Longitudinal dynamics of Epstein-Barr virus-specific cytotoxic T lymphocytes during posttransplant lymphoproliferative disorder

Immune reconstitution after allogeneic hematopoietic stem cell transplantation in children: a single institution study of 59 patients

Purpose

Lymphocyte subset recovery is an important factor that determines the success of hematopoietic stem cell transplantation (HSCT). Temporal differences in the recovery of lymphocyte subsets and the factors influencing this recovery are important variables that affect a patient's post-transplant immune reconstitution, and therefore require investigation.

Methods

The time taken to achieve lymphocyte subset recovery and the factors influencing this recovery were investigated in 59 children who had undergone HSCT at the Department of Pediatrics, The Catholic University of Korea Seoul St. Mary's Hospital, and who had an uneventful follow-up period of at least 1 year. Analyses were carried out at 3 and 12 months post-transplant. An additional study was performed 1 month post-transplant to evaluate natural killer (NK) cell recovery. The impact of pre- and post-transplant variables, including diagnosis of Epstein-Barr virus (EBV) DNAemia posttransplant, on lymphocyte recovery was evaluated.

Results

The lymphocyte subsets recovered in the following order: NK cells, cytotoxic T cells, B cells, and helper T cells. At 1 month post-transplant, acute graft-versus-host disease was found to contribute significantly to the delay of CD16⁺/56⁺ cell recovery. Younger patients showed delayed recovery of both CD3⁺/CD8⁺ and CD19⁺ cells. EBV DNAemia had a deleterious impact on the recovery of both CD3⁺ and CD3⁺/CD4⁺ lymphocytes at 1 year post-transplant.

Conclusion

In our pediatric allogeneic HSCT cohort, helper T cells were the last subset to recover. Younger age and EBV DNAemia had a negative impact on the post-transplant recovery of T cells and B cells.

Detection of the Epstein-Barr virus in blood and bone marrow mononuclear cells of patients with aggressive B-cell non-Hodgkin's lymphoma is not associated with prognosis

The Epstein-Barr virus (EBV) is associated with a large spectrum of lymphoproliferative diseases. Traditional methods of EBV detection include the immunohistochemical identification of viral proteins and DNA probes to the viral genome in tumoral tissue. The present study explored the detection of the EBV genome, using the BALF5 gene, in the bone marrow or blood mononuclear cells of patients with diffuse large B-cell lymphomas (DLBCL) and related its presence to the clinical variables and risk factors. The results show that EBV detection in 21.5% of patients is not associated with age, gender, staging, B symptoms, international prognostic index scores or any analytical parameters, including lactate dehydrogenase (LDH) or β-2 microglobulin (B2M). The majority of patients were treated with R-CHOP-like (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone or an equivalent combination) and some with CHOP-like chemotherapy. Response rates [complete response (CR) + partial response (PR)] were not significantly different between EBV-negative and -positive cases, with 93.2 and 88.9%, respectively. The survival rate was also similar in the two groups, with 5-year overall survival (OS) rates of 64.3 and 76.7%, respectively. However, when analyzing the treatment groups separately there was a trend in EBV-positive patients for a worse prognosis in patients treated with CHOP-like regimens that was not identified in patients treated with R-CHOP-like regimens. We conclude that EBV detection in the bone marrow and blood mononuclear cells of DLBC patients has the same frequency of EBV detection on tumoral lymphoma tissue but is not associated with the risk factors, response rate and survival in patients treated mainly with immunochemotherapy plus rituximab. These results also suggest that the addition of rituximab to chemotherapy improves the prognosis associated with EBV detection in DLBCL.

Identification of novel immunogenic human leukocyte antigen-A 2402-binding epitopes of human papillomavirus type 16 E7 for immunotherapy against human cervical cancer

BACKGROUND

A study was undertaken to identify new immunogenic human leukocyte antigen (HLA)-A 2402-restricted epitopes from human papillomavirus (HPV) type 16 E7 protein for immunotherapy against cervical cancer.

METHODS

Synthetic overlapping peptides were screened by measuring the frequency of CD8(+) cytotoxic T lymphocytes (CTLs) producing intracellular interferon-γ (IFN-γ) using flow cytometry and were validated in SiHa cells with a Cr release cytotoxicity assay. In vivo antitumor effects of peptide-sensitized peripheral blood mononuclear cells (PBMCs) and isolated CD8(+) CTLs were evaluated using BALB/c nude mice with SiHa cell xenotransplants.

RESULTS

Among 14 overlapping 15-amino acid peptides, E7(61-75) (CDSTLRLCVQSTHVD) and E7(67-81) (LCVQSTHVDIRTLED) induced significantly higher IFN-γ production (P < .05) and showed higher in vitro cytotoxicity against SiHa cells than did cells sensitized with the negative control. To determine the exact HLA-A 2402-restricted epitopes, a total of 25 overlapping 9- or 10-amino acid peptides spanning E7(61-75) and E7(67-81) were synthesized. E7(61-69) (CDSTLRLCV) and E7(67-76) (LCVQSTHVDI) induced significantly greater IFN-γ production as well as increased in vitro cytotoxicity against SiHa cells compared with those of other peptides and the negative control (P < .01), and the antitumor effects of these peptide-sensitized PBMCs were induced by CD8(+) CTLs. E7(61-69) -sensitized and E7(67-76) -sensitized PBMCs and isolated CD8(+) CTLs showed a much greater suppression of tumor growth in vivo compared with that of control groups treated with PBS (P < .01). The authors also confirmed the synergistic antitumor effect of cisplatin followed by E7(67-76) -sensitized PBMCs in vivo.

CONCLUSIONS

E7(61-69) and E7(67-76) were identified as novel HPV type 16 E7 epitopes for HLA-A 2402, which could be used for immunotherapy against cervical cancer.

IL-6 and IL-10 in post-transplant lymphoproliferative disorders development and maintenance: a longitudinal study of cytokine plasma levels and T-cell subsets in 38 patients undergoing treatment

IL-6 and IL-10 have previously been implicated in the pathogenesis of post-transplant lymphoproliferative disorders (PTLD) and, like peripheral lymphocyte populations, are markers of immune status that are amenable to study in vivo. Thus, we analyzed cytokine plasma levels as well as lymphocyte subsets in a longitudinal analysis of 38 adult transplant recipients undergoing treatment for PTLD. Pretherapeutically, we found significantly elevated IL-6 (13.8 pg/ml) and IL-10 plasma levels (54.7 pg/ml) - in the case of IL-10, even higher in treatment nonresponders than in responders (116 vs. 14 pg/ml). Over time, however, IL-10 levels did not correlate with the course of disease, whereas those of IL-6 did, falling in responders and rising in nonresponders. These findings were independent of histological EBV-status, treatment type, and total peripheral T-cell counts, which were significantly reduced in patients with PTLD. Our observations support the idea that although IL-10 is important for creating a permissive environment for post-transplant lymphoma development, IL-6 is associated with PTLD proliferation. The analysis of lymphocyte subsets further identified HLA-DR+ CD8+ lymphocyte numbers as significantly different in non-PTLD controls (33%), treatment responders (44%) and nonresponders (70%). Although the specificity of these cells is unclear, their increase might correlate with the impaired tumor-specific cytotoxic-T-lymphocyte (CTL)-response in PTLD.

The presence of Epstein-Barr virus (EBV) in diffuse large B-cell lymphomas (DLBCLs) in Turkey: special emphasis on 'EBV-positive DLBCL of the elderly'

Accumulated evidence has shown the importance of Epstein-Barr virus in the pathogenesis of various lymphomas. This study aimed to determine the prevalence of Epstein-Barr virus expression and its effect on survival amongst diffuse large B-cell lymphoma (DLBCL) cases from two large tertiary care centres in Turkey with a particular interest in identifying cases of 'Epstein-Barr virus-positive DLBCL of the elderly'. Diffuse large B-cell lymphoma cases diagnosed between 1999 and 2009 were retrieved and 340 cases were used to construct tissue microarrays. The presence of Epstein-Barr virus small ribonucleic acids was examined by in situ hybridization using Epstein-Barr virus (EBV)-encoded small RNA (EBER) oligonucleotides. A total of 18 cases (5.3%) showed Epstein-Barr virus expression. Twelve cases were classified as Epstein-Barr virus-positive DLBCL of the elderly. Epstein-Barr virus-positive DLBCL cases showed a significantly inferior overall survival as compared with Epstein-Barr virus-negative cases (p < 0.001). In our study group Epstein-Barr virus expression is not prevalent in DLBCLs. Epstein-Barr virus-positive DLBCL of the elderly is also rare in the Turkish population. The presence of Epstein-Barr virus, however, is associated with poor prognosis.

Predictors of outcome in post-transplant lymphoproliferative disorder: an evaluation of tumor infiltrating lymphocytes in the context of clinical factors

We hypothesized that the number of tumor infiltrating cytotoxic T-cells (CTCs) and regulatory T-cells (Tregs), shown to have prognostic value in other lymphoproliferative disorders, could predict survival in post-transplant lymphoproliferative disorder (PTLD). Sixty-two patients were diagnosed with PTLD between 1987 and 2007, with 44 cases representing monomorphic B-cell PTLDs with diffuse aggressive morphologic features. Of these 44 cases, 31 had sufficient tissue for further study. On univariate analysis, high tumor infiltrating CD3(+) T-cell (> or =550/10 hpf) and TIA-1(+) CTC (> or =300/10 hpf) counts were associated with favorable overall survival (OS), PTLD-specific survival (PTLD-SS), and progression-free survival (PFS) while Treg counts were not predictive of outcome. However, on multivariate analysis, clinical factors were the most powerful predictor of PTLD outcome (performance status and CHOP as first line therapy for OS; performance status and number of extranodal sites for both PTLD-SS and PFS).

Identification of HLA-A*2402-restricted HCMV immediate early-1 (IE-1) epitopes as targets for CD8+ HCMV-specific cytotoxic T lymphocytes

Background

To identify novel HLA-A*2402-restricted human cytomegalovirus (HCMV) immediate early-1 (IE-1) epitopes for adoptive immunotherapy, we explored 120 overlapping 15-amino acid spanning IE-1.

Methods

These peptides were screened by measuring the frequency of polyclonal CD8+ T cells producing intracellular interferon-γ (IFN-γ) using flow cytometry and the epitopes were validated with a HCMV-infected target Cr release cytotoxicity assay.

Results

Initial screening was performed with 12 mini-pools of 10 consecutive peptides made from 120 overlapping peptides15-amino acids in length that spanned IE-1. When peripheral blood mononuclear cells (PBMCs) from HLA-A*2402 HCMV-seropositive donors were sensitized with each of the 12 mini-pools, mini-pools 1 and 2 induced the highest frequency of CD8+ cytotoxic T lymphocytes (CTLs) producing IFN-γ. When PBMCs were stimulated with each of the twenty peptides belonging to mini-pools 1 and 2, peptides IE-1_1–15MESSAKRKMDPDNPD and IE-1_5–19AKRKMDPDNPDEGPS induced the greatest quantities of IFN-γ production and cytotoxicity of HLA-matched HCMV-infected fibroblasts. To determine the exact HLA-A*2402-restricted epitopes within the two IE-1 proteins, we synthesized a total of twenty-one overlapping 9- or 10 amino acid peptides spanning IE-1_1–15 and IE-1_5–19. Peptide IE-1_3–12SSAKRKMDPD induced the greatest quantities of IFN-γ production and target cell killing by CD8+ CTLs.

Conclusion

HCMV IE-1_3–12SSAKRKMDPD is a HLA-A*2402-restricted HCMV IE-1 epitope that can serve as a common target for CD8+ HCMV-specific CTLs.

Age-related Epstein-Barr virus (EBV)-associated B-cell lymphoproliferative disorders: comparison with EBV-positive classic Hodgkin lymphoma in elderly patients

Age-related Epstein-Barr virus-associated B-cell lymphoproliferative disorder (aEBVLPD) is a disease group characterized by EBV-associated large B-cell lymphoma in elderly without predisposing immunodeficiency. In nearly one- third of cases, aEBVLPD occurs as a polymorphous subtype with reactive cell-rich components, bearing a morphologic similarity to classic Hodgkin lymphoma (cHL). The aim of this study was to clarify clinicopathologic differences between the polymorphic subtype of aEBVLPD (n = 34) and EBV(+) cHL (n = 108) in patients aged 50 years or older. Results showed that aEBVLPD was more closely associated with aggressive clinical parameters than cHL, with a higher age at onset (71 vs 63 years); lower male predominance (male-female ratio, 1.4 vs 3.3); and a higher rate of involvement of the skin (18% vs 2%), gastrointestinal tract (15% vs 4%), and lung (12% vs 2%). aEBVLPD was histopathologically characterized by a higher ratio of geographic necrosis, greater increase (> 30%) in cytotoxic T cells among background lymphocytes, higher positivity for CD20 and EBNA2, and absence of CD15 expression. As predicted by the clinical profile, aEBVLPD had a significantly poorer prognosis than EBV(+) cHL (P < .001). The polymorphous subtype of aEBVLPD constitutes an aggressive group with an immune response distinct from EBV(+) cHL, and requires the development of innovative therapeutic strategies.

Age-related EBV-associated B-cell lymphoproliferative disorders constitute a distinct clinicopathologic group: a study of 96 patients

PURPOSE

We have recently reported EBV+ B-cell lymphoproliferative disorders (LPD) occurring predominantly in elderly patients, which shared features of EBV+ B-cell neoplasms arising in the immunologically deteriorated patients despite no predisposing immunodeficiency and were named as senile or age-related EBV+ B-cell LPDs. To further characterize this disease, age-related EBV+ B-cell LPDs were compared with EBV-negative diffuse large B-cell lymphomas (DLBCL).

EXPERIMENTAL DESIGN

Among 1,792 large B-cell LPD cases, 96 EBV+ cases with available clinical data set were enrolled for the present study. For the control group, 107 patients aged over 40 years with EBV-negative DLBCL were selected. We compared clinicopathologic data between two groups and determined prognostic factors by univariate and multivariate analysis.

RESULTS

Patients with age-related EBV+ B-cell LPDs showed a higher age distribution and aggressive clinical features or parameters than EBV-negative DLBCLs: 44% with performance status >1, 58% with serum lactate dehydrogenase level higher than normal, 49% with B symptoms, and higher involvement of skin and lung. Overall survival was thus significantly inferior in age-related EBV+ group than in DLBCLs. Univariate and multivariate analyses further identified two factors, B symptoms and age older than 70 years, independently predictive for survival. A prognostic model using these two variables well defined three risk groups: low risk (no adverse factors), intermediate risk (one factor), and high risk (two factors).

CONCLUSIONS

These findings suggest that age-related EBV+ B-cell LPDs constitute a distinct group, and innovative therapeutic strategies such as EBV-targeted T-cell therapy should be developed for this uncommon disease.

Evaluation of apoptosis in Epstein–Barr virus-associated hemophagocytic lymphohistiocytosis

Epstein-Barr virus (EBV) is known to be a causative agent of hemophagocytic lymphohistiocytosis (HLH). To investigate association of apoptosis in the pathogenesis of EBV-associated HLH, the serum EBV loads, and serum concentrations of soluble tumor necrosis factor receptor 1 (sTNF-R1), soluble Fas ligand, and cytochrome c were examined in 15 patients with EBV-associated HLH and 24 patients with infectious mononucleosis (IM). Levels of sTNF-R1 are known to reflect the biological activity of TNF-alpha and cytochrome c is a specific marker of apoptosis. EBV loads, and concentrations of sTNF-R1 and cytochrome c were significantly higher in patients with EBV-associated HLH than in patients with IM. On the other hand, there were no statistically significant differences in the concentrations of soluble Fas ligand. In patients with EBV-associated HLH, EBV loads, concentrations of sTNF-R1, and cytochrome c were correlated with each other. These results suggest that apoptosis, which is dependent on the EBV load and could be mediated by TNF-alpha, plays a major role in the pathophysiology of EBV-associated HLH.

Post-transplant lymphoproliferative disorder

Post-transplant lymphoproliferative disorder (PTLD) is an increasingly recognized complication of solid organ and hematopoietic stem cell transplantation. PTLD represents a spectrum of polyclonal and monoclonal lymphoproliferation, generally of B cells. Prompt diagnosis is key and requires a high index of suspicion. An increasing variety of highly effective therapies, including immune modulation via reduction in immunosuppression, monoclonal antibodies, and cellular therapy, have dramatically improved the cure rates of this once devastating disease.

RELATIONSHIP BETWEEN CD8+ T-CELL PHENOTYPE AND FUNCTION, EPSTEIN-BARR VIRUS LOAD, AND CLINICAL OUTCOME IN PEDIATRIC RENAL TRANSPLANT RECIPIENTS: A PROSPECTIVE STUDY1

BACKGROUND

The authors studied the relationship between the dynamics of Epstein-Barr virus (EBV) load, CD8 T-cell activation and differentiation, and EBV-associated symptoms in 25 children after kidney transplantation (Tx).

METHODS

Twenty-two patients were enrolled at the time of Tx and three at diagnosis of EBV-induced post-transplant lymphoproliferative disease (PTLD). EBV load was serially measured by a semiquantitative method of DNA amplification in blood cells. The percentages of activated (human leukocyte antigen-DR) and of effector-memory (CD28) CD8 circulating cytolytic T lymphocytes (CTL) were serially evaluated by flow cytometry. The cytotoxic potential of CTL was assessed by a CD3-redirected cytotoxic assay.

RESULTS

For three children with post-Tx uncomplicated primary EBV infection, EBV load peaked by months 1 to 2 after Tx and declined spontaneously by months 3 to 6, whereas expansion of activated and effector-memory CTL was absent (one case) or transient and moderate (two cases). In 15 patients who were EBV-seropositive before Tx and who did not develop EBV-PTLD, transient elevation of EBV load but no noticeable changes in CTL phenotype were observed. In contrast, in one child who was also EBV-seropositive before Tx but who developed EBV-PTLD, a major and sustained elevation of EBV load and of activated and effector-memory CTL was observed. In three patients retrospectively enrolled at diagnosis of EBV-PTLD, sustained elevation of both viral load and activated T cells was also noticed. Finally, increased cytotoxic activity correlated with increased level of activated CTL.

CONCLUSIONS

An association between high and sustained T-cell activation, EBV load, and the occurrence of EBV-PTLD was observed. Furthermore, intense cytotoxic activity was observed in EBV-PTLD, with favorable outcome.

Clinical effects of infusing anti-Epstein-Barr virus (EBV)-specific cytotoxic T-lymphocytes into patients with severe chronic active EBV infection

Immune cell therapy with autologous Epstein-Barr virus (EBV)-specific cytotoxic T-lymphocytes (CTLs) or lymphokine-activated killer (LAK) cells was performed in 2 adults with severe chronic active EBV infection (SCAEBV). The patient in case 1, who had complications of pancytopenia, high fever, and massive splenomegaly, was treated with 13 doses of LAK cell infusion followed by 4 doses of autologous CTL infusion. The patient in case 2, who had liver dysfunction due to natural killer cell-type infection, was treated with 4 doses of autologous CTL infusion. In case 1, the LAK cell infusions were effective in lowering the viral load and improving several biochemical parameters (lactate dehydrogenase, soluble interleukin 2 receptor) and resulted in complete amelioration of the high fever. Subsequent infusions of autologous CTLs reduced the viral load only temporarily and were accompanied by an increase in frequency of EBV-specific T-cells in the blood. However, the patient's main problem of pancytopenia was not resolved. In case 2, infusion of autologous CTLs did not improve the patient's hepatic dysfunction or viral load but caused a significant increase in autoantibody levels. Thus the effect of auto-CTL treatment was limited or deteriorative in SCAEBV patients.

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.

Post-transplant lymphoproliferative disorder: a review

Post-transplant lymphoproliferative disorder (PTLD) represents a spectrum of Epstein-Barr virus-related (EBV) clinical diseases, from a benign mononucleosis-like illness to a fulminant non-Hodgkin's lymphoma. In the setting of hematopoietic stem cell transplantation, PTLD is an often-fatal complication occurring relatively early after transplant. Risk factors for the development of PTLD are well established, and include HLA-mismatching, T-cell depletion, and the use of antilymphocyte antibodies as conditioning or treatment of graft-versus-host disease. Early recognition of PTLD is particularly important in the SCT setting, because PTLD in these patients tends to be rapidly progressive. Familiarity with the clinical features of PTLD and a heightened level of suspicion are critical for making the diagnosis. Surveillance techniques with EBV antibody titers and/or polymerase chain reaction (PCR) may have a role in some high-risk settings. Immune-based therapies such as monoclonal anti-B-cell antibodies, interferon-alpha, and EBV-specific donor T cells, either as treatment for PTLD or as prophylaxis in high-risk patients, represent promising new directions in the treatment of this disease.

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.

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.

Ratio between Epstein-Barr viral load and anti-Epstein-Barr virus specific T-cell response as a predictive marker of posttransplant lymphoproliferative disease

BACKGROUND

Posttransplant lymphoproliferative disease (PTLD) is closely linked to primary Epstein-Barr virus (EBV) infection and a defect of EBV specific cellular immunity is supposed to be the basis of PTLD. However, EBV load is so far the only marker proposed to evaluate PTLD risk, and no study has investigated the role of specific anti-EBV T lymphocytes (EBV-TL).

METHODS

We therefore prospectively measured the EBV-TL by enzyme-linked immunospot (elispot) assay, in correlation to EBV load by real-time quantitative PCR and lymphoproliferation occurrence in 45 liver transplanted children.

RESULTS

EBV load at the time of primary infection was high in all patients irrespective to subsequent emergence of PTLD. Seven patients developed PTLD, all of them following primary EBV infection. All seven had low EBV-TL (<2/mm3) associated with high viral load (>25,000 copies/microg DNA). Both parameters can be combined in a 100% positive predictive index. Healing from lymphoma was characterized by rapid EBV-TL increase concomitant to decreasing viral load. EBV-TL follow-up helped to adapt immunomodulation. No patient had PTLD whenever EBV-TL were above 2/mm3.

CONCLUSIONS

We conclude that high viral load is systematic in patients who underwent primary EBV infection and is indicative of the PTLD risk only if there is low concomitant cellular immune response. Healing from PTLD requires modulation of immunosuppression, and appearance of EBV-TL.

Epstein-Barr virus-specific T-cell cytotoxicity is mediated through the perforin pathway in patients with lymphoproliferative disorders after allogeneic bone marrow transplantation

The in vivo cytotoxic mechanism of Epstein--Barr virus (EBV)-specific cytotoxic lymphocytes was examined in a patient who suffered with EBV-associated lymphoproliferative disease (LPD) after bone marrow transplantation (BMT). His peripheral CD8+ T-cell count was significantly increased and >70% of these cells were EBV-specific by fluorescence-activated cell sorter (FACS) analysis for interferon-gamma production. Intracellular perforin expression was markedly increased in CD8+ T cells by FACS analysis. The lymphocytes from this patient had cytotoxic activity against autologous EBV+ lymphoblastoid cell lines which were completely inhibited by concanamycin A, an inhibitor of perforin, and a anti-human leucocyte antigen (HLA)-class I monoclonal antibody. These results suggest that the cytotoxicity was mediated by the perforin, in an HLA-class I-restricted manner. We performed serial intracellular perforin analyses in another patient who also showed endogenous expansion of EBV-specific CD8+ T cells that coincided with an increased EBV-DNA load. Perforin expression in the CD8+ and CD4+ T cells paralleled the EBV-specific CD8+ T cells and EBV-DNA load, which also suggests that perforin mediates EBV-specific cytolysis in vivo and is responsible for effective immunosurveillance against EBV reactivation after BMT. Evaluation of host immunity against EBV by determining perforin expression in lymphocytes and EBV-specific lymphocytes along with quantification of EBV-DNA may be useful for predicting the clinical course of patients with EBV-associated LPD after BMT.

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.

Diagnostic testing in Epstein-Barr virus infection

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

GM-CSF and IL-2 induce specific cellular immunity and provide protection against Epstein-Barr virus lymphoproliferative disorder

Epstein-Barr virus-associated lymphoproliferative disease (EBV-LPD) is a potentially life-threatening complication in immune-deficient patients. We have used the severe combined immune deficient (SCID) mouse engrafted with human leukocytes (hu-PBL-SCID) to evaluate the use of human cytokines in the prevention of EBV-LPD in vivo. Daily low-dose IL-2 therapy can prevent EBV-LPD in the hu-PBL-SCID mouse, but protection is lost if murine natural killer (NK) cells are depleted. Here we demonstrate that combined therapy with human GM-CSF and low-dose IL-2 is capable of preventing EBV-LPD in the hu-PBL-SCID mouse in the absence of murine NK cells. Lymphocyte depletion experiments showed that human NK cells, CD8(+) T cells, and monocytes were each required for the protective effects of GM-CSF and IL-2 combination therapy. This treatment resulted in a marked expansion of human CD3(+)CD8(+) lymphocytes in vivo. Using HLA tetramers complexed with EBV immunodominant peptides, a subset of these lymphocytes was found to be EBV-specific. These data establish that combined GM-CSF and low-dose IL-2 therapy can prevent the immune deficiencies that lead to fatal EBV-LPD in the hu-PBL-SCID mouse depleted of murine NK cells, and they point to a critical role for several human cellular subsets in mediating this protective effect.