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

Membrane-bound CD95 ligand modulates CD19-mediated B cell receptor signaling and EBV activation

Post-transplant lymphoproliferative disorders (PTLDs) are associated with Epstein-Barr virus (EBV) infection in transplant recipients. Most of lymphoblastoid cell lines (LCLs) derived from EBV-immortalized B cells or PTLDs are sensitive to CD95-mediated apoptosis and cytotoxic T cell (CTL) killing. CD95 ligand (CD95L) exists as a transmembrane ligand (mCD95L) or a soluble form (sCD95L). Using recombinant mCD95L and sCD95L, we observed that sCD95L does not affect LCLs. While high expression of mCD95L in CTLs promotes apoptosis of LCLs, low expression induces clathrin-dependent CD19 internalization, caspase-dependent CD19 cleavage, and proteasomal/lysosomal-dependent CD19 degradation. The CD95L/CD95-mediated CD19 degradation impairs B cell receptor (BCR) signaling and inhibits BCR-mediated EBV activation. Interestingly, although inhibition of the caspase activity restores CD19 expression and CD19-mediated BCR activation, it fails to rescue BCR-mediated EBV lytic gene expression. EBV-specific CTLs engineered to overexpress mCD95L exhibit a stronger killing activity against LCLs. This study highlights that engineering EBV-specific CTLs to express a higher level of mCD95L could represent an attractive therapeutic approach to improve T cell immunotherapy for PTLDs.

In vitro and in vivo evidence that the switch from calcineurin to mTOR inhibitors may be a strategy for immunosuppression in Epstein-Barr virus-associated post-transplant lymphoproliferative disorder

Post-transplant lymphoproliferative disorder is a life-threatening complication of immunosuppression following transplantation mediated by failure of T cells to control Epstein-Barr virus (EBV)-infected and transformed B cells. Typically, a modification or reduction of immunosuppression is recommended, but insufficiently defined thus far. In order to help delineate this, we characterized EBV-antigen-specific T cells and lymphoblastoid cell lines from healthy donors and in patients with a kidney transplant in the absence or presence of the standard immunosuppressants tacrolimus, cyclosporin A, prednisolone, rapamycin, and mycophenolic acid. Phenotypes of lymphoblastoid cell-lines and T cells, T cell-receptor-repertoire diversity, and T-cell reactivity upon co-culture with autologous lymphoblastoid cell lines were analyzed. Rapamycin and mycophenolic acid inhibited lymphoblastoid cell-line proliferation. T cells treated with prednisolone and rapamycin showed nearly normal cytokine production. Proliferation and the viability of T cells were decreased by mycophenolic acid, while tacrolimus and cyclosporin A were strong suppressors of T-cell function including their killing activity. Overall, our study provides a basis for the clinical decision for the modification and reduction of immunosuppression and adds information to the complex balance of maintaining anti-viral immunity while preventing acute rejection. Thus, an immunosuppressive regime based on mTOR inhibition and reduced or withdrawn calcineurin inhibitors could be a promising strategy for patients with increased risk of or manifested EBV-associated post-transplant lymphoproliferative disorder.

Reinforcing the Immunocompromised Host Defense against Fungi: Progress beyond the Current State of the Art

Despite the availability of a variety of antifungal drugs, opportunistic fungal infections still remain life-threatening for immunocompromised patients, such as those undergoing allogeneic hematopoietic cell transplantation or solid organ transplantation. Suboptimal efficacy, toxicity, development of resistant variants and recurrent episodes are limitations associated with current antifungal drug therapy. Adjunctive immunotherapies reinforcing the host defense against fungi and aiding in clearance of opportunistic pathogens are continuously gaining ground in this battle. Here, we review alternative approaches for the management of fungal infections going beyond the state of the art and placing an emphasis on fungus-specific T cell immunotherapy. Harnessing the power of T cells in the form of adoptive immunotherapy represents the strenuous protagonist of the current immunotherapeutic approaches towards combating invasive fungal infections. The progress that has been made over the last years in this field and remaining challenges as well, will be discussed.

"Cerberus" T Cells: A Glucocorticoid-Resistant, Multi-Pathogen Specific T Cell Product to Fight Infections in Severely Immunocompromised Patients

Adoptive immunotherapy (AI) with pathogen-specific T cells is a promising alternative to pharmacotherapy for the treatment of opportunistic infections after allogeneic hematopoietic cell transplantation or solid organ transplantation. However, clinical implementation of AI is limited to patients not receiving high-dose steroids, a prerequisite for optimal T-cell function, practically excluding the most susceptible to infections patients from the benefits of AI. To address this issue, we here rapidly generated, clinical doses of a steroid-resistant T-cell product, simultaneously targeting four viruses (adenovirus, cytomegalovirus, Epstein Barr virus, and BK virus) and the fungus Aspergillus fumigatus, by genetic disruption of the glucocorticoid receptor (GR) gene using CRISPR/CAS9 ribonucleoprotein delivery. The product, “Cerberus” T cells (Cb-STs), was called after the monstrous three-headed dog of Greek mythology, due to its triple potential; specificity against viruses, specificity against fungi and resistance to glucocorticoids. Following efficient on-target GR disruption and minimal off-target editing, the generated Cb-STs maintained the characteristics of pentavalent-STs, their unedited counterparts, including polyclonality, memory immunophenotype, specificity, and cytotoxicity while they presented functional resistance to dexamethasone. Cb-STs may become a powerful, one-time treatment for severely immunosuppressed patients under glucocorticoids who suffer from multiple, life-threatening infections post-transplant, and for whom therapeutic choices are limited.

CRISPR-Cas9-Edited Tacrolimus-Resistant Antiviral T Cells for Advanced Adoptive Immunotherapy in Transplant Recipients

Viral infections, such as with cytomegalovirus (CMV), remain a major risk factor for mortality and morbidity of transplant recipients because of their requirement for lifelong immunosuppression (IS). Antiviral drugs often cause toxicity and sometimes fail to control disease. Thus, regeneration of the antiviral immune response by adoptive antiviral T cell therapy is an attractive alternative. Our recent data, however, show only short-term efficacy in some solid organ recipients, possibly because of malfunction in transferred T cells caused by ongoing IS. We developed a vector-free clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9-based good manufacturing practice (GMP)-compliant protocol that efficiently targets and knocks out the gene for the adaptor protein FK506-binding protein 12 (FKBP12), required for the immunosuppressive function of tacrolimus. This was achieved by transient delivery of ribonucleoprotein complexes into CMV-specific T cells by electroporation. We confirmed the tacrolimus resistance of our gene-edited T cell products in vitro and demonstrated performance comparable with non-tacrolimus-treated unmodified T cells. The alternative calcineurin inhibitor cyclosporine A can be administered as a safety switch to shut down tacrolimus-resistant T cell activity in case of adverse effects. Furthermore, we performed safety assessments as a prerequisite for translation to first-in-human applications.

A High-Avidity T-cell Receptor Redirects Natural Killer T-cell Specificity and Outcompetes the Endogenous Invariant T-cell Receptor

T-cell receptor (TCR) gene transfer redirects T cells to target intracellular antigens. However, the potential autoreactivity generated by TCR mispairing and occurrence of graft-versus-host disease in the allogenic setting due to the retention of native TCRs remain major concerns. Natural killer T cells (NKT) have shown promise as a platform for adoptive T-cell therapy in cancer patients. Here, we showed their utility for TCR gene transfer. We successfully engineered and expanded NKTs expressing a functional TCR (TCR NKTs), showing HLA-restricted antitumor activity in xenogeneic mouse models in the absence of graft-versus-mouse reactions. We found that TCR NKTs downregulated the invariant TCR (iTCR), leading to iTCR⁺TCR⁺ and iTCR^-TCR⁺ populations. In-depth analyses of these subsets revealed that in iTCR^-TCR⁺ NKTs, the iTCR, although expressed at the mRNA and protein levels, was retained in the cytoplasm. This effect resulted from a competition for binding to CD3 molecules for cell-surface expression by the transgenic TCR. Overall, our results highlight the feasibility and advantages of using NKTs for TCR expression for adoptive cell immunotherapies. NKT-low intrinsic alloreactivity that associated with the observed iTCR displacement by the engineered TCR represents ideal characteristics for "off-the-shelf" products without further TCR gene editing.

Infection in Organ Transplantation

The prevention, diagnosis, and management of infectious disease in transplantation are major contributors to improved outcomes in organ transplantation. The risk of serious infections in organ recipients is determined by interactions between the patient's epidemiological exposures and net state of immune suppression. In organ recipients, there is a significant incidence of drug toxicity and a propensity for drug interactions with immunosuppressive agents used to maintain graft function. Thus, every effort must be made to establish specific microbiologic diagnoses to optimize therapy. A timeline can be created to develop a differential diagnosis of infection in transplantation based on common patterns of infectious exposures, immunosuppressive management, and antimicrobial prophylaxis. Application of quantitative molecular microbial assays and advanced antimicrobial therapies have advanced care. Pathogen-specific immunity, genetic polymorphisms in immune responses, and dynamic interactions between the microbiome and the risk of infection are beginning to be explored. The role of infection in the stimulation of alloimmune responses awaits further definition. Major hurdles include the shifting worldwide epidemiology of infections, increasing antimicrobial resistance, suboptimal assays for the microbiologic screening of organ donors, and virus-associated malignancies. Transplant infectious disease remains a key to the clinical and scientific investigation of organ transplantation.

Adoptive immunotherapy for primary immunodeficiency disorders with virus-specific T lymphocytes

BACKGROUND

Viral infections are a leading fatal complication for patients with primary immunodeficiencies (PIDs) who require hematopoietic stem cell transplantation (HSCT). Use of virus-specific T lymphocytes (VSTs) has been successful for the treatment and prevention of viral infections after HSCT for malignant and nonmalignant conditions. Here we describe the clinical use of VSTs in patients with PIDs at 4 centers.

OBJECTIVE

We sought to evaluate the safety and efficacy of VSTs for treatment of viral infections in patients with PIDs.

METHODS

Patients with PIDs who have received VST therapy on previous or current protocols were reviewed in aggregate. Clinical information, including transplantation details, viral infections, and use of antiviral and immunosuppressive pharmacotherapy, were evaluated. Data regarding VST production, infusions, and adverse reactions were compared.

RESULTS

Thirty-six patients with 12 classes of PID diagnoses received 37 VST products before or after HSCT. Twenty-six (72%) patients had received a diagnosis of infection with cytomegalovirus, EBV, adenovirus, BK virus, and/or human herpesvirus 6. Two patients were treated before HSCT because of EBV-associated lymphoproliferative disease. Partial or complete responses against targeted viruses occurred in 81% of patients overall. Time to response varied from 2 weeks to 3 months (median, 28 days). Overall survival at 6 months after therapy was 80%. Four patients had graft-versus-host disease in the 45 days after VST infusion, which in most cases was therapy responsive.

CONCLUSION

VSTs derived from either stem cell donors or third-party donors are likely safe and effective for the treatment of viral infections in patients with PIDs.

Adoptive T-Cell Immunotherapy

Epstein-Barr virus (EBV) is associated with a range of malignancies involving B cells, T cells, natural killer (NK) cells, epithelial cells, and smooth muscle. All of these are associated with the latent life cycles of EBV, but the pattern of latency-associated viral antigens expressed in tumor cells depends on the type of tumor. EBV-specific T cells (EBVSTs) have been explored as prophylaxis and therapy for EBV-associated malignancies for more than two decades. EBVSTs have been most successful as prophylaxis and therapy for post-transplant lymphoproliferative disease (PTLD) , which expresses the full array of latent EBV antigens (type 3 latency), in hematopoietic stem-cell transplant (HSCT) recipients. While less effective, clinical studies have also demonstrated their therapeutic potential for PTLD post-solid organ transplant and for EBV-associated malignancies such as Hodgkin's lymphoma, non-Hodgkin's lymphoma, and nasopharyngeal carcinoma (NPC) that express a limited array of latent EBV antigens (type 2 latency). Several approaches are actively being pursued to improve the antitumor activity of EBVSTs including activation and expansion of T cells specific for the EBV antigens expressed in type 2 latency, genetic approaches to render EBVSTs resistant to the immunosuppressive tumor environment, and combination approaches with other immune-modulating modalities. Given the recent advances and renewed interest in cell therapy, we hope that EBVSTs will become an integral part of our treatment armamentarium against EBV-positive malignancies in the near-future.

Towards gene therapy for EBV-associated posttransplant lymphoma with genetically modified EBV-specific cytotoxic T cells

Epstein-Barr virus (EBV)-associated posttransplant lymphoma (PTLD) is a major cause of morbidity/mortality after hematopoietic stem cell (SCT) or solid organ (SOT) transplant. Adoptive immunotherapy with EBV-specific cytotoxic lymphocytes (CTLs), although effective in SCT, is less successful after SOT where lifelong immunosuppression therapy is necessary. We have genetically engineered EBV-CTLs to render them resistant to calcineurin (CN) inhibitor FK506 through retroviral transfer of a calcineurin A mutant (CNA12). Here we examined whether or not FK506-resistant EBV-CTLs control EBV-driven tumor progression in the presence of immunosuppression in a xenogeneic mouse model. NOD/SCID/IL2rγ(null) mice bearing human B-cell lymphoma were injected with autologous CTLs transduced with either CNA12 or eGFP in the presence/absence of FK506. Adoptive transfer of autologous CNA12-CTLs induced dramatic lymphoma regression despite the presence of FK506, whereas eGFP-CTLs did not. CNA12-CTLs persisted longer, homed to the tumor, and expanded more than eGFP-CTLs in mice treated with FK506. Mice receiving CNA12-CTLs and treated with FK506 survived significantly longer than control-treated animals. Our results demonstrate that CNA12-CTL induce regression of EBV-associated tumors in vivo despite ongoing immunosuppression. Clinical application of this novel approach may enhance the efficacy of adoptive transfer of EBV-CTL in SOT patients developing PTLD without the need for reduction in immunosuppressive therapy.

Rapid generation of EBV-specific cytotoxic T lymphocytes resistant to calcineurin inhibitors for adoptive immunotherapy

Epstein-Barr virus (EBV)-associated posttransplant lymphoproliferative disorder (PTLD) remains a major cause of morbidity and mortality after hematopoietic stem cell (HSCT) or solid organ transplant (SOT). Strategies to reconstitute immunity by adoptive transfer of EBV-specific cytotoxic T lymphocyte (CTL) therapy while highly effective in the HSCT setting where immunosuppression can be withdrawn have been less successful in the SOT setting where continued immunosuppression therapy is necessary. Additionally, the complexity and time taken to generate EBV-CTLs for adoptive transfer limit the clinical applicability. We have developed a system for the rapid generation of EBV-CTLs resistant to immunosuppression based on selection of interferon-gamma (IFN-γ) secreting EBV-CTLs and retroviral transduction with a calcineurin B mutant. With this methodology, EBV-CTLs resistant to the calcineurin inhibitor Tacrolimus (TAC) can be produced in 14 days. These CTLs show high specificity for EBV with negligible alloreactivity in both proliferation and cytotoxicity assays and are able to proliferate and secrete IFN-γ in response to antigen stimulation in the presence of therapeutic doses of TAC. This strategy will substantially facilitate clinical application of this approach for the treatment of PTLD in SOT recipients.

Comparison of different suicide-gene strategies for the safety improvement of genetically manipulated T cells

Use of adoptive T-cell therapy (ACT) is increasing; however, T-cell therapy can result in severe toxicity. Consequently, several suicide-gene strategies that allow selective destruction of the infused T cells have been described. We compared effectiveness of four such strategies in vitro in Epstein Barr virus (EBV)-cytotoxic T lymphocytes (CTLs). Herpes simplex virus thymidine kinase (HSV-TK), human inducible caspase 9 (iCasp9), mutant human thymidylate kinase (mTMPK), and human CD20 codon optimized genes were cloned in frame with 2A-truncated codon optimized CD34 (dCD34) in a retroviral vector. Codon-optimization considerably improved CD20 expression. EBV-CTLs could be efficiently transduced in all constructs, with transgene expression similar to the control vector containing dCD34 alone. Expression was maintained for prolonged cultures. Expression of the suicide genes was not associated with alterations in immunophenotype, proliferation, or function of CTLs. Activation of HSV-TK, iCasp9, and CD20 ultimately resulted in equally effective destruction of transduced T cells. However, while iCasp9 and CD20 effected immediate cell-death induction, HSV-TK-expressing T cells required 3 days of exposure to ganciclovir to reach full effect. mTMPK-transduced cells showed lower T-cell killing all time points. Our results suggest that the faster activity of iCasp9 might be advantageous in treating certain types of acutely life-threatening toxicity. Codon-optimized CD20 has potential as a suicide gene.

Plasma markers of B-cell activation and clonality in pediatric liver and hematopoietic stem cell transplant recipients

BACKGROUND

Transplant recipients are at risk of posttransplant lymphoproliferative disease (PTLD).

METHODS

Thirty-six pediatric transplant recipients were evaluated (18 hematopoietic stem cell and 18 liver recipients; 12 had PTLD). We studied 207 longitudinal plasma samples from these recipients for three markers of B-cell activation or clonality: immunoglobulin free light chains (FLCs), soluble CD30 (sCD30), and monoclonal immunoglobulins (M-proteins).

RESULTS

Kappa FLCs, lambda FLCs, and sCD30 were elevated in 20.8%, 28.0%, and 94.2% of plasma specimens, respectively. Free light chain and sCD30 levels increased significantly 1.18 to 1.82 fold per log10 Epstein-Barr virus (EBV) load in peripheral blood. Five PTLD cases manifested elevated FLCs with an abnormal kappa/lambda ratio, suggesting monoclonal FLC production. M-proteins were present in 91% of PTLD cases versus 50% to 67% of other recipients with high or low EBV loads (P=0.13). Concordance of FLCs, M-proteins, and PTLD tumor light chain restriction was imperfect. For example, one PTLD case with an IgG lambda M-protein had a tumor that was kappa restricted, and another case with an M-protein had a T-cell PTLD. In an additional case, an IgM kappa M-protein and excess kappa FLCs were both detected in plasma at PTLD diagnosis; although the tumor was not restricted at diagnosis, kappa restriction was present 5 years later when the PTLD relapsed.

CONCLUSIONS

Plasma markers of B-cell dysfunction are frequent after transplantation and associated with poor EBV control. These abnormal markers may be produced by oligoclonal B-cell populations or PTLD tumor cells and could potentially help identify recipients at high risk of PTLD.

Ex vivo expansion of tumor-infiltrating lymphocytes from nasopharyngeal carcinoma patients for adoptive immunotherapy

Establishing Epstein-Barr virus (EBV)-specific cytolytic T lymphocytes (EBV-CTLs) from peripheral blood mononuclear cells (PBMCs) for adoptive immunotherapy has been reported in EBV-associated malignancies including Hodgkin's lymphoma and nasopharyngeal carcinoma (NPC). In the current study, we performed ex vivo expansion of tumor-infiltrating lymphocytes (TILs) obtained from NPC biopsy specimens with a rapid expansion protocol using anti-CD3 monoclonal antibody (OKT3), recombinant human interleukin (IL)-2, and irradiated PBMCs from healthy donors to initiate the growth of TILs. Young TIL cultures comprised of more than 90% of CD3⁺ T cells, a variable percentage of CD3⁺CD8⁺ and CD3⁺ CD4⁺ T cells, and less than 10% of CD3⁻CD16⁺ natural killer cells, a similar phenotype of EBV-CTL cultures from PBMCs. Interestingly, TIL cultures secreted high levels of the Th1 cytokines, interferon gamma (IFNγ) and tumor necrosis factor-alpha (TNF-α), and low levels of the Th2 cytokines, IL-4 and IL-10. Moreover, young TILs could recognize autologous EBV-transformed B lymphoblast cell lines, but not autologous EBV-negative blast cells or allogeneic EBV-negative tumor cells. Taken together, these data suggest that ex vivo expansion of TILs from NPC biopsy tissue is an appealing alternative method to establish T cell-based immunotherapy for NPC.

In Vitro and In Vivo Antitumor Effect of Anti-CD33 Chimeric Receptor-Expressing EBV-CTL against CD33 Acute Myeloid Leukemia

Genetic engineering of T cells with chimeric T-cell receptors (CARs) is an attractive strategy to treat malignancies. It extends the range of antigens for adoptive T-cell immunotherapy, and major mechanisms of tumor escape are bypassed. With this strategy we redirected immune responses towards the CD33 antigen to target acute myeloid leukemia. To improve in vivo T-cell persistence, we modified human Epstein Barr Virus-(EBV-) specific cytotoxic T cells with an anti-CD33.CAR. Genetically modified T cells displayed EBV and HLA-unrestricted CD33 bispecificity in vitro. In addition, though showing a myeloablative activity, they did not irreversibly impair the clonogenic potential of normal CD34(+) hematopoietic progenitors. Moreover, after intravenous administration into CD33(+) human acute myeloid leukemia-bearing NOD-SCID mice, anti-CD33-EBV-specific T cells reached the tumor sites exerting antitumor activity in vivo. In conclusion, targeting CD33 by CAR-modified EBV-specific T cells may provide additional therapeutic benefit to AML patients as compared to conventional chemotherapy or transplantation regimens alone.

Characterization and treatment of chronic active Epstein-Barr virus disease: a 28-year experience in the United States

Chronic active EBV disease (CAEBV) is a lymphoproliferative disorder characterized by markedly elevated levels of antibody to EBV or EBV DNA in the blood and EBV RNA or protein in lymphocytes in tissues. We present our experience with CAEBV during the last 28 years, including the first 8 cases treated with hematopoietic stem cell transplantation in the United States. Most cases of CAEBV have been reported from Japan. Unlike CAEBV in Japan, where EBV is nearly always found in T or natural killer (NK) cells in tissues, EBV was usually detected in B cells in tissues from our patients. Most patients presented with lymphadenopathy and splenomegaly; fever, hepatitis, and pancytopenia were common. Most patients died of infection or progressive lymphoproliferation. Unlike cases reported from Japan, our patients often showed a progressive loss of B cells and hypogammaglobulinemia. Although patients with CAEBV from Japan have normal or increased numbers of NK cells, many of our patients had reduced NK-cell numbers. Although immunosuppressive agents, rituximab, autologous cytotoxic T cells, or cytotoxic chemotherapy often resulted in short-term remissions, they were not curative. Hematopoietic stem cell transplantation was often curative for CAEBV, even in patients with active lymphoproliferative disease that was unresponsive to chemotherapy. These studies are registered at http://www.clinicaltrials.gov as NCT00032513 for CAEBV, NCT00062868 and NCT00058812 for EBV-specific T-cell studies, and NCT00578539 for the hematopoietic stem cell transplantation protocol.

Generation of EBV-specific cytotoxic T cells that are resistant to calcineurin inhibitors for the treatment of posttransplantation lymphoproliferative disease

Epstein-Barr virus (EBV)-driven posttransplantation lymphoproliferative disease (PTLD) is a serious complication of immunosuppression after either stem cell transplantation (SCT) or solid organ transplantation (SOT). Adoptive transfer of EBV-specific cytotoxic T lymphocytes (EBV-CTLs) is an effective prophylaxis and treatment for PTLD after SCT, but not for PTLD after SOT when pharmacologic immunosuppression cannot be discontinued. We report the generation of calcineurin (CN) mutants that render EBV-CTL resistant to the immunosuppressants tacrolimus (FK506) and cyclosporin A (CsA): mutant CNa12 confers resistance to CsA but not FK506, and mutant CNa22 confers resistance to FK506 but not CsA, whereas mutant CNb30 renders CTLs resistant to both calcineurin inhibitors. Untransduced EBV-CTLs do not proliferate in the presence of FK506/CsA. However, EBV-CTLs transduced with a retroviral vector coding for these mutants retain the ability to both proliferate and secrete normal levels of interferon-gamma in the presence therapeutic levels of FK506 (CNa12), CsA (CNa22), or both (CNb30). The cytotoxicity and phenotype of EBV-CTL lines were unaffected by expression of these mutant CNs. This approach should allow effective immunotherapy with EBV-CTLs in the SOT setting without risking the graft by reduction in immunosuppression, and represents a generic approach to improving immunotherapy in the face of immunosuppression.

Generation of Epstein-Barr virus-specific cytotoxic T lymphocytes resistant to the immunosuppressive drug tacrolimus (FK506)

Adoptive transfer of autologous Epstein-Barr virus-specific cytotoxic T lymphocytes (EBV-CTLs) to solid organ transplant (SOT) recipients has been shown safe and effective for the treatment of EBV-associated posttransplantation lymphoproliferative disorders (PTLDs). SOT recipients, however, require the continuous administration of immunosuppressive drugs to prevent graft rejection, and these agents may significantly limit the long-term persistence of transferred EBV-CTLs, precluding their use as prophylaxis. Tacrolimus (FK506) is one of the most widely used immunosuppressive agents in SOT recipients, and its immunosuppressive effects are largely dependent on its interaction with the 12-kDa FK506-binding protein (FKBP12). We have knocked down the expression of FKBP12 in EBV-CTLs using a specific small interfering RNA (siRNA) stably expressed from a retroviral vector and found that FKBP12-silenced EBV-CTLs are FK506 resistant. These cells continue to expand in the presence of the drug without measurable impairment of their antigen specificity or cytotoxic activity. We confirmed their FK506 resistance and anti-PTLD activity in vivo using a xenogenic mouse model, suggesting that the proposed strategy may be of value to enhance EBV-specific immune surveillance in patients at high risk of PTLD after transplantation.

EBV-positive human sera contain antibodies against the EBV BMRF-2 protein

We previously showed that the EBV glycoprotein BMRF-2 contains a functional integrin-binding Arg-Gly-Asp (RGD) domain that plays an important role in viral infection and cell-to-cell spread of progeny virions in oral epithelial cells. In this study, we found that EBV-seropositive human sera contain antibodies against BMRF-2. The inhibitory effect of EBV-positive sera on EBV infection of oral epithelial cells was substantially reduced by pre-incubation of serum samples with the BMRF-2 RGD peptide, suggesting that anti-BMRF-2 human antibodies possess neutralizing activity. EBV-specific sera reacted strongly with the BMRF-2 extracellular domain (170-213 aa) containing the RGD motif, whereas they reacted only weakly or not at all with a mutated form of the BMRF-2 extracellular domain containing AAA instead of RGD. These data indicate that RGD motif of BMRF-2 is part of an immunodominant antigenic determinant within the extracellular domain of BMRF-2 that may contribute to EBV neutralization during EBV reactivation.

Late donor cardiectomy after paediatric heterotopic cardiac transplantation

BACKGROUND

Cardiac transplantation is a life-saving procedure in infants and children with advanced cardiomyopathy. However, it is greatly limited by shortage of paediatric donors and the complications of long-term immunosuppression, including post-transplant lymphoproliferative disorder (PTLD). We report the management of an infant who had heterotopic cardiac transplantation for advanced cardiomyopathy with secondary pulmonary hypertension who developed seemingly incurable PTLD.

METHODS

An 8-month-old girl presented in 1994 with signs of severe heart failure, secondary to dilated cardiomyopathy. At age 11 months, the patient underwent a heterotopic cardiac transplantation.

FINDINGS

The patient developed many episodes of PTLD associated with Epstein-Barr virus infection that were resistant to several therapies, including reduction of immunosuppression. Native heart recovery enabled removal of the donor heart 10.5 years after the original operation to allow complete cessation of immunosuppression. Her postoperative course was uncomplicated and the outcome was excellent. 3.5 years after surgery, the patient remains well, in complete remission from her PTLD, and has normal cardiac function.

INTERPRETATION

This case shows several issues relating to the use of heterotopic cardiac transplantation in infants and the capacity of the heart to recover. It also provides new insights into the interaction between the immune system with several aspects of modern management of post-transplantation PTLD.

FUNDING

None.

NK cell-mediated lysis is essential to kill Epstein-Barr virus transformed lymphoblastoid B cells when using rituximab

Rituximab is a humanized chimeric monoclonal antibody, targeted against the pan B cell marker CD20. It is frequently used to treat a variety of B cell lymphomas and immunosuppression associated lymphoproliferations such as posttransplant lymphoproliferative disorder (PTLD). The response rate of rituximab treatment is 65%, but the exact in vivo mechanism of action is not yet fully understood, although antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and direct induction of apoptosis have been suggested as effector mechanism. Rituximab may affect different types of lymphomas through different mechanisms. As lymphoblastoid cell lines (LCLs) are well-established in vitro models of PTLD, we investigated the effect of rituximab on these cells using a custom built automated laser confocal fluorescent microscope. We found that rituximab alone was not effective at inducing cell death of EBV-transformed B cells. The antibody was effective in the complement-mediated CDC. Rituximab could induce NK cell-mediated ADCC but it was more effective in the presence of untreated fresh human plasma compared to heat-inactivated human plasma. Our data suggest that complement-enhanced NK-mediated ADCC is required for effective rituximab mediated killing of EBV-transformed B cells. Determining and monitoring of serum complement levels and in vitro killing efficacy of NK cells of PTLD patients might help to predict resistant cases to rituximab therapy. On the other hand our results suggest a possibility that rituximab should be combined only with cytotoxic drugs that spare NK function when treating PTLD patients.

Mesenchymal stem cells exert differential effects on alloantigen and virus-specific T-cell responses

Mesenchymal stem cells (MSCs) suppress alloantigen-induced T-cell functions in vitro and infusion of third-party MSCs seems to be a promising therapy for graft-versus-host disease (GVHD). Little is known about the specificity of immunosuppression by MSCs, in particular the effect on immunity to pathogens. We have studied how MSCs affect T-cell responses specific to Epstein-Barr virus (EBV) and cytomegalovirus (CMV). We found that EBV- and CMV-induced proliferation and interferon-gamma (IFN-gamma) production from peripheral blood mononuclear cells (PBMCs) was less affected by third-party MSCs than the response to alloantigen and that MSCs had no effect on expansion of EBV and CMV pentamer-specific T cells. Established EBV-specific cytotoxic T cells (CTL) or CMV-CTL cultured with MSCs retained the ability to proliferate and produce IFN-gamma in response to their cognate antigen and to kill virally infected targets. Finally, PBMCs from 2 patients who received MSCs for acute GVHD showed persistence of CMV-specific T cells and retained IFN-gamma response to CMV after MSC infusion. In summary, MSCs have little effect on T-cell responses to EBV and CMV, which contrasts to their strong immunosuppressive effects on alloreactive T cells. These data have major implications for immunotherapy of GVHD with MSCs and suggest that the effector functions of virus-specific T cells may be retained after MSC infusion.

Posttransplant Epstein-Barr virus-associated myogenic tumors: case report and review of the literature

Epstein-Barr virus (EBV) has been implicated in the pathogenesis of different types of malignancies. While nonmelanoma skin cancers, lymphomas and Kaposi sarcomas are the most frequently reported malignancies after solid organ transplantation, EBV-associated smooth muscle tumors (EBV-SMT) after transplantation are rare and thus far only 18 cases in kidney recipients have been reported. A case of a 51-year-old kidney transplant recipient diagnosed with EBV-SMT is reported together with a review of the literature.

Protection from infection with severe acute respiratory syndrome coronavirus in a Chinese hamster model by equine neutralizing F(ab')2

To warrant potential clinical testing, the equine anti-severe acute respiratory syndrome coronavirus (SARS-CoV) F(ab')(2) requires evaluation in as many animal models as possible. In this study, we established a new animal model, the Chinese hamster, susceptible to SARS-CoV infection. SARS-CoV could propagate effectively and sustain high levels for 1 wk in animal lungs. All animals were protected from SARS-CoV infection in preventive settings. Further, when used therapeutically this antibody led to an approximately 4-log(10) decrease in viral burden in infected animal lungs. The pathological changes in lungs correlated closely with the dose of antibody administered. The excellent preventive and therapeutic roles of equine anti-SARS-CoV F(ab')(2) in several animal models, including the novel Chinese hamster model described in this study, have provided exciting data concerning its potential clinical study.

Evaluation of the safety, immunogenicity and pharmacokinetics of equine anti-SARS-CoV F(ab')(2) in macaque

To warrant potential clinical testing, the equine anti-SARS-CoV F(ab')(2) requires evaluation in as many animal models as possible and a safety test in a primate model. In this study, we evaluated the pharmacokinetics, tolerance and immunity of this kind of antibody in macaques and rats. Results showed that the F(ab')(2) fragments had a normal metabolism in injected animals. The general physiological indexes did not differ between animals injected with anti-SARS-CoV F(ab')(2) or saline. However, a mild inflammatory response in local injection site and a moderate immune response against this antibody in the successively injected animals were observed, which however recovered 3 weeks after the last injection. The antibody titring from 1:100 to 400 against the equine anti-SARS-CoV F(ab')(2) in the inoculated hosts could be detected at week 2 during the successive injections of the equine F(ab')(2). The considerable safety of this antibody used in primates and the fact that the immune system of the host can be motivated by post-injection of the F(ab')(2) indicate that this type of anti-SARS-CoV antibody can be used for prevention and treatment of SASR, especially at the early stage of this virus infection. In addition, it can also provide the precious time for the combined use of other anti-SARS-CoV agents such as antiviral drug and vaccine.

Ex vivo generation of cytokine-induced killer cells (CD3+ CD56+) from post-stem cell transplant pediatric patients against autologous-Epstein-Barr virus-transformed lymphoblastoid cell lines

EBV-PTLDs affect as high as 20% of SCT recipients especially those with T-cell depleted grafts while high mortality rates were also noted. Adoptive allogeneic and autologous CTLs have a therapeutic potential in this setting. However, the process of expansion of these cells is tedious and time consuming in both allogeneic and autologous CTL generation. For the allogeneic SCT, another major obstacle is unavailability of donors especially in an unrelated SCT setting. The aim of the present study was therefore to investigate the efficacy of autologous CIK cells (CD3+ CD56+) against autologous EBV-LCLs from post-SCT pediatric patients. We could demonstrate that CIK cells can be generated within two wk and did show the significant cytotoxicity against autologous EBV-LCLs. CIK cells may provide a potent tool for use in post-transplantation adoptive immunotherapy.

Generation of Trispecific Cytotoxic T Cells Recognizing Cytomegalovirus, Adenovirus, and Epstein-Barr Virus

Cytomegalovirus (CMV), adenovirus (Ad), and Epstein-Barr virus (EBV) are a major cause of morbidity and mortality after allogeneic stem cell transplantation (SCT). Adoptive immunotherapy with donor-derived cytotoxic T cells (CTLs) directed against EBV or CMV prevents the clinical manifestations of these viruses. We have designed a protocol for the simultaneous generation of polyclonal CTL specific for CMV, Ad, and EBV, which could be used to restore immunity to multiple viruses after SCT. EBV-transformed lymphoblastoid cell lines (LCLs), transduced with an adenoviral vector carrying a transgene for the immunodominant CMV antigen pp65 (Ad5f35-pp65GFP), were used to stimulate peripheral blood mononuclear cells in 6 normal donors. We detected the simultaneous presence of CD8 CTL recognizing peptide epitopes from all 3 viruses by pentamer staining. Enzyme-linked immunospot assays demonstrated a median 29-fold (8 to 248), 47-fold (2 to 137), or 18-fold (5 to 29) increase in cells secreting interferon-gamma in response to CMV, adenoviral, or EBV antigens, respectively, compared with unmanipulated peripheral blood mononuclear cell, with concomitant loss of alloreactivity. The CTL lines showed cytotoxicity against autologous LCL alone and increased cytotoxicity to autologous LCLs pulsed with CMV pp65 peptides or infected with Ad. In summary, we have developed a protocol for the generation of CTL with trivirus specificity, enabling adoptive transfer of CTL recognizing multiple viruses to restore cellular immunity after SCT.

Epstein Barr virus specific cytotoxic T lymphocytes expressing the anti-CD30zeta artificial chimeric T-cell receptor for immunotherapy of Hodgkin disease

Adoptive transfer of Epstein Barr virus (EBV)-specific cytotoxic T-lymphocytes (EBV-CTLs) has shown that these cells persist in patients with EBV(+) Hodgkin lymphoma (HD) to produce complete tumor responses. Treatment failure, however, occurs if a subpopulation of malignant cells in the tumor lacks or loses expression of EBV antigens. We have therefore determined whether we could prepare EBV-CTLs that retained the antitumor activity conferred by their native receptor while expressing a chimeric antigen receptor (CAR) specific for CD30, a molecule highly and consistently expressed on malignant Hodgkin Reed-Sternberg cells. We made a CD30CAR and were able to express it on 26% (+/- 11%) and 22% (+/- 5%) of EBV-CTLs generated from healthy donors and HD patients, respectively. These CD30CAR(+) CTLs killed both autologous EBV(+) cells through their native receptor and EBV(-)/CD30(+) targets through their major histocompatibility complex (MHC)-unrestricted CAR. A subpopulation of activated T cells also express CD30, but the CD30CAR(+) CTLs did not impair cellular immune responses, probably because normal T cells express lower levels of the target antigen. In a xenograft model, CD30CAR(+) EBV-CTLs could be costimulated by EBV-infected cells and produce antitumor effects even against EBV(-)/CD30(+) tumors. EBV-CTLs expressing both a native and a chimeric antigen receptor may therefore have added value for treatment of HD.

Immune-cell treatment of Epstein–Barr-virus-associated lymphoproliferative disorders

Lymphoproliferative disorders associated with Epstein--Barr virus (EBV) after bone-marrow or organ transplantation express all the immunogenic EBV antigens, and reduction in immunosuppressive treatment can result in permanent resolution. As such, the disease lends itself to EBV-directed immune-cell therapy. Successes have been achieved with both manipulated and unmanipulated T-cell infusions for lymphoproliferations occurring after bone-marrow transplantation. Several practical challenges have been overcome in applying EBV-specific T-cell therapy to the setting of organ-transplant-related lymphoproliferations. These include the generation of autologous cytotoxic T lymphocytes (CTLs), the creation of a partially HLA-matched cryopreserved allogeneic CTL bank, and the generation of autologous EBV-specific CTLs from EBV-naïve pediatric patients. The efficacy of immune-cell therapy in the setting of solid-organ transplantation is less well established than it is after T-cell-depleted allogeneic bone-marrow transplantation, and it is as yet not clear how to best to integrate CTL therapy with the anti-B-cell antibody rituximab, which has significant activity against these lymphoproliferations.

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.

Treatment of solid organ transplant recipients with autologous Epstein Barr virus-specific cytotoxic T lymphocytes (CTLs)

We have investigated the in vivo safety, efficacy, and persistence of autologous Epstein Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) for the treatment of solid organ transplant (SOT) recipients at high risk for EBV-associated posttransplantation lymphoproliferative disease (PTLD). EBV-CTLs generated from 35 patients expanded with normal kinetics contained both CD8 and CD4 lymphocytes and produced significant specific killing of autologous EBV-transformed B lymphoblastoid cell lines (LCLs). Twelve SOT recipients at high risk for PTLD, or with active disease, received autologous CTL infusions without toxicity. Real-time polymerase chain reaction (PCR) monitoring of EBV-DNA showed a transient increase in plasma EBV-DNA suggestive of lysis of EBV-infected cells, although there was no consistent decrease in virus load in peripheral-blood mononuclear cells. Interferon-gamma enzyme-linked immunospot (ELISPOT) assay and tetramer analysis showed an increase in the frequency of EBV-responsive T cells, which returned to preinfusion levels after 2 to 6 months. None of the treated patients developed PTLD. One patient with liver PTLD showed a complete response, and one with ocular disease has had a partial response stable for over one year. These data are consistent with an expansion and persistence of adoptively transferred EBV-CTLs that is limited in the presence of continued immunosuppression but that nonetheless produces clinically useful antiviral activity.

Epstein–Barr virus: the future for screening, treatment and monitoring of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is often not diagnosed until an advanced stage of the disease, and has a poor 5-year survival with current therapies. Thus, screening programs to identify high-risk patients at early disease stages are essential to improve patient outcomes, most likely through using Epstein–Barr virus (EBV) DNA monitoring in conjunction with tumor-specific markers. EBV-specific cytotoxic T lymphocytes (CTLs) have been utilized successfully for long-term regression of EBV-associated B-cell lymphomas, such as post-transplant lymphoproliferative disease. This strategy has recently been adapted to raise latent membrane proteins 1 and 2, and EBV nuclear antigen 1-specific CD8+ and CD4+ T cells to target EBV proteins expressed in NPC tumors. Future challenges will be focused on developing multiple-target therapies, including improving CTL persistence and tumor specificity. Understanding the role of EBV infection and protein expression in NPC will be pivotal in the development of screening protocols and novel treatments, including vaccines.

Post-transplant lymphoproliferative disorder

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

Protection of Mammalian Cells from Severe Acute Respiratory Syndrome Coronavirus Infection by Equine Neutralizing Antibody

The aetiological agent for severe acute respiratory syndrome (SARS) has been determined to be a new type of coronavirus (SARS-CoV) that infects a wide range of mammalian hosts. Up to now, there have been no specific drugs to protect against SARS-CoV infection, thus developing effective strategies against this newly emerged viral infection warrants urgent efforts. Adoptive immune therapy with pathogen-specific heterologous immunoglobulin has been successfully used to control the dissemination of many viral infections. To investigate whether a neutralizing antibody against SARS-CoV raised in an artiodactylous host can have a protective role on primate cells, we prepared serum IgGs and their pepsin-digested F(ab’)2 fragments from horses inoculated with purified SARS-CoV (BJ-01 strain). The protective effect of the F(ab’)2 fragments against SARS-CoV infection was determined in cultured Vero E6 cells by cytopathic effect (CPE), MTT and plaque-forming assays and in a Balb/c mouse model by CPE and quantitative RT-PCR. The results showed the neutralization titres of F(ab’)2 from three horses all reached at least 1:1600, and 50 μg of the F(ab’)2 fragments could completely neutralize 1x104 TCID50 SARS-CoV in vivo. Additionally, we observed that F(ab’)2 against BJ-01 strain could also protect cells from infection by the variant GZ-01 strain in vitro and in vivo. Our work has provided experimental support for testing the protective equine immunoglobulin in future large primate or human trials.

Cellular immunity to Epstein-Barr virus in liver transplant recipients treated with rituximab for post-transplant lymphoproliferative disease

The evaluation of long-term cellular immunity to EBV in pediatric orthotopic liver transplant (OLT) recipients after treatment with the humanized anti-CD20 monoclonal antibody (Rituximab) has not yet been explored. At our institution, one child with EBV-related mononucleosis-like syndrome and five children with polymorphic-EBV-PTLD occurring 6-88 months after OLT were treated with Rituximab. Treatment was well tolerated. All children achieved complete remission. After Rituximab, B-lymphocytes were undetectable in the peripheral blood and EBV-load, monitored with real-time PCR, decreased to undetectable levels in all children from >4000 copies/microg DNA at diagnosis. Four to eight months after Rituximab, EBV-load increased (>4000 copies/microg DNA) in four children, and PTLD recurred in three. Their frequency of EBV-specific T-cell precursors, measured by Elispot analysis, remained lower than in healthy controls. Rituximab effectively induced regression of PTLD in OLT recipients. However, EBV-specific T-cell immunocompetence, which may be crucial for the long-term control of EBV-mediated proliferation, did not improve.

Cellular immunotherapy for viral infection after HSC transplantation

Medical advances such as allogeneic transplantation can expose patients to periods of marked immunosuppression, during which viral infections are an important cause of morbidity and mortality. Control of infection will depend ultimately on the restoration of adequate antiviral immunity, and cellular immunotherapy is an attractive approach to improving immune protection. Developments in basic immunology have led to a greater understanding of the nature of protective immunity in immunocompetent donors, and this knowledge is now being used to direct immunotherapeutic protocols. Moreover, immunological techniques that have recently been developed as research tools, such as peptide-HLA tetramers and cytokine-secretion assays, have potential application for clinical use in this setting.

Experimental infection of NOD/SCID mice reconstituted with human CD34+ cells with Epstein-Barr virus

Epstein-Barr virus (EBV)-induced lymphoproliferative disease is an important complication in the context of immune deficiency. Impaired T-cell immunity allows the outgrowth of transformed cells with the subsequent production of predominantly B-cell lymphomas. Currently there is no in vivo model that can adequately recapitulate EBV infection and its association with B-cell lymphomas. NOD/SCID mice engrafted with human CD34(+) cells and reconstituted mainly with human B lymphocytes may serve as a useful xenograft model to study EBV infection and pathogenesis. We therefore infected reconstituted mice with EBV. High levels of viral DNA were detected in the peripheral blood of all infected mice. All infected mice lost weight and showed decreased activity levels. Infected mice presented large visible tumors in multiple organs, most prominently in the spleen. These tumors stained positive for human CD79a, CD20, CD30, and EBV-encoded RNAs and were light chain restricted. Their characterization is consistent with that of large cell immunoblastic lymphoma. In addition, tumor cells expressed EBNA1, LMP1, and LMP2a mRNAs, which is consistent with a type II latency program. EBV(+) lymphoblastoid cell lines expressing human CD45, CD19, CD21, CD23, CD5, and CD30 were readily established from the bone marrow and spleens of infected animals. Finally, we also demonstrate that infection with an enhanced green fluorescent protein (EGFP)-tagged virus can be monitored by the detection of infected EGFP(+) cells and EGFP(+) tumors. These data demonstrate that NOD/SCID mice that are reconstituted with human CD34(+) cells are susceptible to infection by EBV and accurately recapitulate important aspects of EBV pathogenesis.

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.

Cellular therapy of Epstein-Barr-virus-associated post-transplant lymphoproliferative disease

During the immunodeficiency that follows hemopoietic stem cell transplant or solid organ transplant, lymphoproliferation can develop due to uncontrolled expansion of Epstein-Barr-virus (EBV)-infected B cells that express the full spectrum of EBV latent antigens. As development of post-transplant lymphoproliferative disease (PTLD) in these patients is clearly associated with a deficient EBV-specific cellular immune response, immunotherapy strategies to restore the EBV-specific immune response have been evaluated. In hemopoietic stem cell transplant recipients, adoptively transferred donor-derived EBV-specific T cells have been able to restore immunity and eradicate overt lymphoproliferation. Autologous or closely matched allogeneic EBV-specific cytotoxic T lymphocytes have also shown promise in recipients of solid organ transplant. The use of genetically modified T cells or newer suicide genes may result in improved safety and efficacy. Current challenges are to define indications for immunotherapy or antibody therapy in patients with incipient or overt PTLD.

Establishment and characterization of a bank of cytotoxic T lymphocytes for immunotherapy of epstein-barr virus-associated diseases

Adoptive immunotherapy using Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTL) generated ex vivo can be an effective treatment of EBV-positive posttransplantation lymphoproliferative disease (PTLD). We describe the establishment of a cryopreserved repository of allogeneic virus-specific CTL lines, to our knowledge the first of its kind in the world. CTL lines were grown by weekly stimulation with autologous EBV immortalized lymphoblastoid cell lines (LCLs) from 96 EBV-seropositive blood donors. Analysis of 60 CTL lines grown continuously for 7 to 10 weeks showed an average proportional weekly increase in cell numbers of 1.4, with an overall increase ranging from 1.1 to 83.4. The greatest increase occurred during the early culture period. After four rounds of stimulation, killing of autologous LCLs was generally high (mean 48%); however, most lines required 9 or 10 stimulations to reduce the killing of nonspecific targets. Overall, 79% of CTLs generated showed acceptable levels of specific killing. Phenotypically, the CTL lines consisted of TCRalpha beta+, CD8+ T cells (medians 97% and 90% respectively) with a minority population of CD4+ T cells (median 2%). Most cells expressed the activation and differentiation markers, HLA-DR, CD26, CD45RO, CD69, and CD150. Favorable results have been obtained in an open trial using partially HLA-matched, allogeneic CTLs from this bank to treat PTLD patients. This now represents a single resource that can provide therapeutic CTLs rapidly on a countrywide basis, superseding the time-consuming, expensive practice of generating autologous CTLs from each patient requiring treatment. Additionally, other patient groups, such as those with EBV-positive Hodgkin disease, may benefit from CTL treatment.

Expansion of EBV latent membrane protein 2a specific cytotoxic T cells for the adoptive immunotherapy of EBV latency type 2 malignancies: influence of recombinant IL12 and IL15

BACKGROUND

EBV-associated malignancies with a Type II latency gene expression pattern, such as EBV-positive HD, or nasopharyngeal carcinoma, frequently express the EBV latency Ag LMP2a. Hence, they provide a potential target for adoptive immunotherapy using in vitro-generated LMP2a-specific cytotoxic T lymphocytes (CTL). In this study, LMP2a-specific CTL were specifically amplified and the influence of rIL12 and rIL15 on the culture outcome was tested.

METHODS

PBMC from donors were stimulated twice with autologous DC transduced with an adenovirus vector expressing LMP2a. This led to a significant expansion of LMP2a-tetramer-specific CTL, which were subsequently further expanded with autologous EBV-transformed B-lymphoblastoid cells (LCL). The addition of rIL12 and rIL15 to the standard IL2-containing culture medium enhanced the proliferation of LMP2a-specific CTL.

RESULTS

While rIL15 did not change the pattern of cytokines secreted by LMP2a-CTL, rIL12 enhanced the production of Th1/Tc1 cytokines, such as IFN-n, while suppressing the production of the Th2/Tc2 cytokine IL5.

DISCUSSION

Stimulation of CTL cultures with rIL12 or rIL15 will generate CTL more rapidly, facilitating the application of this approach for patients with these EBV-associated disorders.

Prompt versus preemptive intervention for EBV lymphoproliferative disease

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

Current status of liver transplantation in children

There are two critical issues on opposite ends of the timeline for patients who are eligible for liver transplantation. On the one hand, the crisis in the cadaveric organ supply makes surviving to transplant ever more risky. On the other hand, patients who receive successful transplants face the consequences of long-term immunosuppression and its potentially life-threatening complications. The donor shortage is forcing difficult decisions that affect all patients who await liver transplantation. It is important to scrutinize carefully the results of all policies that govern allocation and the ethics of the solutions we advocate to ensure that no patient subgroup is being at a disadvantage. Current immunosuppression practices are being challenged by an increasing understanding of the immunologic events triggered by the allograft and the goal to free patients from consequences of a lifetime of immunosuppression. Clinicians can expect, and perhaps require, that new immunosuppressive protocols will address how the planned intervention might be expected to advance the understanding of tolerance mechanisms. As knowledge increases, clinicians can anticipate innovative new immunosuppressive proposals. Calcineurin and steroid-free induction, the use of donor-derived bone marrow infusion, recipient pretreatment, costimulatory blockade, and new antibody induction approaches are all being proposed--often in combination--for clinical trials. Researchers face additional challenges in defining endpoints if the goal is not just the short-term reduction in rejection but the minimization, and eventual discontinuation, of immunosuppressive drugs while maintaining excellent long-term graft function. How much "failure" will be accepted and how will it be defined? How will clinicians interpret liver biopsies if they begin to accept that some lymphocytic infiltrates may be beneficial mediators of the ongoing immune activation necessary for the maintenance of tolerance? How will they adjust immunosuppression practices to the dynamic processes in the immune response that maintain tolerance? Remarkable short-term successes in providing transplants for thousands of children with liver failure have brought these challenges into sharp focus. Clinicians must seek to move the life-giving science of transplantation toward a new goal: providing long lifetimes of excellent graft function with minimal toxicity from immunosuppressive drugs and the hope of freedom from immunosuppression altogether. Pediatric liver recipients, whose grafts have inherent tolerogenic potential and for whom we can anticipate decades of life after transplant, may prove to be an ideal study population to further these goals.

Inhibition of ex vivo-expanded cytotoxic T-lymphocyte function by high-dose cyclosporine

BACKGROUND

Donor-derived, ex vivo-expanded cytotoxic T lymphocytes (CTL) can provide stem-cell transplantation (SCT) patients with a renewed capacity for virus-specific immune surveillance. Because SCT patients are often treated with cyclosporine (CsA), we questioned whether ex vivo-expanded CTL were susceptible to inhibition by this immunosuppressive drug.

METHODS

Human Epstein-Barr virus (EBV)-specific CTL were established by cultivating T cells for at least 5 weeks with interleukin (IL)-2 and irradiated, autologous EBV-transformed B-lymphoblastoid cell lines (LCL). In some cases, CsA was added during the last week of T-cell expansion. Effectors were then tested for cytotoxicity toward their targets in a chromium-release assay or by coculture with viable, unlabeled targets, in the presence or absence of CsA. Alloreactive CTL were similarly expanded and tested against major histocompatibility complex-mismatched stimulator cells.

RESULTS

CsA had a marginal effect on CTL function when added at concentrations greater than or equal to 250 ng/mL during the 4- to 6-hour chromium release assay. However, exposure of CTL to CsA for 1 week before assay reduced lytic function significantly. When the CTL lines were cocultured with viable targets in the presence of CsA, effectors were unable to eliminate their targets, which ultimately dominated the culture.

CONCLUSIONS

We suggest that the activity of ex vivo-expanded CTL may be significantly compromised in the presence of high-dose CsA in vivo, particularly if CTL are administered for the purpose of long-term virus-specific immune surveillance.