasis and died of systemic candidiasis. In our series, each PTLD involved the GI tract. The mechanism of this phenomenon is unclear, but these five cases indicate the high incidence of PTLD in pediatric solid organ transplantation.

Epstein–Barr viral load in whole blood of adults with posttransplant lymphoproliferative disorder after solid organ transplantation does not correlate with clinical course

Posttransplant lymphoproliferative disease (PTLD) is closely linked to primary Epstein-Barr virus (EBV) infection. A defect of EBV specific cellular immunity is postulated to play a pivotal role in the etiology of PTLD, but there is some debate as to whether EBV load in the peripheral blood of transplant patients predicts onset of PTLD or relapse after treatment. The current prospective, single-center study was undertaken to investigate the impact of therapy on EBV load in adult patients with PTLD. Fifteen patients with PTLD after solid organ transplantation were included and of these, seven had EBV-associated PTLD. All 15 patients received Rituximab as primary therapy. In cases of treatment failure or relapse after Rituximab treatment, patients received polychemotherapy according to the cyclophosphamide, vincristine, doxorubicin, and prednisone regimen. At onset of PTLD, the median EBV load in the peripheral blood of patients was higher in EBV-associated PTLD than PTLD with no associated EBV infection. After Rituximab therapy, four of seven patients with EBV-associated PTLD achieved long-lasting complete remissions. However, in two of these patients, EBV load increased to reach levels as high as those recorded at onset of PTLD. Another patient showed a dramatic decline of EBV load after the first dose of Rituximab while suffering from progressive disease. The other patient relapsed after Rituximab monotherapy, but his viral load stayed low. In total, discordance in EBV load and clinical course was observed in five of the seven patients with EBV-associated PTLD. We conclude that in adult patients with PTLD, EBV load does not correlate with treatment response and is not suitable as a predictive marker for PTLD relapse.

Surface immunoglobulin-deficient Epstein-Barr virus-infected B cells in the peripheral blood of pediatric solid-organ transplant recipients

Epstein-Barr virus (EBV), a ubiquitous human herpesvirus, normally causes an asymptomatic latent infection with very low levels of circulating virus in the peripheral blood of infected individuals. However, EBV does have pathogenic potential and has been linked to several diseases, including posttransplant lymphoproliferative disease (PTLD), which involves very high circulating viral loads. As a consequence of immunosuppression associated with transplantation, children in particular are at risk for PTLD. Even in the absence of symptoms of PTLD, very high viral loads are often observed in these patients. EBV-infected B cells in the circulations of 16 asymptomatic pediatric solid-organ transplant recipients from Children's Hospital of Pittsburgh were simultaneously characterized for their surface immunoglobulin (sIg) isotypes and EBV genome copy numbers. Patients were characterized as having high and low viral loads on the basis of their stable levels of circulating virus. Patients with high viral loads had both high- and low-copy-number cells. Cells with a high numbers of viral episomes (>20/cell) were predominantly Ig null, and cells with low numbers of episomes were predominantly sIgM positive. Patients with low viral loads carried the vast majority of their viral load in low-copy-number cells, which were predominantly IgM positive. The very rare high-copy-number cells detected in carriers with low viral loads were also predominantly Ig-null cells. This suggests that two distinct types of B-lineage cells contribute to the viral load in transplant recipients, with cells bearing high genome copy numbers having an aberrant Ig-null cellular phenotype.

Epstein–Barr Virus Load Correlating with Clinical Manifestation and Treatment Response in a Patient with Angioimmunoblastic T-Cell Lymphoma

Epstein–Barr virus (EBV)-associated lymphoma may arise secondary to angioimmunoblastic T-cell lymphoma (AITL). The prognosis is poor despite chemotherapy and experimental therapies. We report on a 40-year-old woman with AITL without obvious immunodeficiency in which EBV-associated lymphoma developed. The occurrence and size of enlarged lymph nodes correlated strongly with the EBV load in serum (EBVL). Treatment with valacyclovir at the early stage resulted in a drastic more than 3 log10 decrease of EBVL and complete remission. However, valacyclovir had to be stopped after 6 months due to side effects, and the lymphoma reoccurred 3 months later associated with increasing EBVL. Eventually started cytotoxic chemo- and anti-CD20 therapy resulted only in partial remission. The lymphoma progressed and 33 months after it was diagnosed the patient died. This case report demonstrates the close association of EBVL and AITL and a beneficial effect of antiviral therapy at an initial stage of disease manifestation.

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

We tested blood samples of 25 pediatric renal transplant recipients for Epstein-Barr virus (EBV) DNA load by quantitative polymerase chain reaction (PCR). Eleven of these transplant recipients showed clinical persistent mononucleosis-like symptoms years after transplantation (Tx). A quantitation of EBV DNA by PCR in peripheral blood lymphocyte (PBL) and serum samples revealed variable EBV DNA titers. The majority of EBV PCR results in samples of the 14 asymptomatic transplant recipients was repeatedly below detection limit. In contrast, patients with mononucleosis-like symptoms showed persistent EBV genome titers over a period of 6 months, ranging from 75 to 18 750 copies/10 000 PBL and from 680 to 335 000 copies/mL serum, respectively. One child suffering from this mononucleosis-like condition developed an EBV-associated Burkitt-like lymphoma 29 months after Tx. Whereas clinical and histological investigations did not indicate a post-transplant lymphoproliferative disorder (PTLD) until tumor detection, EBV titers in PBL and serum had been high for at least 8 months. We propose that pediatric transplant recipients who show both, recurrent mononucleosis-like symptoms and a sustained high EBV genome load, are at increased risk for severe EBV-related post-transplant complications.

Response of elevated Epstein-Barr virus DNA levels to therapeutic changes in pediatric liver transplant patients: 56-month follow up and outcome

BACKGROUND

Posttransplant lymphoproliferative disease (PTLD) is a serious complications after liver transplantation. Epstein-Barr virus (EBV) load measured by quantitative competitive polymerase chain reaction (PCR) has been used as an early marker for the development of PTLD and a guide for initiating preemptive therapy. The aim of this study is to report the results of EBV DNA PCR screening in a transplant population and to examine the risk factors for developing elevated EBV DNA PCR and the effect of interventions for reducing EBV DNA levels.

METHODS

Medical records of 44 children who underwent liver transplantation and EBV DNA PCR screening during a 3-year period were reviewed, and the patients were prospectively followed up for another 2 years. Eleven patients who developed elevated EBV DNA PCR levels, defined as >/=40 genomes/105 peripheral blood lymphocytes (PBL) in pretransplant EBV-seronegative patients and >/=200 genomes/105 PBL in pretransplant-seropositive patients, were treated. The initial intervention was reduction of immunosuppression and initiation of anti-viral therapy in all patients, with administration of cytomegalovirus immunoglobulin (CMV-IgG) in two patients. CMV-IgG was then given to five of the patients who did not respond to the initial intervention.

RESULTS

The initial intervention resulted in the reduction of EBV DNA PCR levels to below threshold values in 4 of 11 patients. Five patients who did not respond to the initial interventions were subsequently given intravenous CMV-IgG. The EBV DNA PCR level fell in all five of these patients during the course of treatment with CMV-IgG, with a significant reduction (to threshold levels or by two dilutions) in four of the five patients. No episodes of graft rejection were observed.

CONCLUSION

Eleven patients (25%) developed elevated EBV DNA PCR after liver transplantation. There were no identifiable risk factors for developing elevated EBV DNA PCR. A combination of reducing immunosuppression, adding antiviral agents, and initiating CMV-IgG resulted in a significant reduction of EBV DNA levels in nine (82%) patients during the follow-up period.

Epstein-Barr virus-related lymphoproliferation in children after liver transplant: role of immunity, diagnosis, and management

Tumor occurrence following immunosuppression remains a major concern in children after liver transplantation. More than 50% of these tumors belong to the post-transplant lymphoproliferative diseases (PTLD) and are diagnosed during childhood. These PTLD are mostly related to primary Epstein-Barr virus (EBV) infection and a heavy immunosuppressive regimen. Improvement in their prognosis was reached thanks to a better knowledge of their pathogenesis, risk factors and clinical presentation, linked probably to earlier management. However, their incidence remains stable (occurring in 5-15% of children after liver transplantation) despite different pre-emptive strategies based on these parameters. Moreover, acute graft rejection and subsequent risk of graft loss is a common side-effect of PTLD treatment. EBV viral load determination by quantitative polymerase chain reaction (PCR) is so far the only predictive marker proposed for PTLD prevention and PTLD treatment monitoring, although limited by a lack of specificity. New immunologic techniques have allowed the demonstration of a defect of the EBV-specific cellular immunity in the patients with PTLD. The level of immunity is correlated to the viral load and improves during recovery from PTLD. These recent findings add further knowledge to PTLD pathogenesis and management.

Detection of Epstein-Barr virus genomes in peripheral blood B cells from solid-organ transplant recipients by fluorescence in situ hybridization

Resolution of Epstein-Barr Virus (EBV) infection in pediatric solid-organ transplant recipients often leads to an asymptomatic carrier state characterized by a persistently elevated circulating EBV load that is 2 to 4 orders of magnitude greater than the load typical of healthy latently infected individuals. Elevated EBV loads in immunosuppressed individuals are associated with an increased risk for development of posttransplant lymphoproliferative disease. We have performed fluorescence in situ hybridization (FISH) studies with peripheral blood B cells from carriers of persistent EBV loads in order to directly quantitate the number of EBV genomes per infected cell. Patients were assigned to two groups on the basis of the level of the persistent load (low-load carriers, 8 to 200 genomes/10(5) peripheral blood lymphocytes; high-load carriers, >200 genomes/10(5) peripheral blood lymphocytes). FISH analysis revealed that the low-load carriers predominantly had circulating virus-infected cells harboring one or two genome copies/cell. High-load carriers also had cells harboring one or two genome copies/cell; in addition, however, they carried a distinct population of cells with high numbers of viral genome copies. The increased viral loads correlated with an increase in the frequency of cells containing high numbers of viral genomes. We conclude that low-load carriers possess EBV-infected cells that are in a state similar to normal latency, whereas high-load carriers possess two populations of virus-positive B cells, one of which carries an increased number of viral genomes per cell and is not typical of normal latency.

Significance of serial real-time PCR monitoring of EBV genome load in living donor liver transplantation

BACKGROUND

Quantitative analysis of the Epstein-Barr virus (EBV) genome has been recently reported to be helpful for early identification of EBV viremia which could reduce the risk of post-transplantation lymphoproliferative disorder (PTLD).

AIM

To demonstrate the significance of serial monitoring of EBV genome load by real-time quantitative polymerase chain reaction (PCR) after living donor liver transplantation.

METHODS

From March 1999 to April 2000, the EBV genome load in peripheral blood mononuclear cells (PBMNC) was measured serially in a total of 15 recipients of living donor liver transplantation (LDLT) who had a symptomatic EBV infection.

RESULTS

In 15 patients, the mean values of the highest EBV DNA levels from the patients who had fever, URS, diarrhea, ascites, lymphadenopathy and PTLD were 36 232, 16 040, 15 968, 2485, 336 858 and 60 486 copies/microg DNA, respectively. Patients were treated by reduction or discontinuation of immunosuppressives and/or antiviral agents. The EBV DNA levels decreased in all these patients following the recovery from their symptoms. We encountered two cases of PTLD during this study period. One of them was referred to us after the onset of PTLD and one had been undergoing aggressive immunosuppression treatment for severe rejection. Both were successfully treated.

CONCLUSIONS

Serial quantitative analysis of the EBV genome load by means of real-time PCR are thought to be useful for preventing PTLD through adjustment of the immunosuppression level in response to the viral genome load following symptomatic EBV infection.

Conversion from cyclosporin to tacrolimus in paediatric liver transplant recipients

Substitution of cyclosporin with tacrolimus should be considered for paediatric liver transplant recipients with cyclosporin-associated complications such as hypertension, gum hyperplasia, hirsutism, gynaecomastia and growth retardation, as well as recurrent or refractory acute rejection, chronic duct injury or chronic rejection. Continued experience with well tolerated drug administration and careful monitoring during drug substitution has limited drug toxicity associated with tacrolimus to a level comparable to or less than that associated with cyclosporin. Successful outcome with long term graft salvage has been reported in up to 80% of patients converted to tacrolimus because of acute rejection and 50% of patients converted because of chronic rejection. Nearly all children converted because of cyclosporin-related complications have a successful outcome. Additional benefits of conversion to tacrolimus include improvement in growth and resolution of hypertension, hirsutism and cushingoid facies. Complete corticosteroid withdrawal is possible in up to 78% of children post-conversion. Long term outcome in these patients may be optimised by conversion to tacrolimus at an early stage of acute or chronic transplant rejection in order to minimise the cumulative amount of immunosuppression. Avoidance of cyclosporin-related toxicity and minimisation of corticosteroid therapy may further improve patient compliance to drug therapy.

Recent advances in pediatric liver transplantation

Pediatric liver transplantation has matured into a well-established, highly successful treatment for advanced pediatric liver disease. Recent 1-year success rates range from 85% to 95%. This unprecedented achievement is the result of careful selection criteria and optimal timing of transplantation, technical advances in surgical technique, and improved treatment following transplant. This report highlights many recent published findings representing advances that have led to current successful approaches.

Quantitative analysis of cell-free Epstein-Barr virus genome copy number in patients with EBV-associated hemophagocytic lymphohistiocytosis

To determine whether the EBV genome content in serum or plasma reflects clinical features and outcome in EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), we quantified the cell-free EBV genome copy number by real-time PCR in 38 patients with EBV-HLH, and compared this to the values from 15 patients with infectious mononucleosis (IM). The median (range) cell-free EBV genome copy number at diagnosis was 3.0 x 10(3) (undetectable -5.5 x 10(7)) copies/ml in EBV-HLH, which was significantly higher than the 6.6 x 10(1) (undetectable -1.0 x 10(3)) copies/ml in IM (P = 0.0008). We serially analyzed cell-free EBV genome copy number in 10 cases of EBV-HLH up to 4 months from diagnosis. In four patients who achieved remission, the EBV genome became undetectable soon after starting therapy. In the remaining six patients who responded poorly to therapy, the EBV genome copy number in the serum or plasma remained at high levels except for one case. In addition, we confirmed that the EBV genome became undetectable after hematopoietic stem cell transplantation in 4 EBV-HLH cases. These results suggest that the quantitative analysis of cell-free EBV genome copy number is useful for evaluating disease activity and for predicting the response to therapy in EBV-HLH.

Post-transplant lymphoproliferative syndrome in the pediatric liver transplant population

Post-transplant lymphoproliferative disease remains a complication with a high morbidity and mortality. The present study examined 291 pediatric liver transplants performed in 263 children from October 1984 to December 1999. Post-transplant lymphoproliferative disease has an overall incidence of 12%. Tacrolimus and cyclosporine had a similar incidence of post-transplant lymphoproliferative disease. Fifty-six per cent of patients who developed post-transplant lymphoproliferative disease were Epstein-Barr virus negative at the time of transplantation. Mean time of conversion to Epstein-Barr virus positivity was 1.1 years after liver transplantation. Ten per cent of those who developed post-transplant lymphoproliferative disease never had Epstein-Barr virus detected. Mean time from Epstein-Barr virus positivity to detection of post-transplant lymphoproliferative disease was 2.68 years, and 3.13 years from liver transplantation (OLTx) to post-transplant lymphoproliferative disease. There was a 35% incidence of mortality. Deaths occurred a mean of 0.76 years after diagnosis of post-transplant lymphoproliferative disease. Most cases of post-transplant lymphoproliferative disease had extranodal location. There was one recurrence in 10% of patients, and two in 3%. All recurrent cases were seen in recipients who became Epstein-Barr virus positive after transplantation. There has been a decrease in the incidence of post-transplant lymphoproliferative disease from 15% to 9% to 4%. Post-transplant lymphoproliferative disease should be diagnosed promptly and treated aggressively. The best treatment, however, seems to be prevention, starting in the immediate postoperative period. Survivors should be monitored for both recurrence of post-transplant lymphoproliferative disease and acute cellular rejection.

The role of quantitative Epstein-Barr virus polymerase chain reaction and preemptive immunosuppression reduction in pediatric liver transplantation: a preliminary experience

BACKGROUND

Risk factors for the development of posttransplant lymphoproliferative disease (PTLD), a major cause of morbidity and mortality after pediatric liver transplantation, are primary Epstein-Barr virus (EBV) infection and intensity of immunosuppression. The authors assessed monitoring of EBV replication and preemptive immunosuppression reduction in pediatric liver transplant recipients.

METHODS

The authors prospectively followed monthly EBV-quantitative competitive polymerase chain reaction to measure EBV replication in 23 patients who underwent liver transplant between July 1997 and November 1998. Preemptive immunosuppression reduction was instituted for significant EBV replication. Patients were followed up for at least 1 year and divided in two groups for analysis (group 1, pretransplant seronegative for EBV [13 patients]; group 2, seropositive for EBV [10 patients]).

RESULTS

In group 1, 9 of 13 patients had positive polymerase chain reaction results at a mean time of 22.4 weeks after transplantation. All but one of these patients were asymptomatic. In seven of nine patients, preemptive immunosuppression reduction was undertaken without development of PTLD or rejection. In two of nine patients, immunosuppression could not be continuously reduced, and both patients experienced low-grade and medically responsive PTLD. In no patient in group 2 did an EBV-positive viral load or PTLD develop.

CONCLUSIONS

Prospective longitudinal measurement of EBV by quantitative competitive polymerase chain reaction permits early detection of asymptomatic viral replication. Subsequent preemptive reduction of immunosuppression may prevent the progression to PTLD.

Infectious complications of lung transplantation

Lung transplantation is associated with a high incidence of infection which directly impacts the morbidity and mortality associated with the procedure. In addition, these infections may also have immunologic consequences that play a role in the evolution of lung injury syndromes, resulting in earlier loss of graft than otherwise would be expected to occur. Although bacteria are responsible for the majority of infections following lung transplantation, fungal infections are associated with the highest mortality. This paper is an overview of the major infectious complications encountered in the lung transplant population. The epidemiology, prophylaxis, and treatment of infections following lung transplantation are critical areas for continued research.

Epstein-Barr virus infection in paediatric liver transplant recipients: detection of the virus in post-transplant tonsillectomy specimens

AIMS

Post-transplant lymphoproliferative disease (PTLD) is an important and serious complication in transplant patients. Recent studies have suggested that quantitative assessment of Epstein-Barr virus (EBV) infection in transplant patients might help to identify those at risk of developing PTLD. Therefore, tonsils from paediatric liver transplant recipients were studied for evidence of EBV infection.

METHODS

Tonsils were studied by in situ hybridisation for the detection of the small EBV encoded nuclear RNAs (EBERs). The phenotype of EBV infected cells was determined by double labelling in situ hybridisation and immunohistochemistry. The expression of viral latent and lytic antigens was determined by immunohistochemistry. Tonsils from patients without known immune defects were studied as controls.

RESULTS

Tonsils from transplant patients showed pronounced follicular hyperplasia and minor paracortical hyperplasia. In situ hybridisation revealed variable numbers of EBV infected B cells in the tonsils from transplant patients (range, 2-1000/0.5 cm(2); mean, 434/0.5 cm(2); median, 105/0.5 cm(2)). Lower numbers were detected in the control tonsils (range, 1-200/0.5 cm(2); mean, 47/0.5 cm(2); median, 9/0.5 cm(2)). The latent membrane protein 1 (LMP1) of EBV was not detected and there were only rare cells in two cases showing expression of the EBV encoded nuclear antigen 2 (EBNA2). There was no evidence of lytic infection. None of the patients developed PTLD within a follow up period of up to five years.

CONCLUSIONS

These data indicate that tonsillar enlargement in paediatric liver transplant patients does not necessarily imply a diagnosis of PTLD. Furthermore, the presence of increased numbers of EBV infected cells in tonsils from liver transplant recipients by itself does not indicate an increased risk of developing PTLD.

Diagnosis and management of posttransplant lymphoproliferative disorder in solid-organ transplant recipients

The Epstein-Barr virus (EBV) has a pivotal pathophysiologic role in the development of most lymphoproliferative disorders that occur after solid-organ transplantation. The term "EBV-associated posttransplant lymphoproliferative disorder" (PTLD) includes all clinical syndromes of EBV-associated lymphoproliferation, ranging from uncomplicated posttransplant infectious mononucleosis to true malignancies that contain clonal chromosomal abnormalities. PTLDs are historically associated with a high mortality rate in patients who have a monoclonal form of the disorder. Recently described approaches to pathology, diagnosis, treatment, and preventive strategies of PTLD, however, have the potential to improve outcome.

Pediatric solid-organ transplant recipients carry chronic loads of Epstein-Barr virus exclusively in the immunoglobulin D-negative B-cell compartment

Solid-organ transplant recipients are at risk for development of lymphoproliferative diseases. The purpose of this study was to examine the distribution of Epstein-Barr virus (EBV) load in the peripheral blood of pediatric transplant recipients who had become chronic viral load carriers (>8 copies/10(5) lymphocytes for >2 months). A total of 19 patients with viral loads ranging from 20 to 5,000 viral genome copies/10(5) lymphocytes were studied. Ten patients had no previous diagnosis of posttransplant lymphoproliferative disease (PT-LPD), while nine had recovered from a diagnosed case of PT-LPD. No portion of the peripheral blood viral load was detected in the cell-free plasma fraction. Viral DNA was found in a population of cells characterized as CD19(hi) and immunoglobulin D negative, a phenotype that is consistent with the virus being carried exclusively in the memory B-cell compartment of the peripheral blood. There was no difference in the compartmentalization based upon either the level of the viral load or the past diagnosis of an episode of PT-LPD. These results have implications for the design of tests to detect EBV infection and for the interpretation and use of positive EBV PCR assays in the management of transplant recipients.

Long-term correction of urea cycle disorders

Long-term correction of urea cycle disorders is achieved by correction of the enzymatic defect in hepatocytes. Currently, orthotopic liver transplantation is the primary means of achieving this correction. In the United States most liver transplantations for urea cycle disorders have been restricted to patients with ornithine transcarbamylase deficiency and argininosuccinic aciduria. However, patients with citrullinemia have also received transplants, but more so in Europe and Japan. Recent advances in organ procurement, surgical technique, and immunosuppression have significantly decreased morbidity and mortality. However, unique short-term complications associated with surgery and long-term complications associated with chronic immunosuppression have spurred continued efforts to develop gene replacement therapies for management of acute metabolic decompensations as intercurrent therapy until liver transplantation, and ultimately, for long-term correction. The pathophysiology of urea cycle disorders requires gene vector delivery systems that are highly efficient for liver transduction and transgene expression. To date, adenoviral vectors are unique in fulfilling these criteria, and significant data have been gained in both animal and human studies with early versions of adenoviral vectors. Ultimately, the development of helper-dependent adenoviral vectors may offer the long-term expression and increased margin of safety necessary for adjunctive therapies.