Prompt versus preemptive intervention for EBV lymphoproliferative disease

Posttransplantation lymphoproliferative disorders (PTLDs) caused by uncontrolled expansion of Epstein-Barr virus (EBV)-infected B cells after hematopoietic stem cell transplantation (HSCT) can be predicted by an increase in EBV DNA in peripheral blood mononuclear cells. We used real-time quantitative polymerase chain reaction (RQ-PCR) analysis to determine whether frequent monitoring of EBV DNA to allow preemptive treatment is truly of value in patients after HSCT. More than 1300 samples from 85 recipients were analyzed. No patient with consistently low EBV DNA levels developed PTLD. Nine patients had a single episode with a high EBV load (more than 4000 EBV copies/microg peripheral blood mononuclear cell [PBMC] DNA), and 16 patients had high EBV loads detected on 2 or more occasions. Only 8 of these developed symptoms consistent with PTLD, and all were promptly and successfully treated with EBV-specific cytotoxic T cells or CD20 monoclonal antibody. Hence, quantitative measurement of EBV DNA may best be used to enable the prompt rather than the preemptive treatment of PTLD.

Adoptive T-cell therapy for EBV-associated post-transplant lymphoproliferative disease

Increased understanding of the mechanisms by which T lymphocytes recognize virus and tumor-specific antigens has fueled the use of adoptive immunotherapy for viral and malignant diseases. An ideal candidate for such treatment is Epstein-Barr virus (EBV). EBV-associated post-transplant lymphoproliferative disorder (PTLD) is a serious complication post-solid organ transplant (SOT) or hematopoietic stem cell transplant (HSCT). The disease is essentially the result of suppression of cytotoxic T-cell function and despite various treatment strategies the course may still be fulminant and lethal. Therefore, an adoptive immunotherapeutic approach using ex vivo derived EBV-specific CTL offers a promising solution not only for the treatment but also as prophylaxis for PTLD. The infusion of EBV-CTL has been demonstrated to be safe and effective in allogeneic HSCT recipients and their use post-SOT is being evaluated.

Adoptive T-cell therapy for Epstein-Barr virus-positive Hodgkin's disease

Immunotherapy approaches with antigen-specific cytotoxic T lymphocytes (CTLs) have proved safe and effective prophylaxis and treatment of Epstein-Barr virus (EBV)-associated lymphomas arising after bone marrow transplantation. EBV is also associated with other malignancies including about 40% of cases of Hodgkin's disease making this tumor another potential target for EBV-targeted immunotherapy. While studies with autologous EBV-specific CTLs have shown antiviral activity and immune effects, the clinical responses have been less impressive than those observed in post-transplant lymphomas. There are several possible reasons why the malignant cells in EBV-positive Hodgkin's disease may be less susceptible to immunotherapy approaches, including the fact that they express a more restricted array of EBV-encoded antigens and possess many immune evasion strategies. A number of approaches to overcome these tumor evasion strategies including targeting CTLs to the expressed antigens and genetic modification of CTLs are being evaluated.

Induction of antigen-specific regulatory T cells following overexpression of a Notch ligand by human B lymphocytes

In mice, activation of the Notch pathway in T cells by antigen-presenting cells overexpressing Notch ligands favors differentiation of regulatory T lymphocytes responsible for antigen-specific tolerance. To determine whether this mechanism operates in human T cells, we used Epstein-Barr virus-positive lymphoblastoid cell lines (EBV-LCL) as our (viral) antigen-presenting cells and overexpressed the Notch ligand Jagged-1 (EBV-LCL J1) by adenoviral transduction. The EBV-LCL J1s were cocultured with autologous T cells, and the proliferative and cytotoxic responses to EBV antigens were measured. Transduction had no effect on EBV-LCL expression of major histocompatibility complex (MHC) antigens or of costimulatory molecules CD80, CD86, and CD40. However, we observed a 35% inhibition of proliferation and a >65% reduction in cytotoxic-T-cell activity, and interleukin 10 production was increased ninefold. These EBV-LCL J1-stimulated T lymphocytes act as antigen-specific regulatory cells, since their addition to fresh autologous T cells cultured with autologous nontransduced EBV-LCL cells significantly inhibited both proliferation and cytotoxic effector function. Within the inhibitory population, CD4(+)CD25(+) and CD8(+)CD25(-) T cells had the greatest activity. This inhibition appears to be antigen-specific, since responses to Candida and cytomegalovirus antigens were unaffected. Hence, transgenic expression of Jagged-1 by antigen-presenting cells can induce antigen-specific regulatory T cells in humans and modify immune responses to viral antigens.

Human telomerase reverse transcriptase-specific T-helper responses induced by promiscuous major histocompatibility complex class II-restricted epitopes

An effective tumor vaccine may require the induction of both CTL and T-helper (Th) cell responses against tumor-associated antigens. Human telomerase reverse transcriptase (hTERT) is highly expressed in >85% of cancer cells and thus is a potential target for tumor vaccines. We therefore sought to identify promiscuous Th epitopes in hTERT, which can be presented by more than one MHC class II allele. Each of 10 peptides derived from hTERT that were predicted to bind to MHC class II molecules was found to be able to induce primary human T-cell responses in vitro. We then established CD4(+) T-cell clones specific for these peptides and found that only hTERT(766) (LTDLQPYMRQFVAHL)-specific CD4(+) Th cells were effective in recognizing naturally processed hTERT antigen. We further found that the naturally processed epitopes hTERT(766) and hTERT(672) (which was identified previously) were promiscuous and capable of inducing CD4(+) T-cell responses in the context of several commonly found HLA-DR alleles, including DR1, DR7, and DR15 for hTERT(672), and DR4, DR11, and DR15 for hTERT(766). We further demonstrated that immunization of humanized HLA-DR4 transgenic mice with hTERT(766) peptide elicited antigen-specific Th responses that can recognize the antigenic peptides derived from hTERT protein and various hTERT-positive tumors, such as breast cancer, melanoma, and leukemia. It was also shown that T-cell precursors specific for the naturally processed epitopes are part of the T-cell repertoires in healthy donors and prostate cancer patients. Thus, these promiscuous, naturally processed Th epitopes in hTERT could be used to develop improved cancer vaccines through the simultaneous stimulation of CTL and Th cells against a broad spectrum of hTERT-positive tumors.

Fiber-modified adenoviruses generate subgroup cross-reactive, adenovirus-specific cytotoxic T lymphocytes for therapeutic applications

Adenovirus (Ad) infections are responsible for considerable morbidity and mortality, particularly in pediatric hematopoietic stem cell transplant (HSCT) recipients. To date there is no therapy. The present study was motivated by the potential for using adoptive immunotherapy as either prophylaxis or treatment for Ad infections and associated diseases. The authors have developed a protocol to reactivate Ad-specific memory T cells from peripheral blood mononuclear cells (PBMCs) using a clinical-grade adenoviral vector. Such lines contain a specific CD4 and CD8 T-cell component and are capable of recognizing and lysing target cells infected with wild-type Ad serotypes from different Ad groups. Furthermore, the frequency of Ad-specific precursors can be determined in PBMCs ex vivo and used as a means to assess changes in Ad-specific T-cell memory responses after infusion. This is the first report of a simple and reproducible method to activate and expand Ad-specific cytotoxic T lymphocytes (CTLs), which should be protective against the range of different Ad subtypes that affect transplant recipients.

Selective depletion of donor alloreactive T cells without loss of antiviral or antileukemic responses

Poor immune reconstitution after haploidentical stem cell transplantation results in a high mortality from viral infections and relapse. One approach to overcome this problem is to selectively deplete the graft of alloreactive cells using an immunotoxin directed against the activation marker CD25. However, the degree of depletion of alloreactive cells is variable following stimulation with recipient peripheral blood mononuclear cells (PBMCs), and this can result in graft versus host disease (GVHD). We have refined this approach using recipient Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs) as stimulators to activate donor alloreactive T cells. Our studies demonstrate that allodepletion with an anti-CD25 immunotoxin following stimulation with HLA-mismatched host LCLs more consistently depleted in vitro alloreactivity than stimulation with host PBMCs, as assessed in primary mixed lymphocyte reactions (MLRs). Allodepletion using this approach specifically abrogates cytotoxic T-cell responses against host LCLs. In interferon-gamma (IFN-gamma) enzyme-linked immunospot (ELISPOT) assays, antiviral responses to adenovirus and cytomegalovirus (CMV) were preserved following allodepletion. Likewise, using HLA-A2-pp65 tetramers, we have shown that the frequency of CMV-specific T cells is unaffected by allodepletion. Moreover, the donor anti-EBV response is partially retained by recognition of EBV antigens through the nonshared haplotype. Finally, we studied whether allodepletion affects the response to candidate tumor antigens in myeloid malignancies. Using HLA-A2-PR1 tetramer analysis, we found that the frequency of T cells recognizing the PR1 epitope of proteinase 3 was not significantly different in allodepleted and unmanipulated PBMCs from patients with chronic myeloid leukemia (CML) undergoing transplantation. Based on these data, we have embarked on a phase 1 clinical trial of addback of allo-LCL-depleted donor T cells in the haplo-identical setting.

Diagnosis and treatment of posttransplantation lymphoproliferative disease after hematopoietic stem cell transplantation

Uncontrolled expansion of donor-derived Epstein-Barr virus (EBV)-infected B cells has become a significant problem in recipients of allogeneic hematopoietic stem cell transplantations. Major risk factors for the early development of posttransplantation lymphoproliferative disease include the use of unrelated or HLA-mismatched related donors, selective T-cell depletion of donor marrow, and the use of antithymocyte globulin or monoclonal anti-T-cell antibodies for the prophylaxis and treatment of acute graft-versus-host disease. Over the past few years, the administration of in vitro-generated EBV-specific cytotoxic T cells or anti-B-cell monoclonal antibodies has provided effective options for the prophylaxis or treatment of posttransplantation lymphoproliferative disease. Advances in quantitative polymerase chain reaction-based assays allow both the precise measurement of EBV load in peripheral blood samples and the identification of high-risk patients for early initiation of therapy. A major remaining challenge is to assess the significance of an elevated EBV load posttransplantation and to determine the indications for preemptive treatment.

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.

The dynamics of herpesvirus and polyomavirus reactivation and shedding in healthy adults: a 14-month longitudinal study

Humans are infected with viruses that establish long-term persistent infections. To address whether immunocompetent individuals control virus reactivation globally or independently and to identify patterns of sporadic reactivation, we monitored herpesviruses and polyomaviruses in 30 adults, over 14 months. Epstein-Barr virus (EBV) DNA was quantitated in saliva and peripheral blood mononuclear cells (PBMCs), cytomegalovirus (CMV) was assayed in urine, and JC virus (JCV) and BK virus (BKV) DNAs were assayed in urine and PBMCs. All individuals shed EBV in saliva, whereas 67% had >or=1 blood sample positive for EBV. Levels of EBV varied widely. CMV shedding occurred infrequently but occurred more commonly in younger individuals (P<.03). JCV and BKV virurias were 46.7% and 0%, respectively. JCV shedding was age dependent and occurred commonly in individuals >or=40 years old (P<.03). Seasonal variation was observed in shedding of EBV and JCV, but there was no correlation among shedding of EBV, CMV, and JCV (P>.50). Thus, adults independently control persistent viruses, which display discordant, sporadic reactivations.

Large-scale expansion of dendritic cell-primed polyclonal human cytotoxic T-lymphocyte lines using lymphoblastoid cell lines for adoptive immunotherapy

Dendritic cells (DCs) have been shown to activate cytotoxic T-lymphocytes (CTLs) for many tumor and virus-associated antigens in vitro. In this study, the authors tested the feasibility of using DCs to expand polyclonal, cytomegalovirus (CMV)-specific CTL lines for adoptive immunotherapy. Two stimulations with DCs expressing pp65, the immunodominant antigen of CMV, effectively activated and expanded MHC-class I restricted, CMV-specific CTLs from peripheral blood mononuclear cells. However, limiting monocyte-derived DC numbers precluded the authors from expanding the CTLs to the numbers required for adoptive transfer protocols. Nonspecific stimulation methods failed to expand CTL lines specifically. However, the authors found that lymphoblastoid cell lines (LCLs) expressing pp65 expanded pp65-specific CTL lines without competition from EBV-specific CTLs. An unlimited source of antigen presenting cells that could present antigen in the appropriate MHC context emerged as a critical point for expansion of polyclonal, antigen-specific CTL lines.

Identification of a naturally processed HLA-DR-restricted T-helper epitope in Epstein-Barr virus nuclear antigen type 1

Epstein-Barr virus nuclear antigen type 1 (EBNA1), the only viral protein that is unequivocally expressed in all Epstein-Barr virus (EBV)-associated malignant diseases, is essential for viral DNA replication and maintenance of the viral episome in infected cells. A glycine-alanine repeat domain inhibits antigen processing through the ubiquitin-proteasome pathway for presentation on human leukocyte antigen (HLA) class I molecules. EBNA1 is not protected from the HLA class II processing pathway, and CD4+ HLA class II-restricted T cells recognize the antigen. CD4+ T-helper (Th) cells play critical roles in initiating, regulating, and maintaining immune responses against viral infections and tumors, so that inclusion of EBNA1 as a target antigen may improve immunotherapy for EBV-associated cancers. In this study, the authors used the TEPITOPE software program to predict promiscuous class II epitope candidates. After several HLA-DR-restricted peptides were identified by in vitro analysis of the T-cell response to synthetic peptides, a T-cell clone was established that was specific for one of the peptides. Functional studies were performed with this clone. The CD4+ T helper cells specific for the HLA-DR15-restricted peptide EBNA1(482) (AEGLRALLARSHVER) recognized naturally processed EBNA1 protein. This epitope was presented by several HLA-DR alleles, including DR4, DR7, and DR11. The inclusion of the promiscuous, naturally processed EBNA1(482) epitope in vaccine constructs could enhance immune responses against EBV-positive cancers.

Immunotherapy for Hodgkin's disease

EBV proteins present in the malignant Hodgkin Reed-Sternberg (HR-S) cells of about 40% of patients with Hodgkin's Disease (HD) provide targets for immunotherapy with virus-specific cytotoxic T lymphocytes (CTL). However, Hodgkin tumors use multiple strategies to avoid CTL, including down-regulation of immunodominant EBV antigens, and secretion of cytokines and chemokines such as TGF-beta, that inhibit the activation of CTL and professional antigen-presenting cells (APC). To be effective against this tumor, CTL must resist some or all of these strategies. Thirteen patients with multiply-relapsed HD received EBV-specific CTL, generated ex vivo using the autologous EBV-transformed B cells (LCL) as stimulator cells. After CTL infusion, EBV-specific immunity increased, virus load decreased, CTL homed to sites of malignancy and persisted for up to ten months. Clinically, CTL produced resolution of B symptoms and mixed tumor responses including one complete remission of residual disease remaining after autologous bone marrow transplant. However, no complete remission of bulky disease was achieved. Although LMP2-specific CTL activity could be detected in some of the infused CTL lines, they were present in low frequency. In pre-clinical studies, LMP1 and LMP2-specific CTL could be produced by stimulating PBMC from patients and normal donors with autologous dendritic cells expressing LMP1 or LMP2 from adenoviral vectors. Further, CTL could be rendered resistant to the devastating effects of TGF-beta by transduction with a retrovirus vector expressing a dominant-negative TGF-beta receptor, while transgenic IL-12 could increase the expression of Th1 and decrease that of Th2 cytokines. Future clinical studies will test the efficacy of CTL with improved antigen-specificity and resistance to Hodgkin immune evasion strategies.

Targeting CD19 with genetically modified EBV-specific human T lymphocytes

Human Epstein-Barr virus-specific T cells were genetically modified to express chimeric receptors specific for human CD19, which is expressed on the cell surface of most B cell malignancies. The receptor-modified EBV-specific T cells can be expanded and maintained long term in the presence of EBV-infected B cells. They recognize autologous EBV-infected targets through their conventional T cell receptor, and allogeneic EBV-infected targets and tumor targets through their chimeric receptor. They efficiently lyse both EBV and CD19-positive tumor targets in the absence of background cytotoxicity against CD19-negative targets. Donor-derived EBV-specific T cells expressing chimeric anti-tumor receptors may represent a source of effector cells that could be safely administered to leukemia patients to eradicate minimal residual disease after allogeneic bone marrow transplantation.

Generating CTLs against the subdominant Epstein-Barr virus LMP1 antigen for the adoptive immunotherapy of EBV-associated malignancies

The Epstein-Barr virus (EBV)-encoded LMP1 protein is expressed in EBV-positive Hodgkin disease and is a potential target for cytotoxic T-lymphocyte (CTL) therapy. However, the LMP1-specific CTL frequency is low, and so far the generation of LMP1-specific CTLs has required T-cell cloning. The toxicity of LMP1 has prevented the use of dendritic cells (DCs) for CTL stimulation, and we reasoned that an inactive, nontoxic LMP1 mutant (DeltaLMP1) could be expressed in DCs and would enable the activation and expansion of polyclonal LMP1-specific CTLs. Recombinant adenoviral vectors expressing LMP1 or DeltaLMP1 were tested for their ability to transduce DCs. LMP1 expression was toxic within 48 hours whereas high levels of DeltaLMP1 expression were achieved with minimal toxicity. DeltaLMP1-expressing DCs were able to reactivate and expand LMP1-specific CTLs from 3 healthy EBV-seropositive donors. LMP1-specific T cells were detected by interferon-gamma (IFN-gamma) enzyme-linked immunospot assay (ELISPOT) assays using the HLA-A2-restricted LMP1 peptide, YLQQNWWTL (YLQ). YLQ-specific T cells were undetectable (less than 0.001%) in donor peripheral blood mononuclear cells (PBMCs); however, after stimulation the frequency increased to 0.5% to 3.8%. Lysis of autologous target cells by CTLs was dependent on the level of LMP1 expression. In contrast, the frequency of YLQ-specific CTLs in EBV-specific CTLs reactivated and expanded using lymphoblastoid cell lines was low and no LMP1-specific cytotoxic activity was observed. Thus, DeltaLMP1 expression in DCs is nontoxic and enables the generation of LMP1-specific CTLs for future adoptive immunotherapy protocols for patients with LMP1-positive malignancies such as EBV-positive Hodgkin disease. Targeting LMP1 in these malignancies may improve the efficacy of current adoptive immunotherapy approaches.

Identification of HLA-DP3-restricted peptides from EBNA1 recognized by CD4(+) T cells

The EBV-encoded nuclear antigen 1 (EBNA1) is required for the maintenance and replication of the viral episome in EBV-transformed human B-lymphoblastoid cell lines. It is expressed in all EBV-associated tumors, making it a potentially important target for immunotherapy. However, this promise has not been realized, because an endogenously processed MHC class I-restricted T-cell epitope remains to be identified, and relatively little is known about MHC class II-restricted helper epitopes in the molecule. In this report, we identify a T-cell peptide derived from EBNA1 that is recognized by CD4(+) T cells. More importantly, EBNA1-specific, HLA-DP3-restricted CD4(+) T cells are capable of recognizing MHC class II-matched Burkitt's lymphoma cells, autologous peripheral blood mononuclear cells loaded with the purified EBNA1 protein, as well as target cells transfected with Ii-EBNA1 cDNA. These new findings demonstrate that EBNA1 is processed endogenously and presented to T cells by MHC class II molecules, and, hence, may be useful to incorporate into cancer vaccines to enhance antitumor immunity against EBV-associated tumors.

Autologous Epstein-Barr virus (EBV)-specific cytotoxic T cells for the treatment of persistent active EBV infection

Chronic active Epstein-Barr virus (CAEBV) infection syndrome is a heterogeneous EBV-related disorder characterized by chronic fatigue, fever, lymphadenopathy, and/or hepatosplenomegaly, associated with abnormal patterns of antibody to EBV. CAEBV can range from disabling mild/moderate forms to rapidly lethal disorders. Even patients with mild/moderate disease frequently suffer adverse effects from long-term anti-inflammatory agents and have a quality of life that progressively deteriorates. It is still unknown why these individuals are unable to produce an effective immune response to control EBV, and no effective treatment is currently available. Since ex vivo-expanded EBV-specific cytotoxic T lymphocytes (EBV-CTLs) can safely restore EBV-specific cellular immune responses in immunodeficient patients, we assessed the possibility that adoptive immunotherapy might also effectively treat CAEBV infection. Following stimulation with irradiated EBV-transformed lymphoblastoid cell lines (LCLs), EBV-CTLs were successfully generated from 8 of 8 patients with the mild/moderate form of CAEBV infection. These CTLs were predominantly CD3(+) CD8(+) cells and produced specific killing of the autologous LCLs. There were 5 patients with 1- to 12-year histories of disease who were treated with 1 to 4 injections of EBV-CTLs. Following infusion, there was resolution of fatigue and malaise, disappearance of fever, and regression of lymphadenopathy and splenomegaly. The pattern and titers of anti-EBV antibodies also normalized. No toxicity was observed. There were 4 patients who did not show any relapse of disease within 6 to 36 months follow-up; one patient had recurrence of fatigue and myalgia one year after CTL infusion. We suggest that adoptive immunotherapy with autologous EBV-CTLs may represent a safe and feasible alternative treatment for patients affected with mild/moderate CAEBV infection and that this approach should be evaluated in the more severe forms of the disease.

Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes for the prevention and treatment of EBV-associated post-transplant lymphomas

The Epstein-Barr virus (EBV)-associated lymphoproliferative disorders (LPD) that occur in individuals immunosuppressed by solid organ transplant (SOT) or T cell-depleted stem cell transplantation (SCT) are unequivocally a result of T cell dysfunction. Reconstitution of "at-risk" patients with EBV-specific cytotoxic T lymphocyte (CTL) lines that have been reactivated and expanded in vitro, should prevent the development of post-transplant lymphoproliferative disease or treat pre-existing disease. We have provided over 125 infusions of donor-derived EBV-specific CTL to 60 recipients of T cell-depleted stem cells. As prophylaxis, infusions were safe and effective, as no patient developed EBV-LPD, in contrast to 11.5% of controls who did not receive CTL. The CTL-reconstituted cellular immune responses to EBV, persisted for up to 80 months following infusion and reduced the high virus load seen in about 12% of patients. CTL were also effective in two of three patients who received CTL as treatment for fulminant disease. SOT recipients are also good candidates for CTL therapy, but present problems not seen in bone marrow transplant recipients. First the CTL product must be autologous, since the majority of tumors are recipient-derived and allogeneic CTL are unlikely to survive in vivo. Second most patients continue to receive immunosuppressive drugs, which may compromise the function of infused CTL. Third, unlike SCT recipients SOT recipients do not have an empty niche for EBV-specific CTL. Finally, standard protocols are not effective in generating CTL from seronegative recipients of EBV-carrying organs, who are the patients most at risk for the development of EBV-LPD. For CTL to be an option for the management of EBV in these patients, a sensitive and specific assay for the prediction of high-risk patients is required as well as an effective method for the generation of EBV-specific CTL from seronegative recipients.

Adapting a transforming growth factor beta-related tumor protection strategy to enhance antitumor immunity

Transforming growth factor beta (TGF-beta), a pleiotropic cytokine that regulates cell growth and differentiation, is secreted by many human tumors and markedly inhibits tumor-specific cellular immunity. Tumors can avoid the differentiating and apoptotic effects of TGF-beta by expressing a nonfunctional TGF-beta receptor. We have determined whether this immune evasion strategy can be manipulated to shield tumor-specific cytotoxic T lymphocytes (CTLs) from the inhibitory effects of tumor-derived TGF-beta. As our model we used Epstein-Barr virus (EBV)-specific CTLs that are infused as treatment for EBV-positive Hodgkin disease but that are vulnerable to the TGF-beta produced by this tumor. CTLs were transduced with a retrovirus vector expressing the dominant-negative TGF-beta type II receptor HATGF-betaRII-Deltacyt. HATGF-betaRII-Deltacyt- but not green fluorescence protein (eGFP)-transduced CTLs was resistant to the antiproliferative and anticytotoxic effects of exogenous TGF-beta. Additionally, receptor-transduced cells continued to secrete cytokines in response to antigenic stimulation. TGF-beta receptor ligation results in phosphorylation of Smad2, and this pathway was disrupted in HATGF-betaRII-Deltacyt-transduced CTLs, confirming blockade of the signal transduction pathway. Long-term expression of TGF-betaRII-Deltacyt did not affect CTL function, phenotype, or growth characteristics. Tumor-specific CTLs expressing HATGF-betaRII-Deltacyt should have a selective functional and survival advantage over unmodified CTLs in the presence of TGF-beta-secreting tumors and may be of value in treatment of these diseases.

Epstein-Barr virus-specific human T lymphocytes expressing antitumor chimeric T-cell receptors: potential for improved immunotherapy

Primary T cells expressing chimeric receptors specific for tumor or viral antigens have considerable therapeutic potential. Unfortunately, their clinical value is limited by their rapid loss of function and failure to expand in vivo, presumably due to the lack of costimulator molecules on tumor cells and the inherent limitations of signaling exclusively through the chimeric receptor. Epstein-Barr virus (EBV) infection of B lymphocytes is near universal in humans and stimulates high levels of EBV-specific helper and cytotoxic T cells, which persist indefinitely. Our clinical studies have shown that EBV-specific T cells generated in vitro will expand, persist, and function for more than 6 years in vivo. We now report that EBV-specific (but not primary) T cells transduced with tumor-specific chimeric receptor genes can be expanded and maintained long-term in the presence of EBV-infected B cells. They recognize EBV-infected targets through their conventional T-cell receptor and tumor targets through their chimeric receptors. They efficiently lyse both. EBV-specific T cells expressing chimeric antitumor receptors may represent a new source of effector cells that would persist and function long-term after their transfer to cancer patients.

Generation of EBV-specific CD4+ cytotoxic T cells from virus naive individuals

Adoptive immunotherapy with EBV-specific CTL (EBV-CTL) effectively prevents and treats EBV-driven lymphoproliferation in immunocompromised hosts. EBV-seronegative solid organ transplant recipients are at high risk of EBV-driven lymphoproliferation because they lack EBV-specific memory T cells. For the same reason, standard techniques for generating EBV-CTL in vitro from EBV-naive individuals are unsuccessful. To overcome this problem, we compared several methods of expanding EBV-CTL from seronegative adults and children. First, the standard protocol, using EBV-transformed lymphoblastoid B cell lines (LCL) as the source of APC, was compared with protocols using EBV-Ag-loaded dendritic cells as APC. Surprisingly, the standard protocol effectively generated CTL from all seronegative adults. The additional finding of EBV-DNA in the peripheral blood of three of these four adults suggested that some individuals may develop cellular, but not humoral, immune responses to EBV. By contrast, LCL failed to reactivate EBV-CTL from any of the six EBV-seronegative children. EBV-Ag-loaded dendritic cells could expand EBV-CTL, but only in a minority of children. However, the selective expansion of CD25-expressing T cells, 9-11 days after activation with LCL alone, proved to be a simple and reliable method for generating EBV-CTL from all seronegative children. The majority of these CTL were CD4(+) (71 +/- 26%) and demonstrated HLA class II-restricted, EBV-specific killing. Our results suggest that a negative EBV serology does not accurately identify EBV-negative individuals. In addition, our method for selecting EBV-specific CTL from naive individuals by precursor cell enrichment may be applicable to the immunotherapy of cancer patients with a low frequency of tumor- or virus-specific CTL.

Immunotherapy to reconstitute immunity to DNA viruses

Defects in cytotoxic T-lymphocyte (CTL) function after hemopoietic stem cell transplantation (HSCT) are associated with an increased frequency and severity of viral diseases. Initial investigations of viral infections in immunosuppressed mice and subsequent clinical studies of cytomegalovirus (CMV) and Epstein-Barr virus (EBV) in human stem cell transplant patients have suggested that adoptive transfer of virus-specific T cells may restore protective immunity and control established infections. Current efforts focus on optimizing adoptive immunotherapy approaches and developing strategies for generating T cells specific for multiple viruses to provide broader protection.

Generation of autologous Epstein-Barr virus-specific cytotoxic T cells for adoptive immunotherapy in solid organ transplant recipients

BACKGROUND

Epstein-Barr virus (EBV)-driven posttransplant lymphoproliferative disorders (PTLD) affect 2%-27% of solid organ transplant (SOT) recipients. Adoptive immunotherapy may have therapeutic potential in this setting, but there is little experience in generating autologous EBV-specific cytotoxic T-cell lymphocytes (EBV-CTLs) from SOT recipients, and their efficacy and persistence in an immunosuppressed environment is unknown.

METHODS

EBV-CTLs were generated from eight SOT recipients, using weekly stimulations with autologous lymphoblastoid cell lines (LCLs) and interleukin-2. CTL phenotype and function were evaluated in the presence of therapeutic concentration of cyclosporin A or FK506.

RESULTS

In all cases, CTLs expanded with normal kinetics. The majority was CD3+CD8+ (mean, 76%), with less than 3% of natural killer cells. All ex vivo-generated CTLs produced significantly higher killing of autologous LCLs than of HLA-mismatched LCLs (mean, 56% vs. 14% at 20:1 ratio). No lysis of autologous or allogeneic PHA blasts was observed. The CTL expansion rate was reduced in a concentration-dependent manner in the presence of immunosuppressive drugs; however, neither lytic activity nor phenotype was affected.

CONCLUSIONS

Using methods that are approved for clinical application, EBV-CTLs can be generated from SOT recipients, even those with frank lymphoma, or who are receiving immunosuppressive drugs. These CTLs retain their function in the presence of immunosuppressive agents. Although in vivo efficacy, safety, and persistence can be assessed only in clinical trials, our results suggest that CTLs can be effective for the treatment of PTLD, even when immunosuppression cannot be reduced because of the high risk of graft rejection.

Adenoviral gene transfer into dendritic cells efficiently amplifies the immune response to LMP2A antigen: a potential treatment strategy for Epstein-Barr virus--positive Hodgkin's lymphoma

The EBV-encoded LMP2A protein is consistently expressed in EBV(+) Hodgkin's lymphoma and can be targeted by CTLs. CTLs stimulated conventionally by LCLs have little activity against LMP2A(+) target cells. Here, we describe an alternative approach, based on the in vitro stimulation of CTLs with DCs genetically modified with 2 E1/E3-deleted recombinant adenoviruses, AdGFPLMP2A, encoding a fusion gene of GFP and LMP2A, and AdLMP2A, encoding LMP2A only. Transduction of DCs with AdGFPLMP2A at MOI 1,000 resulted in LMP2A expression in up to 88% of DCs. LMP2A protein was expressed in 40% of DCs transduced with AdLMP2A at an MOI of 100. Higher MOI resulted in DC death. CTL lines activated by transduced DCs had a higher frequency of LMP2A tetramer-specific CTLs than CTL lines activated by LCLs. CTLs stimulated with transduced DCs lysed both autologous fibroblasts infected with vaccinia virus LMP2A (FBvaccLMP2A) and autologous LCLs, which express LMP2A at lower levels. In contrast, CTLs generated from the same donors by stimulation with autologous LCLs showed minimal lysis of FBvaccLMP2A. Moreover, 1 donor who did not respond to LMP2A when CTLs were stimulated with LCLs became a responder when LMP2A was expressed by transduced DCs. Hence, recombinant adenoviruses encoding LMP2A effectively transduce DCs and direct the generation of LMP2A-specific CTLs. This approach will be a potent strategy in Hodgkin's lymphoma immunotherapy.

An Epstein-Barr virus deletion mutant associated with fatal lymphoproliferative disease unresponsive to therapy with virus-specific CTLs

There is a growing interest in using antigen-specific T cells for the treatment of human malignancy. For example, adoptive transfer of Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) has been effective prophylaxis and treatment of EBV-associated lymphoproliferative disease in immunocompromised patients. For all immunotherapies, however, there has been a hypothetical concern that mutations in tumor-specific antigens may lead to tumor escape. We now demonstrate that such events may indeed occur, with lethal outcome. A patient who developed lymphoma after marrow transplantation received donor-derived, EBV-specific CTLs but died with progressive disease. The tumor cells proved substantially less sensitive to cytolysis than the EBV-transformed B-cell line used for CTL generation. The major cytolytic activity of the donor CTL was directed against 2 HLA-A11-restricted epitopes in the viral EBNA-3B antigen. Sequence analysis of this gene in the tumor virus revealed a 245-base pair deletion, which removed these 2 CTL epitopes. Hence, the viral antigen in the tumor had mutated in a way that allowed escape from CTLs. Analysis of EBV polymorphisms demonstrated that before CTL infusion, more than one virus was present, including a virus with wild-type EBNA-3B. After CTL infusion, only the virus with the EBNA-3B deletion could be detected, suggesting that the infused CTLs had selected a resistant strain in vivo. Such an occurrence, even when polyclonal CTL lines are used against genetically stable virus antigens, suggests that escape mutants may be a serious problem when CTL therapy is directed against more unstable tumor cell-derived targets.

The use of cytotoxic t cells for the prevention and treatment of epstein-barr virus induced lymphoma in transplant recipients

Epstein-Barr Virus Lymphoproliferative Diseases (EBV-LPD) can affect patients receiving allogeneic hemopoietic stem cell or solid organ transplant. They are caused by impairment of EBV specific CD8+ cytotoxic T-lymphocyte (CTL) response due to the immunosuppression that follows these procedures. Despite different therapies LPD can still have a rapid and lethal course. A promising solution is the application of adoptive immunotherapy approaches such as ex vivo generated EBV-specific CTLs for prevention and therapy. Their infusion has been demonstrated to be safe and effective in allogeneic hemopoietic stem cell transplant recipients and their use after allogeneic solid organ transplant is also under evaluation.

CD20 monoclonal antibody (rituximab) for therapy of Epstein-Barr virus lymphoma after hemopoietic stem-cell transplantation

After bone marrow transplantation (BMT) using T-cell-depleted marrow from an unrelated donor or HLA-mismatched related donor, the risk of developing lymphoproliferative disease associated with the Epstein-Barr virus (EBV) ranges from 1% to 25%. We have shown that administration of donor-derived EBV-specific cytotoxic T lymphocytes (CTL) is effective prophylaxis and treatment for this complication, and we routinely generate CTL for high-risk patients. However, EBV lymphoma can occur in recipients of matched-sibling transplants for whom CTL are unavailable or in patients for whom CTL administration is contraindicated. We report on 3 such patients, who were successfully and safely treated with rituximab, a CD20 monoclonal antibody. The patients remain disease free 7, 8, and 9 months, respectively, after therapy. We conclude that CD20 antibody may be a useful alternative treatment strategy in patients with EBV lymphoma after BMT. (Blood. 2000;95:1502-1505)

Transduction of human PBMC-derived dendritic cells and macrophages by an HIV-1-based lentiviral vector system

Professional antigen-presenting cells, such as dendritic cells (DCs) and macrophages, are target cells for gene therapy of infectious disease and cancer. However, transduction of DCs and macrophages has proved difficult by most currently available gene transfer methods. Several recent studies have shown that lentiviral vector systems can efficiently transduce many nondividing and differentiated cell types. In this study, we examined the gene transfer to DCs and macrophages using a lentiviral vector system. Human DCs were propagated from the adherent fraction of peripheral blood mononuclear cells (PBMCs) by culture in medium containing GM-CSF, IL-4, and TNF-alpha. Human macrophages were propagated from adherent PBMCs in medium containing GM-CSF. High titers of a replication-defective vesicular stomatitis virus glycoprotein G pseudotyped HIV-1-based vector encoding the enhanced yellow fluorescent protein were produced. In immature DCs (culture days 3 and 5), transduction efficiencies of 25 to 35% were achieved at a multiplicity of infection of 100. However, the transduction efficiency was decreased in more mature DCs (culture day 8 or later). Furthermore, monocyte-derived macrophages were also transduced by the lentiviral vector system. In addition, Alu-LTR PCR demonstrated the integration of the HIV-1 provirus into the cellular genome of the transduced DCs and macrophages. Allogeneic mixed lymphocyte reactions revealed similar antigen-presenting functions of untransduced and lentivirally transduced DCs. Thus, the results of this study demonstrate that both PBMC-derived DCs and macrophages can be transduced by lentiviral vectors.

Transfer of EBV-specific CTL to prevent EBV lymphoma post bone marrow transplant

EBV-associated lymphoproliferative disorders (EBV-LPD) are a significant problem after hemopoietic stem cell transplantation from unrelated donors or mismatched family members. Risk factors include T-cell depletion, MHC mismatch, and intensity of immunosuppression. New therapeutic strategies involve cellular immunotherapy approaches and both donor T-cells and EBV-specific cytotoxic T lymphocytes (CTLs) have proven to be effective therapies. EBV-specific CTL has also proved to have a major impact on the incidence of this complication when used prophylactically.

Autoimmune disease induced by dendritic cell immunization against leukemia

Induction of an optimal immune response will likely be a prerequisite for successful immunotherapy of human leukemias and other malignancies. Dendritic cells are highly effective at inducing an immune response to antigens to which the host is unresponsive, while transgenic expression of the costimulator molecule CD40 ligand (gp39/CD154) and the T cell growth factor interleukin 2 (IL2) are also able to augment immune responsiveness. We therefore investigated whether a combination of these two distinctive approaches to immunostimulation could safely increase the anti-tumor immune response compared to each stimulus alone. We injected BALB/CBYJ mice with syngeneic dendritic cells (DC) exposed to A20 lymphoblastic leukemia cell-derived peptides and proteins which had been acid-eluted from the cell surface. In additional mice, the pulsed DC were mixed with genetically modified syngeneic fibroblasts that were expressing CD40 ligand or secreting interleukin 2 (IL2). Three days after their third, weekly, vaccination, they were challenged with parental A20 cells. Tumor growth was suppressed by responses to pulsed DC alone (P < 0.02). This suppression was further enhanced when pulsed DC were coinjected with fibroblasts expressing CD40 ligand and IL2 (P < 0.0005 compared to DC alone) even though CD40 ligand and IL2-expressing fibroblasts alone offered no significant protection in this model. Mice receiving the full complement of immunostimulants either failed to develop visible tumors or developed small tumors which quickly necrosed and regressed, allowing the mice to become long term tumor-free survivors. Antibody mediated depletion of either CD4+ or CD8+ T-cell subset significantly reduced the level of protection afforded by the vaccination. However, it became evident that this intensive stimulation of the immune system lead not only to tumor eradication but also to destruction of cells bearing normal self antigens. Hence, 60 days after challenge with A20 cells all mice in the DC/IL2/CD40 ligand group developed a severe, systemic autoimmune disorder that resembled graft versus host disease and manifest itself by significant peripheral blood cytotoxicity against autologous fibroblasts, blood dyscrasias, gross hepatosplenomegaly, cachexia and fur loss. This phenomenon depended on CD8+ cytotoxic T lymphocytes. Our results therefore suggest that the most effective strategies of immunotherapy against leukemia may also exceed the threshold of anergic cells, leading to a loss of self tolerance to normal self-antigens and the induction of an CD8+ anti-self effector response.

Lymphoproliferative disorders involving Epstein-Barr virus after hemopoietic stem cell transplantation

Lymphoproliferative disorders involving uncontrolled expansion of donor-derived B cells infected with Epstein-Barr virus (EBV) are a significant problem after hemopoietic stem cell transplantation. Risk factors, which include T cell depletion, major histocompatibility complex mismatch, and intensity of immunosuppression illustrate the importance of T cell immune surveillance. Recent studies have identified viral and host factors that affect the T-cell response to EBV. Monitoring EBV load in the blood by polymerase chain reaction allows early identification of high-risk patients and early institution of therapy. Adoptive immunotherapy approaches using donor T cells have proven effective and EBV-specific cytotoxic T lymphocytes have also been used successfully for prophylaxis. The simplest way of preventing EBV lymphoproliferation, however, may be to deplete B cells from the donor marrow prior to infusion to prevent the transmission of EBV-infected B cells.

Treatment of relapsed Hodgkin's disease using EBV-specific cytotoxic T cells

Donor-derived Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTL) are successful in the prevention and treatment of Epstein-Barr virus (EBV)-associated lymphoproliferative disease (LPD) in allogeneic bone marrow transplant (BMT) recipients [1, 2]. This finding prompted us to use a similar approach to the treatment of relapsed EBV-positive Hodgkin's disease [3]. Autologous EBV-specific CTL lines could be generated on the first or second attempt from 11 of 15 patients with Hodgkin's disease. Peripheral blood TCR zeta-chain levels were low, but increased in the activated CTL lines. Three patients have received gene-marked autologous CTL. The first two patients experienced alleviation of stage B symptoms and a drop in peripheral blood EBV load. However, this situation reversed between 6 and 12 weeks after infusion, when chemotherapy and radiation were reinstated. Both patients eventually progressed and died. The third patient had a pleural effusion, which increased after CTL infusion. Analysis of the pleural effusion revealed both tumor cells and levels of marker gene over 100 fold greater than in peripheral blood. The infused CTL line showed activity against LMP2. The patient initially improved and then remained stable for over eight months after CTL infusion, but now has progressive disease. We currently are evaluating methods for introducing the LMP2 gene into dendritic cells and using these to present LMP2 to autologous T cells. Using both retrovirus and herpesvirus vectors to express LMP2 in dendritic cells, LMP2-specific CTL were successfully generated from individuals who were EBV-seronegative or who were non-responsive to LMP2 when presented on autologous LCL. In future protocols, LMP2-specific CTL will be used for treatment.

Characterization of mutations in the gene doublecortin in patients with double cortex syndrome

Mutations in the X-linked gene doublecortin, which encodes a protein with no dear structural homologues, are found in pedigrees in which affected females show "double cortex" syndrome (DC; also known as subcortical band heterotopia or laminar heterotopia) and affected males show X-linked lissencephaly. Mutations in doublecortin also cause sporadic DC in females. To determine the incidence of doublecortin mutations in DC, we investigated a cohort of eight pedigrees and 47 sporadic patients with DC for mutations in the doublecortin open reading frame as assessed by single-stranded conformational polymorphism analysis. Mutations were identified in each of the eight DC pedigrees (100%), and in 18 of the 47 sporadic DC patients (38%). Identified mutations were of two types, protein truncation mutations and single amino acid substitution mutations. However, pedigrees with DC displayed almost exclusively single amino acid substitution mutations, suggesting that patients with these mutations may have less of a reproductive disadvantage versus those patients with protein truncation mutations. Single amino acid substitution mutations were tightly clustered in two regions of the open reading frame, suggesting that these two regions are critical for the function of the Doublecortin protein.

Infusion of cytotoxic T cells for the prevention and treatment of Epstein-Barr virus-induced lymphoma in allogeneic transplant recipients

Epstein-Barr virus (EBV) causes potentially lethal immunoblastic lymphoma in up to 25% of children receiving bone marrow transplants from unrelated or HLA-mismatched donors. Because this complication appears to stem from a deficiency of EBV-specific cytotoxic T cells, we assessed the safety and efficacy of donor-derived polyclonal (CD4(+) and CD8(+)) T-cell lines as immunoprophylaxis and treatment for EBV-related lymphoma. Thirty-nine patients considered to be at high risk for EBV-induced lymphoma each received 2 to 4 intravenous infusions of donor-derived EBV-specific T lymphocytes, after they had received T-cell-depleted bone marrow from HLA-matched unrelated donors (n = 33) or mismatched family members (n = 6). The immunologic effects of this therapy were monitored during and after the infusions. Infused cells were identified by detection of the neo marker gene. EBV-specific T cells bearing the neo marker were identified in all but 1 of the patients. Serial analysis of DNA detected the marker gene for as long as 18 weeks in unmanipulated peripheral blood mononuclear cells and for as long as 38 months in regenerated lines of EBV-specific cytotoxic T cells. Six patients (15.5%) had greatly increased amounts of EBV-DNA on study entry (>2, 000 genome copies/10(6) mononuclear cells), indicating uncontrolled EBV replication, a complication that has had a high correlation with subsequent development of overt lymphoma. All of these patients showed 2 to 4 log decreases in viral DNA levels within 2 to 3 weeks after infusion and none developed lymphoma, confirming the antiviral activity of the donor-derived cells. There were no toxic effects that could be attributed to prophylactic T-cell therapy. Two additional patients who did not receive prophylaxis and developed overt immunoblastic lymphoma responded fully to T-cell infusion. Polyclonal donor-derived T-cell lines specific for EBV proteins can thus be used safely to prevent EBV-related immunoblastic lymphoma after allogeneic marrow transplantation and may also be effective in the treatment of established disease.

Immunotherapy for Epstein-Barr virus-associated cancers

Epstein-Barr virus (EBV)-associated lymphoproliferative disease (EBV-LPD) is a frequently fatal complication of organ transplantation and human immunodeficiency virus (HIV) infection. We have studied the safety and efficacy of adoptively transferred, gene-marked virus-specific cytotoxic T lymphocytes (CTLs) as prophylaxis and treatment of EBV-LPD in recipients of T-cell-depleted allogeneic bone marrow. In 42 patients treated prophylactically, no toxicity was experienced. None of these patients developed EBV-LPD, in contrast with eight of 53 (15%) patients who did not receive prophylactic CTL. Three patients who had not received CTL developed aggressive disease and received CTL as treatment. Gene-marked CTL homed to tumor sites and selective accumulation of marker gene was detected in tumor tissues. Tumors regressed completely in two patients, but the third died of respiratory failure. Infused CTLs persisted for up to 3 years in vivo, they rapidly reconstituted EBV-specific immune responses to levels seen in normal individuals, and they reduced high viral titers by two to three logs. We are now using autologous EBV-specific CTL to treat patients with relapsed EBV-positive Hodgkin's disease and we are developing methods for the generation of antigen-specific lines. This approach could be applied to patients with HIV who develop EBV-LPD, using CTL derived early in the course of HIV infection.

Gene and cell transfer for specific immunotherapy

The realisation that human tumor cells may express and process tumor specific and tumor associated antigens has increased interest in immunotherapeutic approaches to cancer treatment. This interest has been coupled with a burgeoning ability to genetically modify tumor cells and components of the immune system, in an effort to maximize the anti-neoplastic response. In a number of settings, gene modified tumor vaccines, cytotoxic T cells and dendritic cells are producing both immunomodulation and clinically evident benefits. Continued exploration of this approach seems well justified.

EBV specific CTL: a model for immune therapy

We have been generating Epstein-Barr virus specific cytotoxic T cells for patients at high risk of developing EBV driven lymphoma. To discover the fate of the cells in vivo, we first marked them genetically, using a retroviral vector. Our results in 51 patients show that the approach is safe, that the CTL persist for several years and that they are able to mediate anti-viral and anti-tumor effects. We are now studying other virally-linked malignancies to discover whether a similar approach will be of therapeutic value.

Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes for the treatment of patients with EBV-positive relapsed Hodgkin's disease

Adoptive transfer of Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) is effective prophylaxis and treatment of EBV-positive immunoblastic lymphoma in immunocompromised patients. In 50% of patients with Hodgkin's disease, the tumor cells are EBV antigen-positive and may therefore also be suitable targets for treatment with virus-specific CTLs. However, Hodgkin's disease may produce several inhibitory effects on immune induction and effector function in vivo, which may preclude the generation or effector function of CTLs reactive against EBV viral proteins, including those expressed by the tumor cells. We have investigated whether EBV-specific CTLs could be generated ex vivo from 13 patients with Hodgkin's disease: nine with active relapsed disease and four who were in clinical remission after a first or subsequent relapse. CTL lines were successfully generated from nine of 13 patients (five active disease, four remission). Although these lines had an abnormal pattern of expansion comparable to EBV-specific CTLs generated from normal donors, their phenotype was normal except for reduced expression of the zeta chain of the T-cell receptor (TCR). Their cytotoxicity was also compared to EBV-specific lines generated from normal donors and included activity against LMP2a, one of the three weakly immunogenic viral antigens expressed by Hodgkin's tumor cells. To assess the activity of the CTLs in vivo, they were gene-marked and infused into three patients with multiply relapsed disease. The CTLs persisted for more than 13 weeks postinfusion and retained their potent antiviral effects in vivo, thereby enhancing the patient immune response to EBV. This approach may therefore have value in the treatment of EBV-positive Hodgkin's disease.

Anti-interleukin-10 antibodies in patients with chronic active Epstein-Barr virus infection

The Epstein-Barr virus (EBV) genome encodes a protein in its BamHI C restriction fragment rightward open-reading frame-1 (designated BCRF1 or viral interleukin-10 [vIL-10]) that shares protein homology and biologic properties with human IL-10. Several EBV disorders are characterized by prolonged active EBV infection. Because continued EBV replication could allow for increased vIL-10, ELISA and immunoprecipitation were used to determine whether vIL-10 expression during chronic active EBV infection resulted in vIL-10 and IL-10 antibodies. IL-10 antibodies were assayed in patients diagnosed with chronic and acute infectious mononucleosis (CIM, AIM), nasopharyngeal carcinoma (NPC), and EBV-associated lymphoproliferative disease (LPD), as well as from healthy organ transplant patients and EBV-negative or EBV-positive persons. Whether anti-IL-10 antibodies could inhibit IL-10 biologic activity was determined. vIL-10 antibodies were found in CIM, NPC, and LPD patients and antibodies reactive to IL-10 were found in CIM patients. One CIM patient had IL-10 antibodies that neutralized IL-10 bioactivity in vitro.

Adoptive cellular immunotherapy for EBV lymphoproliferative disease

Reactivation of EBV (Epstein-Barr virus) after bone marrow transplantation can result in EBV-associated lymphoproliferative disease (EBV-LPD). We have administered donor-derived EBV-specific cytotoxic T lymphocytes (CTL) to patients who are at high risk of this complication after receiving a T-cell-depleted allograft from a matched unrelated or mismatched related donor. The cells were marked with the neo gene before infusion so that we could evaluate their persistence and efficacy. CTL infusion produced a virus-specific immune response to EBV that persisted for up to 2 years. None of the 36 patients who received prophylactic CTLs have developed EBV-LPD, compared with a cumulative risk of 14% in patients who did not receive this treatment. Strong evidence of clinically valuable immune activity comes from 6 of these 36 patients whose pre-CTL levels of EBV DNA were elevated to a degree strongly predictive of the onset of lymphoma. In each of these cases, the levels returned to baseline after CTL infusion. 2 patients who were treated for clinically evident EBV-LPD attained prolonged remission after CTL infusion and in situ hybridization and semiquantitative PCR showed that the gene-marked CTL had selectively accumulated at disease sites. The prophylactic CTL treatment lacked acute adverse effects, whereas 1 patient who received CTLs for bulky established disease developed initial tumor swelling and respiratory obstruction. We conclude that EBV-specific CTLs are a safe and effective prophylaxis for EBV lymphoma and can also eradicate established disease. This approach is now being extended to other viruses that produce post-transplant morbidity and to other EBV-associated malignancies.

Control of virus-induced lymphoproliferation: Epstein-Barr virus-induced lymphoproliferation and host immunity

Epstein-Barr virus (EBV) is a latent herpesvirus that is associated with a number of tumors. EBV-infected cells show three patterns of latency ranging from type 1, where only one EBV-encoded antigen is expressed, to type 3, where all nine latent cycle proteins encoded by EBV are expressed. Malignancies exhibiting the type 3 latency pattern are highly immunogenic and occur only in immunocompromised patients. It has recently been shown that adoptive immunotherapy with EBV-specific cytotoxic T lymphocytes is an effective therapy for such tumors. Immunotherapy strategies and approaches to increase tumor immunogenicity are now being evaluated in tumors expressing type 2 latency.

Adenovirus-pulsed dendritic cells stimulate human virus-specific T-cell responses in vitro

Adenovirus infections cause significant morbidity and mortality in immunocompromised patients, yet little is known about the immune response to adenovirus infections. We established a system for the generation of a cytotoxic immune response to adenovirus in vitro. Cytotoxic T cells (CTLs) were derived from normal donors by using peripheral blood dendritic cells as antigen-presenting cells. The CTLs were found to contain a mixture of effector cells that recognized virus peptides in the context of both class I and class II antigens. Endogenous viral gene expression was not required to sensitize cells to lysis by adenovirus-specific CTLs. CTLs raised against subgroup C adenovirus type 5 can lyse cells infected with subgroup B adenovirus type 11, indicating that viruses of different subgroups have epitopes in common. This system holds promise for defining the human immune response to adenovirus, including characterization of the viral protein(s) against which the response is generated, and the identity of the effector cells. Such studies are in progress.

Adoptive immunotherapy for Epstein-Barr virus-related lymphoma

Epstein-Barr virus (EBV) causes opportunistic B cell lymphomas in patients whose cellular immunity is compromised. We have been investigating whether infusions of donor-derived, EBV-specific cytotoxic T cells can prevent and/or treat EBV-related lymphoproliferative disease in children receiving T cell-depleted bone marrow from HLA-matched, unrelated or HLA-mismatched, related donors. In this review, we discuss the rationale for this therapeutic approach, describe our experiences with the regimen thus far, and consider some future directions in immunotherapy.

Long-term restoration of immunity against Epstein-Barr virus infection by adoptive transfer of gene-modified virus-specific T lymphocytes

Adoptive transfer of antigen-specific cytotoxic T lymphocytes (CTLs) offers safe and effective therapy for certain viral infections and could prove useful in the eradication of tumor cells. Whether or not the infused T cells persist for extended periods, retaining their ability to expand in response to antigenic stimulation, is not known. We now report long-term detection of gene-marked Epstein-Barr virus (EBV)-specific CTLs in immunocompromised patients at risk for the development of EBV lymphoproliferative disease. Infusions of CTLs not only restored cellular immune responses against EBV, but also established populations of CTL precursors that could respond to in vivo or ex vivo challenge with the virus for as long as 18 months. Our findings support wider use of antigen-specific CTLs in adoptive immunotherapy.