Engagement of CD83 ligand induces prolonged expansion of CD8+ T cells and preferential enrichment for antigen specificity

Dissociation of its opposing immunologic effects is critical for the optimization of antitumor CD8+ T-cell responses induced by interleukin 21

PURPOSE

Interleukin 21 (IL-21) is a promising new cytokine, which is undergoing clinical testing as an anticancer agent. Although IL-21 provides potent stimulation of CD8(+) T cells, it has also been suggested that IL-21 is immunosuppressive by counteracting the maturation of dendritic cells. The dissociation of these two opposing effects may enhance the utility of IL-21 as an immunotherapeutic. In this study, we used a cell-based artificial antigen-presenting cell (aAPC) lacking a functional IL-21 receptor (IL-21R) to investigate the immunostimulatory properties of IL-21.

EXPERIMENTAL DESIGN

The immunosuppressive activity of IL-21 was studied using human IL-21R(+) dendritic cells. Antigen-specific CD8(+) T cells stimulated with human cell-based IL-21R(-)aAPC were used to isolate the T-cell immunostimulatory effects of IL-21. The functional outcomes, including phenotype, cytokine production, proliferation, and cytotoxicity were evaluated.

RESULTS

IL-21 limits the immune response by maintaining immunologically immature dendritic cells. However, stimulation of CD8(+) T cells with IL-21R(-) aAPC, which secrete IL-21, results in significant expansion. Although priming in the presence of IL-21 temporarily modulated the T-cell phenotype, chronic stimulation abrogated these differences. Importantly, exposure to IL-21 during restimulation promoted the enrichment and expansion of antigen-specific CD8(+) T cells that maintained IL-2 secretion and gained enhanced IFN-gamma secretion. Tumor antigen-specific CTL generated in the presence of IL-21 recognized tumor cells efficiently, demonstrating potent effector functions.

CONCLUSIONS

IL-21 induces opposing effects on antigen-presenting cells and CD8(+) T cells. Strategic application of IL-21 is required to induce optimal clinical effects and may enable the generation of large numbers of highly avid tumor-specific CTL for adoptive immunotherapy.

Post-transplant adoptive T-cell immunotherapy

Immune reconstitution following haematopoietic stem cell transplantation (SCT) is an often slow and incomplete process that leads to increased risk of infection and malignant disease. Immunization in SCT is frequently unsuccessful due to the prolonged lymphopenia, especially of CD4 T cells, seen following transplant. The transfusion of T cells, also called 'adoptive T-cell therapy', has the potential to enhance anti-tumour and overall immunity, and augment vaccine efficacy in the post-transplant setting. Recent advances in tissue culture, cellular immunology and tumour biology are guiding new approaches to adoptive T-cell therapy. This chapter will discuss the challenges that face the field before adoptive T-cell therapy can be translated into routine clinical practice.

Generation of functionally mature dendritic cells from elutriated monocytes using polyinosinic : polycytidylic acid and soluble CD40 ligand for clinical application

Despite the increasing use of dendritic cell (DC) vaccination in clinical trials, optimal conditions for the generation of functionally mature DCs remain to be established. The current standard DC maturation protocol for clinical trials has been used as an inflammatory cytokine cocktail [tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and prostaglandin E(2)], but this cocktail induced insufficient maturation of DCs derived from elutriated monocytes when cultured in X-VIVO 15. The aim of this study was to define effective combinations of stimulators for generating functionally mature DCs from elutriated monocytes under current good manufacturing practice conditions. We compared the functional capacity of DCs in response to all possible pairwise combinations of four different classes of stimuli: TNF-alpha, peptidoglycan, polyinosinic : polycytidylic acid [poly(I:C)] and soluble CD40 ligand (CD40L). Maturation status of DCs stimulated with combination of four stimuli was similar to that of the cytokine cocktail as assessed by the cell surface phenotype. However, only the combination of poly(I:C) + CD40L induced complete functional activation of the whole DC population, assessing IL-12p70 production, allostimulatory activity, migratory response to CCL19 and T helper 1-polarizing capacity. Thus, the protocol based on the combination of poly(I:C) and CD40L is more effective for the induction of clinical-grade DCs from elutriated monocytes than the standard cytokine cocktail.

Human dendritic cells differentiated in hypoxia down-modulate antigen uptake and change their chemokine expression profile

Dendritic cells (DCs) are the most potent antigen-presenting cells and fine-tune the immune response. We have investigated hypoxia's effects on the differentiation and maturation of DCs from human monocytes in vitro, and have shown that it affects DC functions. Hypoxic immature DCs (H-iDCs) significantly fail to capture antigens through down-modulation of the RhoA/Ezrin-Radixin-Moesin pathway and the expression of CD206. Moreover, H-iDCs released higher levels of CXCL1, VEGF, CCL20, CXCL8, and CXCL10 but decreased levels of CCL2 and CCL18, which predict a different ability to recruit neutrophils rather than monocytes and create a proinflammatory and proangiogenic environment. By contrast, hypoxia has no effect on DC maturation. Hypoxic mature DCs display a mature phenotype and activate both allogeneic and specific T cells like normoxic mDCs. This study provides the first demonstration that hypoxia inhibits antigen uptake by DCs and profoundly changes the DC chemokine expression profile and may have a critical role in DC differentiation, adaptation, and activation in inflamed tissues.

The CD83 reporter mouse elucidates the activity of the CD83 promoter in B, T, and dendritic cell populations in vivo

CD83 is the major surface marker identifying mature dendritic cells (DCs). In this study, we report the generation of reporter mice expressing EGFP under the control of the CD83 promoter. We have used these mice to characterize CD83 expression by various immune system cell types both in vivo and ex vivo and under steady-state conditions and in response to stimulation with a Toll-like receptor (TLR) ligand. With those mice we could prove in vivo that the CD83 promoter is highly active in all DCs and B cells in lymphoid organs. Interestingly, this promoter activity in B cells mainly depended on the stage of development, is up-regulated in the late pre-B cell stage, and was maintained on a high level in all peripheral B cells. We also confirmed that CD83 in those cells is mainly intracellular but is up-regulated after TLR stimulation. Otherwise, CD83 promoter activity in T cells seemed to depend on stimulation and could be found mainly in CD4(+)CD25(+) and CD8(+)CD25(+) T cells and in CD4(+) and CD8(+) memory cells. In addition, we identified the murine homologues of the human CD83 splice variants. In contrast to those in human, those extremely rare short transcripts were never found without the expression of the highly dominant full-length form. So, the murine CD83 surface expression is mainly regulated posttranslationally in vivo. Our CD83 reporter mice represent a useful mouse model for monitoring the activation status and migration of DCs and lymphocytes under various conditions, and our results provide much needed clarification of the true nature of CD83 promoter activity.

CD83 regulates splenic B cell maturation and peripheral B cell homeostasis

The central function of murine CD83 that is expressed on thymic epithelial cells is to induce the progression of double-positive thymocytes to single CD4-positive T cells. Several lines of evidence suggest an additional role for CD83 in the regulation of peripheral T and B cell responses. Here we show that CD83 is expressed by immature B cells and regulates their further maturation and survival in the periphery. Employing mixed bone marrow chimeras, we compare wild-type, CD83 over-expressing and CD83-deficient B cells within the same host. CD83 over-expression on the immature B cells themselves led to an accumulation of transitional B cells and a reciprocally reduced maturation of follicular B cells that was strictly correlated to the intensity of CD83 over-expression. The absence of CD83 on B cells resulted in a decreased maturation of marginal zone B cells and conferred a mild selection advantage for B cell survival in the periphery. Consenting with these findings, the over-expression of CD83 specifically and dose dependently interfered with homeostasis of B cells while T cell survival was not affected by CD83 over-expression over a period of 30 weeks. Taken together, our data suggest that CD83 negatively regulates B cell maturation and survival.

Adoptive transfer of pTRP2-specific CTLs expanding by bead-based artificial antigen-presenting cells mediates anti-melanoma response

Cytotoxic CD8(+) T cells are key effectors in the immunotherapy of malignant and viral diseases. However, the lack of efficient methods for their in vitro priming and expansion has become a bottleneck to the development of vaccines and adoptive transfer strategies. Synthetic artificial antigen-presenting cells (aAPCs) are now emerging as an attractive tool for eliciting and expanding CTL responses. This study reported a novel approach for targeting malignant melanoma with pTRP2-specific cytotoxic T lymphocytes (CTLs) expanded from the C57BL/6 splenocytes by multiple stimulations with aAPCs made by coating H-2K(b)-Ig/pTRP2 dimeric complexes, anti-CD28 antibody, 4-1BBL molecules and CD83 molecules to cell-sized latex beads. The induced CTLs exhibited specific lysis against RMA-S cells pulsed with the peptide pTRP2 and H-2K(b+) melanoma cells expressing TRP2, while a murine Lewis lung carcinoma cell line 3LL could not be recognized by the CTLs. The peptide-specific activity was inhibited by anti-H-2K(b) monoclonal antibody Y3. Adoptive Transfer of CTLs specific for malignant melanoma expanding by the aAPCs can mediate effective anti-melanoma response. These results suggested the bead-based aAPCs coated with an MHC-Ig/peptide complex, anti-CD28 antibody, 4-1BBL and CD83 could provide a useful tool for the reproducible expansion of specific CTLs for adoptive immunotherapy.

Local secretion/shedding of tumor-derived CD83 molecules as a novel tumor escape mechanism

CD83, a characteristic marker of activated dendritic cells, is also expressed by tumor cell lines from various origins and by primary lung cancers. Here, we show that CD83+ tumor cells (from a primary lung cancer and from an established breast cancer cell line) release in their culture supernatants a soluble factor that is able to block, in a dose-dependent manner, CD4+ and CD8+ T cell proliferative responses to allogeneic dendritic cells. This factor was removed from the medium by incubation in anti-CD83 covered plates, indicating that it could be one of the known soluble forms of the CD83 molecule, released in the medium by the cultured tumor cells. This phenomenon, happening in vivo, in the tumor microenvironment, could affect profoundly anti-tumor immune responses and should, therefore, be considered in immunotherapeutic approaches to cancer.

Nonstructural proteins 1 and 2 of respiratory syncytial virus suppress maturation of human dendritic cells

Human respiratory syncytial virus (RSV) is the most important agent of serious pediatric respiratory tract disease worldwide. One of the main characteristics of RSV is that it readily reinfects and causes disease throughout life without the need for significant antigenic change. The virus encodes nonstructural protein 1 (NS1) and NS2, which are known to suppress type I interferon (IFN) production and signaling. In the present study, we monitored the maturation of human monocyte-derived myeloid dendritic cells (DC) following inoculation with recombinant RSVs bearing deletions of the NS1 and/or NS2 proteins and expressing enhanced green fluorescent protein. Deletion of the NS1 protein resulted in increased expression of cell surface markers of DC maturation and an increase in the expression of multiple cytokines and chemokines. This effect was enhanced somewhat by further deletion of the NS2 protein, although deletion of NS2 alone did not have a significant effect. The upregulation was largely inhibited by pretreatment with a blocking antibody against the type I IFN receptor, suggesting that suppression of DC maturation by NS1/2 is, at least in part, a result of IFN antagonism mediated by these proteins. Therefore, this study identified another effect of the NS1 and NS2 proteins. The observed suppression of DC maturation may result in decreased antigen presentation and T-lymphocyte activation, leading to incomplete and/or weak immune responses that might contribute to RSV reinfection.

CD83 expression in CD4+ T cells modulates inflammation and autoimmunity

The transmembrane protein CD83 has been initially described as a maturation marker for dendritic cells. Moreover, there is increasing evidence that CD83 also regulates B cell function, thymic T cell maturation, and peripheral T cell activation. Herein, we show that CD83 expression confers immunosuppressive function to CD4(+) T cells. CD83 mRNA is differentially expressed in naturally occurring CD4(+)CD25(+) regulatory T cells, and upon activation these cells rapidly express large amounts of surface CD83. Transduction of naive CD4(+)CD25(-) T cells with CD83 encoding retroviruses induces a regulatory phenotype in vitro, which is accompanied by the induction of Foxp3. Functional analysis of CD83-transduced T cells in vivo demonstrates that these CD83(+)Foxp3(+) T cells are able to interfere with the effector phase of severe contact hypersensitivity reaction of the skin. Moreover, adoptive transfer of these cells prevents the paralysis associated with experimental autoimmune encephalomyelitis, suppresses proinflammatory cytokines IFN-gamma and IL-17, and increases antiinflammatory IL-10 in recipient mice. Taken together, our data provide the first evidence that CD83 expression can contribute to the immunosuppressive function of CD4(+) T cells in vivo.

CD83 regulates lymphocyte maturation, activation and homeostasis

The transmembrane CD83 molecule, a conserved member of the immunoglobulin superfamily, is known as one of the most characteristic cell surface markers for fully matured dendritic cells (DCs) in the peripheral circulation. An essential role for CD83 on murine DCs has not been found; however, evidence shows that its function primarily lies in the regulation of T- and B-lymphocyte maturation and in the regulation of their peripheral responses. Here, we review evidence for a role of CD83 in central lymphocyte maturation and novel, sometimes contradictory findings, regarding the function of CD83 in peripheral immune responses.

Lactoferrin, a major defense protein of innate immunity, is a novel maturation factor for human dendritic cells

Lactoferrin (LF) is an important protein component of the innate immune system that is broadly distributed within the body fluids. LF is endowed with multiple biological activities. Talactoferrin (TLF), a recombinant human LF, is in clinical development as an anticancer agent and is entering Phase III clinical trials. Here, we show that TLF induces the maturation of human dendritic cells (DCs) derived from monocytes. TLF, at physiologically relevant concentrations (100 microg/ml) up-regulates the expression of human leukocyte antigen (HLA) class II, CD83, CD80, and CD86 costimulatory molecule and CXCR4 and CCR7 chemokine receptors, acting primarily through the p38 MAPK signaling pathway. DCs matured by TLF displayed an enhanced release of IL-8 and CXCL10, as well as a significantly reduced production of IL-6, IL-10, and CCL20. They also display a reduced ability to take up antigen and increased capacity to trigger proliferation and release IFN-gamma in the presence of allogeneic human T cells. TLF-matured DCs are able to prime naive T cells to respond to KLH antigen and display a significantly increased capacity to present Flu-MA(58-66) peptide to HLA-A2-matched T cells. These data suggest that a key immunomodulatory function that may be mediated by TLF is to link the innate with adaptive immunity through DC maturation.

Expression of a dendritic cell maturation marker CD83 on tumor cells from lung cancer patients and several human tumor cell lines: is there a biological meaning behind it?

The present paper shows, for the first time, the membrane expression of the dendritic cell maturation marker CD83 on tumor cells from lung cancer patients. CD83 was also detected on freshly cultured fibroblast-like cells from these tissues and on several adherent human tumor cell lines (lung adenocarcinomas P9, A459 and A549, melanomas A375 and C81-61, breast adenocarcinomas SKBR-3 and MCF-7 and colon carcinoma AR42-J), but not in the non-adherent MOT leukemia cell line. CD83 may have immunosuppressive properties and its expression by cancer cells could have a role in facilitating tumor growth.

Failed efficacy of soluble human CD83-Ig in allogeneic mixed lymphocyte reactions and experimental autoimmune encephalomyelitis: implications for a lack of therapeutic potential

Soluble forms of CD83, a dendritic cell-specific surface glycoprotein, have been strongly proposed to be of therapeutic utility in inflammatory conditions such as multiple sclerosis and transplantation. We demonstrate here, however, that eukaryotically expressed, recombinant soluble human CD83-Ig molecules fail to achieve efficacy in model systems for those conditions: mouse experimental autoimmune encephalomyelitis models in vivo or in mixed lymphocyte reactions in vitro. These results raise concern as to the viability of a eukaryotically expressed soluble CD83 strategy for clinical therapeutic use.

Dendritic cell CD83: a therapeutic target or innocent bystander?

CD83 represents an intriguing target for immunotherapy due to its preferential expression on mature DCs, the most efficient of antigen presenting cells. Based on its restricted expression pattern, structure, and the paucity of CD4+ T cells in CD83-deficient mice, multiple immunologically important functions for CD83 during immune responses have been proposed. Indeed, several studies have reported that CD83 blockade using soluble receptor constructs inhibits T cell responses in vitro and in vivo, can affect autoimmune disease development and progression, and can inhibit transplant rejection. However, others have not been able to reproduce some of these findings, and antigen presenting cells deficient in CD83 expression or expressing a mutated form of CD83 induce normal T cell responses in vitro. This review examines the controversy surrounding CD83 function, alleged CD83 ligands, the potential therapeutic utility of recombinant proteins targeting CD83 function, and the importance of soluble serum CD83. While the validity of multiple previous studies needs to be confirmed, CD83 remains a fascinating cell surface molecule with a unique pattern of expression that has multiple confirmed functions in regulating immune system development and function.

HLA Tetramer Based Artificial Antigen-Presenting Cells Efficiently Stimulate CTLs Specific for Malignant Glioma

PURPOSE

The interleukin-13 receptor alpha 2 (IL-13R alpha 2) is a glioma-restricted cell-surface epitope not otherwise detected within the central nervous system. Here, we report a novel approach for targeting malignant glioma with IL-13R alpha 2-specific CTLs.

EXPERIMENTAL DESIGN

Artificial antigen-presenting cells (aAPC) were made by coating human leukocyte antigen (HLA)-A2/pIL-13R alpha 2(345-354) tetrameric complexes, anti-CD28 antibody, and CD83 molecules to cell-sized latex beads, and used to stimulate IL-13R alpha 2-specific CTLs from the peripheral blood mononuclear cells of HLA-A2+ healthy donors. After multiple stimulations, the induced CTLs were analyzed for tetramer staining, IFN-gamma production, and CTL reactivity.

RESULTS

Tetramer staining assay showed that the induced CTLs specifically bound HLA-A2/pIL-13R alpha 2(345-354) tetramers. The CTLs specifically produced IFN-gamma in response to the HLA-A2/pIL-13R alpha 2(345-354)-aAPCs and exhibited specific lysis against T2 cells pulsed with the peptide pIL-13R alpha 2(345-354) and HLA-A2+ glioma cells expressing IL-13R alpha 2(345-354), whereas HLA-A2(-) glioma cell lines that express IL-13R alpha 2(345-354) could not be recognized by the CTLs. The peptide-specific activity was inhibited by anti-HLA class I monoclonal antibody.

CONCLUSION

The induced CTLs specific for IL-13R alpha 2(345-354) peptide could be a potential target of specific immunotherapy for HLA-A2+ patients with malignant glioma.

Induction of cytotoxic T-lymphocytes specific for malignant glioma by HLA dimer-based artificial antigen-presenting cells

AIM

The aim of this study was to investigate the novel approach for targeting malignant glioma.

METHODS

Interleukin-13 receptor alpha2 (IL-13Ralpha2)-specific cytotoxic T-cells (CTLs) were induced from the peripheral blood lymphocytes (PBLs) of human leukocyte antigen (HLA)-A2 positive healthy donors by multiple stimulations with artificial antigen-presenting cells (aAPCs) made by coating HLA-A2-Ig/pIL-13Ralpha2(345-354) dimeric complexes, anti-CD28 antibody, and CD83 molecules to cell-sized latex beads.

RESULTS

The induced CTLs exhibited a specific lysis against T2 cells pulsed with the peptide pIL-13Ralpha2(345-354) and HLA-A2(+) glioma cells expressing IL-13Ralpha2(345-354), while HLA-A2(-) glioma cell lines that express IL-13Ralpha2(345-354) could not be recognized by the CTLs. The peptide-specific activity was inhibited by the anti-HLA class I monoclonal antibody.

CONCLUSIONS

The induced CTLs specific for the IL-13Ralpha2(345-354) peptide could be a potential target of specific immunotherapy for HLA-A2(+) patients with malignant glioma.

Stimulation by means of dendritic cells followed by Epstein-Barr virus-transformed B cells as antigen-presenting cells is more efficient than dendritic cells alone in inducing Aspergillus f16-specific cytotoxic T cell responses

Adoptive immunotherapy with in vitro expanded antigen-specific cytotoxic T lymphocytes (CTLs) may be an effective approach to prevent, or even treat, Aspergillus (Asp) infections. Such lines can be generated using monocyte-derived dendritic cells (DC) as antigen-presenting cells (APC) but requires a relatively high volume of starting blood. Here we describe a method that generates Asp-specific CTL responses more efficiently using a protocol of antigen presented on DC followed by Epstein-Barr virus (EBV)-transformed B lymphoblastoid cell lines (BLCL) as APC. Peripheral blood mononuclear cells were stimulated weekly (2-5x) with a complete pool of pentadecapeptides (PPC) spanning the coding region of Asp f16 pulsed onto autologous mature DC. Cultures were split and stimulated subsequently with either PPC-DC or autologous PPC-pulsed BLCL (PPC-BLCL). Lines from the DC/BLCL arm demonstrated Asp f16-specific cytotoxicity earlier and to a higher degree than lines generated with PPC-DC alone. The DC/BLCL-primed lines showed a higher frequency of Asp f16-specific interferon (IFN)-gamma producing cells but an identical effector cell phenotype and peptide specificity compared to PPC-DC-only-primed lines. Tumour necrosis factor (TNF)-alpha, but not IL-10, appeared to play a role in the effectiveness of BLCL as APC. These results demonstrate that BLCL serve as highly effective APC for the stimulation of Asp f16-specific T cell responses and that a culture approach using initial priming with PPC-DC followed by PPC-BLCL may be a more effective method to generate Asp f16-specific T cell lines and requires less starting blood than priming with PPC-DC alone.

CD83 expression is a sensitive marker of activation required for B cell and CD4+ T cell longevity in vivo

CD83 is a surface marker that differentiates immature and mature human dendritic cell populations. Thymic epithelial cell expression of CD83 is also necessary for efficient CD4+ T cell development in mice. The altered phenotypes of peripheral B and CD4+ T cells, and the reduction of peripheral CD4+ T cells in CD83-/- mice, suggest additional functions for CD83. To assess this, a panel of mAbs was generated to characterize mouse CD83 expression by peripheral leukocytes. As in humans, activation of conventional and plasmacytoid murine dendritic cell subsets led to rapid up-regulation of CD83 surface expression in mice. In primary and secondary lymphoid compartments, a subset of B cells expressed low-level CD83, while CD83 was not detected on resting T cells. However, CD83 was prominently up-regulated on the majority of spleen B and T cells within hours of activation in vitro. In vivo, a low dose of hen egg lysozyme (1 microg) induced significant CD83 but not CD69 expression by Ag-specific B cells within 4 h of Ag challenge. Although B cell development appeared normal in CD83-/- mice, B and CD4+ T cell expression of CD83 was required for lymphocyte longevity in adoptive transfer experiments. Thus, the restricted expression pattern of CD83, its rapid induction following B cell and T cell activation, and its requirement for B cell and CD4+ T cell longevity demonstrate that CD83 is a functionally significant and sensitive marker of early lymphocyte activation in vivo.

CD83 expression in sea bream macrophages is a marker for the LPS-induced inflammatory response

CD83, a cell surface membrane glycoprotein member of the Ig superfamily which is commonly used as standard surface marker for dendritic cells, was cloned from gilthead sea bream macrophages using degenerate primers against conserved motifs of known CD83 sequences. The obtained cDNA contains an open reading frame of 669 nucleotides that translate into a 222 amino acid putative peptide. The deduced protein sequence shows conservation of features shared by vertebrate CD83 and multiple alignment with fish CD83 sequences reveals high homology. In cultured sea bream macrophages CD83 mRNA expression was significantly enhanced in a dose- and time-dependent fashion after stimulation with Escherichia coli LPS. These results indicate that in fish, macrophages express high levels of CD83 mRNA after LPS exposure and CD83 is therefore a good marker for activated mature myeloid cells in fish.

Generation of allo-restricted cytotoxic T lymphocytes against malignant glioma by artificial antigen-presenting cells

The interleukin (IL) 13 receptor alpha2 (IL-13Ralpha2) is a glioma-restricted cell-surface epitope not otherwise detected within the central nervous system. This study reported a novel approach for targeting malignant glioma with IL-13Ralpha2-specific allo-restricted cytotoxic T cells (CTLs) induced from the peripheral blood lymphocytes (PBLs) of HLA-A2-negative healthy donors by multiple stimulations with artificial antigen-presenting cells (aAPCs) made by coating HLA-A2/pIL-13Ralpha2(345-354) tetrameric complexes, anti-CD28 antibody and CD83 molecules to cell-sized latex beads. The induced allo-restricted CTLs exhibited specific lysis against T2 cells pulsed with the peptide pIL-13Ralpha2(345-354) and HLA-A2+ glioma cells expressing IL-13Ralpha2(345-354), while HLA-A2- glioma cell lines that express IL-13Ralpha2(345-354) could not be recognized by the CTLs. The peptide-specific activity was inhibited by anti-HLA class I monoclonal antibody. These results suggested the induced allo-restricted CTLs specific for IL-13Ralpha2(345-354) peptide could be a potential target of specific immunotherapy for HLA-A2+ patients with malignant glioma.

Autologous designer antigen-presenting cells by gene modification of T lymphocyte blasts with IL-7 and IL-12

An effective immune response to antigen requires professional antigen-presenting cell (APC), which not only present antigen, but also provide costimulation and cytokines (eg, IL-12) that drive T cell differentiation down the appropriate effector pathway (Tc1/TH1). For T cell-based immunotherapy protocols, the availability of large numbers of autologous professional APC is a major limitation because professional APC do not proliferate in vitro. T cells themselves can proliferate exponentially in vitro and have the ability to present antigen. They can also express costimulatory molecules after activation. Therefore, we hypothesized that if activated T cells were genetically modified to express proinflammatory cytokines required to polarize T cells toward a Tc1 response, they could fulfill the requirements for an abundant, autologous APC. To test this potential, T cells were activated by CD3/CD28 antibodies and pulsed with model HLA-A2+ peptides derived from CMVpp65, MAGE-3, and MART-1. Activated T-APC readily reactivated CD8 pp65 memory T cells from healthy CMV seropositive donors; however, the activation of MAGE-3 and MART-1-specific CD8 T cells required both IL-7 and IL-12, which could be provided either exogenously or by genetic modification of the T-APC. Responder T cells could be expanded to large numbers with subsequent stimulations using activated, peptide-pulsed T-APC and IL-2. Tumor antigen-specific T cell lines killed both peptide-pulsed target cells and tumor cell lines. Thus, T cells provide a platform for the generation of autologous APC that can be customized to express both antigens and therapeutic molecules for the induction of antigen-specific T cell immunity.

CD83 modulates B cell function in vitro: increased IL-10 and reduced Ig secretion by CD83Tg B cells

The murine transmembrane glycoprotein CD83 is an important regulator for both thymic T cell maturation and peripheral T cell responses. Recently, we reported that CD83 also has a function on B cells: Ubiquitous transgenic (Tg) expression of CD83 interfered with the immunoglobulin (Ig) response to infectious agents and to T cell dependent as well as T cell independent model antigen immunization. Here we compare the function of CD83Tg B cells that overexpress CD83 and CD83 mutant (CD83mu) B cells that display a drastically reduced CD83 expression. Correlating with CD83 expression, the basic as well as the lipopolysaccharide (LPS) induced expression of the activation markers CD86 and MHC-II are significantly increased in CD83Tg B cells and reciprocally decreased in CD83mu B cells. Wild-type B cells rapidly upregulate CD83 within three hours post BCR or TLR engagement by de novo protein synthesis. The forced premature overexpression of CD83 on the CD83Tg B cells results in reduced calcium signaling, reduced Ig secretion and a reciprocally increased IL-10 production upon in vitro activation. This altered phenotype is mediated by CD83 expressed on the B cells themselves, since it is observed in the absence of accessory cells. In line with this finding, purified CD83mu B cells displayed a reduced IL-10 production and slightly increased Ig secretion upon LPS stimulation in vitro. Taken together, our data strongly suggest that CD83 is expressed by B cells upon activation and contributes to the regulation of B cell function.

CD83 influences cell-surface MHC class II expression on B cells and other antigen-presenting cells

CD83 is a member of the Ig superfamily expressed primarily by mature dendritic cells (DCs). In mice, CD83 expression by thymic stromal cells regulates CD4(+) T cell development, with CD83(-/-) mice demonstrating dramatic reductions in both thymus and peripheral CD4(+) T cells. In this study, CD83 expression was also found to affect MHC class II antigen expression within the thymus and periphery. CD83 deficiency reduced cell-surface class II antigen expression by 25-50% on splenic B cells and DCs, thymic epithelial cells and peritoneal macrophages. Reduced class II expression was a stable and intrinsic property that resulted from increased internalization of class II from the surface of CD83(-/-) B cells. Otherwise, class II antigen transcription, intracellular expression, heterodimer structure, antigen processing and antigen presentation were normal. Reduced class II antigen expression was not the primary cause of the CD83(-/-) phenotype since thymocyte and peripheral T cell development was normal in class II(+/-) mice. Comparable blocks in CD4(+) thymocyte development were also observed in CD83(-/-) and CD83(-/-)class II(+/-) littermates. TCR and CD69 expression patterns in CD83(-/-) mice further suggested that double-positive thymocytes proceed through the class II-dependent stages of positive selection in the absence of CD83. These studies further emphasize a role for CD83 in lymphocyte development and immune regulation and reveal an unexpected role for CD83 expression in influencing cell-surface MHC class II turnover.

Long-lived antitumor CD8+ lymphocytes for adoptive therapy generated using an artificial antigen-presenting cell

PURPOSE

Antitumor lymphocytes can be generated ex vivo unencumbered by immunoregulation found in vivo. Adoptive transfer of these cells is a promising therapeutic modality that could establish long-term antitumor immunity. However, the widespread use of adoptive therapy has been hampered by the difficulty of consistently generating potent antitumor lymphocytes in a timely manner for every patient. To overcome this, we sought to establish a clinical grade culture system that can reproducibly generate antigen-specific cytotoxic T lymphocytes (CTL).

EXPERIMENTAL DESIGN

We created an off-the-shelf, standardized, and renewable artificial antigen-presenting cell (aAPC) line that coexpresses HLA class I, CD54, CD58, CD80, and the dendritic cell maturation marker CD83. We tested the ability of aAPC to generate tumor antigen-specific CTL under optimal culture conditions. The number, phenotype, effector function, and in vitro longevity of generated CTL were determined.

RESULTS

Stimulation of CD8(+) T cells with peptide-pulsed aAPC generated large numbers of functional CTL that recognized a variety of tumor antigens. These CTLs, which possess a phenotype consistent with in vivo persistence, survived ex vivo for prolonged periods of time. Clinical grade aAPC(33), produced under current Good Manufacturing Practices guidelines, generated sufficient numbers of CTL within a short period of time. These CTL specifically lysed a variety of melanoma tumor lines naturally expressing a target melanoma antigen. Furthermore, antitumor CTL were easily generated in all melanoma patients examined.

CONCLUSIONS

With clinical grade aAPC(33) in hand, we are now poised for clinical translation of ex vivo generated antitumor CTL for adoptive cell transfer.

Principles of adoptive T cell cancer therapy

The transfusion of T cells, also called adoptive T cell therapy, is an effective treatment for viral infections and has induced regression of cancer in early-stage clinical trials. However, recent advances in cellular immunology and tumor biology are guiding new approaches to adoptive T cell therapy. For example, use of engineered T cells is being tested as a strategy to improve the functions of effector and memory T cells, and manipulation of the host to overcome immunotoxic effects in the tumor microenvironment has led to promising results in early-stage clinical trials. Challenges that face the field and must be addressed before adoptive T cell therapy can be translated into routine clinical practice are discussed.

CD83 knockdown in monocyte-derived dendritic cells by small interfering RNA leads to a diminished T cell stimulation

Mature human dendritic cells (mDCs) are the most powerful APCs known today, having the unique ability to induce primary immune responses. One of the best known surface markers for mDCs is the glycoprotein CD83, which is strongly up-regulated during maturation, together with costimulatory molecules such as CD80 and CD86. When CD83 surface expression was inhibited by interference with the messenger RNA export or by infection with certain viruses, DCs showed a dramatically reduced capability to induce T cell proliferation. However, in these cases side effects on other cellular functions cannot be excluded completely. In this study we present an efficient method to specifically influence CD83 surface expression by the use of RNA interference. We used small-interfering RNA targeted against CD83 and carefully evaluated an electroporation protocol for the delivery of the duplex into the cells. Furthermore, we identified freshly prepared immature DCs as the best target for the application of a CD83 knockdown and we were also able to achieve a long lasting silencing effect for this molecule. Finally, we were able to confirm that CD83 functions as an enhancer during the stimulation of T cells, significantly increases DC-mediated T cell proliferation, and goes hand in hand with clear changes in cytokine expression during T cell priming. These results were obtained for the first time without the use of agents that might cause unwanted side effects, such as low m.w. inhibitors or viruses. Therefore, this method presents a suitable way to influence DC biology.

CD83: an update on functions and prospects of the maturation marker of dendritic cells

CD83 is one of the most characteristic cell surface markers for fully matured dendritic cells (DCs). In their function as antigen presenting cells they induce T-cell mediated immune responses. In this review we provide an overview on well described and proposed functions of this molecule as well as on very recent insights and new hypothesis. Already the CD83 messenger RNA processing differs remarkably from the processing of other cellular mRNAs: instead of the usual TAP mRNA export pathway, the CD83 mRNA is exported by the specific CRM1-mediated pathway, utilized only by a minority of cellular mRNAs. On the protein level, two different isoforms of CD83 exist: a membrane-bound and a soluble form. The isoforms are generated by different subsets of cells, including DCs, T-cells and B-cells, and also differ in their biological function. While the membrane-bound CD83 is of immune stimulatory capacity, activates T-cells and is important for the generation of thymocytes, the soluble CD83 has the opposite effect and has an immune inhibitory capacity. Due to its immune inhibitory function, CD83 has great potential for treatment of autoimmune diseases, for organ transplantations, and for immunotherapy, just to name a few examples. Moreover, some viruses prevent recognition by the host's immune system by specifically targeting CD83 surface expression.

Engineering artificial antigen-presenting cells to express a diverse array of co-stimulatory molecules

To facilitate the therapeutic application of antigen-presenting cells (APCs), we have developed a cell-based artificial APC (aAPC) system by engineering K562 cells with lentiviruses to direct the stable expression and secretion of a variety of co-stimulatory molecules and cytokines. Here we report the use of a combinatorial lentiviral gene transfer approach to achieve long-term stable expression of at least seven genes in the K562 parental cell line. Expression of various combinations of genes on the aAPC enables the precise determination of human T-cell activation requirements, such that aAPCs can be tailored for the optimal propagation of T-cell subsets with specific growth requirements and distinct functions. The aAPCs support ex vivo growth and long-term expansion of functional human CD8 T cells without requiring the addition of exogenous cytokines, in contrast to the use of natural APCs. Distinct populations of T cells can be expanded with aAPCs expressing CD137L (4-1BBL) and/or CD80. Finally, the aAPCs provide an efficient platform to expand genetically modified T cells and to maintain CD28 expression on CD8 T cells. Therefore, K562-based aAPCs have therapeutic potential for adoptive immunotherapies and vaccinations.

CD83 is a regulator of murine B cell function in vivo

The transmembrane glycoprotein CD83 has been described as a specific maturation marker for dendritic cells and several lines of evidence suggest that CD83 regulates thymic T cell maturation as well as peripheral T cell activation. Here we show for the first time that CD83 is involved also in the regulation of B cell function. CD83 is up-regulated on activated B cells in vivo, specifically in the draining lymph nodes of Leishmania major-infected mice. The ubiquitous transgenic (Tg) expression of CD83 interferes with Leishmania-specific T cell-dependent and with T cell-independent antibody production. This defect is restricted to the B cell population since the antigen-specific T cell response of CD83Tg mice to L. major infection is unchanged. The defective immunoglobulin (Ig) response is due to Tg expression of CD83 on the B cells because wild-type B cells display normal antigen-specific responses in CD83Tg hosts and CD83Tg B cells do not respond to immunization in a mixed wild-type/CD83Tg bone marrow chimera. Finally, the treatment of non-Tg C57BL/6 mice with anti-CD83 mAb induces a dramatic increase in the antigen-specific IgG response to immunization, thus demonstrating a regulatory role for naturally induced CD83 on wild-type B cells.

CD83 expression on dendritic cells and T cells: correlation with effective immune responses

Human CD83 is a marker molecule for mature dendritic cells (DC) and is also expressed on activated B and T cells. Although CD83 has been implicated in immune responses, its function on DC and T cells remains unclear. In this study, we wanted to assess the role of CD83 expressed on DC and T cells in the immune response. Down-regulation of CD83 expression on human DC through RNA interference (RNAi) results in a less potent induction of allogeneic T cell proliferation, reduced IFN-gamma secretion by established T cells and decreased capacity in the priming of functional tumor antigen-specific CD8+ T lymphocytes. In addition, CD83 mRNA-electroporated DC are stronger T cell stimulators. However, CD83 overexpression on Melan-A/MART-1-specific tumor-infiltrating lymphocytes (TIL) circumvents the need for CD83 expression on DC. Co-culture of immature DC with TIL or K562 cells overexpressing CD83 results in the production of enhanced levels of pro-inflammatory cytokines, whereas this production is less pronounced or even absent in co-cultures with non-modified TIL or K562 cells. In conclusion, we demonstrate that CD83 expression on T cells and DC modulates the immune response by activating DC and by delivering costimulatory signals for the stimulation of naive and memory T cells, respectively.

Do Langerhans cells behave similarly in elderly and younger patients with chronic periodontitis?

OBJECTIVE

The purpose of this study was to compare the number, the distribution and the expression of markers of maturation of Langerhans cells (LC) in elderly and younger patients with chronic periodontitis in order to evidence the effect of aging on LC in inflammatory gingival tissue.

METHODS

Gingival tissue specimens presenting chronic periodontitis from 8 elderly patients aged >75 (group E) and from 8 younger patients aged 50-60 (considered as controls, group C) were used for immunohistochemistry with monoclonal antibodies against CD45RB (leucocytes), CD1a (LC), markers of LC maturation (DC-LAMP, CD83) and number of immunolabelled cell subsets was evaluated using image analysis.

RESULTS

The difference in the number of CD45RB+ leucocytes in the upper connective tissue between groups was not significant. In group E, the number of CD1a+ LC was significantly decreased (P<0.002) in the epithelium and significantly increased (P<0.0004) in the upper connective tissue. Furthermore, in group E, intraepithelial CD1a+ LC are more often observed in the upper epithelium and their dendritic processes were shorter and less numerous. Concerning the expression of markers of maturation, the numbers of intraepithelial DC-LAMP+ cells and CD83+ cells were significantly increased (P<0.0007 and P<0.02, respectively) in group E.

CONCLUSION

During chronic periodontitis in elderly patients, the decrease in the number of intraepithelial LC and the alteration of dendritic processes could be balanced by a cellular distribution often observed in the upper epithelium associated with changes in cell maturation in response to bacterial elements.

Aberrant Phenotype and Function of Myeloid Dendritic Cells in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is characterized by a systemic autoimmune response with profound and diverse T cell changes. Dendritic cells (DCs) are important orchestrators of immune responses and have an important role in the regulation of T cell function. The objective of this study was to determine whether myeloid DCs from individuals with SLE display abnormalities in phenotype and promote abnormal T cell function. Monocyte-derived DCs and freshly isolated peripheral blood myeloid DCs from lupus patients displayed an abnormal phenotype characterized by accelerated differentiation, maturation, and secretion of proinflammatory cytokines. These abnormalities were characterized by higher expression of the DC differentiation marker CD1a, the maturation markers CD86, CD80, and HLA-DR, and the proinflammatory cytokine IL-8. In addition, SLE patients displayed selective down-regulation of the maturation marker CD83 and had abnormal responses to maturation stimuli. These abnormalities have functional relevance, as SLE DCs were able to significantly increase proliferation and activation of allogeneic T cells when compared with control DCs. We conclude that myeloid DCs from SLE patients display significant changes in phenotype which promote aberrant T cell function and could contribute to the pathogenesis of SLE and organ damage.

Transgenic expression of a CD83-immunoglobulin fusion protein impairs the development of immune-competent CD4-positive T cells

The murine transmembrane glycoprotein CD83 is an important regulator for both thymic T cell maturation and peripheral T cell response. CD83 deficiency leads to a block in the thymic maturation of CD4-positive T cells, and interference with peripheral CD83/CD83 ligand interaction by addition of soluble CD83 suppresses immune responses in vivo and in vitro. Here we report the generation of a mouse transgenic for a fusion protein consisting of the extracellular domain of murine CD83 fused to the constant part of human IgG1 heavy chain. Thymic selection of CD4-positive T cells was unchanged in CD83Ig transgenic and in CD83Ig/OT-2 double-transgenic mice. However, thymic and peripheral CD4-positive T cells derived from CD83Ig/OT-2 transgenic mice displayed a reduced cytokine response to antigenic stimulation in vitro, whereas CD83Ig/OT-1-derived CD8-positive T cells showed normal cytokine secretion. The T cell defect was relevant in vivo, since a sub-lethal infection with Trypanosoma cruzi led to an increased parasitemia and reduced survival rate of CD83Ig transgenic mice compared to wild-type C57BL/6 mice. In contrast, in vivo application of recombinant CD83Ig did not result in an increase in parasitemia. Taken together our data suggest that thymic selection in the presence of CD83Ig leads to an intrinsic T cell defect of CD4-positive T cells resembling the phenotype described for CD4-positive T cells derived from CD83-deficient mouse strains.

Identification of an immunogenic CD8+ T-cell epitope derived from gamma-globin, a putative tumor-associated antigen for juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a rare clonal myeloproliferative disorder. Although allogeneic stem cell transplantation can induce long-term remissions, relapse rates remain high and innovative approaches are needed. Since donor lymphocyte infusions have clinical activity in JMML, T-cell-mediated immunotherapy could provide a nonredundant treatment approach to compliment current therapies. Gamma-globin, an oncofetal protein overexpressed by clonogenic JMML cells, may serve as a target of an antitumor immune response. We predicted 5 gamma-globin-derived peptides as potential human leukocyte antigen (HLA)-A2 restricted cytotoxic T lymphocyte (CTL) epitopes and showed that 4 (g031, g071, g105, and g106) bind A2 molecules in vitro. Using an artificial antigen-presenting cell (aAPC) that can process both the N- and C-termini of endogenously expressed proteins, we biochemically confirmed that g105 is naturally processed and presented by cell surface A2. Furthermore, g105-specific CD8(+) CTLs generated from A2-positive healthy donors were able to specifically cytolyze gamma-globin(+), but not gamma-globin(-) JMML cells in an A2-restricted manner. These results suggest that this aAPC-based approach enables the biochemical identification of CD8(+) T-cell epitopes that are processed and presented by intact cells, and that CTL immunotherapy of JMML could be directed against the gamma-globin-derived epitope g105.

Efficient Presentation of Naturally Processed HLA Class I Peptides by Artificial Antigen-Presenting Cells for the Generation of Effective Antitumor Responses

Appropriate presentation of tumor-associated antigens (TAA) by antigen-presenting cells (APC) is required for the development of clinically relevant antitumor T-cell responses. One common approach, which uses APC pulsed with synthetic peptides, can sometimes generate ineffective immune responses. This failure may, in part, be attributed to the formation of HLA/synthetic pulsed peptide complexes that possess different conformations compared with those of endogenously presented peptides. In addition, endogenous peptides may undergo post-translational modifications, which do not occur with synthetic peptides. Because our goal is to induce immunity that can recognize TAA that are endogenously presented by tumors, we designed an APC that would not only express the required immunoaccessory molecules but also naturally process and present target antigenic peptides. In this study, we generated an artificial APC (aAPC) that can endogenously present any chosen HLA-A*0201 (A2)-restricted peptide by processing a fusion protein that contains a unique "LTK" sequence linked to the antigenic peptide. Proteasome-dependent processing is so effective that the presented peptide can be directly eluted from the cell surface and identified by biochemical methods. Furthermore, we found that aAPC, engineered to endogenously present peptide derived from the melanoma antigen MART1, can be used to prime and expand antitumor CTL that target MART1-expressing tumor cells in a HLA-A2-restricted manner. Our engineered aAPC could serve as an "off-the-shelf" APC designed to constitutively express class I-restricted TAA peptides and could be used to generate effective T-cell responses to treat human disease.