EBV-specific Cytotoxic T Lymphocytes Research Articles

Frequency analysis of HLA-B7-restricted Epstein-Barr virus-specific cytotoxic T lymphocytes in patients with multiple sclerosis and healthy controls

The Epstein-Barr virus (EBV) has been implicated in the pathogenesis of multiple sclerosis (MS), however, the mechanisms by which EBV may be involved in MS are unknown. We here have investigated the frequency of EBV-specific cytotoxic T lymphocytes (CTL) in human leukocyte antigen (HLA)-B7 + patients with MS and healthy controls using enzyme-linked immunospot assays and seven previously characterized HLA-B7-restricted immunogenic EBV peptides. Overall, there were no significant differences in the frequency of EBV-specific CTL between both groups. These data do not support the hypothesis that EBV could play a role in MS by inducing quantitatively altered EBV-specific CTL responses. Other pathogenic mechanisms for EBV in MS remain to be elucidated.

Successful In Vitro Priming of EBV-Specific CD8+ T Cells Endowed with Strong Cytotoxic Function from T Cells of EBV-Seronegative Children

Epstein-Barr virus (EBV)-seronegative transplant recipients are at high risk of developing EBV-associated post-transplant lymphoproliferative disorder (PTLD), and would maximally benefit from an EBV-directed T-cell therapy for prevention or treatment of PTLD. So far, efforts to activate CD8+ EBV-specific cytotoxic T lymphocytes (CTL) endowed with high specific cytotoxicity from EBV-seronegative children have failed. We compared the CD8+ CTL priming efficiency of three different modified activation protocols, based on lymphoblastoid cell lines (LCL) stimulation potentially enhanced by either LCL presentation through dendritic cells, or selection of IFN-gamma+ cultured cells, or culture in the presence of rhIL-12 and rhIL-7, according to the standard protocol for reactivation of EBV-specific CTL. We found that only specific LCL stimulation in the presence of rhIL-12 and rhIL-7 was able to reproducibly expand EBV-specific CD8+ CTL endowed with strong cytotoxic activity from truly EBV-seronegative children. The lines thus activated, which included specificities toward EBV latent and lytic proteins, showed high percentage CD8+ T cells, with <10% naïve CD8+/CCR7+/CD45RA+ cells. Overall, the total number of CD8+ central memory cells, and of CCR7 T-cell effectors was comparable to that observed in healthy EBV-seropositive controls. In conclusion, it is feasible to activate EBV-specific CD8+ CTL with suitable characteristics for in vivo employment from EBV-seronegative children.

Review of Epstein–Barr virus and post‐transplant lymphoproliferative disorder post‐solid organ transplantation (Review Article)

Post-transplant lymphoproliferative disorder (PTLD) following solid organ transplantation is an important form of post-transplant malignancy. PTLD is typically associated with Epstein-Barr virus (EBV) and occurs in the setting of profound immunosuppression resulting in a deficiency of EBV-specific cytotoxic T lymphocytes (CTL). Predisposing factors include EBV mismatch between donor and recipient, use of immunosuppression especially T-cell depletive therapies and genetic predisposition of recipients. The standard approach has been to reduce immunosuppression but is often insufficient to induce tumour regression. Further understanding of the immunobiology of PTLD has resulted in improved monitoring techniques (including EBV viral load determined by polymerase chain reaction) and newer treatment options. Recent work has highlighted a potential role for dendritic cells in both the pathogenesis and treatment of PTLD. Current treatment modalities include adoptive immunotherapy using ex vivo generated autologous EBV-specific CTL or allogeneic CTL, cytokine therapies, antiviral agents, and more recently, rituximab and dendritic-cell based therapies. This review focuses on the developments and progress in the pathogenesis, diagnosis and treatment of PTLD.

Adoptive Immunotherapy for Hodgkin's Lymphoma

Adoptive transfer of tumor-specific T-cells is an attractive strategy for the treatment of patients with refractory or relapsed Hodgkin's lymphoma. However, Hodgkin's lymphomas possess a range of tumor-evasion mechanisms, which must be overcome before the full potential of immunotherapies can be achieved. In this article, we discuss the promise of Epstein-Barr virus-specific cytotoxic T-lymphocytes, the roles of cytokines, and other strategies for overcoming the immune-evasion mechanisms in Hodgkin's lymphoma.

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 ∼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.

Adoptive Transfer of Epstein-Barr Virus-Specific Cytotoxic T-Lymphocytes for the Treatment of Angiocentric Lymphomas

Angiocentric lymphoma, known as natural killer (NK)/T-cell non-Hodgkin's lymphoma, has been reported to be associated with the Epstein-Barr virus (EBV). We performed adoptive transfer of EBV-specific polyclonal T-cell lines in 3 patients with extranodal NK/T-cell lymphoma, nasal type, and evaluated the treatment for safety, immunologic reconstitution, and clinical outcomes. The tissue samples collected from the 3 patients were confirmed by polymerase chain reaction analysis to be EBV positive. In the cases of the first and second patients, EBV-transformed B-lymphoblastoid cell lines (LCLs) and T-cell lines were generated from peripheral lymphocytes of HLA-matched sibling donors. The third patient's T-cell lines were induced with autologous lymphocytes. Polyclonal T-cell infusion was carried out after high-dose radiotherapy because active relapsed disease remained in all of the patients. The first patient received 4 weekly infusions of 2 3 10(7) cells/m(2), and the second and third patients underwent treatment with 2 cycles of infusions of the same dosage. All T-cell lines showed >60% NK activity, cytotoxic T-lymphocyte (CTL) responses of >40% against autologous LCLs, and no CTL activity against patient-derived lymphoblasts. The level of cytotoxicity increased substantially in all patients after cell infusion. The 2 patients who received T-cell therapy twice had stabilized disease for more than 3 years. These safe treatments exhibited no severe inflammatory response, and no serious toxicity developed during T-cell therapy. Our findings demonstrate that adoptively transferred cells may provide reconstitution of EBV-specific CTL responses in patients with active relapsed angiocentric lymphoma. These results provide a rationale for the immunotherapy of angiocentric lymphoma.

Target Antigen Expression on a Professional Antigen-Presenting Cell Induces Superior Proliferative Antitumor T-Cell Responses via Chimeric T-Cell Receptors

Human T cells expressing tumor antigen-specific chimeric receptors fail to sustain their growth and activation in vivo, which greatly reduces their therapeutic value. The defective proliferative response to tumor cells in vitro can partly be overcome by concomitant CD28 costimulatory signaling. We investigated whether T-cell activation via chimeric receptors (chRec) can be further improved by ligand expression on antigen-presenting cells of B-cell origin. We generated Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) expressing a CD19-specific chRec. These CTLs are provided with native receptor stimulation by autologous EBV-transformed B-lymphoblastoid cell lines (LCLs) but exclusively with chRec (CD19-specific) stimulation by allogeneic, human leukocyte antigen (HLA)-mismatched CD19+ LCLs. CD19zeta-transduced EBV-specific CTLs specifically lysed both allogeneic EBV targets and CD19+ tumor cells through the chRec in a major histocompatibility complex-independent manner, while maintaining their ability to recognize autologous EBV targets through the native T-cell receptor. The transduced CTLs failed to proliferate in response to CD19+ tumor targets even in the presence of CD28 costimulatory signaling. By contrast, CD19 expressed on HLA-mismatched LCL-induced T-cell activation and long-term proliferation that essentially duplicated the result from native receptor stimulation with autologous LCLs, suggesting that a deficit of costimulatory molecules on target cells in addition to CD28 is indeed responsible for inadequate chRec-mediated T-cell function. Hence, effective tumor immunotherapy may be favored if engagement of the chRec on modified T cells is complemented by interaction with multiple costimulator molecules. The use of T cells with native specificity for EBV may be one means of attaining this objective.

Virological aspects of Epstein-Barr virus infections.

Epstein-Barr virus (EBV) is usually maintained in an asymptomatic and latent form by the host immune system, and primarily by EBV-specific cytotoxic T cells (CTLs). However, EBV has been linked to several refractory diseases such as EBV-associated hemophagocytic syndrome(EBV-AHS) and chronic active EBV infection (CAEBV). In these ectopic diseases, EBV infects T/NK cells, causing severe immunodeficiency with a very high EBV load. In recent years, the laboratory procedure to assess these types of EBV infections has been improved. In particular, real-time polymerase chain reaction (PCR) has been used to quantify the EBV load, and the MHC: peptide tetramer assay has been used to quantitate EBV-specific CTLs; these tests have been employed for the management of the illnesses associated with EBV infection. Here, we have reviewed the recent progress in the clinical application of these assays. The pathogenesis of EBV-infected T/NK cells, and the host immune response to infection, including the roles carried out by innate immunity and inflammatory cytokines, are likely to be revealed in the future.

CD28 Fails to Costimulate Tumor-Specific Activation of Epstein Barr-Virus-Specific Memory Effector T Cells.

Genetic modification of cytotoxic T cells with tumor antigen-specific chimeric receptors (chRec) specifically redirects their effector functions towards tumor cells. Integration of the signaling domains of the costimulatory molecule CD28 into chRec enhances antigen-specific proliferation of peripheral blood-derived polyclonal human T cell populations. While CD28 plays an essential role in the priming of naïve CD4+ T cells, its contribution to effector memory cytotoxic T cell (CTL) responses is controversial. We investigated the function of chRec containing the signaling domains of CD28 in vitro expanded T cells with specificity for Epstein-Barr-virus (EBV). Chimeric T cell receptors containing an extracellular single-chain antibody domain directed against the tumor ganglioside antigen GD2 fused to the intracellular signaling domains of both the CD28 and the T cell receptor (TCR) ζ chain (14.G2a-CD28ζ), or TCRζ alone (14.G2a-ζ) were expressed in EBV-specific cytotoxic T cell (CTL) lines from three seropositive donors and in peripheral blood T cells preactivated by CD3-/CD28-specific antibody crosslinking by retroviral gene transfer. Following transduction with the chRec genes, 14.G2a-ζ and 14.G2a-CD28ζ EBV-CTL had comparable levels of chRec surface expression (21–28% versus 26–40%). EBV-CTL had an immunophenotype characteristic of memory effector T cells, coexpressing CD3 and CD45RO in the absence of CD45RA and CD27 surface expression. The transduced CTL maintained their capacity to specifically lyse autologous EBV targets in 4 hr 51Cr release assays and to proliferate after stimulation with autologous EBV targets. Intracellular cytokine staining demonstrated efficient and comparable antigen-specific IFN-γ secretion by both 14.G2a-ζ and 14.G2a-CD28ζ-transduced CTL in response to EBV and tumor targets. Furthermore, GD2+ neuroblastoma targets were lysed in a comparable and antigen-specific manner. However, while antigen engagement by 14.G2a-CD28ζ efficiently induced expansion of non-specifically activated polyclonal peripheral blood lymphocytes in an antigen-dependent manner, CD28 signaling failed to overcome the failure of transduced EBV-CTL to specifically proliferate in response to GD2+ tumor cells. Thus, the costimulatory requirement for the highly efficient proliferative activation response of EBV-specific CTL to viral antigen can not be mimicked by combined CD28 and ζ signaling. Exploring the mechanisms and costimulatory requirements of effector memory T cell reactivation may help to exploit the full potential of this highly cytolytic T cell population for adoptive immunotherapy of cancer.

Cell Therapy of Stage IV Nasopharyngeal Carcinoma With Autologous Epstein-Barr Virus–Targeted Cytotoxic T Lymphocytes

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-related malignancy expressing EBV antigens that are possible targets of cell therapy, including latent membrane protein 2 (LMP2). We conducted a clinical trial of EBV-targeted cell therapy with autologous virus-specific cytotoxic T lymphocytes (CTLs) for NPC refractory to conventional treatments. Ten patients with EBV-related stage IV NPC in progression after conventional radiotherapy and chemotherapy received intravenously autologous EBV-specific CTLs reactivated and expanded ex vivo from peripheral blood lymphocytes through stimulation with EBV-transformed autologous B-lymphoblastoid cell lines (LCL). Toxicity, specific cellular immune responses, and clinical tumor responses were evaluated. EBV-specific CTLs could be generated in all patients and were predominantly CD3+/CD8+ T lymphocytes displaying specific killing of autologous EBV-LCL, autologous NPC cells as well as autologous targets bearing the EBV antigen LMP2. Patients received two to 23 infusions of EBV-specific CTLs that were well tolerated with the exception of grade 1 to 2 inflammatory reactions at the tumor site in two cases. Control of disease progression was obtained in six of 10 patients (two with partial response and four with stable disease). Analysis of interferon-gamma-producing cells demonstrated an increased frequency of EBV-specific immunity, with appearance of LMP2-specific responses in four patients, of whom three had clinical benefit. Cell therapy with EBV-targeted autologous CTLs is safe, induces LMP-2-specific immunologic responses, and is associated with objective responses and control of disease progression in patients with stage IV NPC resistant to conventional treatments.

Dendritic Cells Expand Epstein Barr Virus Specific CD8 + T Cell Responses More Efficiently Than EBV Transformed B Cells

Adoptive transfer of Epstein Barr virus (EBV) specific cytotoxic T lymphocytes (CTLs) has been successfully applied in the treatment of EBV associated post-transplant lymphoproliferative disease (PTLD). In most studies EBV transformed B cells (LCLs) have been used for the induction of EBV specific T cell lines. Application of this approach to other EBV associated tumors is difficult, because LCLs focus T cell expansion toward immunodominant EBV antigens that are not expressed in EBV associated Hodgkin’s lymphoma and nasopharyngeal carcinoma. Therefore, we compared dendritic cells (DCs) with LCLs for CD8 + T cell stimulation against dominant and subdominant EBV antigens. DCs expanded tenfold more EBNA3A and LMP2 specific CD8 + T cells than LCL and also stimulated EBV specific CTL from PTLD patients. Both, DCs and LCLs stimulations led to the expansion of high affinity T cells, capable to target EBV transformed B cells. While LCLs and DCs expressed MHC class I and II products at similar levels, DCs showed a higher expression of costimulatory and adhesion molecules. This resulted in more efficient T cell conjugate formation with DCs than with LCLs. We propose the use of DCs for stimulaton of EBV specific T cells in active or passive immunotherapy of EBV associated malignancies.

Expression of Leukocyte Immunoglobulin-Like Receptors and Natural Killer Receptors on Virus-Specific CD8+T Cells during the Evolution of Epstein-Barr Virus-Specific Immune Responsesin Vivo

Antigen-primed cytotoxic T lymphocytes (CTL) may express leukocyte immunoglobulin-like receptors (LILRs) and natural killer receptors (NKRs). Published work suggests that expression of some of these receptors confers survival advantage, leading to the idea that cells expressing such receptors may accumulate as an antigen-specific response evolves. Here we tested this hypothesis by analyzing expression of CD85j (also known as LILRB1 or ILT2), KIRs, CD94, and CD161 by Epstein- Barr virus (EBV)-specific CTL during the primary and persistent phases of EBV infection in humans. During primary infection, few EBV-specific CTL expressed these receptors and this proportion was equally low in early persistent infection. Thus, expression of these molecules does not influence capacity to survive downregulation of the primary response. However, in donors persistently infected with EBV for many years, a significantly higher proportion of EBV-specific CTL expressed CD85j and NKRs, suggesting that cells expressing these receptors can accumulate with time. Using FACS analysis, we confirmed, at a single cell level, that expression of CD85j, defined by staining with the antibody VMP55, was associated with reduced capacity of EBV-specific CD8+ T cells to respond to antigen. Thus, in the later stages of persistent infection, protective immunity to EBV may be reduced due to the preferential accumulation of hyporesponsive EBV-specific CD8+ T cells.

Human cytotoxic T lymphocytes with reduced sensitivity to Fas-induced apoptosis

AbstractEffector-memory T cells expressing Fas (Apo-1/CD95) are switched to an apoptotic program by cross-linking with Fas-ligand (FasL). Consequently, tumors that express FasL can induce apoptosis of infiltrating Fas-positive T lymphocytes and subdue any antitumor host immune response. Since Epstein-Barr virus (EBV)-associated tumors such as Hodgkin lymphoma (HL) and nasopharyngeal carcinoma (NPC) express FasL, we determined whether EBV-specific cytotoxic T lymphocytes (EBV-CTLs) could be modified to resist this evasion strategy. We show that long-term down-modulation of Fas can be achieved in EBV-CTLs by transduction with small interfering RNA (siRNA) encoded in a retrovirus. Modified T cells resisted Fas/FasL-mediated apoptosis compared with control cells and showed minimal cleavage of the caspase3 substrate poly(ADP-ribose) polymerase (PARP) protein after Fas engagement. Prolonged Fas stimulation selected a uniformly Faslow and FasL resistant population. Removal of responsiveness to this single death signal had no other discernible effects on EBV-CTLs. In particular, it did not lead to their autonomous growth since the modified EBV-CTLs remained polyclonal, and their survival and proliferation retained dependence on antigen-specific stimulation and on the presence of other physiologic growth signals. EBV-CTLs with knocked down Fas should have a selective functional and survival advantage over unmodified EBV-CTLs in the presence of tumors expressing FasL and may be of value for adoptive cellular therapy. (Blood. 2005;105:4677-4684)

Epstein Barr virus specific T-cells generated from unstable human atherosclerotic lesions: Implications for plaque inflammation

Objective T-cell activation is an essential feature of atherosclerotic plaque inflammation, which eventually may lead to plaque rupture. In this study, we investigated if EBV, a common herpes virus, is capable of stimulating atherosclerotic plaque derived T-cells and thus could contribute to atherosclerotic plaque inflammation. Methods Plaque derived T-cell cultures were established from symptomatic carotid atherosclerotic plaques of 19 patients. B-cells from the same patients were transformed with EBV to form lymphoblastoid cell lines (B-LCL) that served as antigen presenting cells. The proliferation of T-cells in the presence of autologous B-LCL was analyzed using 3H-thymidine incorporation. The presence of EBV in atherosclerotic material was analyzed by PCR. Results Of the 19 cell obtained T-cell cultures, 11 responded to EBV (58%, mean stimulation index: 10.1 ± 3.1). PCR analysis showed that EBV DNA was present in 15 of the tissue samples (79%). All the specimens that contained EBV responding T-cells also contained EBV. EBV specific T-cells secreted granzymes, as indication of functional cytotoxic potential. Conclusions EBV-specific cytotoxic T-cells and EBV DNA can be frequently observed in human atherosclerotic plaques. This suggests that a T-cell response against EBV could contribute to plaque inflammation, and thus to the onset of acute clinical symptoms.

Treatment of EBV-Related Post-Renal Transplant Lymphoproliferative Disease with a Tailored Regimen Including EBV-Specific T Cells

The treatment of EBV-associated post-transplant lymphoproliferative disease (PTLD) poses a considerable challenge. Efforts have been made to define regimens based on combination of the available therapeutic agents, chosen and tailored on a patient-by-patient basis, with the aim of augmenting event-free patient and graft survival. Recently, autologous EBV-specific cytotoxic T-lymphocytes (CTL) have proved effective in enhancing EBV-specific immune responses and reducing viral load in organ transplant recipients with active infection. We investigated the use of a tailored combined approach including autologous EBV-specific CTL for the treatment of EBV-related PTLD developing after pediatric kidney transplantation. Five patients with disseminated monoclonal (n = 3) or localized polyclonal (n = 2) PTLD unresponsive to reduction of immunosuppression were enrolled. The patients with disseminated PTLD received 4-5 courses of reduced-dosage polychemotherapy, accompanied by rituximab on the first day of each course, while localized disease was removed surgically. At treatment completion, autologous EBV-specific CTL were infused. All patients showed a complete response to treatment, without therapy-related toxicity or rejection, and persist in remission with good renal function at a median follow-up of 31 months. These preliminary results suggest that a combined chemoimmunotherapy regimen including virus-specific T-cells is well tolerated and potentially effective as first-line treatment of EBV-related PTLD.

801. Fas Knockdown Mediated by siRNA in EBV-Specific Cytotoxic T-Lymphocytes (CTL) Reduces Their Sensitivity to Fas/FasL-Induced Apoptosis

Adoptive immunotherapy with Epstein Barr Virus (EBV) specific CTL has been successfully used to treat patients with EBV related malignancies including Post Transplant Lymphoproliferative disorder, Hodgkin's lymphoma and Nasopharyngeal carcinoma. However, these and other potentially immunogenic tumors have evolved evasion strategies that subvert the effectiveness of the immune response. One such strategy involves expression of FasL, which likely impedes the host immune response by accelerating the apoptotic death of Fas-expressing tumor infiltrating T-cells.

Treatment of nasopharyngeal carcinoma with Epstein-Barr virus–specific T lymphocytes

AbstractConventional treatment for nasopharyngeal carcinoma (NPC) frequently fails and is accompanied by severe long-term side effects. Since virtually all undifferentiated NPCs are associated with Epstein-Barr virus (EBV), this tumor is an attractive candidate for cellular immunotherapy targeted against tumor-associated viral antigens. We now demonstrate that EBV-specific cytotoxic T-cell (CTL) lines can readily be generated from individuals with NPC, notwithstanding the patients' prior exposure to chemotherapy/radiation. A total of 10 patients diagnosed with advanced NPC were treated with autologous CTLs. All patients tolerated the CTLs, although one developed increased swelling at the site of pre-existing disease. At 19 to 27 months after infusion, 4 patients treated in remission from locally advanced disease remain disease free. Of 6 patients with refractory disease prior to treatment, 2 had complete responses, and remain in remission over 11 to 23 months after treatment; 1 had a partial remission that persisted for 12 months; 1 has had stable disease for more than 14 months; and 2 had no response. These results demonstrate that administration of EBV-specific CTLs to patients with advanced NPC is feasible, appears to be safe, and can be associated with significant antitumor activity.

Adoptive Immunotherapy for EBV-associated Malignancies

Latent Epstein-Barr virus (EBV) infection is associated with a diverse group of malignancies including Burkitt's lymphoma, Hodgkin's disease, nasopharyngeal carcinoma (NPC), and lymphoproliferative disease (LPD). EBV proteins expressed in these malignancies provide targets for the adoptive immunotherapy with antigen-specific cytotoxic T cells (CTL) and EBV-specific CTL have been used successfully for the prophylaxis and treatment of EBV-LPD post hematopoietic stem cell transplantation (HSCT). The clinical experience with EBV-specific CTL for other EBV-associated malignancies such as Hodgkin's disease and NPC is limited and the results obtained so far indicate that EBV-specific CTL are less effective than for EBV-LPD post HSCT. Decreased CTL efficacy most likely reflect immune evasion strategies by tumor cells such as down regulation of immunodominant EBV proteins and secretion of inhibitory cytokines. To overcome these immune evasion strategies a number of approaches have been developed including targeting CTL to subdominant EBV antigens and genetically modifying CTL to increase their potency.

Fas Down-Modulation in Epstein Barr Virus (EBV)-Specific Cytotoxic T-Lymphocytes (CTLs) Reduces Their Sensitivity to Fas/Fasl-Induced Apoptosis.

Adoptive immunotherapy with Epstein Barr Virus (EBV)-specific CTL has been successfully used to treat patients with EBV related malignancies including Post Transplant Lymphoproliferative disorder, Hodgkin's lymphoma and Nasopharyngeal carcinoma. However, these and other potentially immunogenic tumors have evolved evasion strategies that subvert the effectiveness of the immune response. One such strategy involves expression of FasL, which likely impedes the host immune response by accelerating the apoptotic death of Fas-expressing tumor infiltrating T-cells. EBV-specific CTLs, like most effector memory T cells express high levels of Fas and are highly sensitive to cross-linking of the ligand. We therefore determined whether EBV-specific CTLs could be genetically modified to resist FasL-mediated immune evasion. We used retroviral siRNA (pSUPER.retro) directed against the Fas gene product to knockdown receptor expression in tumor-antigen specific CTLs. Transduction of CTLs with siRNA targeting Fas mRNA significantly knocked down Fas expression compared to control cells (Fas MFI 107 ± 47 vs. 402 ± 47, p<0.001). This effect was paralleled by a significant reduction of apoptosis induced by the Fas agonistic antibody (clone CH-11) in modified CTLs compared to control cells (23% ± 3% vs. 44% ± 7% p=0.006). Fas down-modulation was stable over time in CTLs modified, and addition of CH-11 antibody to the culture selected a uniformly Faslow CTL population (Fas MFI 79 ± 29) that was entirely resistant to FasL mediated lysis. However, germ line deletions as well as function-impairing mutations of Fas and FasL can induce T-lymphoproliferation and autoimmune diseases. We therefore compared the growth characteristics and the antigen specificity of unmodified and Fas knockdown CTLs. Survival and proliferation of genetically modified CTLs remain completely dependent on antigen specific stimulation and the presence of other physiological growth signals. Moreover, as assessed by the analysis of the Vb TcR repertoire, IFN-g-release (Elispot) and tetramer staining the modified CTLs remained polyclonal and conserved their antigen specificity. These data suggest that responsiveness to this single death signal may be removed from an effector-memory population of CTLs without adversely affecting their safety. Tumor-antigen-specific CTLs with lower expression of Fas receptor should have a selective functional and survival advantage over unmodified CTLs in the presence of tumors expressing FasL, and may be of value for adoptive cellular therapy of such malignancies.

Success of Adoptive Immunotherapy Followed by Stem Cell Transplantation in the Management of Epstein Barr Virus (EBV)-Driven Primary Central Nervous System Lymphoma (PCNSL) in Immunodeficient Child.

EBV-driven PCNSL is a rare form of B-cell non-Hodgkin's lymphoma (NHL) seen in immuno-compromised (particularly AIDs) patients. The prognosis is gloomy and most patients die of their disease as radiotherapy and chemotherapy are usually ineffective in inducing durable remission. We report successful treatment of an 8 years old girl who presented with multifocal EBV-driven B-cell PCNSL with adoptive immunotherapy. Due to rarity of the disease particularly in children, she was investigated for and found to have an underlying primary immunodeficiency associated with defective immunity to herpes viruses. Her underlying immune defect did not fit with any of the currently well characterized congenital immune deficiency syndromes, but as also demonstrated in one of her two brothers, it seemed to have been inherited in an autosomal recessive fashion. Both were persistently lymphopenic (0.3–1.1 X 109/L), with proportionate reduction of T, B, and NK cells. Immunoglobulin classes were normal, as were specific antibody responses to tetanus. Mitogen responses to PHA, serum IgG2 levels and post-vaccination responses to Hib and Pneumococcus were low in both children. Antibody response to EBV was abnormal in both children with development of IgG antibodies to the capsular antigen (VCA) but not the nuclear antigen (EBNA). She was initially treated with conventional chemotherapy (intrathecal as well as systemic high dose Cytarabine and Methrotrexate), Rituximab, anti-virals and immunoglobulins. Neurological deterioration gradually progressed despite four weeks of such treatment. She eventually became bed ridden with quadreparesis and significant bulbar palsy requiring intubation for airway protection. In view of conventional treatment failure, immunotherapy with ex-vivo expanded EBV-specific cytotoxic T-lymphocytes (CTL) from a partially HLA matched donor was initiated. These were given weekly for seven consecutive weeks. There were no untoward effects. She made a remarkable neurological recovery within few weeks and became fully mobile in four months when she received non-myeloablative stem cell transplantation. Post transplant peripheral EBV reactivation (presenting as infectious mononucleosis-like disease without neurological manifestations) was promptly controlled with Rituximab and further doses of allogeneic EBV-CTLs. The child is now well five months post transplantation with evidence of immune reconstitution and remains in complete remission. GVHD prophylaxis has now been totally withdrawn. This is the first report of the successful use of EBV-specific cytotoxic T-lymphocytes in the treatment of primary CNS lymphoma in an immunocompromised patient. It offers new hope in a condition, which until now has been associated with a bleak outlook. The clinical response to immunotherapy is a clear demonstration that although the migration of resting blood lymphocytes across the inter-endothelial tight junctions forming the blood-brain-barrier may be largely restricted in physiological conditions, the migration of activated T lymphocytes into the brain in this clinical setting is unimpeded.