Early intervention in post-transplant lymphoproliferative disorders based on Epstein-Barr viral load

Host factors associated with the kinetics of Epstein-Barr virus DNA load in patients with primary Epstein-Barr virus infection

The aims of this study were to elucidate the kinetics of Epstein-Barr virus (EBV) DNA load in serially collected peripheral blood mononuclear cells of patients with primary EBV infection, and to determine the correlated host factors. Blood samples were collected from 24 patients with primary EBV infection. EBV DNA copy numbers were measured using real-time polymerase chain reaction. Based on the kinetics of EBV DNA load, the 24 patients were divided into two groups: rapid regression and slow regression. Eighteen of the 24 patients (75%) were included in the slow regression and 6 (25%) in the rapid regression group. No statistically significant differences were observed between the two groups in clinical features and laboratory findings. However, acute phase (3 to 10 days after the onset of the illness) serum samples from six children in the slow regression and four in the rapid regression group revealed significantly higher serum interleukin (IL)-1β (P= 0.018), IL-12 (P= 0.009), tumor necrosis factor-α (P= 0.019), interferon-inducible protein 10, and monokine induced by interferon γ concentrations in the rapid regression than the slow regression group. On the other hand, sera from six children in the slow regression and four in the rapid regression group in the convalescent phase (14 to 21 days after the onset of the illness) showed no statistically significant differences between the two groups in these biomarker concentrations. Based on this, it was concluded that the kinetics of EBV DNA load can be divided to two different patterns after primary EBV infection, and immune response might be associated with viral clearance.

Monitoring and preemptive rituximab therapy for Epstein-Barr virus reactivation after antithymocyte globulin containing nonmyeloablative conditioning for umbilical cord blood transplantation

Epstein Barr viremia (EBV) and posttransplantation lymphoproliferative disorder (PTLD) are complications of hematopoietic stem cell transplantation (HSCT). The use of antithymocyte globulin (ATG) in recipients of umbilical cord HSCT is a known risk factor for the development of PTLD. In this high-risk population, we implemented an EBV monitoring program with preemptive therapy with rituximab (375 mg/m(2) intravenously [i.v.]) for EBV viremia (>1000 copies/mL). Eight of 35 patients treated with a UCB HSCT between 2007 and 2009, developed EBV viremia. Two of 7 developed PTLD (with 1 of the 2 dying of PTLD), despite prophylactic rituximab use. When compared with our previously described cohort where 6 of 30 developed EBV viremia and 5 of 6 patients developed PTLD (with 2 of 5 dying of PTLD), the incidence of PTLD appears to be less when prophylactic rituximab is administered. Despite small numbers, our observations suggest that in this high-risk population, EBV monitoring accompanied by preemptive therapy may reduce the risk of progression to life-threatening PTLD; further follow-up of this cohort and a larger multi-institutional prospective study of this preemptive strategy is warranted.

Poor outcome in post transplant lymphoproliferative disorder with pulmonary involvement after allogeneic hematopoietic SCT: 13 years' experience in a single institute

EBV-induced post transplant lymphoproliferative disorder (PTLD) continues to be a major complication after transplantation. Between January 1993 and April 2006, 12 cases of B-cell lymphoproliferative disorder were identified among 577 patients after allogeneic hematopoietic SCT (HSCT) with an overall incidence of 2.51% at 1 year. Grades II-IV acute GVHD, CMV antigenemia and the use of antithymocyte globulin (ATG) were independent risk factors for PTLD. At diagnosis, all of the tumors were CD20-positive and 11 (92%) were EBV-encoded RNA (EBER)-positive. Of the 12 patients with B-cell lymphoproliferative disorder, 8 had pulmonary involvement and 10 had extranodal involvement. Eleven patients received weekly rituximab therapy at a dose of 375 mg/m(2); the median interval between the onset of symptoms and rituximab therapy was 6 days. The overall mortality rate was 92% and seven (64%) of the deaths were directly attributable to disseminated PTLD within days or weeks of presentation. In our series, pulmonary PTLD followed an extremely aggressive course and poor response to current therapy, even though rituximab was included in the therapeutic regimens.

Monitoring of Epstein-Barr virus load after hematopoietic stem cell transplantation for early intervention in post-transplant lymphoproliferative disease

Epstein-Barr virus (EBV)-associated post-transplant lymphoproliferative disease is a life-threatening complication following hematopoietic stem cell transplantation. A quantitative polymerase chain reaction to evaluate EBV-genome copy numbers based on a nested polymerase chain reaction and an end-point dilution was used. Applying this assay EBV load was prospectively screened weekly in 123 patients after transplantation. The results demonstrate that EBV reactivations with more than 1,000 EBV-genome copies measured in 10(5) peripheral blood mononuclear cells were observed in 31 patients (25.2%). Three patients developed lymphoproliferative disease with extremely high EBV-genome copies in peripheral blood mononuclear cells (>100,000 copies/10(5) cells) and plasma. After combined antiviral and immune therapy two of three patients showed a dramatic decrease of EBV load and survived, while the third patient died of lymphoma. A subclinical EBV reactivation was observed in 24 cases (19.5%) with EBV-genome copies in 10(5) peripheral blood mononuclear cells ranging between 2,500 and mostly 10,000. After reduction of immunosuppression the EBV levels normalized. In four patients, the high copy number of > or =80,000 copies/10(5) peripheral blood mononuclear cells and plasma positivity prompted us to start pre-emptive therapy with rituximab and cidofovir for prevention of lymphoproliferative disease. After drug administration the high EBV load was reduced remarkably. Ninety-two patients (74.8%) who had < or =1,000 copies/10(5) peripheral blood mononuclear cells did not develop EBV-associated lymphoproliferative disease. In conclusion, monitoring of EBV load is a sensitive and useful parameter in the surveillance of EBV reactivation for early intervention in EBV-associated lymphoproliferative disease as well as for follow-up of the efficacy of therapy.

Marked increased risk of Epstein-Barr virus-related complications with the addition of antithymocyte globulin to a nonmyeloablative conditioning prior to unrelated umbilical cord blood transplantation

Umbilical cord blood (UCB) is increasingly used as an alternative source of hematopoietic stem cells for transplantation for patients who lack a suitable sibling donor. Despite concerns about a possible increased risk of Epstein-Barr virus (EBV) posttransplantation lymphoproliferative disorder (PTLD) after UCB transplantation, early reports documented rates of PTLD comparable to those reported after HLA-matched unrelated marrow myeloablative (MA) transplantations. To further investigate the incidence of EBV PTLD after UCB transplantation and potential risk factors, we evaluated the incidence of EBV-related complications in 335 patients undergoing UCB transplantation with an MA or nonmyeloablative (NMA) preparative regimen. The incidence of EBV-related complications was a 4.5% overall, 3.3% for MA transplantations, and 7% for NMA transplantations. However, the incidence of EBV-related complications was significantly higher in a subset of patients treated with an NMA preparative regimen that included antithymocyte globulin (ATG) versus those that did not (21% vs 2%; P < .01). Nine of 11 patients who developed EBV PTLD were treated with rituximab (anti-CD20 antibody), with the 5 responders being alive and disease free at a median of 26 months. Use of ATG in recipients of an NMA preparative regimen warrants close monitoring for evidence of EBV reactivation and potentially preemptive therapy with rituximab.

Treatment of Epstein-Barr virus--associated lymphoproliferative disorder (EBV-PTLD) and pure red cell aplasia (PRCA) with Rituximab following unrelated cord blood transplantation: a case report and literature review

OBJECTIVE

We report the first case of EBV-PTLD and pure red cell aplasia (PRCA) after an unrelated cord blood transplant in China, who was successfully treated with Rituximab.

METHODS

Case report and literature review.

RESULTS

A 5-year-old girl with CML underwent a major ABO-incompatible HLA-identical unrelated cord blood transplantation (U-CBT) in January 2003. The post transplant course was complicated by PRCA. She presented on day +75 with fever, followed by rapid enlargement of tonsils, and a cluster of lymph nodes in the cervical and submandibular regions. A cervical lymph node biopsy revealed the histopathologic findings consistent with PTLD. The immunoblasts were shown to contain EBV viral genomic DNA by PCR, and immunocytochemistry study for the latent membrane protein 1 (LMP-1) and in situ hybridization for Epstein-Barr encoded RNAs1 (EBER1) were both positive. She responded rapidly to Rituximab and achieved complete resolution of clinical findings and symptoms of both EBV-PTLD and PRCA.

CONCLUSION

EBV-PTLD may occur with increasing frequency due to the increasing numbers of transplant recipients, transplant physician should be aware of this life-threatening complication. Rituximab alone may be an effective therapeutic strategy for patients who develop EBV-PTLD and PRCA after U-CBT.

Real-time Fluorescent PCR Techniques to Study Microbial-Host Interactions

This chapter describes how real-time polymerase chain reaction (PCR) performs and how it may be used to detect microbial pathogens and the relationship they form with their host. Research and diagnostic microbiology laboratories contain a mix of traditional and leading-edge, in-house and commercial assays for the detection of microbes and the effects they impart upon target tissues, organs, and systems. The PCR has undergone significant change over the last decade, to the extent that only a small proportion of scientists have been able or willing to keep abreast of the latest offerings. The chapter reviews these changes. It discusses the second-generation of PCR technology-kinetic or real-time PCR, a tool gaining widespread acceptance in many scientific disciplines but especially in the microbiology laboratory.

Real-time PCR in the microbiology laboratory

Use of PCR in the field of molecular diagnostics has increased to the point where it is now accepted as the standard method for detecting nucleic acids from a number of sample and microbial types. However, conventional PCR was already an essential tool in the research laboratory. Real-time PCR has catalysed wider acceptance of PCR because it is more rapid, sensitive and reproducible, while the risk of carryover contamination is minimised. There is an increasing number of chemistries which are used to detect PCR products as they accumulate within a closed reaction vessel during real-time PCR. These include the non-specific DNA-binding fluorophores and the specific, fluorophore-labelled oligonucleotide probes, some of which will be discussed in detail. It is not only the technology that has changed with the introduction of real-time PCR. Accompanying changes have occurred in the traditional terminology of PCR, and these changes will be highlighted as they occur. Factors that have restricted the development of multiplex real-time PCR, as well as the role of real-time PCR in the quantitation and genotyping of the microbial causes of infectious disease, will also be discussed. Because the amplification hardware and the fluorogenic detection chemistries have evolved rapidly, this review aims to update the scientist on the current state of the art. Additionally, the advantages, limitations and general background of real-time PCR technology will be reviewed in the context of the microbiology laboratory.

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.

Immunotherapy for Epstein-Barr virus-associated cancers in children

Latent Epstein-Barr virus (EBV) infection is associated with several malignancies, including Burkitt's lymphoma, Hodgkin's disease, nasopharyngeal carcinoma, and post-transplant lymphoproliferative disease (LPD). The presence of EBV antigens in these tumors provides a target for immunotherapy approaches, and immunotherapy with EBV-specific cytotoxic T cells (CTLs) has proved effective in post-transplant LPDs, which are highly immunogenic tumors expressing type III latency. The malignant cells in Hodgkin's disease and nasopharyngeal carcinoma express type II latency and hence a more restricted pattern of EBV antigens. Trials with autologous EBV-specific CTL responses are under way in both of these diseases, and while some activity has been seen, no patient has yet been cured. This reduced CTL efficacy may reflect either downregulation of immunodominant EBV proteins, which are major CTL targets, or the ability of these tumors to evade the immune response by secreting inhibitory cytokines. Further improvement of EBV-specific CTL therapy for these type II latency tumors will require improved methods to activate and expand CTLs specific for the subdominant EBV genes expressed and to genetically modify the expanded CTLs to render them resistant to inhibitory cytokines. If these strategies to improve the therapeutic potential of immunotherapy for EBV-associated tumors prove successful, this type of treatment may be adapted to other tumors expressing known (viral) antigens.

Tetramer-assisted identification and characterization of epitopes recognized by HLA A*2402-restricted Epstein-Barr virus-specific CD8+ T cells

We determined cytotoxic T lymphocyte (CTL) epitopes through screening with a computer-assisted algorithm and an enzyme-linked immunospot (ELISPOT) assay using in vitro-reactivated polyclonal Epstein-Barr virus (EBV)-specific CD8(+) T cells as responders. In addition, to confirm that the epitopes were generated after endogenous processing and presentation of the EBV proteins, a novel T-cell receptor (TCR) down-regulation assay was introduced, in which a fluorescent tetrameric major histocompatibility complex (MHC)/peptide complex was employed for detecting TCR down-regulation after stimulation with the epitope presented on antigen-presenting cells. Through such screening, 3 HLA A*2402-restricted epitopes were identified: IYVLVMLVL, TYPVLEEMF, and DYNFVKQLF, derived from LMP2, BRLF1, and BMLF1 proteins, respectively. TCR down-regulation assays disclosed that, in contrast to the other 2 epitopes, IYVLVMLVL was not presented on HLA A24-positive fibroblast cells infected with recombinant vaccinia viruses expressing LMP2. Furthermore, ELISPOT assays with an epitope-specific CTL clone demonstrated that the presentation was partially restored by pretreatment of the fibroblast cells with interferon-gamma. The epitope was presented on transporters associated with antigen processing (TAP)-negative T2 cells transfected with plasmids encoding HLA A*2402 and the minimal epitope, indicating that the presentation is TAP independent. In conclusion, the 3 epitopes thus defined could be useful for studying EBV-specific CD8(+) T-cell responses among populations positive for HLA A*2402.

Development of real-time PCR assays for the quantitative detection of Epstein-Barr virus and cytomegalovirus, comparison of TaqMan probes, and molecular beacons

Human Epstein-Barr virus (EBV) and cytomegalovirus (CMV) can cause serious complications in immunocompromised patients. Rapid diagnosis of EBV and CMV infection is critical in the management of the disease so that anti-viral therapy can be started early. Here we describe the development of real-time PCR assays using TaqMan probes and molecular beacons and compare the performance of both assays with a well-established, validated, gel-based PCR method for the quantification of EBV and CMV in patients' samples. The TaqMan and molecular beacon assays were linear between 10 to 10(7) viral genomes/reaction. Both assays generated calibration curves with strong correlation and low intra-assay and interassay variation. Results of EBV and CMV viral load determination inpatient samples obtained by the gel-based and real-time PCR were very similar. The real-time PCR assays showed increases in viral load before clinical measures of viral disease and decreases in viral load during anti-viral therapy in two of six pediatric patients. The data indicate that these TaqMan and molecular beacon approaches are accurate, rapid, and reliable assays for the diagnosis and monitoring of EBV and CMV infections in patients.

Overview of Epstein-Barr virus-associated diseases in Japan

Epstein-Barr virus (EBV) associated diseases and studies performed in Japan are reviewed. Infectious mononucleosis is a common disease in Japanese infants. Chronic and severe EBV-infections include severe chronic active EBV-infection (SCAEBV), EBV-associated hemophagocytic syndrome, and mosquito allergy with granular lymphocyte proliferative disorder (GLPD). Autoimmune lymphoproliferative syndrome (ALPS), a disease caused by a defect in the Fas-Fas ligand pathway of cell-death, may develop into lymphoproliferative disease after early exposure to EBV. More than ten cases of X-linked lymphoproliferative syndrome (XLP) were discovered in Japanese children, and the frequency of post-transplant lymphoproliferative disorder (PTLD) increased after the number of patients receiving organ transplantation increased. Recently, an association of EBV with gastric carcinoma and hepatocellular carcinoma has been suggested. EBV-infected cells, such as B-cells, T-cells, NK-cells, and epithelial cells in EBV-associated diseases have also been clarified.

Diagnosis of Epstein-Barr virus-associated diseases

Epstein-Barr virus (EBV) is a common DNA virus distributed worldwide. Usually the initial infection involves the upper respiratory tract without any problems and almost the entire population more than 25 years old test positive for anti-EBV antibodies. However, EBV often causes not only acute lytic infection but also chronic active infection with B cells and even T cells. In addition the EBV genome has been detected in tumors of hematopoietic or epithelial cell origin such as Burkitt's lymphomas, Hodgkin's disease, NK/T cell lymphomas, nasopharyngeal carcinomas (NPCs) and gastric adenocarcinomas. It is clearly important to make a correct diagnosis for EBV associated diseases and monitor the EBV load in individual patients for an appropriate therapy. In this paper recent advances in serological, immunological and molecular approaches for detection of EBV associated disease are described.

Biological aspects of Epstein-Barr virus (EBV)-infected lymphocytes in chronic active EBV infection and associated malignancies

Most primary Epstein-Barr virus (EBV) infections are clinically inapparent, but occasionally EBV infection can cause acute infectious mononucleosis. EBV has been linked to a variety of hematologic and non-hematologic malignancies. Chronic active EBV (CAEBV) infection designates a recently identified EBV-associated syndrome characterized by a variety of serious hematological disorders, including malignant lymphoma. EBV was found to infect circulating T- and/or NK-cells in patients with CAEBV infection. These EBV-infected T- and/or NK-cells express EBNA-1, LMP-1, and LMP-2A, a type II form of EBV latency, which is also observed in nasopharyngeal carcinoma (NPC), Hodgkin's disease (HD), and peripheral T-cell lymphoma. CAEBV infections may thus represent a subset of EBV-associated T- and/or NK-cell lymphoproliferative disorders.

Epstein-Barr viral load as a tool to diagnose and monitor post-transplant lymphoproliferative disease

Epstein-Barr virus (EBV)-induced post-transplant lymphoproliferative disease (PTLD) continues to be a rare but severe complication following transplantation. EBV viral load is used as a tool to identify patients at risk for developing PTLD. However, studies on EBV viral load are hard to compare since study design as well as EBV detection method and calculation of results are highly variable. In the majority of cases EBV viral load is increased in patients with PTLD compared to patients without disease. There is, however, some overlap. Some individual patients with only low viral load show PTLD while others show the opposite. The major future goals will be to standardize EBV-DNA detection in order to generate comparable data in different centers and to establish cut-off values to distinguish patients with PTLD from patients without with a high precision.

Real-time PCR in virology

The use of the polymerase chain reaction (PCR) in molecular diagnostics has increased to the point where it is now accepted as the gold standard for detecting nucleic acids from a number of origins and it has become an essential tool in the research laboratory. Real-time PCR has engendered wider acceptance of the PCR due to its improved rapidity, sensitivity, reproducibility and the reduced risk of carry-over contamination. There are currently five main chemistries used for the detection of PCR product during real-time PCR. These are the DNA binding fluorophores, the 5' endonuclease, adjacent linear and hairpin oligoprobes and the self-fluorescing amplicons, which are described in detail. We also discuss factors that have restricted the development of multiplex real-time PCR as well as the role of real-time PCR in quantitating nucleic acids. Both amplification hardware and the fluorogenic detection chemistries have evolved rapidly as the understanding of real-time PCR has developed and this review aims to update the scientist on the current state of the art. We describe the background, advantages and limitations of real-time PCR and we review the literature as it applies to virus detection in the routine and research laboratory in order to focus on one of the many areas in which the application of real-time PCR has provided significant methodological benefits and improved patient outcomes. However, the technology discussed has been applied to other areas of microbiology as well as studies of gene expression and genetic disease.

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.

Prospective monitoring of the Epstein-Barr virus DNA by a real-time quantitative polymerase chain reaction after allogenic stem cell transplantation

Epstein-Barr virus (EBV)-related lymphoproliferative disorder (LPD) is a serious complication of haematopoietic stem cell transplantation (HSCT). To clarify the frequency, natural course and risk factors for LPD, we prospectively monitored 38 allogeneic (allo)-HSCT patients, focusing on the use of anti-thymocyte globulin (ATG). We used a recently developed real-time polymerase chain reaction assay to monitor EBV genome load. The subjects consisted of 19 patients given ATG for conditioning and 19 patients not given ATG. Of the 19 patients given ATG, 47.4% (nine patients) had a significant increase in EBV genome load (10(2.5) copies/microg DNA). Of these nine patients, two developed LPD. Therefore, 10.5% of the patients receiving allo-HSCT with ATG developed LPD. In contrast, none of the 19 patients without ATG had a significantly increased EBV load. The increases in viral load were observed in the second or third month after HSCT. We found that the peak viral loads of LPD patients were > 10(4.0 ) copies/microg DNA. On the other hand, the viral loads of most patients with no symptoms were < 10(2.5) copies/microg DNA. In conclusion, routine monitoring of EBV load during the second and third months after transplantation may benefit patients undergoing HSCT with ATG. We propose that an EBV load > 10(2.5) copies/microg DNA is the reactivation of EBV, and that an EBV load > 10(4.0) copies/microg DNA is indicative of developing LPD.

Efficient identification of HLA-A*2402-restricted cytomegalovirus-specific CD8(+) T-cell epitopes by a computer algorithm and an enzyme-linked immunospot assay

Antigenic peptides recognized by virus-specific cytotoxic T lymphocytes (CTLs) are useful tools for studying the CTL responses exclusively among those who own the major histocompatibility complex (MHC) class I molecules that present the peptides. For widening the application, an efficient strategy to determine such epitopes in the context of a given MHC is highly desirable. A rapid and efficient strategy is presented for the determination of CTL epitopes in the context of given MHC molecules of interest through multiple screenings consisting of a computer-assisted algorithm and MHC stabilization and enzyme-linked immunospot assays. A major cytomegalovirus (CMV)-specific CTL epitope, QYDPVAALF, in the amino acid sequence of its lower matrix 65 kd phosphoprotein (pp65) presented by HLA-A*2402 molecules was identified from 83 candidate peptides. The results indicate that the CMV-specific CTL response is highly focused to pp65 in the context of HLA-A*2402. Endogenous processing and presentation was confirmed using a peptide-specific CD8(+) T-cell clone as the effectors and autologous fibroblast cells infected with recombinant vaccinia virus expressing pp65 gene or CMV as antigen-presenting cells. Flow cytometric analysis of intracellular interferon-gamma production revealed 0.04% to 0.27% of CD8(+) T cells in peripheral blood of HLA-A24(+) and CMV-seropositive donors to be specific for the peptide. The tetrameric MHC-peptide complexes specifically bound to the reactive T-cell clone and 0.79% of CD8(+) T cells in peripheral blood from a seropositive donor. The peptide could be a useful reagent to study CTL responses to CMV among populations positive for HLA-A*2402.

Unrelated donor marrow transplantation in children with severe aplastic anaemia using cyclophosphamide, anti-thymocyte globulin and total body irradiation

We report a favourable outcome in 15 patients with severe aplastic anaemia (SAA) who were < 20 years of age and who underwent bone marrow transplantation (BMT) from a human leucocyte antigen (HLA)-matched unrelated donor. All patients were non-responders to intensive immunosuppressive therapy (IST) and were multiply transfused. The conditioning regimen consisted of cyclophosphamide (60 mg/kg/d, on d -4 and -3), anti-thymocyte globulin (2.5 mg/kg/d, on d -5 to -2) and total body irradiation (2.5 Gy x 2/d, on d -2 and -1). Patients received cyclosporine and methotrexate for prophylaxis of graft-versus-host disease (GVHD), except for the last four who received tacrolimus instead of cyclosporine. Donor/recipient pairs were identical for HLA class I and II antigens by serological typing, but four pairs were found to have a mismatch at the HLA-A, -B or -DRB1 locus by high-resolution typing. All patients achieved rapid engraftment and are alive at 2-86 months after transplantation (median follow-up, 51 months). Moderate to severe acute GVHD occurred in 5 out of 15 patients (33%); only one patient developed extensive chronic GVHD. Considering our encouraging results, unrelated donor transplantation for SAA is recommended as a salvage therapy in non-responders to IST.

Fatal outcome in a patient developing Epstein-Barr virus-associated lymphoproliferative disorder (EBV-LPD) without measurable disease

A 51-year-old female patient in the first chronic phase of CML received an allogeneic PBSCT from a matched unrelated donor. The transplant was manipulated by CD34+ cell selection. On day +193 after transplantation the patient was readmitted to the hospital with recurrent fever of unknown origin and cough. Clinical, radiographic and sonographic evaluation revealed no characteristic findings besides a mild splenomegaly. Screening for EBV, CMV, RSV and HSV did not indicate an active infection. On day +203 the patient developed generalized seizures, respiratory failure and died within 24 h in multiorgan failure. The macroscopic postmortem was still not enlightening; the histological examination however, demonstrated diffuse organ infiltration by monoclonal lymphoblastoid cells due to EBV-LPD.

Epstein-Barr virus (EBV) reactivation is a frequent event after allogeneic stem cell transplantation (SCT) and quantitatively predicts EBV-lymphoproliferative disease following T-cell--depleted SCT

Reactivation of the Epstein-Barr virus (EBV) after allogeneic stem cell transplantation (allo-SCT) may evoke a protective cellular immune response or may be complicated by the development of EBV-lymphoproliferative disease (EBV-LPD). So far, very little is known about the incidence, recurrence, and sequelae of EBV reactivation following allo-SCT. EBV reactivation was retrospectively monitored in 85 EBV-seropositive recipients of a T-cell--depleted (TCD) allo-SCT and 65 EBV-seropositive recipients of an unmanipulated allo-SCT. Viral reactivation (more than 50 EBV genome equivalents [gEq]/mL) was monitored frequently by quantitative real-time plasma polymerase chain reaction until day 180 after SCT. Probabilities of developing viral reactivation were high after both unmanipulated and TCD-allogeneic SCT (31% +/- 6% versus 65% +/- 7%, respectively). A high CD34(+) cell number of the graft appeared as a novel significant predictor (P =.001) for EBV reactivation. Recurrent reactivation was observed more frequently in recipients of a TCD graft, and EBV-LPD occurred only after TCD-SCT. High-risk status, TCD, and use of antithymocyte globulin were predictive for developing EBV-LPD. Plasma EBV DNA quantitatively predicted EBV-LPD. The positive and negative predictive values of a viral load of 1000 gEq/mL were, respectively, 39% and 100% after TCD. Treatment-related mortality did not differ significantly between TCD and non-TCD transplants, but the incidence of chronic graft-versus-host disease was significantly less in TCD patients. It is concluded that EBV reactivation occurs frequently after TCD and unmanipulated allo-SCT, especially in recipients of grafts with high CD34(+) cell counts. EBV-LPD, however, occurred only after TCD, and EBV load quantitatively predicted EBV-LPD in recipients of a TCD graft. (Blood. 2001;98:972-978)