Administration of neomycin-resistance-gene-marked EBV-specific cytotoxic T lymphocytes to recipients of mismatched-related or phenotypically similar unrelated donor marrow grafts

Cancer Therapy With TCR-Engineered T Cells: Current Strategies, Challenges, and Prospects

To redirect T cells against tumor cells, T cells can be engineered ex vivo to express cancer-antigen specific T cell receptors (TCRs), generating products known as TCR-engineered T cells (TCR T). Unlike chimeric antigen receptors (CARs), TCRs recognize HLA-presented peptides derived from proteins of all cellular compartments. The use of TCR T cells for adoptive cellular therapies (ACT) has gained increased attention, especially as efforts to treat solid cancers with ACTs have intensified. In this review, we describe the differing mechanisms of T cell antigen recognition and signal transduction mediated through CARs and TCRs. We describe the classes of cancer antigens recognized by current TCR T therapies and discuss both classical and emerging pre-clinical strategies for antigen-specific TCR discovery, enhancement, and validation. Finally, we review the current landscape of clinical trials for TCR T therapy and discuss what these current results indicate for the development of future engineered TCR approaches.

The Tumor Microenvironment in Post-Transplant Lymphoproliferative Disorders

Post-transplant lymphoproliferative disorders (PTLDs) cover a broad spectrum of lymphoproliferative lesions arising after solid organ or allogeneic hematopoietic stem cell transplantation. The composition and function of the tumor microenvironment (TME), consisting of all non-malignant constituents of a tumor, is greatly impacted in PTLD through a complex interplay between 4 factors: 1) the graft organ causes immune stimulation through chronic antigen presentation; 2) the therapy to prevent organ rejection interferes with the immune system; 3) the oncogenic Epstein-Barr virus (EBV), present in 80% of PTLDs, has a causative role in the oncogenic transformation of lymphocytes and influences immune responses; 4) interaction with the donor-derived immune cells accompanying the graft. These factors make PTLDs an interesting model to look at cancer-microenvironment interactions and current findings can be of interest for other malignancies including solid tumors. Here we will review the current knowledge of the TME composition in PTLD with a focus on the different factors involved in PTLD development.

The doubling potential of T lymphocytes allows clinical-grade production of a bank of genetically modified monoclonal T-cell populations

BACKGROUND AIMS

To produce an anti-leukemic effect after hematopoietic stem cell transplantation we have long considered the theoretical possibility of using banks of HLA-DP specific T-cell clones transduced with a suicide gene. For that application as for any others, a clonal strategy is constrained by the population doubling (PD) potential of T cells, which has been rarely explored or exploited.

METHODS

We used clinical-grade conditions and two donors who were homozygous and identical for all HLA-alleles except HLA-DP. After mixed lymphocyte culture and transduction, we obtained 14 HLA-DP-specific T-cell clones transduced with the HSV-TK suicide gene. Clones were then selected on the basis of their specificity and functional characteristics and evaluated for their doubling potential.

RESULTS

After these steps of selection the clone NAT-DP4^(TK), specific for HLA-DPB1*04:01/04:02, which produced high levels of interferon-γ (IFNγ), tumor necrosis factor (TNF), interleukin-2 (IL-2) and granulocyte-macrophage colony-stimulating factor (GM-CSF), was fully sequenced. It has two copies of the HSV-TK suicide transgene whose localizations were determined. Four billion NAT-DP4^(TK) cells were frozen after 50 PDs. Thawed NAT-DP4^(TK) cells retain the potential to undergo 50 additional PDs, a potential very far beyond that required to produce a biological effect. This PD potential was confirmed on 6/16 additional different T-cell clones. This type of well-defined clone can also support a second genetic modification with CAR constructs.

CONCLUSION

The possibility of choosing rare donors and exploiting the natural proliferative potential of T lymphocytes may dramatically reduce the clinical and immunologic complexity of adoptive transfer protocols that rely on the use of third-party T-cell populations.

Specific Adoptive T-Cell Therapy for Viral and Fungal Infections

Despite advances in anti-infective agents, viral and fungal infections after hematopoietic stem cell transplantation (HSCT) continue to cause life-threatening complications that limit the success of HSCT. Early adoptive T-cell immunotherapy studies showed that administration of allogeneic virus-specific cytotoxic T lymphocytes (vCTL) can prevent and control viral infections and reconstitute antiviral immunity to cytomegalovirus (CMV) and Epstein-Barr virus (EBV). Advances in immunobiology, in vitro culture technology, and current good manufacturing practice (cGMP) have provided opportunities for advancing adoptive cell therapy for viral infections: (1) T cells have been expanded targeting multiple pathogens; (2) vCTL production no longer requires viral infection or viral vector transduction of antigen-presenting cells (APCs); (3) the source of lymphocytes is no longer restricted to donors who are immune to the pathogens; (4) naive T cells have been redirected with chimeric antigen receptor T cells (CARTs) or armed with bispecific antibody-armed T cells (BATs) to mediate vCTL activity; (5) these technologies could be combined to targeted multiple viral or fungal pathogens; and (6) pathogen-specific T-cell products manufactured from third parties and banked for “off-the-shelf” use post-HSCT may soon become a reality.

Phase I Clinical Trial of 4-1BB-based Adoptive T-Cell Therapy for Epstein-Barr Virus (EBV)-positive Tumors

Although adoptive cell therapy using Ag-specific T cells has been tested successfully in the clinic, the production of these T cells has been challenging. By applying our simple and practical 4-1BB-based method for the generation of Ag-specific CD8 T cells, here we determined the maximum tolerated dose, toxicity profile, immunologic responses, and clinical efficacy of autologous Epstein-Barr virus (EBV)/LMP2A-specific CD8 T cells (EBV-induced Natural T cell; EBViNT) in patients with relapsed/refractory EBV-positive tumors. This was a single-center, phase I, dose-escalation trial study evaluating 4 escalating dosing schedules of single injected EBViNT. CD8 T-cell responses against different LMP2A peptides in each patient were determined, and the most effective peptides were used to produce EBViNT. The produced autologous EBViNTs were single infused to patients with EBV-associated malignancy who had failed to standard treatments and were of HLA-A02 or A24 type. Of 11 patients enrolled, 8 patients received a single infusion of EBViNT: 4 with nasopharyngeal carcinomas, 1 with Hodgkin lymphoma, 2 with extranodal NK/T lymphomas, and 1 with diffuse large B-cell lymphoma. Single infusion of EBViNT was well tolerated by all the patients and generated objective antitumor responses in 3 of them. EBViNT infusion induced 2 waves of interferon-γ response: 1 approximately 1 week and the other 4-8 weeks after the treatment. The strength of the second wave was related to the efficacy of the treatment. The current trial shows that EBViNT therapy is safe and may provide a new option for treating EBV-positive recurrent cancer patients resistant to conventional therapy.

Immunotherapeutic approaches for the treatment of childhood, adolescent and young adult non-Hodgkin lymphoma

With the introduction of the anti-CD20 monoclonal antibody rituximab, B-cell non-Hodgkin lymphoma was the first malignancy successfully treated with an immunotherapeutic agent. Since then, numerous advances have expanded the repertoire of immunotherapeutic agents available for the treatment of a variety of malignancies, including many lymphoma subtypes. These include the introduction of monoclonal antibodies targeting a variety of cell surface proteins, including the successful targeting of immunoregulatory checkpoint receptors present on T-cells or tumour cells. Additionally, cellular immunotherapeutic approaches utilize T- or Natural Killer-cells generated with chimeric antigen receptors against cell surface proteins or Epstein-Barr virus-associated latent membrane proteins. The following review describes the current state of immunotherapy for non-Hodgkin lymphoma including a summary of currently available data and promising agents currently in clinical development with future promise in the treatment of childhood, adolescent and young adult non-Hodgkin lymphoma.

Targeting cytomegalovirus-infected cells using T cells armed with anti-CD3 × anti-CMV bispecific antibody

Human cytomegalovirus (CMV) reactivation and infection can lead to poor outcomes after allogeneic stem cell transplantation. We hypothesized that anti-CD3 activated T cells (ATCs) armed with chemically heteroconjugated anti-CD3 × polyclonal anti-CMV bispecific antibody (CMVBi) will target and eliminate CMV-infected cells. Arming doses of CMVBi as low as 0.01 ng/10(6) ATCs was able to mediate specific cytotoxicity (SC) directed at CMV-infected target cells significant above unarmed ATCs at mutiplicities of infection (MOI) between 0.01 and 1. At effector-to-target ratios (E:T) of 25:1, 12.5:1, 6.25:1, and 3.125:1, armed ATCs significantly enhanced killing of CMV-infected targets compared with unarmed ATCs. At an MOI of 1.0, the mean % SC directed at CMV-infected targets cells for CMVBi-armed ATCs at E:T of 3.12, 6.25, and 12.5 were 79%, 81%, and 82%, respectively; whereas the mean % SC for unarmed ATCs at the same E:T were all <20%. ATCs, Cytogam(®), or CMVBi alone did not lyse uninfected or CMV-infected targets. Co-cultures of CMVBi-armed ATCs with CMV-infected targets induced cytokine and chemokine release from armed ATCs. This nonmajor histocompatibility complex restricted strategy for targeting CMV could be used to prevent or treat CMV infections after allogeneic stem cell transplantation or organ transplantation.

Exploiting the interplay between innate and adaptive immunity to improve immunotherapeutic strategies for Epstein-Barr-virus-driven disorders

The recent demonstration that immunotherapeutic approaches may be clinically effective for cancer patients has renewed the interest for this strategy of intervention. In particular, clinical trials using adoptive T-cell therapies disclosed encouraging results, particularly in the context of Epstein-Barr-virus- (EBV-) related tumors. Nevertheless, the rate of complete clinical responses is still limited, thus stimulating the development of more effective therapeutic protocols. Considering the relevance of innate immunity in controlling both infections and cancers, innovative immunotherapeutic approaches should take into account also this compartment to improve clinical efficacy. Evidence accumulated so far indicates that innate immunity effectors, particularly NK cells, can be exploited with therapeutic purposes and new targets have been recently identified. We herein review the complex interactions between EBV and innate immunity and summarize the therapeutic strategies involving both adaptive and innate immune system, in the light of a fruitful integration between these immunotherapeutic modalities for a better control of EBV-driven tumors.

Accelerated production of antigen-specific T cells for preclinical and clinical applications using gas-permeable rapid expansion cultureware (G-Rex)

The clinical manufacture of antigen-specific cytotoxic T lymphocytes (CTLs) for adoptive immunotherapy is limited by the complexity and time required to produce large numbers with the desired function and specificity. The culture conditions required are rigorous, and in some cases only achieved in 2-cm wells in which cell growth is limited by gas exchange, nutrients, and waste accumulation. Bioreactors developed to overcome these issues tend to be complex, expensive, and not always conducive to CTL growth. We observed that antigen-specific CTLs undergo 7 to 10 divisions poststimulation. However, the expected CTL numbers were achieved only in the first week of culture. By recreating the culture conditions present during this first week-low frequency of antigen-specific T cells and high frequency of feeder cells-we were able to increase CTL expansion to expected levels that could be sustained for several weeks without affecting phenotype or function. However, the number of 24-well plates needed was excessive and cultures required frequent media changes, increasing complexity and manufacturing costs. Therefore, we evaluated novel gas-permeable culture devices (G-Rex) with a silicone membrane at the base allowing gas exchange to occur uninhibited by the depth of the medium above. This system effectively supports the expansion of CTL and actually increases output by up to 20-fold while decreasing the required technician time. Importantly, this amplified cell expansion is not because of more cell divisions but because of reduced cell death. This bioprocess optimization increased T-cell output while decreasing the complexity and cost of CTL manufacture, making cell therapy more accessible.

NCI First International Workshop on The Biology, Prevention and Treatment of Relapse after Allogeneic Hematopoietic Cell Transplantation: report from the committee on prevention of relapse following allogeneic cell transplantation for hematologic malignancies

Prevention of relapse after allogeneic hematopoietic stem cell transplantation is the most likely approach to improve survival of patients treated for hematologic malignancies. Herein we review the limits of currently available transplant therapies and the innovative strategies being developed to overcome resistance to therapy or to fill therapeutic modalities not currently available. These novel strategies include nonimmunologic therapies, such as targeted preparative regimens and posttransplant drug therapy, as well as immunologic interventions, including graft engineering, donor lymphocyte infusions, T cell engineering, vaccination, and dendritic cell-based approaches. Several aspects of the biology of the malignant cells as well as the host have been identified that obviate success of even these newer strategies. To maximize the potential for success, we recommend pursuing research to develop additional targeted therapies to be used in the preparative regimen or as maintenance posttransplant, better characterize the T cell and dendritic cells subsets involved in graft-versus-host disease and the graft-versus-leukemia/tumor effect, identify strategies for timing immunologic or nonimmunologic therapies to eliminate the noncycling cancer stem cell, identify more targets for immunotherapies, develop new vaccines that will not be limited by HLA, and develop methods to identify populations at very high risk for relapse to accelerate clinical development and avoid toxicity in patients not at risk for relapse.

Treatment of lymphoma with adoptively transferred T cells

BACKGROUND

Chemotherapy-resistant lymphomas can be cured with allogeneic hematopoietic cell transplantation, demonstrating the susceptibility of these tumors to T cell mediated immune responses. However, high rates of transplant-related morbidity and mortality limit this approach. Efforts have, therefore, been made to develop alternative T cell based therapies, and there is growing evidence that adoptive therapy with T cells targeted to lymphoma-associated antigens may be a safe and effective new method for treating this group of diseases.

OBJECTIVE/METHODS

We review publications on adoptive therapy with ex vivo expanded T cells targeting viral antigens, as well as genetically modified autologous T cells, as strategies for the treatment of lymphoma, with the goal of providing an overview of these approaches.

RESULTS/CONCLUSIONS

Epstein-Barr virus specific T cell therapy is an effective and safe method of treating Epstein-Barr virus associated lymphomas; however, most lymphoma subtypes do not express EBV antigens. For these diseases, adoptive immunotherapy with genetically modified T cells expressing chimeric T cell receptors targeting lymphoma-associated antigens such as CD19 and CD20 appears to be a promising alternative. Recent innovations including enhanced co-stimulation, exogenous cytokine administration and use of memory T cells promise to overcome many of the limitations and pitfalls initially encountered with this approach.

The prevention and treatment of cytomegalovirus infection in haematopoietic stem cell transplantation

Allogeneic haematopoietic stem cell transplantation (HSCT) is an intensive medical treatment involving myeloablative chemo-radiotherapy followed by stem cell rescue using allogeneic haematopoietic stem cells harvested from HLA-matched donors, which is primarily used for the treatment of haematological malignancies. Cytomegalovirus (CMV) infection is one of the major causes of morbidity and death after HSCT. This focused research review highlights the advances made with research into CMV in the HSCT setting. It provides the reader with an overview of current CMV research into the prevention and management of CMV infection.

In vivo expansion of LMP 1- and 2-specific T-cells in a patient who received donor-derived EBV-specific T-cells after allogeneic stem cell transplantation

Immunotherapy approaches with antigen-specific cytotoxic T lymphocytes (CTLs) have provided 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 approximately 40% of cases of Hodgkin's disease, making this tumor another potential target for EBV-targeted immunotherapy. This study describes a patient with multiple relapsed EBV positive Hodgkin's Disease who received both autologous and allogeneic EBV CTL lines. After multiple chemotherapeutic and radiotherapy regimens including two autologous stem cell transplants, he received two doses of gene-marked autologous EBV-specific CTL which resulted in disease stabilization for 6 months. The gene-marked EBV-CTL persisted for 12 months in the peripheral blood after which he proceeded to unrelated donor stem cell transplant followed by immunotherapy with donor-derived EBV-specific CTL. Despite low levels of donor chimerism, the patient remains in complete remission 5 years post-allogeneic SCT. Comparison of the autologous and the donor-derived CTL lines showed that the donor line had specificity for two tumor-associated EBV antigens, latent membrane protein (LMP)1 and 2 compared to the autologous line, which only had specificity for LMP2 epitopes. Following infusion of the donor-derived CTL, functional analyses showed that T-cells reactive with both LMP1 and LMP2 epitopes expanded in the peripheral blood, suggesting that strategies to increase their frequency may result in a broader cytotoxic response against EBV+ Hodgkin tumors.

Musculoskeletal gene therapy and its potential use in the treatment of complicated musculoskeletal infection

Tissue repair is a major issue in orthopedics. Many musculoskeletal tissues, including cartilage, meniscus, and the anterior cruciate ligament, heal poorly after injury. Recent studies have led to the identification of numerous growth factors and other gene products that can promote the regeneration of damaged musculoskeletal tissues. In the last century, the discovery and evolving use of antibiotics has significantly decreased the prevalence and severity of infectious diseases. In many orthopedic scenarios, however, treatment of infections can be difficult, and often involves a prolonged course of antibiotics with concomitant surgical interventions and loss of tissue. Although studies have demonstrated the successful transfer of target genes and the associated manipulation of the musculoskeletal tissue environment, researchers have made few attempts designed to use gene therapy to treat infectious musculoskeletal diseases in animal models. Before it is possible to use gene-based approaches to treat such diseases effectively, researchers must perform more studies to investigate the potential problems that may arise when using gene therapy in an infectious environment.

CD4+CD25+ Regulatory T Cells in Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (SCT) is a well-established treatment modality for malignant and nonmalignant hematologic diseases. High-dose radio- and/or chemotherapy eradicate the hematopoietic system of the patient and induce sufficient immunosuppression to enable donor stem cell engraftment. The replacement of the recipient's immune system with that of the donor significantly contributes to the success of this treatment, since donor immune cells facilitate stem cell engraftment, provide protection from infections, and eliminate residual malignant or nonmalignant host hematopoiesis, thereby protecting from disease relapse in patients transplanted for leukemia or lymphoma (graft-versus-leukemia effect, GVL). Mediators of these beneficial effects are mature T cells within the stem cell graft. However, donor T cells can also attack host tissues and induce a life-threatening syndrome called graft-versus-host disease (GVHD). The challenge of allogeneic SCT is to find a balance between beneficial and harmful T cell effects, which at present is only insufficiently achieved by the use of immunosuppressive drugs. In the future, it might be possible to replace or support such medications by using the intrinsic regulatory capacity of the transplanted immune system, as represented by T cell subpopulations with suppressive activity, such as CD4+ CD25+ regulatory T (Treg) cells. In various mouse model systems, these cells have been shown to suppress GVHD while preserving the GVL effect. As the characterization of their human counterparts is rapidly progressing, their application in allogeneic SCT might soon be explored in clinical trials.

The generation and characterization of LMP2-specific CTLs for use as adoptive transfer from patients with relapsed EBV-positive Hodgkin disease

Cellular adoptive immunotherapy for virus-associated malignant disease is an attractive strategy, since viral antigens provide targets for specific T lymphocytes. In Epstein-Barr virus (EBV)-positive Hodgkin disease (HD), a limited number of EBV-encoded antigens such as the latent membrane antigens (LMP) 1 and 2 are expressed on the malignant Reed-Sternberg cells. The authors aimed to generate cytotoxic T lymphocytes (CTLs) from patients with relapsed HD by specifically targeting LMP2A. Patients with relapsed HD have highly immunosuppressive tumors and have been heavily pretreated with cytotoxic agents. As a result, monocytes and lymphocytes are numerically reduced and functionally impaired. Approaches using dendritic cells (DCs) as the sole antigen-presenting cell to expand LMP2-specific CTL lines in vitro have proved impractical. The authors now show how small amounts of patient peripheral blood can be used to produce DCs expressing LMP2 after Ad5F35 transduction, and how an initial reactivation of LMP2-specific CTLs can be followed by stimulation with lymphoblastoid cell lines overexpressing LMP2 from the same vector. Large numbers of LMP2-specific cytotoxic lymphocytes are produced that contain both CD4+ and CD8+ T cells (favoring long-term persistence in vivo) and recognize multiple LMP2 epitopes (minimizing the risk of tumor antigen loss variants). This approach is being used in a current clinical trial.

Treatment options for post-transplant lymphoproliferative disorder and other Epstein-Barr virus-associated malignancies

Epstein-Barr virus (EBV) is associated with a range of malignancies that largely arise from a defect in EBV-specific cytotoxic T lymphocyte (CTL) immunity and function. Much work has focused on the reconstitution of CTL immunity to EBV in transplant patients, in whom immunosuppression modalities render them susceptible to post-transplant lymphoproliferative disease (PTLD). Adoptive transfer of autologous CTLs is effective at both preventing and curing PTLD in solid organ transplant recipients and can produce a long-term memory response and protection against recurring disease. In this review, the benefits and restrictions of administering EBV-specific CTLs for the treatment of PTLD are discussed and compared with emerging therapies including the generation of allogeneic human leukocyte antigen-matched CTL banks and the anti-CD20 monoclonal antibody therapy, MabThera. Furthermore, studies involving other EBV-associated disorders have described the potential benefit of adoptive transfer of EBV-specific CTLs for Hodgkin's disease, nasopharyngeal carcinoma, chronic active EBV infection, and Burkitt's lymphoma. The challenges of tailor-making therapies for individual diseases and EBV antigen expression latencies are highlighted, in addition to considering vaccination strategies for optimal treatment.

Epstein-Barr virus and post-transplant lymphoproliferative disease

There is convincing evidence that Epstein-Barr virus (EBV) is associated with post-transplant lymphoproliferative disease (PTLD). Primary EBV infection following transplantation occurs in as many as 90% of cases of PTLD in children and pretransplant EBV seronegativity is a recognized risk factor for developing PTLD. Other risk factors include young age at the time of transplant, the type of transplant that the recipient receives and the type and intensity of immunosuppression. The clinical presentation is often nonspecific and tissue biopsy is necessary to establish the diagnosis. There appears to be a correlation between PTLD and EBV viral load measured by polymerase chain reaction (PCR) of the peripheral blood and quantitative PCR may be a useful guide in the management of PTLD. Antiviral drugs and cytomegalovirus-immunoglobulin G may have a role in preventing PTLD. Because PTLD results from functional over-immunosuppression, the initial treatment is reduction of immunosuppression. Antiviral agents, interferon, immuno-based monoclonal therapy, cell-based therapy and chemotherapy also have a potential role in treating this disorder. At the present time there is no standardized approach to the evaluation and treatment of PTLD.

Resolution of oral non-Hodgkin's lymphoma by reduction of immunosuppressive therapy in a renal allograft recipient: a case report and review of the literature

A case of oral non-Hodgkin's lymphoma arising in a patient with insulin-dependent diabetes who had undergone renal allograft transplantation is described. The resolution of the disease was achieved by a reduction in her immunosuppressive therapy. The differential diagnosis is discussed, and the management of posttransplantation lymphoproliferative disorders is reviewed.

Cellular therapy for haematological malignancies

The aim of this review was to summarize the recent progress made in the field of cellular therapeutics in haematological malignancy. The review also examined the role that the National Transfusion Services might play in the manufacture of new cellular therapeutic agents, given both their expertise in the safe provision of blood products and their possession of accredited cell manipulation facilities. Cellular therapy is entering an era in which novel cellular products will find increasing clinical use, particularly in the areas of haematopoietic stem cell transplantation and immunotherapy. The production of novel cell-based therapies, both in Europe and North America, is now under strict regulatory control and therefore collaboration with the National Transfusion Services in the manufacture of these agents may well be beneficial if the production standards demanded by the regulatory authorities are to be fulfilled.

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.

Generation of EBV-specific CTLs suitable for adoptive immunotherapy of EBV-associated lymphoproliferative disease following allogeneic transplantation

Lymphoproliferative disease induced by EBV (EBV-LPD) is a complication of allogeneic transplantation caused by T-cell immunodeficiency. EBV-LPD responds poorly to conventional treatment modalities. Recently, adoptive transfer of EBV-specific, HLA-class I-restricted CTL lines was shown to be effective both as prophylaxis and as treatment of EBV-LPD. The CTL lines are produced by in vitro selection of EBV-specific memory T cells contained in MNC of EBV-seropositive individuals by repeated stimulation with irradiated EBV-transformed cells. The non-EBV-reactive and potentially alloreactive cells remain unactivated. Twenty-one CTL lines were initiated. All were successfully generated and shown to be HLA-restricted and EBV-specific as well as CD8/CD4 and CD45RO positive T cells. The majority of the CTL lines were generated from BMT donors, but two CTL lines were obtained from solid organ transplant recipients receiving immunosuppression. Evidence of probable in vivo efficacy is presented. Development of efficient adoptive T-cell strategies for EBV-positive malignancies could serve as a model for treatment of other viral or malignant disorders.

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.

Purification of Ag-specific T lymphocytes after direct peripheral blood mononuclear cell stimulation followed by CD25 selection. I. Application to CD4(+) or CD8(+) cytomegalovirus phosphoprotein pp65 epitope determination

The two main constraints that currently limit a broader usage of T cell therapy against viruses are the delay required to obtain specific T cells and the safety of the selection procedure. In the present work we developed a generally applicable strategy that eliminates the need for APC for timing reasons, and the need for infectious viral strains for safety concerns. As a model, we used the selection of T lymphocytes specific for the immunodominant CMV phosphoprotein pp65. PBMC from healthy seropositive donors were first depleted of IL-2R alpha-chain CD25(+) cells and were then stimulated for 24-96 h with previously defined peptide Ags or with autologous PBMC infected with a canarypox viral vector encoding the total pp65 protein (ALVAC-pp65). Subsequent immunomagnetic purification of newly CD25-expressing cells allowed efficient recovery of T lymphocytes specific for the initial stimuli, i.e., for the already known immunodominant epitope corresponding to the peptides used as a model or for newly defined epitopes corresponding to peptides encoded by the transfected pp65 protein. Importantly, we demonstrated that direct PBMC stimulation allowed recovery not only of CD8(+) memory T lymphocytes, but also of the CD4(+) memory T cells, which are known to be crucial to ensure persistence of adoptively transferred immune memory. Finally, our analysis of pp65-specific T cells led to the identification of several new helper and cytotoxic epitopes. This work thus demonstrates the feasibility of isolating memory T lymphocytes specific for a clinically relevant protein without the need to prepare APC, to use infectious viral strains, or to identify immunodominant epitopes.

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.

Ex vivo generation of effective Epstein-Barr virus (EBV)-specific CD8+ cytotoxic T lymphocytes from the peripheral blood of immunocompetent Epstein Barr virus-seronegative individuals

BACKGROUND

Although readily accomplished from immunocompetent Epstein-Barr virus- (EBV) seropositive individuals, the effective ex vivo generation of EBV-specific cytotoxic T lymphocytes (CTL) from the peripheral blood mononuclear cells (PBMC) of EBV-seronegative subjects has proven to be a challenge. The focus of our study was to ascertain optimized culture conditions required for the ex vivo generation of EBV-reactive autologous CTL from the PBMC of EBV-seronegative volunteers.

METHOD

Freshly isolated PBMC obtained from immunocompetent EBV-seronegative and -seropositive individuals were used to generate EBV-specific autologous CTL lines using both conventional and a novel, modified ex vivo culture technique.

RESULTS

In contrast to responses observed in EBV-seropositives after two to three rounds of ex vivo stimulation, gamma-irradiated autologous lymphoblastoid cell lines (LCL) were incapable of eliciting an effective anti-EBV cytotoxic response when freshly-isolated PBMC from EBV-seronegative individuals were used as responders. Under these culture conditions, CD4+ T cells with preferential expression of the Th2-type cytokine IL-4 were predominantly expanded in the PBMC obtained from EBV-seronegative individuals. However, the addition of recombinant human (rh) IL-12 during the primary phase of ex vivo stimulation resulted in augmentation of EBV-specific cytolysis of autologous LCL by CD8+ T cells. Furthermore, there was down-regulation in the secretion of IL-4 and up-regulation in that of the Th1-type cytokine IFN-gamma by responder CD4+ and CD8+ T cells.

CONCLUSIONS

Taken together these data suggest that the addition of rhIL-12 during the primary phase of ex vivo stimulation of freshly isolated PBMC from EBV-seronegative individuals results in skewing of the immune response predominantly towards a CD4+ Th1-type (IFN-gamma) with the generation of an efficacious CTL-mediated anti-EBV reactivity. This novel ex vivo approach for generating effective autologous EBV-specific CTL could be adopted to treat refractory post-transplant lymphoproliferative disorders, which may be encountered in EBV-seropositive-->EBV-seronegative organ transplant recipients. Additionally, these ex vivo generated anti-EBV T cells could also be infused perioperatively to enhance prophylactically immunity against EBV infection in high-risk EBV-seronegative organ allograft recipients.

Posttransplantation lymphoproliferative disorder in children: clinical, histopathologic, and imaging features

Posttransplantation lymphoproliferative disorder (PTLD) is a condition in patients who receive transplants in which chronic immunosuppression leads to an unregulated expansion of lymphoid cells; the condition ranges from hyperplasia to malignant lymphoid proliferation. Risk factors affecting the incidence of PTLD include allograft type, Epstein-Barr virus infection, and immunosuppression. In this article, we review the clinical, histopathologic, and imaging features of PTLD in children. Because PTLD can affect nearly any organ system, a wide variety of clinical manifestations is possible. The heterogeneous nature of the disease is also reflected on imaging studies. The goals of imaging in patients with PTLD are to detect disease, guide biopsy, and direct appropriate follow-up imaging rather than to establish a specific diagnosis. Because the clinical and imaging manifestations of PTLD are nonspecific and are not reliably predictive of histopathologic subtype, tissue biopsy is necessary for final diagnosis.

The T cell repertoire selected in vitro against EBV: diversity, specificity, and improved purification through early IL-2 receptor alpha-chain (CD25)-positive selection

Polyclonal T cell lines specific for EBV proteins have proved efficient in preventing EBV-related immunoblastic lymphoma after allogeneic bone marrow transplantation. To gain insight into the composition of the EBV-specific T cell repertoire that ensured patient protection, we performed for the first time an extensive characterization of eight cytotoxic T cell lines selected in vitro against EBV-transformed autologous lymphoblastoid cell lines (BLCL). These T cell lines consist of 50-100 distinct T cell clones, of which 32-96% are specific for autologous BLCL. Moreover, we demonstrate that reactivities against only five EBV proteins (BZLF1, BMLF1, EBNA-3A, EBNA-3C, and LMP2) cover 86% (32/37) of the specificities detected. In addition, we describe an improved method of T cell harvesting using a CD25 selection procedure which reduces the time required to obtain specific T cells and improves the purity of EBV-specific T cells, thus showing promise for use in adoptive transfer protocols.

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.

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.

Activation and adoptive transfer of Epstein-Barr virus-specific cytotoxic T cells in solid organ transplant patients with posttransplant lymphoproliferative disease

The treatment of Epstein-Barr virus (EBV)-associated lymphoproliferative disease (PTLD) in EBV seronegative solid organ transplant recipients who acquire their EBV infection after engraftment poses a considerable challenge because of underlying immunosuppression that inhibits the virus-specific cytotoxic T cell (CTL) response in vivo. We have developed a protocol for activating autologous EBV-specific CTL lines from these patients and show their potential use for immunotherapy against PTLD in solid organ transplant patients. Peripheral blood mononuclear cells from a panel of solid organ transplant recipients with and without active PTLD were used to assess EBV-specific memory CTL responses. The activation protocol involved cocultivation of peripheral blood mononuclear cells with an autologous lymphoblastoid cell line under conditions that favored expansion of virus-specific CTL and hindered the proliferation of allospecific T cells. These CTL consistently showed (i) strong EBV-specificity, including reactivity through defined epitopes in spite of concurrent immunosuppressive therapy, and (ii) no alloreactivity toward donor alloantigens. More importantly, adoptive transfer of these autologous CTLs into a single patient with active PTLD was coincident with a very significant regression of the PTLD. These results demonstrate that a potent EBV-specific memory response can be expanded from solid organ recipients who have acquired their primary EBV infection under high levels of immunosuppressive therapy and that these T cells may have therapeutic potential against PTLD.

A gamma-herpesvirus sneaks through a CD8(+) T cell response primed to a lytic-phase epitope

To determine whether established CD8(+) T cell memory to an epitope prominent during the replicative phase of a gamma-herpesvirus infection protects against subsequent challenge, mice were primed with a recombinant vaccinia virus expressing the p56 peptide and then boosted by intranasal exposure to an influenza A virus incorporating p56 in the neuraminidase protein. Clonally expanded populations of functional, p56-specific CD8(+) T cells were present at high frequency in both the lung and the lymphoid tissue 1 month later, immediately before respiratory challenge with gammaHV-68. This prime-and-boost regime led to a massive reduction of productive gammaHV-68 infection in the respiratory tract and, initially, to much lower levels of latency in both the regional lymph nodes and the spleen. The CD8(+) T cell response to another epitope (p79) was diminished, there was less evidence of B cell activation, and the onset of the CD4(+) T cell-dependent splenomegaly was delayed. Within 3-4 weeks of the gammaHV-68 challenge, however, the extent of latent infection in the lymph nodes and spleen was equivalent, and both groups developed the prominent infectious mononucleosis-like syndrome that is characteristic of this infection. The reverse protocol (influenza then vaccinia) seemed to be slightly less effective. Even though immune CD8(+) T cells may be present at the time and site of virus challenge, establishing a high level of CD8(+) T cell memory to lytic-phase epitopes alone does not protect against the longer-term consequences of this gammaHV infection.

CD4(+) T cell-mediated control of a gamma-herpesvirus in B cell-deficient mice is mediated by IFN-gamma

The lack of B cells and antibody does not prevent mice from dealing effectively with a pathogenic gamma-herpesvirus. Both CD4(+) and CD8(+) T cells contribute to the control of virus replication in the respiratory tract, with the depletion of either lymphocyte subset leading to increased titers in the lung. However, the further neutralization of IFN-gamma diminishes the effectiveness of the CD4(+) T cell response and causes substantially increased mortality. Experiments with bone marrow radiation chimeras indicate that the immune CD4(+) effectors operate optimally when there is the potential for direct interaction with virus-infected targets expressing MHC class II glycoproteins, suggesting that the IFN-gamma produced by these lymphocytes is functioning at short range. The numbers of latently infected cells in the spleens of carrier mice are also significantly increased by the concurrent depletion of both the CD4(+) population and IFN-gamma. These experiments raise the possibility that the defective control of intercurrent gamma-herpesvirus infections in patients with AIDS not only is due solely to the absence of helper T cells but also reflects the loss of an important set of CD4(+) effectors.

Cytokine mRNA profiles in Epstein-Barr virus-associated post-transplant lymphoproliferative disorders

Cytokine mRNA patterns were analyzed in 11 post-transplant lymphoproliferative disorder (PTLD) specimens using qualitative reverse-transcriptase polymerase chain reaction (RT-PCR). In each case, a pattern of IL2-, IFN gamma-, IL4+, IL10+ was seen. A similar pattern was observed in a spleen sample from 1 patient with contemporaneous PTLD elsewhere. Semiquantitative RT-PCR for cytokine message was performed using RNA from bronchoalveolar lavage (BAL) specimens obtained from 2 patients with pulmonary PTLD. In both cases, IL4 message predominated. Reduction of message coincided with resolution of the tumors. The pattern differed from that seen in 1 patient with acute pulmonary rejection, in which RT-PCR of BAL cells showed predominance of IL6 and IFN gamma. We conclude that at least some PTLDs exist within a T-helper cell type 2 (Th2)-like cytokine microenvironment. The presence of a similar mRNA pattern in an extratumoral specimen at the time of PTLD suggests that it may reflect a systemic phenomenon. Disappearance of this pattern following PTLD resolution indicates its dynamic nature and is consistent with the hypothesis that specific cytokines contribute to the development of PTLDs.

Prevention of EBV-induced B-lymphoproliferative disorder by ex vivo marrow B-cell depletion in HLA-phenoidentical or non-identical T-depleted bone marrow transplantation

HLA-mismatched bone marrow transplantation (BMT) is hampered by three major complications: graft rejection, acute graft-versus-host disease (aGVHD) and delayed immune reconstitution. Infusion of anti-LFA1 plus anti-CD2 monoclonal antibodies (MAb), combined with ex-vivo T-cell depletion of the graft, was efficient in preventing graft rejection and aGVHD. Nevertheless, disease-free survival was limited by the high frequency of lethal infections, including EBV-induced lymphoproliferative disease (BLPD), which originates mostly from donor B cells, with an incidence of 5-30%. To decrease the rate of this complication, ex-vivo B-cell depletion was attempted. This study compares a group of 19 patients who received a T- and B-cell-depleted marrow from an HLA-mismatched related donor with a retrospective control group of 19 patients, who had received T-cell-depleted marrow by the same method. The level of T-cell depletion was similar in the two groups. For B-cell depletion, two different methods were compared. The median number of B cells infused in the study group was 0.46/kg. Engraftment and aGVHD incidence were similar in the two groups. No EBV donor-derived BPLD occurred in the study group, compared with seven in the control group, four of whom died because of EBV-BPLD. Event-free survival was significantly different between the two groups. We conclude that ex-vivo B-cell depletion of the graft may be a useful means of preventing EBV-BPLD, and warrants further study on a larger group of patients.

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 theneo 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/106 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.

© 1998 by The American Society of Hematology.

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 theneo 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 (&gt;2,000 genome copies/106 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.

© 1998 by The American Society of Hematology.

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.

AIDS-related malignancies

In the US over one million persons are currently infected with the HIV, over half a million have had AIDS, and over 300,000 have died from AIDS. Worldwide, it is estimated that more than 17 million people are currently infected with HIV, and over 1,200,000 cases of AIDS have been reported to the World Health Organization. By some estimates, up to 40% of patients with AIDS will ultimately develop some form of cancer. Non-Hodgkin's lymphoma, Kaposi's sarcoma and invasive cervical cancer have a higher incidence in persons with HIV infection and all three are AIDS-defining illnesses. In addition, several reports suggest that a number of other malignancies may occur at an increased incidence in persons with HIV infection, including squamous-cell carcinoma of the head, neck and anus, plasmacytoma, melanoma, small-cell lung cancer, basal-cell cancer, and germ-cell tumours. Clinicians should become familiar with HIV-related malignancies as their incidence is expected to further increase as more effective therapies for HIV and associated opportunistic infections allow patients to live longer in an advanced state of immunodeficiency. In the current article, we will review the clinical and therapeutic aspects of the most common AIDS-related malignancies including non-Hodgkin's and Hodgkin's lymphomas, Kaposi's sarcoma and anogenital epithelial neoplasias.

Feasibility of cellular adoptive immunotherapy for Epstein-Barr virus-associated lymphomas using haploidentical donors

Epstein-Barr virus (EBV)-associated lymphomas following bone marrow or solid organ transplantation are often sensitive to immunomodulatory therapies. These have included withdrawal or reduction in immunosuppressive therapy in the solid organ transplant setting and adoptive cellular therapies in the bone marrow transplant (BMT) setting. We describe a strategy for generating EBV-specific cytotoxic T cell therapy lines with substantial killing activity against haploidentical targets. Weekly stimulation of peripheral blood mononuclear cells (PBMCs) for 3 weeks with the irradiated cells of an autologous EBV-transformed B lymphoblastoid cell line (B-LCL), followed by stimulation in the presence of IL-2, yielded T cell lines that were cytolytic for haploidentical B-LCLs but did not lyse haploidentical targets not expressing EBV antigens.

Gene therapy for infectious diseases

Gene therapy is being investigated as an alternative treatment for a wide range of infectious diseases that are not amenable to standard clinical management. Approaches to gene therapy for infectious diseases can be divided into three broad categories: (i) gene therapies based on nucleic acid moieties, including antisense DNA or RNA, RNA decoys, and catalytic RNA moieties (ribozymes); (ii) protein approaches such as transdominant negative proteins and single-chain antibodies; and (iii) immunotherapeutic approaches involving genetic vaccines or pathogen-specific lymphocytes. It is further possible that combinations of the aforementioned approaches will be used simultaneously to inhibit multiple stages of the life cycle of the infectious agent.

Cord blood mononuclear cell transformation assay for screening for the presence of Epstein-Barr virus

EBV-induced lymphoproliferative disease (EBV-LPD) is a serious and potentially fatal complication following stem cell transplantation. Strategies have been developed for the cultivation of donor-derived, EBV-specific cytotoxic T lymphocytes (CTL) for stem cell transplant (SCT) patients affected with these disorders, using donor-derived, EBV-transformed B lymphoblastoid cell lines (BLCL) as stimulators. Although cultivation of EBV-transformed BLCL is possible without using an exogenous source of EBV, transformation of autologous B cells with endogenous virus may be slow and inconsistent. Therefore, if exogenous strains of EBV are used to generate BLCL, it may be beneficial to patients to ensure that these cell lines are not producing virus that potentially could be conveyed at the time of CTL infusion. A reliable method of screening for EBV using a cord blood transformation assay has been developed and is described.

Virus-specific cytotoxic T lymphocytes as prophylaxis for Epstein-Barr virus lymphoproliferative disease in pediatric bone marrow transplant recipients

Epstein-Barr virus lymphoproliferative disease (EBV LPD) is a well-recognized, life-threatening complication of bone marrow transplantation (BMT). The incidence of EBV LPD is increasing as more transplants are performed from mismatched and unrelated donors. Significant strides have been made in the diagnosis, prevention, and treatment of EBV LPD in marrow transplant recipients. Immunovirological assays can provide early identification of patients at risk for developing EBV LPD. Prophylaxis and treatment by the adoptive transfer of EBV-specific T cells and the subsequent long-term restoration of immunity against EBV-associated lymphoproliferation have provided positive outcomes in the management of this uniformly fatal complication of BMT. The purpose of this article is to provide a review of EBV LPD and to present a newly developed strategy for EBV LPD prophylaxis in pediatric BMT recipients.