CD40 triggering of chronic lymphocytic leukemia B cells results in efficient alloantigen presentation and cytotoxic T lymphocyte induction by up-regulation of CD80 and CD86 costimulatory molecules

BAP31 Plays an Essential Role in Mouse B Cell Development via Regulation of BCR Signaling

B cell receptor-associated protein 31 (BAP31) is a transmembrane protein that is widely expressed and primarily located in the endoplasmic reticulum (ER). B cells play a crucial role in the immune system, and BAP31 significantly contributes to the functions of various immune cells. However, the specific role of BAP31 in B lymphocytes development remains unknown. In this study, we utilized a mouse model with BAP31 deleted from B cells to investigate its effects. Our findings reveal a block in early B cell development in the bone marrow and a significant decrease in the number of B cells in peripheral lymphoid organs taken from BAP31 B cell conditional knockout (BAP31-BCKO) mice. B cell receptor (BCR) signaling is crucial for the normal development and differentiation of B lymphocytes. BAP31, an endoplasmic reticulum membrane protein, directly regulates the BCR signaling pathway and was shown to be significantly positively correlated with B cell activation and proliferation. These findings establish BAP31 as a crucial regulator of early B cell development.

Defining the Basal and Immunomodulatory Mediator-Induced Phosphoprotein Signature in Pediatric B Cell Acute Lymphoblastic Leukemia (B-ALL) Diagnostic Samples

It is theorized that dysregulated immune responses to infectious insults contribute to the development of pediatric B-ALL. In this context, our understanding of the immunomodulatory-mediator-induced signaling responses of leukemic blasts in pediatric B-ALL diagnostic samples is rather limited. Hence, in this study, we defined the signaling landscape of leukemic blasts, as well as normal mature B cells and T cells residing in diagnostic samples from 63 pediatric B-ALL patients. These samples were interrogated with a range of immunomodulatory-mediators within 24 h of collection, and phosflow analyses of downstream proximal signaling nodes were performed. Our data reveal evidence of basal hyperphosphorylation across a broad swath of these signaling nodes in leukemic blasts in contrast to normal mature B cells and T cells in the same sample. We also detected similarities in the phosphoprotein signature between blasts and mature B cells in response to IFNγ and IL-2 treatment, but significant divergence in the phosphoprotein signature was observed between blasts and mature B cells in response to IL-4, IL-7, IL-10, IL-21 and CD40 ligand treatment. Our results demonstrate the existence of both symmetry and asymmetry in the phosphoprotein signature between leukemic and non-leukemic cells in pediatric B-ALL diagnostic samples.

γδT Cells Are Required for CD8+ T Cell Response to Vaccinia Viral Infection

Vaccinia virus (VV) is the most studied member of the poxvirus family, is responsible for the successful elimination of smallpox worldwide, and has been developed as a vaccine vehicle for infectious diseases and cancer immunotherapy. We have previously shown that the unique potency of VV in the activation of CD8+ T cell response is dependent on efficient activation of the innate immune system through Toll-like receptor (TLR)-dependent and -independent pathways. However, it remains incompletely defined what regulate CD8+ T cell response to VV infection. In this study, we showed that γδT cells play an important role in promoting CD8+ T cell response to VV infection. We found that γδT cells can directly present viral antigens in the context of MHC-I for CD8+ T cell activation to VV in vivo, and we further demonstrated that cell-intrinsic MyD88 signaling in γδT cells is required for activation of γδT cells and CD8+ T cells. These results illustrate a critical role for γδT cells in the regulation of adaptive T cell response to viral infection and may shed light on the design of more effective vaccine strategies based on manipulation of γδT cells.

CD4+ T cells sustain aggressive chronic lymphocytic leukemia in Eμ-TCL1 mice through a CD40L-independent mechanism

Chronic lymphocytic leukemia (CLL) is caused by the progressive accumulation of mature CD5+ B cells in secondary lymphoid organs. In vitro data suggest that CD4+ T lymphocytes also sustain survival and proliferation of CLL clones through CD40L/CD40 interactions. In vivo data in animal models are conflicting. To clarify this clinically relevant biological issue, we generated genetically modified Eμ-TCL1 mice lacking CD4+ T cells (TCL1+/+AB0), CD40 (TCL1+/+CD40-/-), or CD8+ T cells (TCL1+/+TAP-/-), and we monitored the appearance and progression of a disease that mimics aggressive human CLL by flow cytometry and immunohistochemical analyses. Findings were confirmed by adoptive transfer of leukemic cells into mice lacking CD4+ T cells or CD40L or mice treated with antibodies depleting CD4 T cells or blocking CD40L/CD40 interactions. CLL clones did not proliferate in mice lacking or depleted of CD4+ T cells, thus confirming that CD4+ T cells are essential for CLL development. By contrast, CD8+ T cells exerted an antitumor activity, as indicated by the accelerated disease progression in TCL1+/+TAP-/- mice. Antigen specificity of CD4+ T cells was marginal for CLL development, because CLL clones efficiently proliferated in transgenic mice whose CD4 T cells had a T-cell receptor with CLL-unrelated specificities. Leukemic clones also proliferated when transferred into wild-type mice treated with monoclonal antibodies blocking CD40 or into CD40L-/- mice, and TCL1+/+CD40-/- mice developed frank CLL. Our data demonstrate that CD8+ T cells restrain CLL progression, whereas CD4+ T cells support the growth of leukemic clones in TCL1 mice through CD40-independent and apparently noncognate mechanisms.

Enhanced immunogenicity of leukemia-derived exosomes via transfection with lentiviral vectors encoding costimulatory molecules

Background: Tumor cell-derived exosomes (TEXs) have been widely used to induce antitumor immune responses in animal models and clinical trials. Similarly, leukemia cell-derived exosomes (LEXs) can induce antileukemia immune responses in animal models. However, the antileukemia immunity induced by LEXs is less effective, which may be due to an inadequate costimulatory capacity.

Methods: In this study, we transduced L1210 leukemia cells with a lentiviral vector encoding two B7 costimulatory molecules (CD80, CD86) and obtained LEXs that highly expressed CD80 and CD86. The antileukemia immune response derived from these LEXs was examined in vitro and in vivo in animal models.

Results: We found that B7 gene-modified LEXs, including LEX-CD80, LEX-CD86, and LEX-8086, could significantly boost the expression of CD80 and CD86 in dendritic cells (DCs) and promote the secretion of functional cytokines such as TNF-α and IL-12. Moreover, these B7 gene-modified LEXs, particularly LEX-CD8086, could effectively induce CD4⁺ T cell proliferation, Th1 cytokine secretion, and an antigen-specific anti-leukemia cytotoxic T lymphocyte (CTL) response. Additional animal studies indicated that immunization with B7 gene-modified LEXs, in particular LEX-CD8086, could significantly retard tumor growth compared to the control LEXnull group.

Conclusions: This study sheds light on the feasibility of obtaining LEXs that overexpress costimulatory molecules via genetically modified leukemia cells, thereby enhancing their anti-leukemia immunity and providing a potential therapeutic strategy that contributes to leukemia immunotherapy.

Paraneoplastic Pemphigus: Paraneoplastic Autoimmune Disease of the Skin and Mucosa

Paraneoplastic pemphigus (PNP) is a rare but life-threatening mucocutaneous disease mediated by paraneoplastic autoimmunity. Various neoplasms are associated with PNP. Intractable stomatitis and polymorphous cutaneous eruptions, including blisters and lichenoid dermatitis, are characteristic clinical features caused by humoral and cell-mediated autoimmune reactions. Autoreactive T cells and IgG autoantibodies against heterogeneous antigens, including plakin family proteins and desmosomal cadherins, contribute to the pathogenesis of PNP. Several mechanisms of autoimmunity may be at play in this disease on the type of neoplasm present. Diagnosis can be made based on clinical and histopathological features, the presence of anti-plakin autoantibodies, and underlying neoplasms. Immunosuppressive agents and biologics including rituximab have been used for the treatment of PNP; however, the prognosis is poor due to underlying malignancies, severe infections during immunosuppressive treatment, and bronchiolitis obliterans mediated by autoimmunity. In this review, we overview the characteristics of PNP and focus on the immunopathology and the potential pathomechanisms of this disease.

Chronic Lymphocytic Leukemia B-Cell Normal Cellular Counterpart: Clues From a Functional Perspective

Chronic lymphocytic leukemia (CLL) is characterized by the clonal expansion of small mature-looking CD19+ CD23+ CD5+ B-cells that accumulate in the blood, bone marrow, and lymphoid organs. To date, no consensus has been reached concerning the normal cellular counterpart of CLL B-cells and several B-cell types have been proposed. CLL B-cells have remarkable phenotypic and gene expression profile homogeneity. In recent years, the molecular and cellular biology of CLL has been enriched by seminal insights that are leading to a better understanding of the natural history of the disease. Immunophenotypic and molecular approaches (including immunoglobulin heavy-chain variable gene mutational status, transcriptional and epigenetic profiling) comparing the normal B-cell subset and CLL B-cells provide some new insights into the normal cellular counterpart. Functional characteristics (including activation requirements and propensity for plasma cell differentiation) of CLL B-cells have now been investigated for 50 years. B-cell subsets differ substantially in terms of their functional features. Analysis of shared functional characteristics may reveal similarities between normal B-cell subsets and CLL B-cells, allowing speculative assignment of a normal cellular counterpart for CLL B-cells. In this review, we summarize current data regarding peripheral B-cell differentiation and human B-cell subsets and suggest possibilities for a normal cellular counterpart based on the functional characteristics of CLL B-cells. However, a definitive normal cellular counterpart cannot be attributed on the basis of the available data. We discuss the functional characteristics required for a cell to be logically considered to be the normal counterpart of CLL B-cells.

Metformin inhibits cell cycle progression of B-cell chronic lymphocytic leukemia cells

B-cell chronic lymphocytic leukemia (CLL) was believed to result from clonal accumulation of resting apoptosis-resistant malignant B lymphocytes. However, it became increasingly clear that CLL cells undergo, during their life, iterative cycles of re-activation and subsequent clonal expansion. Drugs interfering with CLL cell cycle entry would be greatly beneficial in the treatment of this disease.

1, 1-Dimethylbiguanide hydrochloride (metformin), the most widely prescribed oral hypoglycemic agent, inexpensive and well tolerated, has recently received increased attention for its potential antitumor activity. We wondered whether metformin has apoptotic and anti-proliferative activity on leukemic cells derived from CLL patients.

Metformin was administered in vitro either to quiescent cells or during CLL cell activation stimuli, provided by classical co-culturing with CD40L-expressing fibroblasts.

At doses that were totally ineffective on normal lymphocytes, metformin induced apoptosis of quiescent CLL cells and inhibition of cell cycle entry when CLL were stimulated by CD40-CD40L ligation. This cytostatic effect was accompanied by decreased expression of survival- and proliferation-associated proteins, inhibition of signaling pathways involved in CLL disease progression and decreased intracellular glucose available for glycolysis.

In drug combination experiments, metformin lowered the apoptotic threshold and potentiated the cytotoxic effects of classical and novel antitumor molecules.

Our results indicate that, while CLL cells after stimulation are in the process of building their full survival and cycling armamentarium, the presence of metformin affects this process.

Improving therapy of chronic lymphocytic leukemia with chimeric antigen receptor T cells

Adoptive cell immunotherapy for the treatment of chronic lymphocytic leukemia (CLL) has heralded a new era of synthetic biology. The infusion of genetically engineered, autologous chimeric antigen receptor (CAR) T cells directed against CD19 expressed by normal and malignant B cells represents a novel approach to cancer therapy. The results of recent clinical trials of CAR T cells in relapsed and refractory CLL have demonstrated long-term disease-free remissions, underscoring the power of harnessing and redirecting the immune system against cancer. This review will briefly summarize T-cell therapies in development for CLL disease. We discuss the role of T-cell function and phenotype, T-cell culture optimization, CAR design, and approaches to potentiate the survival and anti-tumor effects of infused lymphocytes. Future efforts will focus on improving the efficacy of CAR T cells for the treatment of CLL and incorporating adoptive cell immunotherapy into standard medical management of CLL.

IL-12 involvement in myogenic differentiation of C2C12 in vitro

Recently, the extracellular microenvironment has been shown to be critical for the correct differentiation of stem cells to specific tissues. Many factors, including physical (e.g. biomaterial stiffness and topography) and biological (as growth factors, cytokines and chemokines) components, cooperate to create an ideal microenvironment for muscle stem cells, with many of these factors having been widely investigated. We previously demonstrated that the use of non-proliferating muscle-specific and unrelated cells as feeder layers for skeletal muscle progenitor cell differentiation resulted in significant differences in the ability to form myotubes, suggesting the importance of biological factors in myogenic differentiation. In this study, we investigated the biological factors involved in this process, analyzing the expression profile of 84 genes coding for cytokines and chemokines. We successfully identified a novel role for the cytokine IL-12 in the myogenic differentiation of C2C12 mouse skeletal muscle cells. Experiments involving the overexpression or silencing of the IL-12 gene in C2C12 showed that IL-12 enhanced the myogenic differentiation process. Moreover, when IL-12 was overexpressed in non-biologically related feeder cells, the new co-culture system was able to improve myogenic differentiation of C2C12 seeded on top. Although IL-12 is known to be a cytokine involved in inflammatory responses, it also appears to be involved in the myogenic differentiation process, acting as a positive regulator of this mechanism. This fact is expected to prove to be important for the development of functional biomaterials.

B-CLL cells acquire APC- and CTL-like phenotypic characteristics after stimulation with CpG ODN and IL-21

CpG oligodeoxynucleotides (CpG) and IL-21 are two promising agents for the treatment of B-cell chronic lymphocytic leukemia (B-CLL). Recently, we reported that the combination of CpG and IL-21 (CpG/IL-21) can induce granzyme B (GrB)-dependent apoptosis in B-CLL cells. Here, we demonstrate that treatment of B-CLL cells with CpG and IL-21 results in the development of antigen-presenting cell (APC)-like cells with cytotoxic features. These properties eventually give rise to B-CLL cell apoptosis, independently of their cytogenetic phenotype, whereas normal B-cell survival is not negatively affected by CpG/IL-21. APC- and CTL-typical molecules found to be up-regulated in CpG/IL-21-stimulated B-CLL cells include GrB, perforin, T-bet, monokine-induced by IFN-γ and IFN-γ-inducible protein 10 (IP-10), as well as molecules important for cell adhesion, antigen cross-presentation and costimulation. Also induced are molecules involved in GrB induction, trafficking and processing, whereas the GrB inhibitor Serpin B9 [formerly proteinase inhibitor-9 (PI-9)] is down-modulated by CpG/IL-21. In conclusion, CpG/IL-21-stimulated B-CLL cells acquire features that are reminiscent of killer dendritic cells, and which result in enhanced immunogenicity, cytotoxicity and apoptosis. Our results provide novel insights into the aberrant immune state of B-CLL cells and may establish a basis for the development of an innovative cellular vaccination approach in B-CLL.

Phorbol myristate acetate, but not CD40L, induces the differentiation of CLL B cells into Ab-secreting cells

In this study, we investigated the capacity of chronic lymphocytic leukemia (CLL) B cells to undergo terminal differentiation into Ig-secreting plasma cells in T cell-independent and T cell-dependent responses. We used a two-step model involving stimulation with phorbol myristate acetate (PMA) and CD40L, together with cytokines (PMA/c and CD40L/c), for 7 days. We describe immunophenotypic modifications, changes in the levels of mRNA and protein for transcription factors and morphological and functional events occurring during the differentiation of CLL B cells into antibody-secreting cells (ASCs). The induction of differentiation differed significantly between the CD40L/c and PMA/c culture systems. The PMA/c culture system allowed CLL B cells to differentiate into IgM-secreting cells with an immunophenotype and molecular profile resembling those of preplasmablasts. By contrast, CD40L/c-stimulated cells had a phenotype and morphology similar to those of activated B cells and resembling those of the CLL B cells residing in the lymph node and bone marrow. These data suggest that the CLL B cells are not frozen permanently at a stage of differentiation and are able to differentiate into ASCs as appropriate stimulation are provided. The data presented here raise questions about the molecular processes and stimulation required for CLL B-cell differentiation and about the inability of CD40 ligand to induce differentiation of the CLL B cells.

Multidimensional scaling analysis identifies pathological and prognostically relevant profiles of circulating T-cells in chronic lymphocytic leukemia

Antitumor immunity in chronic lymphocytic leukemia (CLL) is hampered by highly dysfunctional T-cells. Although certain T-cell subsets have been reported to be of prognostic significance in this disease, their interplay is complex and it remains incompletely understood which of these subsets significantly drive CLL progression. Here, we determined immunological profiles of 24 circulating T-cell subsets from 79 untreated individuals by multiparametric flow cytometry. This screening cohort included healthy donors, patients with monoclonal B-cell lymphocytosis (MBL), Rai 0 CLL and advanced CLL. We applied multidimensional scaling analysis as rigorous and unbiased statistical tool to globally assess the composition of the circulating T-cell environment and to generate T-cell scores reflecting its integrity. These scores allowed clear distinction between advanced CLL and healthy controls, whereas both MBL and Rai 0 CLL showed intermediate scores mirroring the biological continuum of CLL and its precursor stages. T-cell stimulation and suppression assays as well as longitudinal T-cell profiling showed an increasingly suppressive regulatory function initiating at the MBL stage. Effector function was impaired only after transition to CLL and partially recovered after chemoimmunotherapy. In an independent validation cohort of 52 untreated CLL cases, aberrant T-cell profiles were significantly associated with shorter time to treatment independently of other prognostic parameters. Random forest modeling predicted regulatory T-cell, gamma/delta and NKT-cells, as well as exhaustion of the CD8+ subset as potential drivers of progression. Our data illustrate a pathological T-cell environment in MBL that evolves toward a more and more suppressive and prognostically relevant profile across the disease stages.

Understanding the immunodeficiency in chronic lymphocytic leukemia: potential clinical implications

Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults. Although significant advances have been made in the treatment of CLL in the last decade, it remains incurable. Treatments may be too toxic for some elderly patients, who constitute most of the individuals with this disease, and there remain subgroups of patients for which this therapy has minimal activity. This article summarizes the current understanding of the immune defects in CLL. It also examines the potential clinical implications of these findings.

CD62L as a therapeutic target in chronic lymphocytic leukemia

PURPOSE

Despite advances in the treatment of chronic lymphocytic leukemia (CLL), the disease remains incurable with standard therapies and relapse is inevitable. A growing body of evidence indicates that alterations in the adhesion properties of neoplastic cells play a pivotal role in the development and progression of CLL.

EXPERIMENTAL DESIGN

The expression of 71 cell surface molecules was examined on CLL peripheral blood mononuclear cells (PBMCs) over 3 weeks in culture. The most highly upregulated marker, CD62L, was examined further for expression on CD5(+)/CD19(+) CLL cells in vitro and in lymph node and bone marrow biopsies. The prosurvival role of CD62L was examined using a functional blocking antibody and therapeutic potential evaluated by comparison with current chemotherapy agents.

RESULTS

Blocking CD62L resulted in apoptosis of CLL cells but not PBMCs from healthy donors suggesting a novel role for CD62L in CLL cell survival. The beneficial effect of coculturing CLL cells with bone marrow stromal cells or endothelial cells does not protect CLL cells from anti-CD62L-related toxicity. Moreover, combining fludarabine or mafosfamide with the anti-CD62L in vitro produced an additive effect both with and without stromal cells.

CONCLUSION

This is the first reported data showing that blocking the activation and homing marker, CD62L, regulates CLL cell survival in vitro. These data also suggest that therapeutic antibodies against CD62L may provide additional clinical benefit to patients with CLL receiving current standard chemotherapy protocols.

Distinct transcriptional control in major immunogenetic subsets of chronic lymphocytic leukemia exhibiting subset-biased global DNA methylation profiles

Chronic lymphocytic leukemia (CLL) can be divided into prognostic subgroups based on the IGHV gene mutational status, and is further characterized by multiple subsets of cases with quasi-identical or stereotyped B cell receptors that also share clinical and biological features. We recently reported differential DNA methylation profiles in IGHV-mutated and IGHV-unmutated CLL subgroups. For the first time, we here explore the global methylation profiles of stereotyped subsets with different prognosis, by applying high-resolution methylation arrays on CLL samples from three major stereotyped subsets: the poor-prognostic subsets #1 (n = 15) and #2 (n = 9) and the favorable-prognostic subset #4 (n = 15). Overall, the three subsets exhibited significantly different methylation profiles, which only partially overlapped with those observed in our previous study according to IGHV gene mutational status. Specifically, gene ontology analysis of the differentially methylated genes revealed a clear enrichment of genes involved in immune response, such as B cell activation (e.g., CD80, CD86 and IL10), with higher methylation levels in subset #1 than subsets #2 and #4. Accordingly, higher expression of the co-stimulatory molecules CD80 and CD86 was demonstrated in subset #4 vs. subset #1, pointing to a key role for these molecules in the crosstalk of CLL subset #4 cells with the microenvironment. In summary, investigation of three prototypic, stereotyped CLL subsets revealed distinct DNA methylation profiles for each subset, which suggests subset-biased patterns of transcriptional control and highlights a key role for epigenetics during leukemogenesis.

Heat shock protein-90 inhibitor, NVP-AUY922, is effective in combination with fludarabine against chronic lymphocytic leukemia cells cultured on CD40L-stromal layer and inhibits their activated/proliferative phenotype

Chronic lymphocytic leukemia (CLL) involves disease infiltration into active proliferation centers within the lymph nodes and marrow. Successful treatment of CLL must involve targeting the leukemic cells in these supportive microenvironments. Our recent data suggest that inhibition of heat shock protein-90 (Hsp90) may be an effective treatment for CLL. We sought to further these data to determine whether the Hsp90 inhibitor, AUY922 (Novartis), is effective against CLL cells in a supportive in vitro environment. AUY922 significantly attenuated changes in immunophenotype and signal transducer and activator of transcription 3 (STAT3) signaling induced by CD40L-fibroblast co-culture but had no effect on the viability of CLL cells in this model. However, AUY922 in combination with fludarabine was significantly more effective at inducing apoptosis in cells in co-culture than either drug alone, an effect that was irrespective of ATM/TP53 dysfunction. In conclusion, our data suggest that further studies and clinical trials of AUY922 in combination with fludarabine may be warranted.

Immune reconstitution in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is associated with a profound immune defect, which results in increased susceptibility to recurrent infections as well as a failure to mount effective antitumor immune responses. Current chemotherapy-based regimens are not curative and often worsen this immune suppression, so their usefulness is limited, particularly in the frail and elderly. This article reviews the immune defect in CLL and discusses strategies aimed at repairing or circumventing this defect. In particular, it focuses on recent developments in the areas of CD40 ligand (CD40L/CD154) gene therapy, immunomodulatory agents such as lenalidomide, and adoptive transfer of T cells bearing chimeric antigen receptors.

The cumulative amount of serum-free light chain is a strong prognosticator in chronic lymphocytic leukemia

Identification of patients at risk of early disease progression is the mainstay of tailored management in chronic lymphocytic leukemia (CLL). Although application of established biomarkers is limited by intrinsic detection/readout complexities, abnormality of κ and λ serum-free light chain ratio [sFLC (κ/λ)] was proposed as a straightforward prognosticator in CLL. By analyzing 449 therapy-naive patients, we show that an abnormal sFLC(κ/λ), along with CD38, ZAP-70, IGHV mutations, cytogenetics and stage, independently predicts treatment-free survival (TFS) but becomes prognostically irrelevant if the cumulative amount of clonal and nonclonal FLCs [sFLC(κ + λ)], a variable associated with cytogenetic risk, exceeds the threshold of 60.6 mg/mL. Patients with sFLC(κ + λ) above cut-off displayed a poorer TFS outcome, irrespective of sFLC(κ/λ). Only ZAP-70, cytogenetics, stage, and TFS remained associated with sFLC(κ + λ) in a multivariate model. By assigning 1 point each for these variables, the 3-year probability of TFS was 94.8%, 84.5%, 61.6%, and 21.1% for patients scoring 0, 1, 2, and 3 + 4, respectively (P < .0001). These data, and the demonstration that monoclonal and polyclonal B cells concur to FLC synthesis in tumor tissues, suggest that sFLC(κ/λ) and sFLC(κ + λ) mirror distinct biologic processes in CLL. sFLC(κ + λ) assessment represents a sensitive and cost-effective tool for identifying CLL patients requiring early treatment.

Toll-like receptor signaling pathway in chronic lymphocytic leukemia: distinct gene expression profiles of potential pathogenic significance in specific subsets of patients

BACKGROUND

Signaling through the B-cell receptor appears to be a major contributor to the pathogenesis of chronic lymphocytic leukemia. Toll-like receptors bridge the innate and adaptive immune responses by acting as co-stimulatory signals for B cells. The available data on the expression of Toll-like receptors in chronic lymphocytic leukemia are limited and derive from small series of patients.

DESIGN AND METHODS

We profiled the expression of genes associated with Toll-like receptor signaling pathways in 192 cases of chronic lymphocytic leukemia and explored potential associations with molecular features of the clonotypic B-cell receptors.

RESULTS

Chronic lymphocytic leukemia cells express all Toll-like receptors expressed by normal activated B cells, with high expression of TLR7 and CD180, intermediate expression of TLR1, TLR6, TLR10 and low expression of TLR2 and TLR9. The vast majority of adaptors, effectors and members of the NFKB, JNK/p38, NF/IL6 and IRF pathways are intermediately-to-highly expressed, while inhibitors of Toll-like receptor activity are generally low-to-undetectable, indicating that the Toll-like receptor-signaling framework is competent in chronic lymphocytic leukemia. Significant differences were identified for selected genes between cases carrying mutated or unmutated IGHV genes or assigned to different subsets with stereotyped B-cell receptors. The differentially expressed molecules include receptors, NFκB/MAPK signaling molecules and final targets of the cascade.

CONCLUSIONS

The observed variations are suggestive of distinctive activation patterns of the Toll-like receptor signaling pathway in subgroups of cases of chronic lymphocytic leukemia defined by the molecular features of B-cell receptors. Additionally, they indicate that different or concomitant signals acting through receptors other than the B-cell receptor can affect the behavior of the malignant clone.

Cladribine and Fludarabine Nucleoside Change the Levels of CD Antigens on B-Lymphoproliferative Disorders

The purine analogs, fludarabine nucleoside (FdA), and cladribine (CdA) (1 μM, 24 hours), significantly changed the levels of some surface antigens on the human B-cell lines MEC2 and Raji. Changes in the surface proteins were identified using a Cluster of Differentiation (CD) antibody microarray that captures live cells and confirmed by flow cytometry. For Raji cells, CdA up-regulated CD10, CD54, CD80, and CD86, with repression of CD22, while FdA up-regulated CD20, CD54, CD80, CD86 and CD95. For MEC2 cells, CdA up-regulated CD11a, CD20, CD43, CD45, CD52, CD54, CD62L, CD80, CD86, and CD95, but FdA had no effect. Up-regulation of particular CD antigens induced on a B-cell lymphoproliferative disorder by a purine analog could provide targets for therapeutic antibodies with synergistic cell killing.

CD154 expression triggered by purine analogues in vitro: Correlation with treatment response and autoimmune events in chronic lymphocytic leukemia

OBJECTIVE

Despite a fludarabine-based treatment is the first choice of therapy in chronic lymphocytic leukemia (CLL), not all patients achieve a partial or complete response and some of them develop autoimmune manifestations. The aim of this study was to evaluate the influence of CD154 on these adverse effects because CD154 is involved in both B-cell survival and autoimmunity.

MATERIALS AND METHODS

Peripheral blood mononuclear cells (PBMC) from 36 patients with CLL were cultured in vitro with fludarabine or 2-chlorodeoxyadenosine for 24, 48, and 72 hours.

RESULTS

Seven patients (19.4%) presented CD154 expression in PBMC cultured with purine analogues in vitro for 24 and/or 48 hours, while no expression was found when cultured in media alone. These seven patients showed a decreased apoptotic rate in vitro after purine analogues compared with those patients who did not express CD154 (p = 0.01 for fludarabine; p < 0.001 for 2-chlorodeoxyadenosine). CD154 expression was found to have prognostic value for response to fludarabine in vivo and was associated with the development of autoimmune manifestations (odds ratio = 25; 95% confidence interval = 3.5-166.7; p < 0.001).

CONCLUSION

Our preliminary results suggest that CD154 expression in CLL patients, which may be induced by purine analogues, is associated with resistance to fludarabine and with development of autoimmune manifestations.

Comparative analysis of MVA-CD40L and MVA-TRICOM vectors for enhancing the immunogenicity of chronic lymphocytic leukemia (CLL) cells

Adenoviral transduction with CD40L and poxviral transduction with B7-1, ICAM-1, and LFA-3 (TRICOM) have been used to enhance the antigen-presenting capacity of chronic lymphocytic leukemia (CLL) cells. This study compares the same vector (modified vaccinia virus strain Ankara (MVA)) encoding CD40L or TRICOM for its ability to enhance the immunogenicity of CLL cells. CLL cells from some patients showed differential responses to each vector in terms of induction of autologous T-cell responses. This study supports the rationale for the use of CLL cells modified ex vivo with pre-specified recombinant MVA vectors as a whole tumor-cell vaccine for immunotherapy in CLL patients.

Effects of Preactivated Autologous T Lymphocytes on CD80, CD86 and CD95 Expression by Chronic Lymphocytic Leukemia B Cells

Profound immune dysfunction is a constant feature in B-cell chronic lymphocytic leukemia (B-CLL) patients. Immunological abnormalities include hypogammaglobulinemia, impaired immunoglobulin class switching and diminished germinal center formation. This state of immune suppression renders B-CLL patients highly susceptible to infections, which contribute greatly to morbidity and mortality in this disease. Impaired T cell function in B-CLL is well-documented and has been suggested to result from inhibitory effects exerted by malignant B lymphocytes. Because the presence of leukemic cells may represent a major obstacle to efficient T cell activation, T lymphocytes were separated from CLL B cells, stimulated with phorbol 12-myristate 13-acetate (PMA) and ionomycin for 4h, and then cocultured with autologous leukemic B cells both at a 1:1 ratio or at the same ratio as in vivo for 24-40 h. CLL B cell expression of CD86 and CD95 was markedly upregulated using this approach, whereas CD80 expression was augmented only in a minority of patients; these effects were partially preserved even when preactivated T cells were rechallenged with CLL B cells at the same low T/B cell ratio as that observed in vivo. Finally, CD80 upregulation on CLL B cells appeared to be mainly dependent on CD40L-mediated stimulation, whereas CD86 and CD95 expression was efficiently augmented by soluble factors released by preactivated T lymphocytes. In conclusion, efficient activation of T lymphocytes in B-CLL may be achieved which, in turn, may result in enhanced antigen-presenting capacity and susceptibility to apoptosis of leukemic cells via CD86 and CD95 upregulation, respectively.

Therapeutic interventions targeting CD40L (CD154) and CD40: the opportunities and challenges

CD40 was originally identified as a receptor on B-cells that delivers contact-dependent T helper signals to B-cells through interaction with CD40 ligand (CD40L, CD154). The pivotal role played by CD40-CD40L interaction is illustrated by the defects in B-lineage cell development and the altered structures of secondary lymphoid tissues in patients and engineered mice deficient in CD40 or CD40L. CD40 signaling also provides critical functions in stimulating antigen presentation, priming of helper and cytotoxic T-cells and a variety of inflammatory reactions. As such, dysregulations in the CD40-CD40L costimulation pathway are prominently featured in human diseases ranging from inflammatory conditions to systemic autoimmunity and tissue-specific autoimmune diseases. Moreover, studies in CD40-expressing cancers have provided convincing evidence that the CD40-CD40L pathway regulates survival of neoplastic cells as well as presentation of tumor-associated antigens to the immune system. Extensive research has been devoted to explore CD40 and CD40L as drug targets. A number of anti-CD40L and anti-CD40 antibodies with diverse biological effects are in clinical development for treatment of cancer and autoimmune diseases. This chapter reviews the role of CD40-CD40L costimulation in disease pathogenesis, the characteristics of therapeutic agents targeting this pathway and status of their clinical development.

Chronic lymphocytic leukemia cells bind and present the erythrocyte protein band 3: possible role as initiators of autoimmune hemolytic anemia

The mechanisms underlying the frequent association between chronic lymphocytic leukemia (CLL) and autoimmune hemolytic anemia are currently unclear. The erythrocyte protein band 3 (B3) is one of the most frequently targeted Ags in autoimmune hemolytic anemia. In this study, we show that CLL cells specifically recognize B3 through a still unidentified receptor. B3 interaction with CLL cells involves the recognition of its N-terminal domain and leads to its internalization. Interestingly, when binding of erythrocyte-derived vesicles as found physiologically in blood was assessed, we observed that CLL cells could only interact with inside-out vesicles, being this interaction strongly dependent on the recognition of the N-terminal portion of B3. We then examined T cell responses to B3 using circulating CLL cells as APCs. Resting B3-pulsed CLL cells were unable to induce T cell proliferation. However, when deficient costimulation was overcome by CD40 engagement, B3-pulsed CLL cells were capable of activating CD4(+) T cells in a HLA-DR-dependent fashion. Therefore, our work shows that CLL cells can specifically bind, capture, and present B3 to T cells when in an activated state, an ability that could allow the neoplastic clone to trigger the autoaggressive process against erythrocytes.

High expression of CD40 on B-cell precursor acute lymphoblastic leukemia blasts is an independent risk factor associated with improved survival and enhanced capacity to up-regulate the death receptor CD95

CD40 and CD27, members of the tumor necrosis factor receptor (TNFR) family, are critical regulators of lymphocyte growth and differentiation. In B-cell precursor acute lymphoblastic leukemia (BCP-ALL), we prospectively assessed the impact of CD40 and CD27 on outcome in 121 children treated according to the CoALL06-97 protocol. Expression of both CD40 and CD27 was found to be significantly higher in low- than in high-risk patients as defined by standard clinical risk parameters such as age and white blood cell count. In addition, in multivariable analysis, a very high percentage of CD40(+) blasts at diagnosis was identified as an independent favorable prognostic factor for relapse-free survival. Of note, high CD40 expression particularly protected against late relapse. In B cells, CD40 is known to enhance both antigen-presenting capacity and sensitivity to proapoptotic signals. Yet, although CD40 ligation does result in significant up-regulation of CD80/CD86 in our cohort, it is up-regulation of the death receptor CD95 that significantly correlates with the percentage of CD40(+) blasts. Thus very high expression of CD40 on BCP-ALL blasts is an independent prognostic marker indicative of superior relapse-free survival that may in part be due to CD40-dependent death receptor up-regulation.

Differential immune effects mediated by Toll-like receptors stimulation in precursor B-cell acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is the most common paediatric malignancy and, although current therapy is widely effective, relapse remains a significant clinical problem for which new treatment strategies are required. The ligation of Toll-like receptors (TLR) on antigen-presenting cells stimulates the generation of strong T-cell helper type 1 (Th1) adaptive immune responses. Although TLR9 ligation has been shown to enhance immunogenicity of a number of leukaemia cell types, there have been few reports of the effects mediated through other TLR. In this study we analysed both the expression of TLR by B-cell precursor ALL cell lines and the effects of individual TLR ligation on the ability of ALL cells to stimulate allogeneic T cells. While ligation of TLR2, TLR 7 and TLR9 led to detectable changes in ALL costimulatory molecule expression, only TLR2 and TLR9 stimulation influenced T-cell responses. The TLR2 ligand Pam3CysSerLys4 provoked the most significant changes in T-cell response, dramatically augmenting interferon-gamma production. These results suggest that TLR ligands, in addition to TLR9 agonists, may provide a strategy to enhance the generation of anti-ALL immune activity by skewing responding T cells towards a Th1 response.

Responses to human CD40 ligand/human interleukin-2 autologous cell vaccine in patients with B-cell chronic lymphocytic leukemia

PURPOSE

Human CD40 ligand activates the malignant B-cell chronic lymphocytic leukemia cells and enhances their capacity to present tumor antigens. Human interleukin-2 further potentiates the immunogenicity of human CD40 ligand in preclinical murine models.

EXPERIMENTAL DESIGN

We prepared autologous B-cell chronic lymphocytic leukemia cells that expressed both human CD40 ligand (>90% positive) and human interleukin-2 (median secretion, 1,822 pg/mL/10(6) cells; range, 174-3,604 pg). Nine patients were enrolled in a phase I trial, receiving three to eight s.c. vaccinations.

RESULTS

Vaccinations were administered without evidence of significant local or systemic toxicity. A B-cell chronic lymphocytic leukemia-specific T-cell response was detected in seven patients. The mean frequencies of IFN-gamma, granzyme-B, and IL-5 spot-forming cells were 1/1,230, 1/1,450, and 1/4,500, respectively, representing a 43- to 164-fold increase over the frequency before vaccine administration. Three patients produced leukemia-specific immunoglobulins. Three patients had >50% reduction in the size of affected lymph nodes. Nonetheless, the antitumor immune responses were observed only transiently once immunization ceased. High levels of circulating CD4+/CD25+/LAG-3+/FoxP-3+ immunoregulatory T cells were present before, during and after treatment and in vitro removal of these cells increased the antileukemic T-cell reactivity.

CONCLUSIONS

These results suggest that immune responses to B-cell chronic lymphocytic leukemia can be obtained with human CD40 ligand/human interleukin-2-expressing s.c. vaccines but that these responses are transient. High levels of circulating regulatory T cells are present, and it will be of interest to see if their removal in vivo augments and prolongs the antitumor immune response.

Increased expression of CD152 (CTLA-4) by normal T lymphocytes in untreated patients with B-cell chronic lymphocytic leukemia

Patients with chronic lymphocytic leukemia (CLL) have defects in both cellular and humoral immunity. Since CD152 (CTLA-4) plays a critical role in downregulating T-cell responses, we studied the expression of surface and cytoplasmic CD152 (sCD152 and cCD152, respectively) in freshly isolated T cells from treatment-naïve patients with CLL. CD4+ and CD8+ T cells from these patients demonstrated significantly increased sCD152 and cCD152 compared to normal donors. Furthermore, these patients had an increased proportion of the regulatory CD4(+)/CD25(+)/CD152+ subset that correlated with advanced Rai stage, unfavorable cytogenetics and low serum IgG and IgA levels. The expression of sCD152 by T cells also correlated with ZAP-70 expression by CLL B cells. The proportion of CD4(+)/CD25+ cells was also correlated with unmutated immunoglobulin heavy chain variable gene status. Blockade of CD152 with monoclonal antibody (mAb) in proliferation assays was associated with potent T-cell proliferation in response to autologous and allogeneic CD40-activated CLL B cells. In summary, T cells from patients with CLL may be primed for anergy by expressing increased amounts of CD152; anti-CD152 mAb may represent a therapeutic opportunity to enhance an immune response against autologous leukemia cells.

Transduction of CLL cells by CD40 ligand enhances an antigen-specific immune recognition by autologous T cells

Several features of chronic lymphocytic leukemia (CLL) suggest that immune-based strategies may have therapeutic potential. A promising approach is provided by the transduction of CLL cells with CD40 ligand (CD40L) by viral vectors to enhance their immunogenicity. We compared the antigen-presenting capacity of CD40L-transduced CLL cells with mock-transduced or CD40L-stimulated CLL cells (CD40-CLL). A significantly higher number of T cells could be expanded using CD40L-transduced CLL cells as antigen-presenting cells (APCs) compared with the control group (P = .008). Using 5 different CLL-associated tumor antigens, including fibromodulin, MDM2 (murine double minute 2), survivin, p53, and KW-13, we show in interferon-γ (IFN-γ) enzyme-linked immunospot (ELISPOT) assays after 35 days of in vitro culture that the number of antigen-specific autologous T cells was also significantly higher when CD40L-transduced CLL cells were used as APCs (P &lt; .001). Thus, CD40L-transduced CLL cells are able to induce an antigen-specific T-cell response and might be superior to CD40-CLL cells for immune-based therapeutic strategies in CLL.

Immunotherapy in allogeneic hematopoietic stem cell transplantation--not just a case for effector cells

The concept that in allogeneic hematopoietic stem cell transplantation (alloHSCT) the immune system plays a prominent role in the control of leukemic disease is supported by the clinical observation that immunological effector mechanisms contribute to the elimination of leukemic blasts. The failure to induce prolonged remission after alloHSCT has led to resurgent interest in complementing concepts of immune modulation to improve the antileukemic reponse. While the general focus has been placed on manipulation of cytotoxic effector cell populations, we will explore the dual role of leukemia cells as both antigen-presenting and target cells and describe various vaccination strategies to facilitate a protective antileukemic immune response in this setting. In addition, we will introduce mesenchymal stem cells (MSC) as another cell population recently recognized for their immunomodulatory properties. The potential benefits and hazards of MSC-cotransplantation in alloHSCT with regard to the graft versus leukemia (GvL) and the graft versus host (GvH) response will be discussed.

B-cell expansion in the presence of the novel 293-CD40L-sCD40L cell line allows the generation of large numbers of efficient xenoantigen-free APC

BACKGROUND

CD40-activated B lymphocytes have been used successfully as potent APC for the induction of T-cell responses. However, the 3T3-CD40L cell line, regularly used for engagement of CD40 on the B-cell surface, is a potential source of xenoantigens. This may affect the specificity of T cells stimulated with CD40-activated B cells, especially when generation of T-cell lines specific for endogenously processed Ag is desired.

METHODS

To develop a system that allows efficient expansion of B cells in the absence of sources of xenoantigens, we created a human 293-CD40L-sCD40L cell line that produces soluble CD40L and expresses CD40L on the cell surface. B cells from patients with hematologic malignancies were expanded on the 293-CD40L-sCD40L cells and used for stimulation of either naive or in vivo primed donor T cells in three HLA-identical patient-donor combinations.

RESULTS

The 293-CD40L-sCD40L cell line was able to stimulate B-cell growth with an efficiency superior to that of the commonly used 3T3-CD40L cell line. In all cases T-cell lines and, subsequently, T-cell clones were generated that showed reactivity against patient and not donor B cells, suggesting their specificity for minor histocompatibility antigens (mHAg).

DISCUSSION

B cells activated with GMP grade 293-CD40L-sCD40L can be used in a variety of applications. In particular, they may be suitable for ex vivo stimulation of T cells prior to donor lymphocyte infusion (DLI), which may enhance its graft versus leukemia (GvL) effect.

Potential approach to immunotherapy of chronic lymphocytic leukemia (CLL): enhanced immunogenicity of CLL cells via infection with vectors encoding for multiple costimulatory molecules

Chronic lymphocytic leukemia (CLL) is a disease of CD5(+) B lymphocytes (designated as CLL cells) that are inefficient antigen-presenting cells. Their poor ability to present antigens to the T cells, largely due to an inadequate costimulatory capacity, is manifested as a failure to stimulate proliferation of both allogeneic and autologous T cells. We have investigated the ability of in vitro manipulated CLL cells, via hyperexpression of a triad of costimulatory molecules (B7-1, intercellular adhesion molecule 1 [ICAM-1], and leukocyte-function-associated antigen 3 [LFA-3], designated TRICOM), to stimulate effective antitumor T-cell responses. A recombinant modified vaccinia virus strain Ankara (MVA), which is a highly attenuated, replication-impaired virus variant, was successfully used to infect and deliver the simultaneous expression of the 3 human costimulatory molecules in TRICOM on the surface of the CLL cells. Proliferation of allogeneic and autologous T cells was observed when MVA-TRICOM-infected CLL cells were used as stimulators in proliferation assays. Cytotoxic T lymphocytes, generated in vitro by stimulation of autologous T cells with MVA-TRICOM-infected CLL cells, showed cytotoxicity against unmodified/uninfected CLL cells. Therefore, our findings suggest that the use of CLL cells infected ex vivo with MVA-TRICOM or direct injection of MVA-TRICOM in patients with CLL has potential for the immunotherapy of CLL.

Serum alters the uptake and biologic activity of CpG oligodeoxynucleotides in B cell chronic lymphocytic leukemia

Immunostimulatory CpG-containing oligodeoxynucleotides (CpG ODN) have a number of effects on B cells, including upregulation of immunogenic molecules, and, therefore, appear attractive as potential components of immunotherapy for B cell chronic lymphocytic leukemia (B-CLL). Previous in vitro studies investigating the effect of CpG ODN on B-CLL cells used serum-low conditions and did not account for the longer-half life of CpG ODN in vitro. The present study was designed to explore how the presence of serum and exposure time affect CpG ODN-mediated changes on B-CLL cells. The optimal concentration for CpG ODN-mediated effects in the presence of 100% serum or plasma was higher (10-20 microg/ml) than for serum-low conditions. Maximal CpG ODN-mediated effects required the presence of ODN for no longer than 3 hours. The inhibition of CpG ODN-mediated effects by serum correlated with lower uptake of ODN into B-CLL cells in the presence of serum. A threshold effect on biologic response was observed, with a given amount of ODN internalized, resulting in phenotypic changes. In conclusion, systemic short-term application of CpG ODN appears to be sufficient to induce phenotypic changes, but higher doses of CpG ODN than previously thought may be necessary because of inhibition of their uptake by serum.

Induction of CD95 upregulation does not render chronic lymphocytic leukemia B-cells susceptible to CD95-mediated apoptosis

B-cell chronic lymphocytic leukemia (B-CLL) is characterized by a progressive accumulation of long-lived and well-differentiated clonal B-lymphocytes in peripheral blood, lymphoid tissue and bone marrow. Although B-CLL pathogenesis is not entirely understood, the progressive increase in lymphocyte counts coupled with the very low proportion of proliferating cells suggests that B-CLL may be primarily determined by defective apoptosis. Consistently, freshly analyzed CLL B-cells express very low levels of membrane CD95, one of the best-known receptors involved in triggering apoptosis. In this study, CD95 upregulation on CLL B-cells was induced by culturing clonal B-cells in the presence of supernatants from preactivated autologous T-lymphocytes. Intracellular cytokine staining of preactivated autologous T-lymphocytes using monoclonal antibodies (moAbs) specific for Th1 or Th2 cytokines, namely interleukin (IL)-2, IL-4, IL-5, IL-10 and interferon (IFN)-gamma, showed these cells to be positive for IL-2 and IFN-gamma. Blocking experiments using moAbs specific for IL-2 and/or IFN-gamma revealed that CD95 upregulation on CLL B-cells was mainly driven by IFN-gamma. However, CD95-expressing CLL B-cells were demonstrated to be resistant to CD95-mediated apoptosis, thus arguing against strategies aimed at exploiting CD95-mediated apoptosis for immunotherapy of B-CLL.

Good prognosis cytogenetics in B-cell chronic lymphocytic leukemia is associated in vitro with low susceptibility to apoptosis and enhanced immunogenicity

Chromosomal abnormalities in B-cell chronic lymphocytic leukemia (B-CLL) have been shown to correlate with prognosis. Little is known about the relationship between chromosomal abnormalities and biological behavior of B-CLL cells in vitro. The present study was designed to explore the impact of chromosomal abnormalities determined by interphase fluorescence in situ hybridization (FISH) on the in vitro survival and immunogenicity of B-CLL. Considerable heterogeneity was noted in the in vitro survival and expression of costimulatory, adhesion, and antigen-presenting molecules by B-CLL cells. Spontaneous apoptosis of B-CLL cells in vitro was significantly lower in samples with good prognosis cytogenetics when compared to samples with poor prognosis cytogenetics. In contrast, B-CLL cells from samples with good prognosis cytogenetics exhibited higher basal expression of molecules involved in costimulation, cellular adhesion, and antigen presentation, and induced significantly more T-cell proliferation in mixed lymphocyte cultures. We conclude that chromosomal aberrations of B-CLL cells correlate with the in vitro biological behavior of B-CLL. Our data indicate that good prognosis cytogenetics correlates with less spontaneous apoptosis but greater in vitro immunogenicity. These findings could have significant implications on the design of future therapeutic approaches in patients with CLL, and the likelihood of response based on cytogenetics.

B-Lymphocytes activated by CD40 ligand induce an antigen-specific anti-tumour immune response by direct and indirect activation of CD8(+) T-cells

In this report, we describe the ability of CD40-ligand (CD40L)-activated, antigen-loaded B-cells to initiate antigen-specific anti-tumour immune responses in vivo. Mice immunized by means of intravenous administration of CD40L-activated B-cells loaded with an MHC class-I-binding peptide, and challenged with a tumour cell line expressing the same class-I epitope, showed a marked delay in tumour growth, compared to non-immunized controls or to mice receiving either freshly isolated B-cells or B-cells activated with lipopolysaccharide or interleukin-4. The ability of CD40L-activated B-cells to induce antigen-specific T-cell activation appeared to be through a combination of cross-presentation of antigen from activated B-cells to resident antigen-presenting cells and direct T-cell activation by the administered B-cells themselves. Immunization with CD40L-activated B-cells may, therefore, represent a means by which to stimulate anti-tumour CD8(+) T-cell responses in vivo.

Immunostimulatory oligodeoxynucleotides induce apoptosis of B cell chronic lymphocytic leukemia cells

Immunostimulatory oligodeoxynucleotides (IS ODN) can mediate a number of immunologic effects. We previously demonstrated that treatment of B cell chronic lymphocytic leukemia (B-CLL) cells with one class of IS ODN, CpG ODN, alters their phenotype and increases their immunogenicity. Here, we demonstrate that in contrast to the classic understanding of CpG ODN as inhibitors of B cell apoptosis, IS ODN including CpG ODN induce apoptosis in B-CLL cells. It is important that these changes are seen not only with CpG ODN but with ODN that lack the classical CpG motif. B-CLL cells from 20 subjects were treated in vitro with IS ODN for up to 7 days. IS ODN treatment resulted in increased numbers of apoptotic cells in 13 out of 20 B-CLL samples. IS ODN enhanced apoptosis in samples with 13q deletion as a single aberration and had a heterogeneous effect on apoptosis in samples with other aberrations including 17p deletion, 11q deletion, or trisomy 12. Induction of apoptosis did not correlate with expression of the CpG ODN receptor Toll-like receptor 9. Apoptosis was dependent on the activation of caspases and was accompanied by up-regulation of CD95/Fas and its ligand. We conclude that IS ODN including CpG ODN can induce apoptosis of most B-CLL samples. The ability of IS ODN to induce apoptosis differs based on cytogenetic status. Up-regulation of CD95/Fas may play a role in IS ODN-induced apoptosis of B-CLL.

Molecular transfer of CD40 and OX40 ligands to leukemic human B cells induces expansion of autologous tumor-reactive cytotoxic T lymphocytes

Clinical benefits from monoclonal antibody therapy for B-chronic lymphocytic leukemia (B-CLL) have increased interest in developing additional immunotherapies for the disease. CD40 ligand is an accessory signal for T-cell activation and can overcome T-cell anergy. The OX40-OX40 ligand pathway is involved in the subsequent expansion of memory antigen-specific T cells. We expressed both CD40L and OX40L on B-CLL cells by exploiting the phenomenon of molecular transfer from fibroblasts overexpressing these ligands. We analyzed the effects of the modified B-CLL cells on the number, phenotype, and cytotoxic function of autologous T cells in 7 B-CLL patients. Transfer of CD40L and OX40L was observed in all and was followed by the up-regulation of B7-1 and B7-2. The culture of CD40L/OX40L-expressing B-CLL cells with autologous T cells generated CD4+/CD8+ cytotoxic T-cell lines, which secreted interferon-gamma (IFN-gamma) and granzyme-B/perforin in response to autologous, but not to allogeneic, B-CLL cells or to autologous T-cell blasts. CD40L or OX40L alone was insufficient to expand tumor-reactive T cells. The combination of CD40L and OX40L on B-CLL cells may allow the generation of therapeutic immune responses to B-CLL, either by active immunization with modified tumor cells or by adoptive immunotherapy with tumor-reactive autologous T cells.

Treatment of bladder carcinomas using recombinant BCG DNA vaccines and electroporative gene immunotherapy

Intravesical immunotherapy with live Mycobacterium bovis bacillus Calmette-Guérin (BCG) is the treatment of choice for superficial bladder cancers. Nevertheless, a significant proportion of patients do not respond to this therapy, and adverse effects are common. Here, we report the cloning of recombinant mycobacterial DNA vaccines and demonstrate the ability of multicomponent and multisubunit DNA vaccines to enhance Th1-polarized cytokine-mediated responses as well as effector cell responses. Splenocytes from immunized groups of mice were restimulated in vitro and examined for cytotoxicity against murine bladder tumur (MBT-2) cells. We used four combined recombinant BCG DNA vaccines (poly-rBCG) for electroporative gene immunotherapy (EPGIT) in vivo, and found that tumor growth was significantly inhibited and mouse survival was prolonged. Increased immune cell infiltration and induction of apoptosis were noted after treatment with poly-rBCG alone, with the murine interleukin-12 (mIL-12) vaccine alone, and-most significantly-with the poly-rBCG+mIL-12 vaccine combination. Electroporation of poly-rBCG+mIL-12 resulted in complete tumor eradication in seven of eight mice (P<.01) within 28 days. Thus, EPGIT using multicomponent multisubunit BCG is highly effective in the treatment of bladder cancer. This approach presents new possibilities for the treatment of bladder cancer using recombinant BCG DNA vaccines.

Autoreactive, cytotoxic T lymphocytes specific for peptides derived from normal B-cell differentiation antigens in healthy individuals and patients with B-cell malignancies

PURPOSE

To investigate potential immunotherapeutic strategies in B lymphocytic malignancies we looked for CTLs recognizing CD19 and CD20 epitopes.

EXPERIMENTAL DESIGN

Three CD19 and CD20 peptides binding to HLA-A*0201 were identified and used to detect peptide specific CTLs by a quantitative real-time PCR to measure IFN-gamma mRNA expression in 23 healthy individuals and 28 patients (18 chronic lymphocytic leukemia (CLL), 7 follicular lymphoma, 2 acute lymphocytic leukemia, and 1 large cell lymphoma). Peptide-specific CTLs were expanded in culture with CD40-activated B cells to test lytic activity in three patients.

RESULTS

In healthy individuals, CD8+ T-cell responses were detected in one to CD19(74-82), in three to CD20(127-135), and three to CD20(188-196). Seven of 27 patients (6 with CLL) had CD8+ T cells recognizing CD19(74-82). Seven patients responded to CD20(127-135) and three to CD20(188-196). All were CLL patients. CD19(74-82)-specific CTLs from three patients were expanded over 4 weeks. These cells were HLA-A*0201 specific and lytic for peptide-loaded antigen-presenting cells but not to malignant or unpulsed B cells.

CONCLUSIONS

CTLs that recognize CD19 and CD20 epitopes exist in healthy individuals and may be increased in CLL patients. They are of low avidity and require high doses of peptide for activation. Strategies to increase T-cell avidity would be necessary for T-cell immunotherapeutic approaches using the peptides studied.

CD40 activation of BCP-ALL cells generates IL-10–producing, IL-12–defective APCs that induce allogeneic T-cell anergy

The use of leukemia cells as antigen-presenting cells (APCs) in immunotherapy is critically dependent on their capacity to initiate and sustain an antitumor-specific immune response. Previous studies suggested that pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL) cells could be manipulated in vitro through the CD40-CD40L pathway to increase their immunostimulatory capacity. We extended the APC characterization of CD40L-activated BCP-ALL for their potential use in immunotherapy in a series of 19 patients. Engaging CD40 induced the up-regulation of CCR7 in 7 of 11 patients and then the migration to CCL19 in 2 of 5 patients. As accessory cells, CD40L-activated BCP-ALL induced a strong proliferation response of naive T lymphocytes. Leukemia cells, however, were unable to sustain proliferation over time, and T cells eventually became anergic. After CD40-activation, BCP-ALL cells released substantial amounts of interleukin-10 (IL-10) but were unable to produce bioactive IL-12 or to polarize TH1 effectors. Interestingly, adding exogenous IL-12 induced the generation of interferon-γ (IFN-γ)–secreting TH1 effectors and reverted the anergic profile in a secondary response. Therefore, engaging CD40 on BCP-ALL cells is insufficient for the acquisition of full functional properties of immunostimulatory APCs. These results suggest caution against the potential use of CD40L-activated BCP-ALL cells as agents for immunotherapy unless additional stimuli, such as IL-12, are provided.

Generation of B-cell chronic lymphocytic leukemia (B-CLL)-reactive T-cell lines and clones from HLA class I-matched donors using modified B-CLL cells as stimulators: implications for adoptive immunotherapy

Allogeneic stem cell transplantation following reduced-intensity conditioning is being evaluated in patients with advanced B-cell chronic lymphocytic leukemia (B-CLL). The curative potential of this procedure is mediated by donor-derived alloreactive T cells, resulting in a graft-versus-leukemia effect. However, B-CLL may escape T-cell-mediated immune reactivity since these cells lack expression of costimulatory molecules. We examined the most optimal method to transform B-CLL cells into efficient antigen-presenting cells (APC) using activating cytokines, by triggering toll-like receptors (TLRs) using microbial pathogens and by CD40 stimulation with CD40L-transfected fibroblasts. CD40 activation in the presence of IL-4 induced strongest upregulation of costimulatory and adhesion molecules on B-CLL cells and induced the production of high amounts of IL-12 by the leukemic cells. In contrast to primary B-CLL cells as stimulator cells, these malignant APCs were capable of inducing the generation of B-CLL-reactive CD8(+) CTL lines and clones from HLA class I-matched donors. These CTL lines and clones recognized and killed primary B-CLL as well as patient-derived lymphoblasts, but not donor cells. These results show the feasibility of ex vivo generation of B-CLL-reactive CD8(+) CTLs. This opens new perspectives for adoptive immunotherapy, following allogeneic stem cell transplantation in patients with advanced B-CLL.

Indolent B-cell malignancies: immune recognition and antiself

B-cell malignancies appear to be ideal candidates for treatment with immunotherapeutic approaches. Monoclonal antibodies that target cell-surface determinants have been used as single agents in B-cell malignancies, in combination with chemotherapy, and coupled to other agents to create radioimmunoconjugates and immunotoxins. Another approach is to take advantage of the graft-vs.-lymphoma effect seen following allogeneic bone marrow transplantation. To exploit this effect without inducing the complication of graft-vs.-host disease, it is necessary to understand the mechanisms whereby lymphoma cells escape T-cell-mediated responses. CD40 activation may offer a means of increasing the immunogenicity of lymphoma cells and of stimulating allogeneic T-cell proliferation and cytokine production. Vaccination using tumor-specific antigens shows promise as a therapeutic strategy. Pre-clinical studies with immunoglobulin idiotype peptides have shown that humoral and cellular immune responses can be stimulated by antibodies to these peptides, but better tumor antigens need to be identified that can reliably generate cytotoxic T-cell responses. Candidate antigens include heteroclitic peptides from the immunoglobulin V region and newly identified antigens including the cytochrome P450 1B1. Clinical trials are ongoing in all these fields.

Vaccine therapy in NHL: future promises and current limitations

Recent advances in genomics are revealing new molecular targets for vaccination strategies in cancer, and unraveling the immune pathways that must be activated. Initially, work focused on idiotypic antigen expressed by the clonal immunoglobulin (Ig) of B-cell tumors. This involved assembling the encoding V(H) and V(L) genes as single-chain Fv (scFv), which has been fused to Fragment C (FrC) of tetanus toxin to enhance recognition and response. The fusion gene induces strong anti-idiotypic protection against lymphoma in experimental models, and is now in clinical trials with encouraging results emerging. This principle of fusing a pathogen-derived sequence is widely applicable. A coat protein from a potato virus substituted for the FrC sequence has also been found to be capable of promoting anti-tumor immunity. The current design is effective in inducing anti-idiotypic (Id) antibody and CD4+ T-cell attack. For intracellular tumor antigens expressed as MHC Class I-associated peptides, a design consisting of a gene encoding a single domain of FrC linked to a candidate peptide sequence has been developed. This induces fast cytotoxic T-cell attack on peptide-expressing tumor cells. Injection of DNA appears safe and clinical trials will test the efficacy of this approach, and probably lead to improvements in these flexible vaccines.

Effect of tetravalent bispecific CD19×CD3 recombinant antibody construct and CD28 costimulation on lysis of malignant B cells from patients with chronic lymphocytic leukemia by autologous T cells

To develop an effective antitumor immunotherapy for B-lineage non-Hodgkin's lymphoma, we constructed a tetravalent tandem diabody (tanDb) specific for both human CD19 (B-cell marker) and CD3 (T-cell antigen). Here, we report the effective killing of malignant primary B cells from patients with B-cell chronic lymphocytic leukemia (B-CLL) by autologous T cells induced by tanDb at very low E:T ratios. Mononuclear cells from patients with B-CLL were cultured with bispecific antibody fragments in either the presence or absence of monospecific anti-CD28 antibody. Use of tetravalent tanDbs caused almost quantitative elimination of malignant B cells from the blood samples of 19 patients and some cytotoxic activity in 3 of 23 analyzed cases. In contrast, the structurally similar but bivalent diabody and single-chain diabody demonstrated nearly no antitumor activity in an autologous system. tanDb-induced activation and proliferation of T cells occurred only in the presence of CD19+ target cells. Expression of the B7-1 (CD80) and B7-2 (CD86) molecules on the surface of leukemia cells made unnecessary the additional CD28-costimulation of T cells. When only a few tanDb molecules were present, the effect of CD28 costimulation on T-cell activation was more pronounced. Depending on the patient sample, we observed a 10- to 1,000-fold decrease of the half-maximal concentrations of tanDb for cell lysis. Upon CD28 crosslinking by agonistic MAb, specific tumor cell lysis was found at tanDb concentrations as low as 0.5 pM. These data demonstrate that the tetravalent CD19xCD3 tanDb might be a promising tool for the immunotherapy of human B-cell leukemias and lymphomas.

Functional transfer of CD40L gene in human B-cell precursor ALL blasts by second-generation SIN lentivectors

Three different second-generation lentiviral self-inactivating vectors containing CMV, EF1alpha and PGK promoter, respectively, and all carrying the exogenous GFP gene, were compared for expression in human B-cell precursor ALL blasts. At a comparable percentage of transduction and vector DNA copy number, CMV clearly showed better efficiency of transcription. Human bone marrow stromal cells were favored compared to the MRC-5 cell line, as support for cell viability during infection. Cells were infected and analyzed after variable culture times ranging from 4 to 12 days, to reduce the possibility of pseudotransduction. In 10/14 samples, we detected more than 20% GFP-positive cells after exposure to high-titer viral supernatants. We then tested a similar vector carrying the human CD40L cDNA and, in similar infection conditions, obtained more than 20% transduction in 6/6 samples. The levels of transduction obtained were sufficient to induce the upregulation of CD83 molecule in cocultured immature dendritic cells.

Stimulation of non-Hodgkin's lymphoma via HVEM: an alternate and safe way to increase Fas-induced apoptosis and improve tumor immunogenicity

Stimulation by CD40 ligand (L) improves B-cell malignancy immunogenicity, and also induces proliferative signals. To avoid these tumorigenic effects, we studied an alternate way of tumor-cell stimulation by homologous to lymphotoxin, inducible expression, competing for GpD of herpesvirus, which binds to the herpesvirus entry mediator (HVEM), and is expressed on T-lymphocytes (LIGHT), the ligand for HVEM, a new member of the tumor necrosis factor (TNF)/TNF-receptor (-R) family. HVEM is constitutively expressed on the surface of tumor B cells. We focused our attention on mantle cell lymphoma, a subtype of B-cell malignancy of poor prognosis. Triggering by LIGHT, in contrast to CD40L stimulation, did not increase lymphoma proliferation nor decrease chemotherapy entrance. We observed an upregulation of the TNFR apoptosis-inducing ligand Fas, and in contrast to CD40L-induced protection, an enhancement of lymphoma sensitivity to Fas-induced apoptosis. LIGHT triggering increased lymphoma cell recognition in a mixed lymphocyte response. In conclusion, LIGHT-mediated triggering renders B-cell lymphomas more immunogenic and sensitive to apoptosis, without inducing proliferation. Since LIGHT triggering also enhances the functions of T-lymphocytes and dendritic cells, it could be a unique way to restore an efficient cancer control by its pleiotropic effects on immune effectors and tumor cells.