Phenotype, function, and in vivo migration and survival of allogeneic dendritic cell progenitors genetically engineered to express TGF-beta

Regulation of the Migration of Distinct Dendritic Cell Subsets

Dendritic cells (DCs), a class of antigen-presenting cells, are widely present in tissues and apparatuses of the body, and their ability to migrate is key for the initiation of immune activation and tolerogenic immune responses. The importance of DCs migration for their differentiation, phenotypic states, and immunologic functions has attracted widespread attention. In this review, we discussed and compared the chemokines, membrane molecules, and migration patterns of conventional DCs, plasmocytoid DCs, and recently proposed DC subgroups. We also review the promoters and inhibitors that affect DCs migration, including the hypoxia microenvironment, tumor microenvironment, inflammatory factors, and pathogenic microorganisms. Further understanding of the migration mechanisms and regulatory factors of DC subgroups provides new insights for the treatment of diseases, such as infection, tumors, and vaccine preparation.

LPS enhances CTB-INSULIN induction of IDO1 and IL-10 synthesis in human dendritic cells

Autoantigen-specific immunotherapy promises effective treatment for devastating tissue specific autoimmune diseases like multiple sclerosis (MS) and type 1 diabetes (T1D). Because activated dendritic cells (DCs) stimulate the differentiation of autoreactive T cells involved in the initiation of autoimmunity, blocking the activation of DCs may be an effective strategy for inhibiting tissue specific autoimmunity. Following this approach, immature DCs were shown to remain inactive after treatment with chimeric fusion proteins composed of the cholera toxin B subunit adjuvant linked to autoantigens like proinsulin (CTB-INS). Mass spectrometer analysis of human DCs treated with CTB-INS suggest that upregulation of the tryptophan catabolic enzyme indoleamine 2, 3-dioxygenase (IDO1) is responsible for inhibiting DC activation thereby resulting in a state of immunological tolerance within the DC. Here we show that the fusion protein CTB-INS inhibits human monocyte derived DC (moDC) activation through stimulation of IDO1 biosynthesis and that the resultant state of DC tolerance can be further enhanced by the presence of residual E. coli lipopolysaccharide (LPS) present in partially purified CTB-INS preparations. Additional experiments showed that LPS enhancement of DC tolerance was dependent upon stimulation of IDO1 biosynthesis. LPS stimulation of increased levels of IDO1 in the DC resulted in increased secretion of kynurenines, tryptophan degradation products known to suppress DC mediated pro-inflammatory T cell differentiation and to stimulate the proliferation of regulatory T cells (Tregs). Further, the presence of LPS in CTB-INS treated DCs stimulated the biosynthesis of costimulatory factors CD80 and CD86 but failed to upregulate maturation factor CD83, suggesting CTB-INS treated DCs may be maintained in a state of semi-activation. While treatment of moDCs with increasing amounts of LPS free CTB-INS was shown to increase DC secretion of the anti-inflammatory cytokine IL-10, the presence of residual LPS in partially purified CTB-INS preparations dramatically increased IL-10 secretion, suggesting that CTB-INS may enhance DC mediated immunological tolerance by stimulating the proliferation of anti-inflammatory T cells. While the extraction of LPS from bacterial generated CTB-INS may remove additional unknown factors that may contribute to the regulation of IDO1 levels, together, our experimental data suggest that LPS stimulates the ability of CTB-INS to induce IDO1 and IL-10 important factors required for establishment of a state of functional immunological tolerance in human DCs. Regulation of the ratio of LPS to CTB-INS may prove to be an effective method for optimization of readily available "off the shelf" CTB-INS mediated immune-therapy for tissue specific autoimmune diseases including type 1 diabetes.

Immune checkpoints and the regulation of tolerogenicity in dendritic cells: Implications for autoimmunity and immunotherapy

The immune system is responsible for defending the host from a large variety of potential pathogens, while simultaneously avoiding immune reactivity towards self-components. Self-tolerance has to be tightly maintained throughout several central and peripheral processes; immune checkpoints are imperative for regulating the immunity/tolerance balance. Dendritic cells (DCs) are specialized cells that capture antigens, and either activate or inhibit antigen-specific T cells. Therefore, they play a key role at inducing and maintaining immune tolerance. DCs that suppress the immune response have been called tolerogenic dendritic cells (tolDCs). Given their potential as a therapy to prevent transplant rejection and autoimmune damage, several strategies are under development to generate tolDCs, in order to avoid activation and expansion of self-reactive T cells. In this article, we summarize the current knowledge relative to the main features of tolDCs, their mechanisms of action and their therapeutic use for autoimmune diseases. Based on the literature reviewed, autologous antigen-specific tolDCs might constitute a promising strategy to suppress autoreactive T cells and reduce detrimental inflammatory processes.

Generation, Characteristics and Clinical Trials of Ex Vivo Generated Tolerogenic Dendritic Cells

Dendritic cells (DCs) play a key role not only in the initiation of primary immune responses, but also in the development and maintenance of immune tolerance. Numerous protocols have been developed to generate tolerogenic DCs (tolDCs) ex vivo, and the therapeutic efficacy of ex vivo-generated tolDCs has been demonstrated in autoimmune disease animal models. Based on successes in small animal models, several clinical trials have been completed or are on-going in patients with autoimmune diseases such as rheumatoid arthritis, type 1 diabetes, multiple sclerosis, and Crohn's disease. Here we describe the methods used to generate tolDCs ex vivo, and the common features shared by tolDCs. In addition, we overview five completed clinical trials with reported outcomes and summarize the tolDC-based clinical trials that are currently registered with the U.S. National Institutes of Health. Although the number of tolDC-based clinical trials is much smaller than the hundreds of clinical trials using immunogenic DCs, tolDC-based treatment of autoimmune diseases is becoming a reality, and could serve as an innovative cellular therapy in the future.

THERAPY OF ENDOCRINE DISEASE: Islet transplantation for type 1 diabetes: so close and yet so far away

Over the past decades, tremendous efforts have been made to establish pancreatic islet transplantation as a standard therapy for type 1 diabetes. Recent advances in islet transplantation have resulted in steady improvements in the 5-year insulin independence rates for diabetic patients. Here we review the key challenges encountered in the islet transplantation field which include islet source limitation, sub-optimal engraftment of islets, lack of oxygen and blood supply for transplanted islets, and immune rejection of islets. Additionally, we discuss possible solutions for these challenges.

Dendritic Cell-Mediated Phagocytosis but Not Immune Activation Is Enhanced by Plasmin

Removal of dead cells in the absence of concomitant immune stimulation is essential for tissue homeostasis. We recently identified an injury-induced protein misfolding event that orchestrates the plasmin-dependent proteolytic degradation of necrotic cells. As impaired clearance of dead cells by the innate immune system predisposes to autoimmunity, we determined whether plasmin could influence endocytosis and immune cell stimulation by dendritic cells – a critical cell that links the innate and adaptive immune systems. We find that plasmin generated on the surface of necrotic cells enhances their phagocytic removal by human monocyte-derived dendritic cells. Plasmin also promoted phagocytosis of protease-resistant microparticles by diverse mouse dendritic cell sub-types both in vitro and in vivo. Together with an increased phagocytic capacity, plasmin-treated dendritic cells maintain an immature phenotype, exhibit reduced migration to lymph nodes, increase their expression/release of the immunosuppressive cytokine TGF-β, and lose their capacity to mount an allogeneic response. Collectively, our findings support a novel role for plasmin formed on dead cells and other phagocytic targets in maintaining tissue homeostasis by increasing the phagocytic function of dendritic cells while simultaneously decreasing their immunostimulatory capacity consistent with producing an immunosuppressive state.

Dendritic cell-based approaches for therapeutic immune regulation in solid-organ transplantation

To avoid immune rejection, allograft recipients require drug-based immunosuppression, which has significant toxicity. An emerging approach is adoptive transfer of immunoregulatory cells. While mature dendritic cells (DCs) present donor antigen to the immune system, triggering rejection, regulatory DCs interact with regulatory T cells to promote immune tolerance. Intravenous injection of immature DCs of either donor or host origin at the time of transplantation have prolonged allograft survival in solid-organ transplant models. DCs can be treated with pharmacological agents before injection, which may attenuate their maturation in vivo. Recent data suggest that injected immunosuppressive DCs may inhibit allograft rejection, not by themselves, but through conventional DCs of the host. Genetically engineered DCs have also been tested. Two clinical trials in type-1 diabetes and rheumatoid arthritis have been carried out, and other trials, including one trial in kidney transplantation, are in progress or are imminent.

Zinc finger protein A20 inhibits maturation of dendritic cells resident in rat liver allograft

BACKGROUND

In organ transplant field, although viewed traditionally as instigators of organ allograft rejection, donor-derived interstitial dendritic cells (DCs), including those resident in liver, or host DCs have also been implicated in transplant tolerance in experimental models. This functional dichotomy of DC is governed by various factors, the most important of which appears to be their stage of maturation. This study was designed to examine the effect of zinc finger protein A20 on maturation of DCs resident in rat liver allograft.

MATERIALS AND METHODS

Allogeneic (Dark Agouti [DA] rat to Lewis rat) liver transplantation was performed. Adenovirus carrying the full length of A20 was introduced into liver allografts by ex vivo perfusion via the portal vein during preservation (group A20), physiological saline (group PS), and empty Ad vector rAdEasy (group rAdEasy) that served as controls. Acute liver allograft rejection was assessed, and DCs resident in liver allografts were isolated on day 7 after transplantation. Nuclear factor kappa B (NF-κB)-binding activities, surface expression of costimulatory molecules (CD40, CD80, and CD86), expression of interleukin (IL) 12 messenger RNA (mRNA), and allocostimulatory capacity of DCs were measured with electrophoretic mobility shift assay, flow cytometry, reverse transcription-polymerase chain reaction, and mixed lymphocyte reaction (MLR), respectively.

RESULTS

Ex vivo transfer of A20 adenovirus by portal vein infusion resulted in overexpression of A20 protein in liver allograft after transplantation. On day 7 after transplantation, histologic examination revealed a mild rejection in group A20 but a more severe rejection in group PS and group rAdEasy. DCs from group A20 liver allografts exhibited features of immature DC with detectable but very low level of NF-κB activity, IL-12 mRNA expression, and surface expression of costimulatory molecules (CD40, CD80, and CD86), whereas DCs from group rAdEasy and group PS liver allograft displayed features of mature DC with high level of NF-κB activity, IL-12 mRNA expression, and surface expression of costimulatory molecules (CD40, CD80, and CD86). DCs from group PS and group rAdEasy liver allograft were potent inducers of DNA synthesis and interferon γ production in MLR, and DCs from group A20 liver allografts induced only minimal levels of cell proliferation and interferon γ production in MLR.

CONCLUSIONS

These data suggest that A20 overexpression could effectively inhibit maturation of DCs resident in liver allograft and consequently suppress acute liver allograft rejection.

Influence of tumors on protective anti-tumor immunity and the effects of irradiation

Innate and adaptive immunity plays important roles in the development and progression of cancer and it is becoming apparent that tumors can influence the induction of potentially protective responses in a number of ways. The prevalence of immunoregulatory T cell populations in the circulation and tumors of patients with cancer is increased and the presence of these cells appears to present a major barrier to the induction of tumor immunity. One aspect of tumor-mediated immunoregulation which has received comparatively little attention is that which is directed toward natural killer (NK) cells, although evidence that the phenotype and function of NK cell populations are modified in patients with cancer is accumulating. Although the precise mechanisms underlying these localized and systemic immunoregulatory effects remain unclear, tumor-derived factors appear, in part at least, to be involved. The effects could be manifested by an altered function and/or via an influence on the migratory properties of individual cell subsets. A better insight into endogenous immunoregulatory mechanisms and the capacity of tumors to modify the phenotype and function of innate and adaptive immune cells might assist the development of new immunotherapeutic approaches and improve the management of patients with cancer. This article reviews current knowledge relating to the influence of tumors on protective anti-tumor immunity and considers the potential influence that radiation-induced effects might have on the prevalence, phenotype, and function of innate and adaptive immune cells in patients with cancer.

TGF-beta1 on osteoimmunology and the bone component cells

TGF-β1 is an immunoregulatory cytokine that regulates immune cell proliferation, survival, differentiation, and migration. Compelling evidence has demonstrated a strong association between the immune and skeletal systems (so called Osteoimmunology), such as the critical role of TGF-β1 in the development and maintenance of the skeletal tissue. This review provides an overview of the mechanisms in which TGF-β1 interacts with bone component cells, such as osteoblasts, osteoclasts, chondrocytes, mesenchymal stem cells, and hematopoietic stem cells, in concert with other cytokines and hormones.

Retroviral and lentiviral vectors for the induction of immunological tolerance

Retroviral and lentiviral vectors have proven to be particularly efficient systems to deliver genes of interest into target cells, either in vivo or in cell cultures. They have been used for some time for gene therapy and the development of gene vaccines. Recently retroviral and lentiviral vectors have been used to generate tolerogenic dendritic cells, key professional antigen presenting cells that regulate immune responses. Thus, three main approaches have been undertaken to induce immunological tolerance; delivery of potent immunosuppressive cytokines and other molecules, modification of intracellular signalling pathways in dendritic cells, and de-targeting transgene expression from dendritic cells using microRNA technology. In this review we briefly describe retroviral and lentiviral vector biology, and their application to induce immunological tolerance.

Functional study of immature dendritic cells co-transfected with IL-10 and TGF-beta 1 genes in vitro

Dendritic cells (DC) have important functions in T cell immunity and T cell tolerance. Previous studies suggest that immature dendritic cells (imDCs) might be involved in the induction of peripheral T cell tolerance. While interleukin-10 (IL-10) functions at different levels of the immune response, transforming growth factor-beta 1 (TGF-beta 1) is considered to be a key factor in immune tolerance. In this study, we investigated the effects of immature DC (imDC) co-transfected with IL-10 and TGF-beta 1 genes (IL-10-TGF-beta 1-imDC) on inducing immune tolerance. Moreover, we compared the effects of IL-10-TGF-beta 1-imDC with IL-10 transfected imDC (IL-10-imDC) and TGF-beta 1-transfected imDC (TGF-beta 1-imDC), respectively. IL-10-TGF-beta 1-imDC resulted in the down-regulation of MHC class II, CD80 and CD86. IL-10-TGF-beta 1-imDC could induce T cell hyporesponsiveness, and was reluctant to proliferate. IL-10-TGF-beta 1-imDC was more effective than IL-10-imDC and TGF-beta 1-imDC, respectively. In summary, co-expression of IL-10 and TGF-beta 1 affected the immunity of imDCs and enhanced their tolerogenicity. It might be a promising therapy for donor-specific tolerance after organ transplantation.

Rapamycin-conditioned donor dendritic cells differentiate CD4CD25Foxp3 T cells in vitro with TGF-beta1 for islet transplantation

Dendritic cells (DCs) conditioned with the mammalian target of rapamycin (mTOR) inhibitor rapamycin have been previously shown to expand naturally existing regulatory T cells (nTregs). This work addresses whether rapamycin-conditioned donor DCs could effectively induce CD4(+)CD25(+)Foxp3(+) Tregs (iTregs) in cell cultures with alloantigen specificities, and whether such in vitro-differentiated CD4(+)CD25(+)Foxp3(+) iTregs could effectively control acute rejection in allogeneic islet transplantation. We found that donor BALB/c bone marrow-derived DCs (BMDCs) pharmacologically modified by the mTOR inhibitor rapamycin had significantly enhanced ability to induce CD4(+)CD25(+)Foxp3(+) iTregs of recipient origin (C57BL/6 (B6)) in vitro under Treg driving conditions compared to unmodified BMDCs. These in vitro-induced CD4(+)CD25(+)Foxp3(+) iTregs exerted donor-specific suppression in vitro, and prolonged allogeneic islet graft survival in vivo in RAG(-/-) hosts upon coadoptive transfer with T-effector cells. The CD4(+)CD25(+)Foxp3(+) iTregs expanded and preferentially maintained Foxp3 expression in the graft draining lymph nodes. Finally, the CD4(+)CD25(+)Foxp3(+) iTregs were further able to induce endogenous naïve T cells to convert to CD4(+)CD25(+)Foxp3(+) T cells. We conclude that rapamycin-conditioned donor BMDCs can be exploited for efficient in vitro differentiation of donor antigen-specific CD4(+)CD25(+)Foxp3(+) iTregs. Such in vitro-generated donor-specific CD4(+)CD25(+)Foxp3(+) iTregs are able to effectively control allogeneic islet graft rejection.

Therapy with FasL-gene-modified dendritic cells confers a protective microenvironment in murine pregnancy

Analysis of the expression of FasL in the local decidua of pregnant mice and examination of the apoptosis of T cells in peripheral blood and local decidua indicated that adoptive transference of FasL-gene-modified dendritic cells may induce pregnancy immune tolerance by increasing FasL expression in the maternal-fetal interface and inducing the apoptosis of T cells in local decidua but not the peripheral blood.

Dendritic cells transduced with lentiviral vectors expressing VIP differentiate into VIP-secreting tolerogenic-like DCs

Dendritic cells (DCs) initiate immune responses as well as tolerance. We showed previously that the neuropeptide vasoactive intestinal peptide (VIP) suppresses innate immune responses, modulates adaptive responses by generating regulatory T cells (Treg) through the induction of tolerogenic DCs (tDCs), and has therapeutic effects in models of autoimmune/inflammatory disorders. Systemic VIP administration is limited by its short biological half-life and by its pleiotropic effects on the cardiovascular system and gastrointestinal tract. Therefore, we used lentiviral vectors to genetically engineer VIP-expressing bone marrow-derived DC (BMDC) and characterized the transduced LentiVIP-DC in terms of phenotype and therapeutic effects in models of experimental autoimmune encephalomyelitis (EAE) and cecal ligation and puncture (CLP) sepsis. LentiVIP-DCs secrete VIP, and resemble tDCs through lack of co-stimulatory molecule upregulation, lack of proinflammatory cytokine secretion, increased interleukin (IL)-10 production, and poor stimulation of allogeneic T cells. A single inoculation of LentiVIP-DC in EAE or CLP mice had therapeutic effects, which correlated with reduced expression of proinflammatory cytokines and increased IL-10 production in spinal cord and peritoneal fluid, respectively. In contrast to systemic VIP administration that requires repeated, high-dose inoculations, local delivery of VIP by LentiVIP-DC may represent a promising therapeutic tool for the treatment of autoimmune diseases and inflammatory disorders.

Selected allogeneic dendritic cells markedly enhance human tumour antigen-specific T cell response in vitro

BACKGROUND

Alloreaction is known to accumulate several theoretical advantages that can improve dendritic cell (DC)-based anti-infective or antitumour strategies. Allogeneic DC have already been tested in experimental and clinical studies, but their efficacy compared with their autologous counterparts was rarely investigated and conclusions diverge.

OBJECTIVE

This study compared antigen-specific T cell responses following priming with autologous versus allogeneic DC and examined the possibility of screening these responses in order to select allogeneic DC that lead to a great amplification.

RESULTS

Allogeneic DC obtained from donors matched with the single HLA-A2 allele were efficient in generating in vitro peptide-specific T cell responses. When randomly chosen, allogeneic DC generated a broad range of antigen-specific T cell responses in comparison with autologous DC. When screened and selected, allogeneic DC markedly enhanced peptide-specific T cell priming and allowed a more efficient boosting of resulting T cells. These selected allogeneic DC provided a favourable cytokinic and cellular environment that can help concurrent antigen-specific responses.

CONCLUSION

Ex vivo selected allogeneic DC provide adjuvant effects that lead to amplification of concomitant antigen-specific T cell responses.

Gene therapy in transplantation

Gene therapy is an exciting and novel technology that offers the prospect of improving transplant outcomes beyond those achievable with current clinical protocols. This review explores both the candidate genes and ways in which they have been deployed to overcome both immune and non-immune barriers to transplantation success in experimental models. Finally, the major obstacles to implementing gene therapy in the clinic are considered.

Semi-allogeneic dendritic cells can induce antigen-specific T-cell activation, which is not enhanced by concurrent alloreactivity

BACKGROUND

Alloreactive T-cell responses are known to result in the production of large amounts of proinflammatory cytokines capable of activating and maturing dendritic cells (DC). However, it is unclear whether these allogeneic responses could also act as an adjuvant for concurrent antigen-specific responses.

OBJECTIVE

To examine effects of simultaneous alloreactive and antigen-specific T-cell responses induced by semi-allogeneic DC.

METHODS

Semi-allogeneic DC were generated from the F(1) progeny of inbred strains of mice (C57BL/6 and C3H, or C57BL/6 and DBA). We directly primed antigen-specific CD8(+) and CD4(+) T-cells from OT-I and OT-II mice, respectively, in the absence of allogeneic responses, in vitro, and in the presence or absence of alloreactivity in vivo.

RESULTS

In vitro, semi-allogeneic DC cross-presented ovalbumin (OVA) to naïve CD8(+) OT-I transgenic T-cells, primed naïve CD4(+) OT-II transgenic T-cells and could stimulate strong alloreactive T-cell proliferation in a primary mixed lymphocyte reaction (MLR). In vivo, semi-allogeneic DC migrated efficiently to regional lymph nodes but did not survive there as long as autologous DC. In addition, they were not able to induce cytotoxic T-lymphocyte (CTL) activity to a target peptide, and only weakly stimulated adoptively transferred OT-II cells. The CD4(+) response was unchanged in allo-tolerized mice, indicating that alloreactive T-cell responses could not provide help for concurrently activated antigen-specific responses. In an EL4 tumour-treatment model, vaccination with semi-allogeneic DC/EL4 fusion hybrids, but not allogeneic DC/EL4 hybrids, significantly increased mouse survival.

CONCLUSION

Expression of self-Major histocompatibility complex (MHC) by semi-allogeneic DC can cause the induction of antigen-specific immunity, however, concurrently activated allogeneic bystander responses do not provide helper or adjuvant effects.

Biological and Biomaterial Approaches for Improved Islet Transplantation

Islet transplantation may be used to treat type I diabetes. Despite tremendous progress in islet isolation, culture, and preservation, the clinical use of this modality of treatment is limited due to post-transplantation challenges to the islets such as the failure to revascularize and immune destruction of the islet graft. In addition, the need for lifelong strong immunosuppressing agents restricts the use of this option to a limited subset of patients, which is further restricted by the unmet need for large numbers of islets. Inadequate islet supply issues are being addressed by regeneration therapy and xenotransplantation. Various strategies are being tried to prevent beta-cell death, including immunoisolation using semipermeable biocompatible polymeric capsules and induction of immune tolerance. Genetic modification of islets promises to complement all these strategies toward the success of islet transplantation. Furthermore, synergistic application of more than one strategy is required for improving the success of islet transplantation. This review will critically address various insights developed in each individual strategy and for multipronged approaches, which will be helpful in achieving better outcomes.

Transforming growth factor beta 1(TGF-beta1) down-regulates TNFalpha-induced RANTES production in rheumatoid synovial fibroblasts through NF-kappaB-mediated transcriptional repression

Transforming growth factor (TGF)-beta1 is a pleiotropic cytokine with many functions, including those related to growth modulation, immunosuppression, and pro-inflammation, in a wide variety of cell types. In this study, we investigated the ability of TGF-beta1 to regulate RANTES production by activated rheumatoid synovial fibroblasts. Fibroblast-like synoviocytes (FLS) were cultured in the presence of TGF-beta1 and IL-1beta, IL-15, TNFalpha, or IL-17, and the secretion of RANTES into culture supernatants was measured by enzyme-linked immunosorbent assay (ELISA). Expression of RANTES encoded mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR), and NF-kappaB binding activity for RANTES transcription was determined by electrophoretic mobility shift assay (EMSA). We found that the concentrations of RANTES in synovial fluid (SF) from rheumatoid arthritis (RA) patients were lower than in SF from osteoarthritis (OA) patients, whereas the concentrations of TGF-beta1 were higher in RA SF than in OA SF. TGF-beta1 dose-dependently inhibited TNFalpha-induced production of RANTES protein and mRNA from RA FLS. Addition of RA SF with high-level TGF-beta1 mimicked the effect of TGF-beta1 on TNFalpha-induced RANTES production, which was inhibited by treatment with anti-TGF-beta1 neutralizing antibody. TGF-beta1 blocked the degradation of cytosolic IkappaB-alpha and the translocation of activated NF-kappaB to the nucleus. EMSA showed that the inhibitory effect of TGF-beta1 was associated with decreased binding of NF-kappaB to the RANTES promoter. These results suggest that elevated TGF-beta1 in rheumatoid synovial tissue may suppress joint inflammation by inhibiting RANTES secretion from synovial fibroblasts, thus blocking the infiltration of immune cells. These findings may provide an explanation for the mechanism by which TGF-beta1 regulates immune function in RA.

The evolving role of gene-based treatment in surgery

Background

The completion of the sequencing of the human genome in 2003 marked the dawn of a new era of human biology and medicine. Although these remarkable scientific advances improve the understanding of human biology, the question remains how this rapidly expanding knowledge of functional genomics affects the role of surgeons. This article reviews the potential therapeutic application of gene therapy for various surgical conditions.

Methods

The core of this review was derived from a Medline database literature search.

Results and conclusion

The currently available vectors in the field of gene therapy and their limitations for clinical applications were analysed. The achievements of gene therapy in clinical trials and the future ramifications for surgery were also explored. Whether gene therapy takes a major role in surgical practice will depend greatly on the success of future vector development. Advances in viral vector technology to reduce the inflammatory effect, and improvements in the efficiency of gene delivery using non-viral vector technology, would allow this form of therapy to become more clinically applicable.

Immunoregulation of dendritic cells

The paradigm of tolerogenic/immature versus inflammatory/mature dendritic cells has dominated the recent literature regarding the role of these antigen-presenting cells in mediating immune homeostasis or self-tolerance and response to pathogens, respectively. This issue is further complicated by the identification of distinct subtypes of dendritic cells that exhibit different antigen-presenting cell effector functions. The discovery of pathogen-associated molecular patterns and toll-like receptors provides the mechanistic basis for dendritic cell recognition of specific pathogens and induction of appropriate innate and adaptive immune responses. Only recently has insight been gained into how dendritic cells contribute to establishing and/or maintaining immunological tolerance to self. Soluble and cellular mediators have been reported to effectively regulate the function of dendritic cells by inducing several outcomes ranging from non-inflammatory dendritic cells that lack the ability to induce T lymphocyte activation to dendritic cells that actively suppress T lymphocyte responses. A thorough discussion of these stimuli and their outcomes is essential to understanding the potential for modulating dendritic cell function in the treatment of inflammatory disease conditions.

Prolongation of cardiac allograft survival by systemic administration of immature recipient dendritic cells deficient in NF-kappaB activity

OBJECTIVE

To develop a more applicable approach that uses recipient-derived dendritic cells (DC) for organ transplantation.

SUMMARY BACKGROUND DATA

Systemic administration of immature donor DC that are deficient in costimulatory molecules delays the onset of allograft rejection. However, this approach requires in vitro DC propagation and would not be applicable to deceased donor organ transplantation.

METHODS

DC were propagated from C3H (H2) mouse bone marrow with GM-CSF; their maturation was arrested by treatment with oligodeoxyribonucleotides (ODN) specifically against nuclear factor (NF)-kappaB. The DC were pulsed with B10 (H2) splenocyte lysate. DC phenotype was examined by flow cytometry. Their allostimulatory activity was assessed in vitro by MLR and CTL assays and in vivo by the influence on B10 cardiac allograft survival. Cytokine profiles were analyzed by ELISA and RNase protection assay. NF-kappaB activity in DC nuclear protein was detected by gel shifting assay.

RESULTS

Compared with mature DC, NF-kappaB ODN-treated immature DC pulsed with B10 (H2) spleen cell lysate elicited markedly lower proliferative responses and correlated with reduced IFN-gamma and increased IL-10 production. In contrast to administration of mature C3H DC pulsed with B10 antigen that accelerated rejection of B10 cardiac allografts, a single injection of NF-kappaB ODN DC pulsed with donor antigens significantly prolonged allograft survival in an antigen-specific manner. This was associated with induction of T-cell hyporesponsiveness and enhanced T-cell apoptosis.

CONCLUSIONS

An approach to use recipient DC as a "vaccine" strategy provides a more feasible approach for deceased-donor organ transplantation.

Ovine dendritic cells transduced with an adenoviral CTLA4eEGFP fusion protein construct induce hyporesponsiveness to allostimulation

CTLA4 (CD152) is a transmembrane molecule expressed on activated T cells and functions as a negative regulator of T cell activation upon binding to the costimulatory molecules CD80/86. In this study, CTLA4eEGFP constructs were engineered by cloning the extracellular domains of ovine and human CTLA4 (CTLA4e) 'in frame' with the enhanced green fluorescent protein (EGFP). Recombinant adenoviral vectors were generated by incorporation of the CTLA4eEGFP sequence into the adenoviral genome using homologous recombination in Esherichia coli. The functional activity of the adenoviral vectors was shown by the secretion of the CTLA4eEGFP upon infection of ovine fibroblasts and the binding of the fusion protein to the target ovine and human dendritic cells expressing CD80/86 receptors by flow cytometry. The EGFP tag facilitated molecular size determinations and quantification of the secreted ovine CTLA4 fusion protein by immunoprecipitation and enzyme-linked immunosorbent assay (ELISA), respectively, using anti-GFP mAbs. Ovine dendritic cells obtained from pseudoafferent lymphatic cannulation of sheep were characterized based on high major histocompatibility complex (MHC) class II expression and cross-reactivity with monoclonal antibodies to the human dendritic cell markers, CD83 and CMRF-56. In addition, ovine dendritic cells (DC) were transfected with the adenoviral CTLA4eEGFP and when used as stimulators in a mixed lymphocyte reaction showed a reduced capacity to induce allogeneic lymphocyte proliferation. This study verifies that the ovine CTLA4eEGFP fusion protein functions similarly to its human homologue and that DC modified with adenoviral CTLA4-EGFP may provide an effective therapeutic approach in targeting alloreactive T cells to prolong allograft acceptance in a preclinical ovine model of renal transplantation.

Antisense Oligonucleotides Down-Regulating Costimulation Confer Diabetes-Preventive Properties to Nonobese Diabetic Mouse Dendritic Cells

Phenotypically "immature" dendritic cells (DCs), defined by low cell surface CD40, CD80, and CD86 can elicit host immune suppression in allotransplantation and autoimmunity. Herein, we report the most direct means of achieving phenotypic immaturity in NOD bone marrow-derived DCs aiming at preventing diabetes in syngeneic recipients. CD40, CD80, and CD86 cell surface molecules were specifically down-regulated by treating NOD DCs ex vivo with a mixture of antisense oligonucleotides targeting the CD40, CD80, and CD86 primary transcripts. The incidence of diabetes was significantly delayed by a single injection of the engineered NOD DCs into syngeneic recipients. Insulitis was absent in diabetes-free recipients and their splenic T cells proliferated in response to alloantigen. Engineered DC promoted an increased prevalence of CD4(+)CD25(+) T cells in NOD recipients at all ages examined and diabetes-free recipients exhibited significantly greater numbers of CD4(+)CD25(+) T cells compared with untreated NOD mice. In NOD-scid recipients, antisense-treated NOD DC promoted an increased prevalence of these putative regulatory T cells. Collectively, these data demonstrate that direct interference of cell surface expression of the major costimulatory molecules at the transcriptional level confers diabetes protection by promoting, in part, the proliferation and/or survival of regulatory T cells. This approach is a useful tool by which DC-mediated activation of regulatory T cells can be studied as well as a potential therapeutic option for type 1 diabetes.

Prolongation of liver allograft survival by dendritic cells modified with NF-κB decoy oligodeoxynucleotides

AIM: To induce the tolerance of rat liver allograft by dendritic cells (DCs) modified with NF-κB decoy oligodeoxynucleotides (ODNs).

METHODS: Bone marrow (BM)-derived DCs from SD rats were propagated in the presence of GM-CSF or GM-CSF + IL-4 to obtain immature DCs or mature DCs. GM-CSF+IL-4-propagated DCs were treated with double-strand NF-κB decoy ODNs containing two NF-κB binding sites or scrambled ODNs to ascertain whether NF-κB decoy ODNs might prevent DC maturation. GM-CSF-propagated DCs, GM-CSF + NF-κB decoy ODNs or scrambled ODNs-propagated DCs were treated with LPS for 18 h to determine whether NF-κB decoy ODNs could prevent LPS-induced IL-12 production in DCs. NF-κB binding activities, costimulatory molecule (CD40, CD80, CD86) surface expression, IL-12 protein expression and allostimulatory capacity of DCs were measured with electrophoretic mobility shift assay (EMSA), flow cytometry, Western blotting, and mixed lymphocyte reaction (MLR), respectively. GM-CSF-propagated DCs, GM-CSF + IL-4 -propagated DCs, and GM-CSF + NF-κB decoy ODNs or scrambled ODNs-propagated DCs were injected intravenously into recipient LEW rats 7 d prior to liver transplantation and immediately after liver transplantation. Histological grading of liver graft rejection was determined 7 d after liver transplantation. Expression of IL-2, IL-4 and IFN-γ mRNA in liver graft and in recipient spleen was analyzed by semiquantitative RT-PCR. Apoptosis of liver allograft-infiltrating cells was measured with TUNEL staining.

RESULTS: GM-CSF-propagated DCs, GM-CSF+NF-κB decoy ODNs-propagated DCs and GM-CSF+ scrambled ODNs-propagated DCs exhibited features of immature DCs, with similar low level of costimulatory molecule(CD40, CD80, CD86) surface expression, absence of NF-κB activation, and few allocostimulatory activities. GM-CSF + IL-4-propagated DCs displayed features of mature DCs, with high levels of costimulatory molecule (CD40, CD80, CD86) surface expression, marked NF-κB activation, and significant allocostimulatory activity. NF-κB decoy ODNs completely abrogated IL-4-induced DC maturation and allocostimulatory activity as well as LPS-induced NF-κB activation and IL-12 protein expression in DCs. GM-CSF + NF-κB decoy ODNs-propagated DCs promoted apoptosis of liver allograft-infiltrating cells within portal areas, and significantly decreased the expression of IL-2 and IFN-γ mRNA but markedly elevated IL-4 mRNA expression both in liver allograft and in recipient spleen, and consequently suppressed liver allograft rejection, and promoted liver allograft survival.

CONCLUSION: NF-κB decoy ODNs-modified DCs can prolong liver allograft survival by promoting apoptosis of graft-infiltrating cells within portal areas as well as down-regulating IL-2 and IFN-γ mRNA and up-regulating IL-4 mRNA expression both in liver graft and in recipient spleen.

Marked prolongation of murine cardiac allograft survival using recipient immature dendritic cells loaded with donor-derived apoptotic cells

We investigated whether recipient dendritic cells (DCs), pretreated with nuclear factor-kappaB oligodeoxyribonucleotide decoy (NF-kappaB ODN decoy) and loaded with ultraviolet B-irradiated donor apoptotic splenocytes (Apo-SCs), were able to induce murine cardiac allograft tolerance. Heterotopic vascularized heart transplantation was performed from BALB/c to C57BL/6 mice, and recipients (C57BL/6) were given one injection of recipient DCs pretreated with NF-kappaB ODN decoy and loaded with donor (BALB/c) apoptotic SCs (decoy Apo-SCs DCs) through the portal vein at 7 days, before heart transplantation in the absence of immunosuppression. The cardiac allograft survival time and the expressive levels of intragraft cytokine genes [interleukin (IL)-2, IL-10, and interferon-gamma] were evaluated. Our results indicated that injection of decoy Apo-SCs DCs significantly prolonged vascularized heart allograft survival and led to skewing of intragraft cytokine expression towards T helper 2 (IL-10). The mechanisms can be useful for therapy of allograft rejection with minimization of systemic immunosuppression.

Augmented regeneration of partial liver allograft induced by nuclear factor-kappaB decoy oligodeoxynucleotides-modified dendritic cells

AIM

To investigate the effect of NF-kappaB decoy oligodeoxynuleotides (ODNs) - modified dendritic cells (DCs) on regeneration of partial liver allograft.

METHODS

Bone marrow (BM)- derived DCs from SD rats were propagated in the presence of GM-CSF or GM-CSF+IL-4 to obtain immature DCs or mature DCs, respectively. GM-CSF-propagated DCs were treated with double-strand NF-kappaB decoy ODNs containing two NF-kappaB binding sites or scrambled ODNs. Allogeneic (SD rat to LEW rat) 50% partial liver transplantation was performed. Normal saline (group A), GM-CSF -propagated DCs (group B), GM-CSF+IL-4 - propagated DCs (group C), and GM-CSF+NF-kappaB decoy ODNs (group D) or scrambled ODNs -propagated DCs (group E) were injected intravenously into recipient LEW rats 7 days prior to liver transplantation and immediately after transplantation. DNA synthesis (BrdU labeling) and apoptosis of hepatocytes were detected with immunostaining and TUNEL staining postoperative 24 h, 48 h, 72 h and 84 h, respectively. Liver graft-resident NK cell activity, hepatic IFN-gamma mRNA expression and recipient serum IFN-gamma level at the time of the maximal liver allograft regeneration were measured with (51)Cr release assay, semiquantitative RT-PCR and ELISA, respectively.

RESULTS

Regeneration of liver allograft was markedly promoted by NF-kappaB decoy ODNs-modified immature DCs but was significantly suppressed by mature DCs, the DNA synthesis of hepatocytes peaked at postoperative 72 h in group A, group B and group E rats, whereas the DNA synthesis of hepatocytes peaked at postoperative 84 h in group C rats and 48 h in group D rats, respectively. The maximal BrdU labeling index of hepatocytes in group D rats was significantly higher than that in the other groups rats. NF-kappaB decoy ODNs-modified immature DCs markedly suppressed but mature DCs markedly promoted apoptosis of hepatocytes, liver-resident NK cell activity, hepatic IFN-gamma mRNA expression and recipient serum IFN-gamma production. At the time of the maximal regeneration of liver allograft, the minimal apoptosis of hepatocytes, the minimal activity of liver-resident NK cells, the minimal hepatic IFN-gamma mRNA expression and serum IFN-gamma production were detected in group D rats. The apoptotic index of hepatocytes, the activity of liver- resident NK cells, the hepatic IFN-gamma mRNA expression level and the serum IFN-gamma level in group D rats were significantly lower than that in the other groups rats at the time of the maximal regeneration of liver allograft.

CONCLUSION

The data suggest that the augmented regeneration of partial liver allograft induced by NF-kappaB decoy ODNs-modified DCs may be attributable to the reduced apoptotic hepatocytes, the suppressed activity of liver-resident NK cells and the reduced IFN-gamma production.

Blockade of CD40 pathway enhances the induction of immune tolerance by immature dendritic cells genetically modified to express cytotoxic T lymphocyte antigen 4 immunoglobulin

BACKGROUND

Immature dendritic cells (DCs) have the tolerogenic potential to induce alloantigen-specific immune tolerance. Cytotoxic T lymphocyte antigen 4 immunoglobulin (CTLA4Ig) gene-modified immature DCs have been shown to maintain their tolerogenicity and prolong allograft survival to some extent. We investigated whether blockade of CD40 pathway by anti-CD40 ligand (L) monoclonal antibody (mAb) could enhance the immune tolerance induction by immature DCs genetically modified to express CTLA4Ig (DC-CTLA4Ig).

METHODS

The tolerogenic properties of DC-CTLA4Ig were analyzed. In the vascularized heterotopic heart transplantation murine model, 2 x 10(6) DC-CTLA4Ig were infused intravenously into recipients, with or without a concomitant administration of anti-CD40L mAb 7 days before transplantation. Host responses to donor alloantigen were quantified by mixed leukocyte reaction and CTL assays. Donor major histocompatibility complex class II (Iab) expression in recipient lymph nodes was detected posttransplantation by semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

The allostimulatory activity of DC-CTLA4Ig was reduced. DC-CTLA4Ig also induced alloantigen-specific T-cell hyporesponsiveness and polarized T helper 2 cytokine production. Pretreatment of the recipients with DC-CTLA4Ig modestly prolonged allograft survival, without long-term allograft acceptance. Combined administration of DC-CTLA4Ig and anti-CD40L mAb significantly prolonged cardiac allograft survival, with long-term (>100 days) survival of 50% of the allografts in the pretreated recipients. More potent donor-specific inhibition of immune response against alloantigens and increased microchimerism were observed in these recipients.

CONCLUSIONS

Blockade of CD40 pathway with anti-CD40L mAb potentiates the tolerogenic potential of DC-CTLA4Ig and enhances the induction of antigen-specific immune tolerance more effectively.

Administration of dendritic cells transduced with antisense oligodeoxyribonucleotides targeting CD80 or CD86 prolongs allograft survival

BACKGROUND

The expression of costimulatory molecules on antigen-presenting cells is crucial in determining T-cell immune responses. We examined the effects of transduction with high-affinity antisense oligodeoxyribonucleotides (ODNs) designed to target the mRNA of CD80 or CD86 on the phenotype and function of dendritic cells (DCs).

MATERIALS AND METHODS

DCs were propagated from C57BL/10 (B10; H2b) bone marrow cells in granulocyte macrophage-colony stimulating factor and interleukin (IL)-4, and transduced with anti-CD80 or anti-CD86 antisense ODNs (base-mismatched ODNs as controls). The effect of antisense ODN on phenotype was examined by flow cytometry. The allostimulatory function of DCs was assessed by mixed leukocyte reaction and cytotoxic activity in vitro, and the influence on allograft survival was assessed in vivo.

RESULTS

ODNs were effectively incorporated by DCs, which were enhanced by the presence of lipofectamine. Antisense ODNs targeting CD80 or CD86 mRNA specifically suppressed the expression of CD80 or CD86 in DCs and inhibited their capacity to elicit the proliferative responses, donor-specific cytotoxic T-lymphocyte activity in C3H (H2k) spleen T cells. This was associated with decreased IL-2, but elevated IL-4 production, and an increase in T-cell apoptosis. In contrast with the administration of control DCs into C3H recipients that exacerbated rejection of B10 cardiac allografts, injection of DCs transduced with anti-CD80 or CD86 antisense ODN significantly prolonged the survival of heart allografts.

CONCLUSION

Transduction with antisense ODN targeting CD80 or CD86mRNA is a feasible and effective approach to modify DCs that renders them tolerogenic by inducing T-cell hyporesponsiveness and apoptosis. This may lead to the development of new therapeutic strategies in transplantation.

Prevention of diabetes in NOD mice by administration of dendritic cells deficient in nuclear transcription factor-kappaB activity

Abnormalities of dendritic cells (DCs) have been identified in type 1 diabetic patients and in nonobese diabetic (NOD) mice that are associated with augmented nuclear transcription factor (NF)-kappaB activity. An imbalance that favors development of the immunogenic DCs may predispose to the disease, and restoration of the balance by administration of DCs deficient in NF-kappaB activity may prevent diabetes. DCs propagated from NOD mouse bone marrow and treated with NF-kappaB-specific oligodeoxyribonucleotide (ODN) in vitro (NF-kappaB ODN DC) were assessed for efficacy in prevention of diabetes development in vivo. Gel shift assay with DC nuclear extracts confirmed specific inhibition of NF-kappaB DNA binding by NF-kappaB ODN. The costimulatory molecule expression, interleukin (IL)-12 production, and immunostimulatory capacity in presenting allo- and islet-associated antigens by NF-kappaB ODN DC were significantly suppressed. NF-kappaB ODN renders DCs resistant to lipopolysaccharide stimulation. Administration of 2 x 10(6) NF-kappaB ODN DCs into NOD mice aged 6-7 weeks effectively prevented the onset of diabetes. T-cells from pancreatic lymph nodes of NF-kappaB ODN DC-treated animals exhibited hyporesponsiveness to islet antigens with low production of interferon-gamma and IL-2. These findings provide novel insights into the mechanisms of autoimmune diabetes and may lead to development of novel preventive strategies.

Apoptosis and transplantation tolerance

Self-tolerance is maintained by several mechanisms including deletion (via apoptosis) and regulation. Acquired tolerance to allogeneic tissues and organs exploits similar strategies. One key difference between alloantigens and peptide antigens is the enormous number of T cells that are alloreactive. Accumulating evidence suggests that in the face of this large mass of potentially graft-destructive T cells, tolerance requires an initial wave of deletion. This creates a more level playing field in which a smaller number of regulatory T cells can then act to maintain an established tolerant state. Deletion of alloreactive T cells by apoptosis actively promotes immunoregulation as well, by interfering with proinflammatory maturation of antigen presenting cells. This article reviews the immune response to alloantigens, the development and use of both necrotic and apoptotic means of cell death during the evolution of the immune response, and the likely role and mechanisms by which apoptosis promotes, and may even be required for, transplantation tolerance.

Gene- and cell-based therapeutics for type I diabetes mellitus

Type 1 diabetes mellitus, an autoimmune disorder is an attractive candidate for gene and cell-based therapy. From the use of gene-engineered immune cells to induce hyporesponsiveness to autoantigens to islet and beta cell surrogate transplants expressing immunoregulatory genes to provide a local pocket of immune privilege, these strategies have demonstrated proof of concept to the point where translational studies can be initiated. Nonetheless, along with the proof of concept, a number of important issues have been raised by the choice of vector and expression system as well as the point of intervention; prophylactic or therapeutic. An assessment of the current state of the science and potential leads to the conclusion that some strategies are ready for safety trials while others require varying degrees of technical and conceptual refinement.

Converting nonhuman primate dendritic cells into potent antigen-specific cellular immunosuppressants by genetic modification

T cell depletion plus donor bone marrow cell (BMC) infusion induces long-term kidney allograft survival in a limited number of rhesus macaque recipients. Therefore, there is a need to enhance the tolerogenic activity of donor BMCs. The tolerogenic effect of donor BMCs is ascribed to a veto activity, mediated by a CD8+ subset that upregulates immunoregulatory effector molecules, transforming growth factor-beta1 (TGF-beta), and FasL, after interaction with donor-reactive cytotoxic T lymphocyte precursors (CTLp), leading to clonal inactivation/deletion of donor-reactive CTLp. Of note, the receptors for TGF-beta1- and FasL-induced signal transduction are upregulated in activated T cells. Since mature dendritic cells (DCs) are exceptionally efficient activators of T cells, we postulated that mature DCs modified to overexpress TGF-beta1 and FasL might exert potent veto (i.e., inactivating/deleting) activity independent of CD8 expression. A fusion protein comprising antihuman CD40 single-chain antibody and soluble coxsackie-adenovirus receptor enabled high-efficiency transduction of rhesus monocyte-derived DCs (Rh MDDCs) by recombinant adenovirus (Ad). Mature Rh MDDCs transduced with Ad encoding active TGF-beta1 retained a mature phenotype yet exhibited potent alloantigen-specific cellular immunosuppression. Such modified MDDCs have the potential to promote tolerance induction to allografts in vivo.

Active suppression of allogeneic proliferative responses by dendritic cells after induction of long-term allograft survival by CTLA4Ig

Costimulatory blockade using cytotoxic T lymphocyte-associated antigen 4 immunoglobulin (CTLA4Ig) efficiently down-regulates immune responses in animal models and is currently used in autoimmune and transplantation clinical trials, but the precise cellular and molecular mechanisms involved remain unclear. Rats that received allogeneic heart transplants and were treated with adenoviruses coding for CTLA4Ig show long-term allograft survival. The immune mechanisms regulating induction of long-term allograft acceptance were analyzed in splenocytes using mixed leukocyte reactions (MLRs). MLRs of splenocytes but not purified T cells from CTLA4Ig-treated rats showed higher than 75% inhibition compared with controls. Splenocytes from CTLA4Ig-treated rats inhibited proliferation of naive and allogeneically primed splenocytes or T cells. MLR suppression was dependent on soluble secreted product(s). Production of soluble inhibitory product(s) was triggered by a donor antigen-specific stimulation and inhibited proliferation in an antigen-nonspecific manner. CTLA4Ig levels in the culture supernatant were undetectable and neither interleukin-10 (IL-10), transforming growth factor beta 1 (TGF beta 1), IL-4, nor IL-13 were responsible for suppression of MLRs. Inhibition of nitric oxide (NO) production or addition of IL-2 could not restore proliferation independently, but the combined treatment synergistically induced proliferation comparable with controls. Stimulation of APCs using tumor necrosis factor (TNF)-related activation-induced cytokine (TRANCE) or CD40L and addition of IL-2 normalized MLRs of CTLA4Ig-treated splenocytes. Finally, dendritic cells (DCs), but not T cells, from CTLA4Ig-treated rats inhibited naive MLRs. Altogether, these results provide evidence that after in vivo CTLA4Ig treatment, splenocytes, and in particular DCs, can inhibit alloantigen-induced proliferative responses through secretion of inhibitory products, thus promoting alloantigen-specific tolerance in vivo.

Stroma formation and angiogenesis by overexpression of growth factors, cytokines, and proteolytic enzymes in human skin grafted to SCID mice

Reorganization of skin during wound healing, inflammatory disorders, or cancer growth is the result of expression changes of multiple genes associated with tissue morphogenesis. We wanted to identify proteins involved in skin remodeling and select those that may be targeted for agonistic or antagonist therapeutic approaches in various disease processes. Full-thickness human skin was grafted to severe combined immunodeficient mice and injected intradermally with 38 different adenoviral vectors inserted with 37 different genes coding for growth factors, cytokines, proteolytic enzymes and their inhibitors, adhesion receptors, oncogenes, and tumor suppressor genes. Responses were characterized for infiltration of inflammatory cells, vascular density, matrix formation, fibroblast-like cell proliferation, and epidermal hyperplasia. Of the 17 growth factor vectors, 16 induced histological changes in human skin. Members of the VEGF and angiopoietin families induced neovascularization. PDGFs and TGF-betas stimulated connective tissue formation, and the chemokines IL-8 and MCP-1 attracted inflammatory neutrophils and monocytes, respectively. The serine protease uPA induced a vascular response similar to that of VEGF. Vectors with adhesion receptors, oncogenes and tumor suppressor genes had, with few exceptions, little effects on skin architecture. The overall results suggest that adenoviral vectors can effectively remodel the architecture of human skin for studies in morphogenesis, inflammatory skin disorders, wound healing, and cancer development.

Functional changes of dendritic cells derived from allogeneic partial liver graft undergoing acute rejection in rats

AIM: To investigate functional change of dendritic cells (DCs) derived from allogeneic partial liver graft undergoing acute rejection in rats.

METHODS: Allogeneic (SD rat to LEW rat) whole and 50% partial liver transplantation were performed. DCs from liver grafts 0 h and 4 d after transplantation were isolated and propagated in the presence of GM-CSF in vitro. Morphological characteristics of DCs propagated for 4 d and 10 d were observed by electron microscopy. Phenotypical features of DCs propagated for 10 d were analyzed by flow cytometry. Expression of IL-12 protein and IL-12 receptor mRNA in DCs propagated for 10 d was also measured by Western blotting and semiquantitative RT-PCR, respectively. Histological grading of rejection were determined.

RESULTS: Allogeneic whole liver grafts showed no features of rejection at day 4 after transplantation. In contrast, allogeneic partial liver grafts demonstrated moderate to severe rejection at day 4 after transplantation. DCs derived from allogeneic partial liver graft 4 d after transplantation exhibited typical morphological characteristics of DC after 4 d’ culture in the presence of GM-CSF. DCs from allogeneic whole liver graft 0 h and 4 d after transplantation did not exhibit typical morphological characteristics of DC until after 10 d’ culture in the presence of GM-CSF. After 10 d’ propagation in vitro, DCs derived from allogeneic whole liver graft exhibited features of immature DC, with absence of CD40, CD80 and CD86 surface expression, and low levels of IL-12 proteins (IL-12 p35 and IL-12 p40) and IL-12 receptor (IL-12Rβ₁ and IL-12Rβ₂) mRNA, whereas DCs from allogeneic partial liver graft 4 d after transplantation displayed features of mature DC, with high levels of CD40, CD80 and CD86 surface expression, and as a consequence, higher expression of IL-12 proteins (IL-12 p35 and IL-12 p40) and IL-12 receptors (IL-12Rβ₁ and IL-12Rβ₂) mRNA than those of DCs both from partial liver graft 0 h and whole liver graft 4 d after transplantation (P < 0.001) was observed.

CONCLUSION: DCs derived from allogeneic partial liver graft undergoing acute rejection display features of mature DC.

Dendritic cells genetically engineered to express IL-4 exhibit enhanced IL-12p70 production in response to CD40 ligation and accelerate organ allograft rejection

C57BL/10 (B10; H2(b)) bone marrow-derived myeloid dendritic cells (DC) propagated in GM-CSF + IL-4 were transduced with r adenoviral (Ad) vectors encoding either control neomycin-resistance gene (Ad-Neo) or murine IL-4 (Ad-IL-4) on day 5 of culture following CD11c immunomagnetic bead purification. Both Ad-Neo- and Ad-IL-4-transduced DC displayed upregulated surface MHC class II and costimulatory molecules (CD40, CD80, CD86). Ad-IL-4 DC secreted higher levels of bioactive IL-12p70 after CD40 ligation or LPS stimulation than either Ad-Neo or unmodified DC. Only Ad-IL-4 DC produced IL-12p70 in primary MLR, in which they induced augmented proliferative responses of naïve allogeneic C3H/HeJ (C3H; H2(k)) T-cells. Compared with Ad-Neo DC, Ad-IL-4 DC were also more effective in priming naïve allogeneic recipients to exhibit specifically enhanced anti-donor T-cell proliferative and CTL responses. T-cells primed in vivo 7 days previously with Ad-IL-4 DC displayed enhanced secretion of Th2 (IL-4, IL-10) but also higher Th1 cytokine (IFNgamma) production following ex vivo challenge with donor alloAg. Moreover, pretreatment of vascularized heart graft recipients with i.v. Ad-IL-4 DC, 1 week before transplant, significantly accelerated rejection and antagonized the therapeutic effect of anti-CD40L (CD154) mAb. These data contrast markedly with recently reported inhibitory effects of autologous Ad-IL-4 DC on autoimmune inflammatory disease.

Islet/pancreas transplantation: challenges for pediatrics

Beta cell replacement is a valid alternative to exogenous insulin injections to treat type 1 diabetic patients. The rate of success obtained after whole-pancreas transplantation, performed alone or in combination with kidney, and, as shown recently, by islet transplantation, justifies optimism and sets the stage for a larger clinical application of these approaches. Lifetime immunosuppression, however, required to protect the graft against recurrent autoimmune destruction and allorejection, raises serious doubts about the safety of its employment in children. While it is evident that children may be helped even more than adults by the possibility to correct diabetic metabolic disorders without exogenous insulin, and to lower in a more effective way the chance to develop secondary complications, the drawbacks of the currently used immunosuppressive drugs largely overcome the potential benefits. A great step forward for immediate applicability of transplantation to children involves the optimization of tolerogenic protocols and a better understanding of the concept of immune ignorance. Functional tolerance should be sufficient to entail the absence of immune reactivity against self- and graft antigens, while maintaining immune reactivity against other non-self, non-donor antigens. In addition, novel strategies aimed at utilizing surrogate beta cells obtained from non-islet cells, or by genetic manipulation of beta-cell precursors merit consideration as the use of xenogeneic donors. However, much work is still needed for their safe clinical implementation.

TGF-beta 1 synergizes with GM-CSF to promote the generation of glial cell-derived dendriform cells in vitro

Microglia are often considered a type of tissue macrophages analogous Langerhans' cells, while dendritic cells (DC) can be generated in vitro from cultured microglia in the presence of GM-CSF. In this study, we show that TGF-beta 1, in the presence of GM-CSF, promoted the growth and differentiation of glial cell-derived dendritic cells (GC-DC). TGF-beta 1-driven GC-DC exhibited an immature state reflected by low CD11c expression, augmented endocytosis, and reduced antigen presentation. Expression of Fas was inhibited in GM-CSF+TGF-beta 1-supplemented cell cultures and may relate to a long life span of GC-DC treated with GM-CSF+TGF-beta 1. IL-10 and IL-12 mRNA on GC-DC was not affected upon exposure to GM-CSF alone or to GM-CSF+IFN-gamma, GM-CSF+IL-10 or GM-CSF+TGF-beta 1. In sharp contrast, TGF-beta 1, in the presence of GM-CSF, dramatically up-regulated the expression of TNF-alpha and TGF-beta 1 mRNA. These results demonstrate that TGF-beta 1 seems to play a crucial role in the differentiation, functional skewing, and cytokine profile of GC-DC. TGF-beta 1-driven GC-DC awaits further investigation to facilitate a better understanding of the glia-T cell dialog as well as the pathogenesis and immunotherapy of central nervous system inflammatory and degenerative diseases.

Marked prolongation of cardiac allograft survival by dendritic cells genetically engineered with NF-kappa B oligodeoxyribonucleotide decoys and adenoviral vectors encoding CTLA4-Ig

Bone marrow-derived dendritic cells (DCs) can be genetically engineered using adenoviral (Ad) vectors to express immunosuppressive molecules that promote T cell unresponsiveness. The success of these DCs for therapy of allograft rejection has been limited in part by the potential of the adenovirus to promote DC maturation and the inherent ability of the DC to undergo maturation following in vivo administration. DC maturation occurs via NF-kappaB-dependent mechanisms, which can be blocked by double-stranded "decoy" oligodeoxyribonucleotides (ODNs) containing binding sites for NF-kappaB. Herein, we describe the combined use of NF-kappaB ODNs and rAd vectors encoding CTLA4-Ig (Ad CTLA4-Ig) to generate stably immature murine myeloid DCs that secrete the potent costimulation blocking agent. These Ad CTLA4-Ig-transduced ODN DCs exhibit markedly impaired allostimulatory ability and promote apoptosis of activated T cells. Furthermore, administration of Ad CTLA4-Ig ODN-treated donor DCs (C57BL10; B10(H-2b)) before transplant significantly prolongs MHC-mismatched (C3HHeJ; C3H(H-2k)) vascularized heart allograft survival, with long-term (>100 days) donor-specific graft survival in 40% of recipients. The mechanism(s) responsible for DC tolerogenicity, which may involve activation-induced apoptosis of alloreactive T cells, do not lead to skewing of intragraft Th cytokine responses. Use of NF-kappaB antisense decoys in conjunction with rAd encoding a potent costimulation blocking agent offers promise for therapy of allograft rejection or autoimmune disease with minimization of systemic immunosuppression.

Rhesus monocyte-derived dendritic cells modified to over-express TGF-beta1 exhibit potent veto activity

BACKGROUND

The tolerogenic activity of allogeneic bone marrow cells (BMCs) associates with functional inactivation of alloreactive T cells and has been attributed to a veto effect. Studies in mice and rhesus monkeys indicated that the CD8alpha molecule expressed on a subpopulation of allogeneic BMCs is necessary to induce signal transduction within the BMCs to increase veto effector molecules such as transforming growth factor (TGF)-beta1. In vitro activation of alloreactive cytotoxic T-lymphocyte precursor enhances their susceptibility to veto-mediated functional inactivation by specific alloantigen-bearing BMCs. Accordingly, we examined a hypothesis that mature rhesus monkey (Rh) monocyte-derived dendritic cells (MDDCs) modified by gene transfer to over-express active TGF-beta1 might mediate veto activity without the need to express CD8alpha.

METHODS

Rh MDDCs were modified by recombinant adenovirus (Ad) transduction and characterized by phenotype and functional studies.

RESULTS

Rh MDDC transduction with Ad vectors using conventional methods was remarkably inefficient. However, a single-chain anti-CD40/soluble Coxsackie and adenovirus receptor-fusion protein (G28/sCAR) permitted high-efficiency transduction of Rh MDDCs by retargeting Ad to Rh MDDC CD40. Mature Rh MDDCs that were transduced to overexpress active TGF-beta1 (AdTGF-beta1 Rh MDDC) significantly suppressed alloimmune responses in [ H]thymidine uptake mixed leukocyte reaction assays. We showed by the carboxyfluorescein succinimidyl ester dilution method that allogeneic mature AdTGF-beta1 Rh MDDCs inhibited proliferation of CD4 and CD8 responder T cells. Notably, AdTGF-beta1 Rh MDDC abrogated alloimmune responses induced by control AdGFP Rh MDDC in an antigen-specific manner.

CONCLUSIONS

These results suggest that nonhuman primate mature MDDCs can be genetically engineered to function as alloantigen-specific cellular immunosuppressants, an approach that has potential to facilitate induction of allograft tolerance in vivo.

Role of dendritic cells in graft-versus-host disease

A major barrier to successful allogeneic hematopoietic stem cell transplantation is graft-versus-host disease (GVHD). Until recently, the role of antigen presentation in the development of this disorder was unknown. The experimental finding that recipient antigen-presenting cells (APCs) were required for the development of CD8(+) T cell-dependent GVHD has led to a fundamental reappraisal of our ideas concerning the pathogenesis of this disease. Following transplantation, the origin (donor or recipient), number, lineage, and function of APCs within the recipient are altered significantly. Studies that test the influence of each of these factors upon graft-versus-host responses, including graft-versus-tumor responses, are beginning to emerge and suggest that APCs, such as dendritic cells, constitute a potential target for therapeutic manipulation.

Alternatives to immunosuppressive drugs in human islet transplantation

Although intensive insulin therapy has resulted in improved metabolic control and decreases in the incidence of complications, the occurrence of severe hypoglycemia remains an issue, as does the continued potential for complications. Islet transplantation, a promising treatment for type I diabetes, has been shown to improve blood sugar levels and decrease or even abrogate the incidence of hypoglycemia. The lack of tissue availability and the toxic effects of immunosuppressants, however, limit the application of islet transplantation as a cure for diabetes. This article discusses possible alternatives to immunosuppressive drugs in human islet transplantations.

Retroviral delivery of transforming growth factor-beta1 to myeloid dendritic cells: inhibition of T-cell priming ability and influence on allograft survival

BACKGROUND

Transforming growth factor (TGF)-beta inhibits the maturation and function of antigen-presenting cells. Our purpose was to evaluate the impact of retroviral delivery of human TGF-beta1 to murine myeloid dendritic cell (DC) progenitors on (i) their in vitro properties, (ii) their in vivo function, and (iii) their influence on organ allograft survival.

METHODS

C57BL10 (B10; H2b) bone marrow cells were lineage depleted and stimulated with granulocyte-macrophage colony-stimulating factor for 6 days. Replicating DC progenitors were transduced on days 2, 3, and 4 of culture by ecotropic retrovirus encoding human TGF-beta1 using centrifugal enhancement. Secretion of TGF-beta1 and other cytokines was quantified by enzyme immunoassay. Allogeneic C3H/HeJ (C3H; H2k) T-cell proliferative responses and generation of cytotoxic T lymphocytes in mixed leukocyte reaction were determined by [3H]thymidine incorporation and 51Cr release assays, respectively. DC migration was analyzed by immunohistochemistry, and their impact on survival of intra-abdominal heart transplants was determined.

RESULTS

Maximal TGF-beta1 transduction efficiency was 60%. The TGF-beta-transduced DC showed pronounced impairment (>80%) of T-cell allostimulatory activity in vitro. After their IV injection, B10 TGF-beta-transduced DC (IAb+) were detected in T-cell areas of spleens of allogeneic C3H recipients. Splenic T-cell responses to donor alloantigens of mice that received TGF-beta-transduced DC were severely impaired. This was accompanied by marked inhibition of interleukin-2 and interferon-gamma production in response to restimulation with donor alloantigen. Survival of B10 cardiac allografts in C3H mice given B10 TGF-beta-transduced DC (2x106 IV, 7 days before transplantation), was extended modestly but significantly.

CONCLUSION

Retroviral transduction of myeloid DC progenitors to overexpress TGF-beta is associated with marked impairment of their T-cell allostimulatory activity but with only modest prolongation of organ allograft survival.

Gene therapy in transplantation

Gene transfer and gene therapy represent a relatively new field that has grown and expanded enormously in the last 5-10 years. The application of gene transfer and gene medicines to transplantation is currently in its infancy. Consideration for gene medicines in transplantation requires delivery of vectors, either to the graft or to the immune system. Delivery of vectors to the graft provides a choice of potential immunologic targets including: costimulatory signals; inhibitory cytokines; adhesion molecules; and molecules relating to apoptosis. In addition, non-immunologic targets, that increase graft protective mechanisms by reducing ischemic and immunologic damage, represent significant targets for gene transfer. Delivery of vectors to the immune system includes potential targets to modify the immune system, and results in tolerance. Other considerations for gene therapy include the development of additional technologies, such as gene conversion or transgenesis coupled with xenotransplantation, which may provide genetically modified organs. Another important aspect of gene transfer relates to regulation of the transgene expression. A variety of issues concerning innate immunity, adaptive immunity, response to vector components, response to transgene products, and entry of vectors into the antigen presentation and processing pathway require further investigation and refinement of approaches. Lastly, regulatable promoters and the understanding of their interaction with individual cells, tissues and organs, and their interaction with innate and adaptive immunity, are of paramount importance to improving the efficacy and utility of gene transfer. There is no doubt that there is much exciting basic and translational science to be accomplished in the next decade in order to solve these potential barriers and advance gene medicines into the clinical realm in transplantation.