Gene therapy in transplantation

Current state of type 1 diabetes immunotherapy: incremental advances, huge leaps, or more of the same?

Thus far, none of the preclinically successful and promising immunomodulatory agents for type 1 diabetes mellitus (T1DM) has conferred stable, long-term insulin independence to diabetic patients. The majority of these immunomodulators are humanised antibodies that target immune cells or cytokines. These as well as fusion proteins and inhibitor proteins all share varying adverse event occurrence and severity. Other approaches have included intact putative autoantigens or autoantigen peptides. Considerable logistical outlays have been deployed to develop and to translate humanised antibodies targeting immune cells, cytokines, and cytokine receptors to the clinic. Very recent phase III trials with the leading agent, a humanised anti-CD3 antibody, call into question whether further development of these biologics represents a step forward or more of the same. Combination therapies of one or more of these humanised antibodies are also being considered, and they face identical, if not more serious, impediments and safety issues. This paper will highlight the preclinical successes and the excitement generated by phase II trials while offering alternative possibilities and new translational avenues that can be explored given the very recent disappointment in leading agents in more advanced clinical trials.

Dendritic cell-based therapy in Type 1 diabetes mellitus

Dendritic cell (DC) immunotherapy is a clinical reality. Despite two decades of considerable data demonstrating the feasibility of using DCs to prolong transplant allograft survival and to prevent autoimmunity, only now are these cells entering clinical trials in humans. Type 1 diabetes is the first autoimmune disorder to be targeted for treatment in humans using autologous-engineered DCs. This review will highlight the role of DCs in autoimmunity and the manner in which they have been engineered to treat these disorders in rodent models, either via the induction of immune hyporesponsiveness, which may be cell- and/or antigen-specific, or indirectly by upregulation of other immune cell networks.

Delivery of nucleic acids via disulfide-based carrier systems

Nucleic acids are not only expected to assume a pivotal position as "drugs" in the treatment of genetic and acquired diseases, but could also act as molecular cues to control the microenvironment during tissue regeneration. Despite this promise, the efficient delivery of nucleic acids to their side of action is still the major hurdle. One among many prerequisites for a successful carrier system for nucleic acids is high stability in the extracellular environment, accompanied by an efficient release of the cargo in the intracellular compartment. A promising strategy to create such an interactive delivery system is to exploit the redox gradient between the extra- and intracellular compartments. In this review, emphasis is placed on the biological rationale for the synthesis of redox sensitive, disulfide-based carrier systems, as well as the extra- and intracellular processing of macromolecules containing disulfide bonds. Moreover, the basic synthetic approaches for introducing disulfide bonds into carrier molecules, together with examples that demonstrate the benefit of disulfides at the individual stages of nucleic acid delivery, will be presented.

Overexpression of indoleamine dioxygenase in rat liver allografts using a high-efficiency adeno-associated virus vector does not prevent acute rejection

The aim of this study was to evaluate the ability of local overexpression of indoleamine dioxygenase (IDO) to abrogate rat liver transplant rejection by the use of an adeno-associated virus vector [recombinant adeno-associated virus 2/8 (rAAV2/8)] to deliver the transgene to the allograft prior to transplantation. A green fluorescent protein (GFP)-expressing vector [recombinant adeno-associated virus 2/8-liver-specific promoter 1-enhanced green fluorescent protein (rAAV2/8-LSP1-eGFP)] was used to examine the kinetics of expression and optimal dosing for transduction of Piebald Virol Glaxo (PVG) rat livers. A vector encoding the rat IDO gene (rAAV2/8-LSP1-rIDO) was constructed and tested by its ability to induce tryptophan catabolism and kynurenine production in vitro and in vivo. PVG donor rats were injected, via the portal vein, with rAAV2/8-LSP1-rIDO 2 weeks before transplantation into PVG strain isograft or Lewis (LEW) strain allograft recipients. With the enhanced GFP vector, 29.5% and 47.4% of hepatocytes were found to express GFP at 3 and 6 weeks after injection, respectively. In untransplanted PVG animals, the rAAV2/8-LSP1-rIDO vector induced, 3 weeks after administration, a 1.8-fold increase (P = 0.0161) in liver IDO activity, which was associated with a fall in serum tryptophan to 0.5 times the baseline level (P < 0.001). PVG recipients of PVG liver isografts pretreated with the IDO-expressing vector had a 45% lower level of serum tryptophan than recipients of isografts pretreated with the GFP-expressing vector (P = 0.03). LEW recipients of PVG liver allografts pretreated with the rat IDO vector had a median survival time of 12 days, whereas recipients of allografts pretreated with rAAV2/8-LSP1-eGFP had a median survival time of 13 days (P = 0.38). Both groups displayed similar histological features of acute cellular rejection. In conclusion, rAAV2/8 vectors produce highly efficient, though delayed, hepatocyte transduction in vivo and provide a useful gene delivery tool for transplantation models. However, gene delivery using IDO was unsuccessful in prolonging rat liver allograft survival.

Interleukin-10 Gene Transfection of Donor Pancreas Grafts Protects against Rejection after Heterotopic Pancreas Transplantation in a Rat Model

OBJECTIVE

The aim of this study was to assess the effect of immunoregulatory cytokine interleukin-10 (IL-10) gene therapy on pancreas tissue rejection in a heterotopic pancreas transplantation model.

BACKGROUND

Modulation of inflammatory responses by anti-inflammatory cytokines (e.g., IL-10) has been suggested to minimize organ rejection. In this context, modulation of cytokines using gene therapy could be a new therapeutic modality in preventing organ rejection.

METHODS

The study was performed using male inbred Wistar rats as recipients and Sprague-Dawley rats as donors. 24 h before transplantation, groups of rats, named IL-10 (n = 20) and green fluorescent protein (GFP, n = 20), were injected with viral vectors Ad5CMVhIL10 or Ad5CMVGFP. Sham-operated rats (n = 20) underwent saline injection only before transplantation. The pancreatic tissue from each of these donor rats was subsequently transplanted into the corresponding groups of streptozotocin-induced diabetic recipient rats. Recipients were thus transfected with either IL-10 (n = 20), GFP-only carrying viral vectors (n = 20) or no viral vectors (normal saline, n = 20). A selected number of animals from each recipient group (n = 5) was sacrificed at weekly intervals for 3 weeks and some were further followed up to 12 weeks before sacrifice. Histological assessment of the pancreatic tissue was made based on rejection and GFP expression. Blood glucose levels were checked daily in all groups until sacrifice. Upon sacrifice, serum cytokine and insulin levels were measured. Histopathological correlations between blood glucose levels, serum insulin levels and serum IL-10 levels were made.

RESULTS

IL-10 gene therapy significantly attenuated pancreas rejection compared to controls, provided more normal blood glucose levels and elevated plasma insulin levels. Upon assumed natural deactivation of transferred viruses after 4 weeks, differences between groups in terms of rejection, blood glucose and insulin levels disappeared.

CONCLUSION

These findings suggest that IL-10 gene therapy significantly reduced pancreas rejection.

Toward a cure for type 1 diabetes mellitus: diabetes-suppressive dendritic cells and beyond

Insulin has been the gold standard therapy for diabetes since its discovery and commercial availability. It remains the only pharmacologic therapy for type 1 diabetes (T1D), an autoimmune disease in which autoreactive T cells specifically kill the insulin-producing beta cells. Nevertheless, not even molecularly produced insulin administered four or five times per day can provide a physiologic regulation able to prevent the complications that account for the morbidity and mortality of diabetic patients. Also, insulin does not eliminate the T1D hallmark: beta-cell-specific autoimmunity. In other words, insulin is not a 'cure'. A successful cure must meet the following criteria: (i) it must either replace or maintain the functional integrity of the natural, insulin-producing tissue, the endocrine islets of Langerhans' and, more specifically, the insulin-producing beta cells; (ii) it must, at least, control the autoimmunity or eliminate it altogether; and (iii) it must be easy to apply to a large number of patients. Criterion 1 has been partially realized by allogeneic islet transplantation. Criterion 2 has been partially realized using monoclonal antibodies specific for T-cell surface proteins. Criterion 3 has yet to be realized, given that most of the novel therapies are currently quasi-patient-specific. Herein, we outline the current status of non-insulin-based therapies for T1D, with a focus on cell-based immunomodulation which we propose can achieve all three criteria illustrated above.

Laboratory formulated magnetic nanoparticles for enhancement of viral gene expression in suspension cell line

One factor critical to successful gene therapy is the development of efficient delivery systems. Although advances in gene transfer technology including viral and non-viral vectors have been made, an ideal vector system has not yet been constructed. Due to the growing concerns over the toxicity and immunogenicity of viral DNA delivery systems, DNA delivery via improve viral routes has become more desirable and advantageous. The ideal improve viral DNA delivery system should be a synthetic materials plus viral vectors. The materials should also be biocompatible, efficient, and modular so that it is tunable to various applications in both research and clinical settings. The successful steps towards this improve viral DNA delivery system is demonstrated: a magnetofection system mediated by modified cationic chitosan-coated iron oxide nanoparticles. Dense colloidal cationic iron oxide nanoparticles serve as an uptake-enhancing component by physical concentration at the cell surface in presence of external magnetic fields; enhanced viral gene expression (3-100-fold) due to the particles is seen as compared to virus vector alone with little virus dose.

Immunoregulatory dendritic cells to prevent and reverse new-onset Type 1 diabetes mellitus

Herein, the authors provide an overview of where dendritic cells lie in the immunopathology of autoimmune Type 1 diabetes mellitus and how dendritic cell-based therapy may be usefully translated to treat and reverse the disease. The immunopathology of Type 1 diabetes mellitus offers a number of windows at which immunotherapy can be applied to delay, stop and even reverse the autoimmune processes, especially in light of the recent antibody-based accomplishment of improvement in residual beta-cell mass function. As in almost all cell-specific inflammatory processes, dendritic cells are central regulators of diabetes onset and progression. This realisation, along with accumulating data confirming a role for dendritic cells in maintaining and inducing tolerance in multiple therapeutic settings, has prompted a line of investigation to identify the most effective embodiments of dendritic cells for diabetes immunotherapy.

Immune Accessory Functions of Human Endothelial Cells Are Modulated by Overexpression of B7-H1 (PDL1)

B7-H1 (PDL1) is a B7-related protein that inhibits T-cell responses. Human endothelial cells (EC), which can support polyclonal stimulation (by anti-CD3 or Phytohemagglutinin (PHA)) or direct alloantigen stimulation of T cells, basally express B7-H1 and increase expression in response to IFN-gamma or coculture with allogeneic T cells. Previous studies have suggested that endogenous B7-H1 on EC reduces T-cell responses. We engineered overexpression of B7-H1 in EC (B7H1-EC) to evaluate whether this manipulation could reduce T-cell responses even further. Compared with green fluorescent protein-transduced EC (GFP-EC), B7H1-EC support less anti-CD3 or PHA-induced proliferation of CD4+ memory T cells; naive CD4+ T-cell or CD8+ T-cell responses were less inhibited. The effect of transduced B7H1-EC was more apparent when the EC were fixed prior to coculture, a manipulation that reduces the strength of costimulation and prevents upregulation of the endogenous B7-H1 molecule. T-cell activation markers, including CD25, CD62L, CD152 (CTLA-4), and CD154 (CD40L), were not altered by EC overexpression of B7-H1, whereas there was a reduction in CD69. B7-H1 reduced secretion of IL-2 and IL-10 by memory T cells. B7H1-EC were less able to stimulate allogeneic proliferation of CD4+ memory T cells than control EC. These data suggest that B7-H1 overexpression may be a useful approach for reducing allogeneic CD4+ memory T-cell responses to EC.

Genetic Heterogeneity and Efficiency of Two Different Methods of Adenovirus-Mediated Gene Transfer in a Rat Liver Transplantation Model

PURPOSE

We used recombinant adenoviral vectors for gene therapy in liver transplantation, and investigated the efficacy of gene transfer and expression on the grafts and genetic heterogeneity, with two exogenous gene transfer methods in three different syngeneic rat strains.

METHODS

We transferred adenoviral vector encoding Escherichia coli beta-galactosidase via a donor tail vein 3 days before transplantation; via a recipient tail vein immediately after grafting; and ex vivo by perfusion and clamping during transplantation.

RESULTS

The high efficacy of beta-galactosidase gene transfer and expression was seen in both delivery systems, with 70% positivity for hepatocytes on day 3, which persisted for at least 3 weeks after transplantation. The efficacy of gene transfer and expression was similar in the three strains (DA, Lewis, and PVG).

CONCLUSIONS

These data suggest that adenovirus-mediated gene transfer delivers effective gene therapy by tail vein injection of a donor or a recipient, or by ex vivo graft perfusion in rat liver transplantation. It is not necessary to consider the differences in the strains. Furthermore, ex vivo graft perfusion is probably more suitable not only for rat liver transplantation but also possibly for future clinical application.

Influence of polyclonal anti-thymocyte globulins upon ischemia-reperfusion injury in a non-human primate model

BACKGROUND

Polyclonal anti-thymocyte globulins (ATGs) are used to induce immunosuppression and to treat acute rejection after transplantation. ATGs induce apoptosis and in peripheral T-lymphocytes having the potential to inhibit leukocyte adhesion. We analysed the influence of three different ATGs upon the microvasculature and the different cell-subpopulations after ischemia/reperfusion (IRI).

MATERIALS AND METHODS

Extremities of cynomolgus monkeys were surgically isolated and flushed with Ringer's lactate at 4 degrees C. After 60 min of ischemia the limbs were reperfused with matching human blood. ATGs were added to the blood 30 min prior to the reperfusion. Four groups were generated: Tecelac-ATG group, Fresenius(S)-ATG group, Thymoglobulin-ATG group and a control group. Blood analyses were performed in blood samples taken after the beginning of the reperfusion. Biopsies from muscular tissue were obtained after the experiments.

RESULTS

The number of circulating leukocytes was lower in the ATG-groups than in control. Morpho-cytological analyses showed depletion of peripheral lymphocytes. Histological examination showed less tissue damage, reduced presence of fibrin and adherent thrombocytes in the ATG-treated groups. Leukocyte infiltration, both in muscle and vascular structures, was significantly diminished in the ATG-groups in comparison to control.

DISCUSSION

Our results show that ATGs have a favourable impact on early mechanisms of IRI. ATGs showed a reduction of the number of adherent leukocytes and muscle infiltrates suggesting that preoperative therapy with ATGs may have an advantageous effect on primary non-function and on chronic rejection as well as a positive influence upon IRI.

Transforming growth factor-beta1 gene transfer is associated with the development of regulatory cells

Adenovirus-mediated transfection of mouse cardiac allografts with active human transforming growth factor-beta 1 (TGF-beta1) prolongs transplant survival provided that recipients are initially depleted of CD8+ T cells. To test if graft survival was prolonged by persistent TGF-beta1 transgene expression, long-term transfected allografts were re-transplanted into naïve mice that were transiently depleted of CD8+ T cells. Re-transplanted allografts were acutely rejected, indicating that TGF-beta1 transgene expression did not suppress effector cell function. We next asked whether TGF-beta1 gene transfer was associated with the development of regulatory cells. When splenocytes obtained from mice bearing long-term TGF-beta1-transfected allografts were adoptively transferred into recipients of non-transfected cardiac allografts, prolonged allograft survival was observed, and increased levels of the regulatory T cell transcription factor Foxp3 were present. To further test for regulation, differentiated effector cells were obtained from mice that had rejected cardiac allografts and were adoptively transferred into mice bearing long-term TGF-beta1 transfected cardiac allografts. The effector cells failed to mediate rejection in mice bearing TGF-beta1-transfected allografts and we observed a significant increase in intra-graft Foxp3 expression. These findings indicate that TGF-beta1 gene transfer allows for the development of regulatory cells that control graft-reactive T cell responses once therapeutic levels of the transgene product are no longer produced.

In vivo molecular imaging characterizes pulmonary gene expression during experimental lung transplantation

Experimental gene therapy is a promising strategy to prevent ischemia-reperfusion (I/R) injury and allograft rejection after lung transplantation, and methods will eventually be needed to characterize pulmonary transgene expression in vivo in humans. Therefore, we studied positron emission tomography (PET) as a means of performing in vivo molecular imaging in rodent models of lung transplantation. Rats were transfected endotracheally with adenovirus encoding a fusion gene of a mutant Herpes simplex virus-1 thymidine kinase and the green fluorescent protein gene (the former serving as an imaging reporter gene). Twenty-four hours after transfection, lungs were transplanted in groups representing normal transplantation, I/R injury and acute allograft rejection. Imaging was obtained either 24 h after transplantation to study reperfusion injury or 4 days after transplantation to study graft rejection. After imaging, lungs were excised and analyzed for thymidine kinase activity. Imaging detected transgene expression in transplanted lungs even in the presence of acute rejection or I/R injury. The PET imaging signal correlated with in vitro lung tissue assays of thymidine kinase activity (r(2) = 0.534). Thus, noninvasive molecular imaging with PET is a feasible, sensitive and quantitative method for characterizing pulmonary transgene expression in experimental lung transplantation.

Induction of tumor immunity and cytotoxic t lymphocyte responses using dendritic cells transduced by adenoviral vectors encoding HBsAg: comparison to protein immunization

Dendritic cells (DC) are specialized antigen-presenting cells with powerful immunostimulatory properties. Their use for induction of anti-tumor immunity has been limited by several factors, including identification of appropriate tumor-associated antigens, delivery of antigens to DC, and maintaining DC in a highly activated state. Here, DC propagated in vitro were transduced with an adenoviral (Ad) vector to express hepatitis B surface antigen (HBsAg), an antigen present in hepatocellular carcinoma (HCC). Many patients with HCC demonstrate evidence of prior HBV exposure, suggesting that the presence of the virus in a quiescent state may promote tumorigenesis. Ad-HBsAg-transduced DC stimulated strong cytotoxic T lymphocyte (CTL) responses to HBsAg-expressing tumor cells, and protected mice from lethal tumor challenge. Immunity was antigen-specific, as wild-type tumor (HBsAg -) grew normally. Furthermore, DC transduced with an irrelevant vector had no effect. Vaccination with HBsAg protein, a clinically utilized preparation that confers immunity to HBV infection, did not protect against tumor challenge even though it induced a strong antibody response. These studies describe for the first time the contributions of humoral and cellular immune responses to tumor immunity induced by Ad-transduced DC compared to protein vaccination.

Nanoparticulate System for Efficient Gene Transfer into Refractory Cell Targets

A biocompatible, nanoparticulate formulation has been designed to retain, protect, and deliver adenoviral gene constructs over an extended time course. Such devices can be administered locally or systemically with low toxicity. A multipolymeric nanoparticulate system, featuring very high stability in physiologic media, was designed to allow efficient in vitro gene transfer. The efficacy of nanoparticulate delivery is effective in cell systems that are normally refractory to gene transfer, such as pancreatic islets and antigen-presenting cells. The findings suggest a nonspecific uptake system that permits adenoviral particle release within the transfected cells. A comparison with literature data revealed that our system is efficient at much lower levels (at least three orders of magnitude) of infectious viral particles.

Prolongation of islet allograft survival following ex vivo transduction with adenovirus encoding a soluble type 1 TNF receptor–Ig fusion decoy

Islet transplantation is a viable long-term therapeutic alternative to daily insulin replacement for type I diabetes. The allogeneic nature of the transplants poses immunological challenges for routine clinical utility. Gene transfer of immunoregulatory molecules and those that improve insulin release kinetics provides rational approaches to facilitate allogeneic islet transplantation as a potential therapy. We have examined the efficacy of a soluble type 1 tumor necrosis factor receptor (TNFR) immunoglobulin-Fc fusion transgene (TNFR-Ig) to protect human islets from cytokine-induced apoptosis in culture, as well as in facilitating allogeneic islet transplants in diabetic mice. Cultured human islets were transduced with an adenoviral vector encoding human TNFR-Ig (Ad-TNFR-Ig). TNFR-Ig protein was secreted by cultured islets, as well as by transduced mouse islet transplants recovered from mouse recipients. Glucose-induced insulin release kinetics were comparable among untransduced, Ad-TNFR-Ig-infected human islets and vector-transduced islets exposed to cytokines. In parallel, Ad-TNFR-Ig-infected islets were protected from cytokine-induced apoptosis activation. Finally, diabetic mice transplanted with allogeneic islets expressing TNFR-Ig returned to and maintained normoglycemia significantly longer than untransduced islet recipients. These data support the potential utility of TNFR-Ig gene transfer to islets as a means of facilitating allogeneic islet transplantation.

Prolonged survival of rat liver allograft with adenoviral gene transfection of human immunodeficiency virus type 1 nef

HIV-1 nef is believed to allow immune evasion by modifying cell surface molecules because of certain mechanisms such as downregulation of the major histocompatibility complex (MHC) class I molecule complex as well as upregulation of FasL. In the present study, we successfully generated a recombinant adenovirus vector containing HIV-1 nef. We detected the expression of nef in liver infected with AxCANef by immune staining and Western blotting, and confirmed its expression as persistent for more than 4 weeks. Furthermore, the surface expression of MHC class I was downregulated in AxCANef-infected hepatic cells. In addition, we also observed nef-induced FasL upregulation of gene-transfected hepatic cells. Using a DA-to-Lewis orthotopic liver transplantation model, we transfected AxCANef to a liver graft to determine whether nef expression could have an effect on recipient survival. AxCANef significantly prolonged recipient survival time (14.5 days) compared with the uninfected group (11 days) (P <.001) and the AxCALacZ-infected group (11 days) (P <.001). Histologic analysis showed reduction in the number of accumulated inflammatory cells and an increase in apoptotic cells in grafts expressing nef. In conclusion, we showed that the nef gene could prolong survival of rat liver allografts, and this result suggested the potential clinical use of its transfection.

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.

Gene and cell therapies for diabetes mellitus: strategies and clinical potential

The last 5 years have witnessed an explosion in the use of genes and cells as biomedicines. While primarily aimed at cancer, gene engineering and cell therapy strategies have additionally been used for Mendelian, neurodegenerative and metabolic disorders. The main focus of gene and cell therapy strategies in metabolism has been diabetes mellitus. This disease is a disorder of glucose homeostasis, either due to the immune-mediated eradication of pancreatic beta cells in the islets of Langerhans (type 1 diabetes) or resulting from insulin resistance and obesity syndromes where the insulin-producing capability of the beta cell is ultimately exhausted in the face of insensitivity to the effects of insulin in the peripheral glucose-utilising tissues (type 2 diabetes). A significant number of animal studies have demonstrated the potential in restoring normoglycaemia by islet transplantation in the context of immunoregulation achieved by gene transfer of immunoregulatory genes to allo- and xenogeneic islets ex vivo. Additionally, gene and cell therapy has also been used to induce tolerance to auto- and alloantigens and to generate the tolerant state in autoimmune rodent animal models of type 1 diabetes or rodent recipients of allogeneic/xenogeneic islet transplants. The achievements of gene and cell therapy in type 2 diabetes are less evident, but seminal studies promise that this modality can be relevant to treat and perhaps prevent the underlying causes of the disease. Here we present an overview of the current status of gene and cell therapy for type 1 and 2 diabetes and we propose potential therapeutic options that could be clinically useful. For type 1 diabetes, transplantation of islets engineered to evade or suppress the recipient immune response is the most readily-available technology today. A number of gene delivery vectors encoding proteins that impair a variety of immune cells have already been examined and proven versatile. More challenging but, nonetheless, just over the horizon are attempts to promote tolerance to islet allografts. Type 2 diabetes will likely require a better understanding of the processes that determine insulin sensitivity in the periphery. Targeting tissues such as muscle and fat with vectors encoding genes whose products promote insulin sensitivity and glucose uptake is an approach that does not carry with it the side-effects often associated with pharmacologic agents currently in use. In the end, progress in vector design, elucidation of antigen-specific immunity and insulin sensitivity will provide the framework for gene drug use in the treatment of type 1 and type 2 diabetes.

Gene transfer of manganese superoxide dismutase extends islet graft function in a mouse model of autoimmune diabetes

Islet transplantation is a promising cure for diabetes. However, inflammation, allorejection, and recurrent autoimmune damage all may contribute to early graft loss. Pancreatic islets express lower levels of antioxidant genes than most other tissues of the body, and beta-cells in particular are sensitive to oxidative damage. Therefore, damage from oxidative stress may pose a major obstacle to islet replacement therapy in that both the islet isolation and transplantation processes generate oxygen radicals. To determine whether antioxidant gene overexpression in isolated pancreatic islets can prevent oxidative damage and prolong islet function after transplantation, we used the NOD mouse model to study oxidative stress encountered during both transplantation and autoimmune attack. We transferred an antioxidant gene, manganese superoxide dismutase (MnSOD), by adenoviral infection into isolated islets that were transplanted into streptozotocin-treated NODscid recipient mice. Functioning islet grafts were subsequently exposed to diabetogenic spleen cells and monitored until graft failure. The results show that islet grafts overexpressing MnSOD functioned approximately 50% longer than control grafts. This significant prolongation of graft function suggests that the antioxidant activity of MnSOD is beneficial to transplanted islet survival and may be used in combination with other strategies aimed at islet graft protection.

Cationic lipid and polymer-based gene delivery to human pancreatic islets

Transplantation of pancreatic islets has great potential for treating Type I diabetes. Ex vivo gene therapy may promote re-vascularization or inhibit apoptosis of the islets and promote graft. In this study, we investigated the feasibility of non-viral gene delivery using Enhanced Green Fluorescent Protein (EGFP) and human Vascular Endothelial Growth Factor (hVEGF(165)) expression plasmids as model reporter and therapeutic genes. LipofectAMINE/pDNA and Superfect/pDNA complexes showed high transfection efficiency in rapidly dividing Jurkat cells, but low transfection in non-dividing human islets. LipofectAMINE/pCAGGS-hVEGF transfected islets showed relatively higher levels of hVEGF than in those transfected with LipofectAMINE/pCMS-EGFP complexes or 5% glucose. To exclude endogenously secreted hVEGF, real time RT-PCR experiment was repeated using pCAGGS vector-specific forward primer and hVEGF gene-specific reverse primer. In this case, both non-transfected islets and the islets transfected with LipofectAMINE/pCMS-EGFP complexes showed negligible amplification of hVEGF. On glucose challenge, insulin release from LipofectAMINE/pCAGGS-hVEGF transfected human islets increased from 10.78 +/- 4.56 to 65 +/- 5 ng/ml, suggesting little adverse effect on islet beta cell response to glucose challenge. The low transfection efficiency is due to the islets being a cluster of approximately 1000 non-dividing cells. This underscores the importance of experimentation with the actual human islets.

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.

Genetically modified adenovirus vector containing an RGD peptide in the HI loop of the fiber knob improves gene transfer to nonhuman primate isolated pancreatic islets

The ability to transfer immunoregulatory, cytoprotective, or antiapoptotic genes into pancreatic islets (PIs) may allow enhanced post-transplantation survival. The available gene transfer vectors differ greatly in their ability to infect and express genes in different cell types. One limitation associated with the use of viral vectors is related to the virus reliance on the presence of its primary binding site. Tropism of the viral vectors can be altered using retargeting strategies. Results on phage biopanning proved that the RGD motif has in vivo targeting capabilities. This motif interacts especially with cellular integrins of the alphavbeta3 and alphavbeta5 types, highly expressed on pancreatic islets. In this report, we have explored the utility of a retargeted adenovirus vector (Ad) containing an RGD motif in the HI loop of the fiber knob in order to improve the infection efficiency to intact isolated nonhuman primate PIs and reduce toxicity after the genetic modification. Nonhuman primate Pis were isolated by a semi-automated technique. Steptozotocin-induced diabetic mice with severe combined immunodeficiency disease (SCID) were used as recipients. A recombinant Ad containing a heterologous RGD peptide and expressing luciferase (AdRGDLuc) or green fluorescent protein (AdRGDGFP) were generated in our laboratory. Similar Ads without the RGD peptide were used as a control (AdLuc and AdGFP). Higher transfection efficiency was demonstrated using AdRGDGFP compared with AdGFP (>80% of the islet cells were infected at 10 particle-forming units (pfu)/cell using AdRGDGFP vs. 7% after infection with AdGFP).More than 90% of the infected cells were insulin-producing cells. Significantly higher transgene expression was demonstrated after infection with AdRGDLuc compared with AdLuc at different titers. Analysis of the glucose-stimulated insulin response demonstrated better performance of PI transfected with AdRGDLuc at low titers (10 pfu/cell in order to achieve > 80% transfection efficiency) compared with AdLuc at high titers. Finally, long-term euglycemia (>250d) was observed in 89% of the animals that received PI infected with AdRGDLuc compared with none of the animals that received PI infected with AdLuc. The present study provides new information about the possibility of tropism modification of Ad vectors to increase the transfection efficiency and transgene expression to isolated PI. Incorporation of the RGD sequence in the HI loop of the fiber knob allows highly efficient transfection efficiency to nonhuman primate insulin-producing cells and adequate long-term function of the p-cell after transplantation.

Contemporary immunosuppression in renal transplantation

Over the past 3 decades, renal allograft survival has improved significantly as a result of the development of powerful immunosuppressive agents. Nevertheless, the overall half-life of renal allografts has increased marginally during that time period, owing to drug-related nephrotoxicity and chronic rejection. New immunosuppressive agents are being evaluated because of the need for a reduction in the dose of nephrotoxic calcineurin inhibitors and corticosteroids. Additional agents have demonstrated the ability to retard the onset of chronic rejection in preclinical transplant models. In concert with these efforts, approaches are in development to alleviate the ever increasing shortage of donor organs, including the as yet unrealized goals of successful and practical xenotransplantation and the bioartificial kidney. Further identification and development of novel agents that target the specific components of the allograft response will provide the key to the achievement of donor-specific tolerance, the "Holy Grail" of solid organ transplantation.

Human myeloid dendritic cells transduced with an adenoviral interleukin-10 gene construct inhibit human skin graft rejection in humanized NOD-scid chimeric mice

Human myeloid DC were generated from peripheral blood mononuclear cells by monocyte adhesion and subsequent culture with rhGM-CSF and rhIL-4. We transduced immature (day 5 of culture) myeloid DC with an E1-deleted replication-deficient adenoviral vector encoding the cytokine IL-10 (AdV IL-10) and a control adenovirus MX-17 (AdV MX 17). Human DC transduced with AdV IL-10 showed inhibition of the mixed leukocyte culture, reduced cell surface expression of co-stimulatory molecules (CD80/CD86) and were unable to produce the potent allo-stimulatory cytokine, interleukin-12. In order to test the in vivo properties of these cells a humanized immunodeficient mouse skin transplantation model was developed. Immunodeficient NOD-scid mice were engrafted with human skin, reconstituted via intraperitoneal injection with allogeneic mononuclear cells (MNC) mixed with 1 x 10(6) DC that were autologous to the skin donor and that had been transduced with either AdV IL-10 or AdV MX-17. Skin grafts were removed at day 7 and 14 after reconstitution and studied histologically for evidence of rejection. In animals that received DC modified with AdV IL-10 there was reduced skin graft rejection as characterized by reduced mononuclear cell infiltration and less dermo-epidermal junction destruction compared with those animals that received DC modified with the control virus alone. Injection of equivalent numbers of donor-derived fibroblasts transduced with AdV IL-10 were ineffective at modifying rejection of skin grafts. Immunosuppressive cytokine gene therapy targeting human DC is a novel means of inhibition of the alloimmune response.

Efficient naked plasmid cotransfection of lung grafts by extended lung/plasmid exposure time

BACKGROUND

Multiple gene cotransfection may be an effective strategy to modulate concurrent pathologic events after lung transplantation. We investigated in vivo naked plasmid lung cotransfection during cold preservation and the role of lung parenchyma/naked plasmid exposure time.

METHODS

F344 rats underwent left main bronchus instillation of pCF1-CAT (chloramphenicol acetyl transferase) (130 microg) +/- pCF1-beta-Gal (beta-galactosidase) (130 microg) in saline. Part Ia: 4 degrees C preservation versus cotransfection. Lung isografts (4 groups, n = 8) were stored after transfection for 1 (2 groups: one received only pCF1-CAT), 6, and 18 hours. Recipient sacrifice was after 48 hours. Part Ib: 4 degrees C preservation versus transgene expression. Rats were sacrificed 48 hours after transfection in a nontransplant setting (2 groups, n = 8; one received only pCF1-CAT). In a third group (n = 8) lungs were harvested 24 hours after transfection, stored for 18 hours, and recipients were sacrificed after 24 hours. The CAT and beta-Gal enzymatic-linked immunosorbent assays were performed. Part II: Lung/plasmid exposure time. In three groups (n = 6) after pCF1-CAT transfection the left main bronchus was not clamped, clamped for 10 minutes, or clamped for 1 hour. Sacrifice was after 48 hours.

RESULTS

Part Ia: Lung CAT protein was (in picograms per 100 microg of total protein): median, 42 (range, 25 to 95) after 1 hour (only CAT); 67 (19 to 296) after 1 hour, 32 (6 to 157) after 6 hours; and 9 (5 to 243) after 18 hours. Lung beta-Gal protein was (in picograms per 100 microg of total protein): median, 20 (range, 5 to 353) after 1 hour; 17 (6 to 157) after 6 hours; 4 (1 to 74) after 18 hours (1 hour versus 18 hours, p = 0.04 for both proteins). CAT and beta-Gal production were significantly correlated (p = 0.0001, r = 0.924). Part Ib: Lung CAT protein was (in picograms per 100 microg of total protein): median, 2 (range, 0.6 to 10) no transplant, only CAT; 7 (0.3 to 13) no transplant; 3 (0.9 to 14) transplant. Part II: Left lung CAT protein was (in picograms per 100 microg of total protein): median, 31 (range, 6 to 83) no clamp; 74 (25 to 430) 10 minutes of clamp; 111 (30 to 263) 1 hour of clamp. Right lung CAT protein was (in picograms per 100 microg of total protein): median, 0.06 (range, 0 to 0.9) no clamp; 1 (0 to 6) 10 minutes of clamp; 1 (0 to 18) 1 hour of clamp.

CONCLUSIONS

Efficient lung isograft endobronchial cotransfection results from using naked plasmid. Cold preservation affects transfection efficiency but not transgene expression. Lung parenchyma/naked plasmid exposure time determines transfection efficiency.

DNA-liposome versus adenoviral mediated gene transfer of transforming growth factor beta1 in vascularized cardiac allografts: differential sensitivity of CD4+ and CD8+ T cells to transforming growth factor beta1

We have developed a model of transforming growth factor (TGF)beta1 gene transfer into mouse vascularized cardiac allografts to study the use of gene transfer as an immunosuppressive therapy in transplantation. Donor hearts were perfused with either DNA-liposome complexes or adenoviral vectors that encode the active form of human TGFbeta1. DNA-liposome mediated transfection prolonged allograft survival in approximately two-thirds of transplant recipients, while adenoviral delivery of TGFbeta1 was not protective. Protective TGFbeta1 gene transfer was associated with reduced Th1 responses and an inhibition of the alloantibody isotype switch. The protective effects of TGFbeta1 gene transfer were overridden by exogenous interleukin-12 administration. Interestingly, alloreactive CD4+ and CD8+ cells exhibited distinct sensitivities to TGFbeta1 gene transfer: CD4+ Th1 function was abrogated by this modality, although CD8+ Th1 function was not. Transient depletion of recipient CD8+ cells markedly prolonged the survival of grafts transfected with either DNA-liposome complexes or adenoviral vectors. Transgene expression persisted for at least 60 days, and Th1 responses were not detectable until CD8+ T cells repopulated the periphery. However, long-term transfected allografts appeared to exhibit exacerbated fibrosis and neointimal development. These manifestations of chronic rejection were absent in long-term transfected isografts, suggesting that long-term expression of active TGFbeta1 alone is not sufficient to induce fibrosis of the grafts. Collectively, these data illustrate the utility of immunosuppressive gene therapy as a treatment for transplantation when combined with additional conditioning regimens. Further, they illustrate that alloreactive CD4+ and CD8+ cells may be differentially influenced by cytokine manipulation strategies.

Adenovirus-mediated gene therapy to liver grafts: successful gene transfer by donor pretreatment

BACKGROUND

We have previously shown excellent adenoviral (Ad) gene transfection to transplanted liver grafts with the clamp technique (CT) where viral vector was delivered ex vivo and trapped in cold preserved liver grafts. In this study, we adopted a new gene therapy approach to achieve early transgene expression by donor pretreatment with viral vector and compared the efficacy of these two methods by using Ad vector encoding enhanced green fluorescent protein (AdEGFP) marker gene.

METHODS

AdEGFP (1 x 10(9)plaque forming units) was delivered to the liver grafts by: (1) single intravenous injection to donor Lewis rats 48 hours before harvesting, (2) ex vivo cold infusion into the harvested liver with CT, or (3) a combination of both methods. Liver grafts were stored in University of Wisconsin solution at 4 degrees C for 18 hours and then orthotopically transplanted into syngeneic recipients, and the expression of EGFP was studied.

RESULTS

With intravenous pretreatment of donor liver grafts, EGFP-expressing cells were detected as early as 3 hours after transplant, and moderate expression was seen by 12 hours. In contrast, EGFP was not detected until 12 to 24 hours after transplant with CT. High levels of EGFP-producing cells were seen with each technique at 7 days ( approximately 30% transfection efficiency). A combination of both methods did not enhance infectivity. Liver preservation injury was comparable between groups.

CONCLUSIONS

Gene transfer by donor pretreatment with AdEGFP induces early and efficient gene transduction to liver grafts compared with back-table delivery with CT. This method is simple and provides early transgene expression in liver grafts that potentially could be used to deliver genes to decrease preservation injury or rejection.

Feasibility of CTLA4Ig gene delivery and expression in vivo using retrovirally transduced myeloid dendritic cells that induce alloantigen-specific T cell anergy in vitro

Dendritic cells (DC) are highly specialised, bone marrow (BM)-derived antigen-presenting cells (APC) that initiate and regulate immune responses. They provide costimulatory signals (in particular, CD40 and the CD28 ligands CD80 and CD86) necessary for naive T cell activation. Functional expression of CD80 and CD86 is blocked by the fusion protein cytotoxic T lymphocyte antigen 4-immunoglobulin (CTLA4Ig), that promotes tolerance induction in animals. Here, replicating mouse (B10; H2b) myeloid DC progenitors, were retrovirally transduced to express CTLA4Ig using the centrifugal enhancement method. Gene product was detected by immunocyto- or histochemistry. Maximal DC transduction efficiency was 62%. Compared with control, zeomycin-resistance gene (Zeo)-transduced DC, CTLA4Ig-expressing cells showed markedly impaired capacity to stimulate naive allogeneic (C3H; H2k) T cell proliferation and cytotoxic T lymphocyte (CTL) generation. Their ability to induce alloantigen-specific T cell hyporesponsiveness was reversed by exogenous IL-2 in secondary mixed leukocyte reactions (MLR). Following local (s.c.) transfer to allogeneic recipients, the genetically modified DC trafficked to T cell areas of draining lymphoid tissue, where transgene expression was detected. Ex vivo analysis of proliferative and CTL responses revealed donor-specific inhibition of alloimmune reactivity by the CTLA4Ig-transduced DC. This effect was associated with marked inhibition of interferon (IFN)-gamma production, but significant augmentation of IL-4 and IL-10 secretion. Thus, retroviral transduction of DC permits in vivo delivery of CTLA4Ig to the precise microenvironment where antigen (Ag) presentation occurs. Comparatively nonimmunogenic retroviral vectors, that allow permanent transgene expression in DC, and promote localized delivery of the immunosuppressive transgene product, promote immune deviation and Ag-specific T cell hyporesponsiveness.

Transduction of dendritic cell progenitors with a retroviral vector encoding viral interleukin-10 and enhanced green fluorescent protein allows purification of potentially tolerogenic antigen-presenting cells

BACKGROUND

Dendritic cells (DC) are important antigen-presenting cells that play critical roles in the initiation and modulation of immune responses. Genetic engineering of DC to express immunosuppressive molecules is a novel approach to the inhibition of allograft rejection. Retroviral delivery of viral interleukin (vIL)-10 to replicating myeloid DC progenitors (DCp) impairs their T-cell stimulatory capacity and promotes the induction of antigen-specific T-cell hyporesponsiveness. However, transduction efficiency with retroviral vectors is comparatively low. Enhanced green fluorescent protein (EGFP) is important both as a marker of gene transduction and for the selection of transduced cells. Our aims were to construct a retroviral vector encoding both vIL-10 and EGFP, to positively select transduced DC, and to assess the impact of these highly purified, vIL-10-secreting antigen-presenting cells on allogeneic T-cell responses.

METHODS

DCp propagated from bone marrow of C57BL10 (H2b) mice in granulocyte-macrophage colony-stimulating factor (GM-CSF)+IL-4 were transduced with a retroviral vector encoding both vIL-10 and EGFP by centrifugal enhancement. Gene transfer efficiency was determined by flow cytometry. Transduced cells were flow sorted, and vIL-10 secretion was quantified by ELISA. DC function was assessed by the ability of the cells to induce naive allogeneic (C3H; H2k) T-cell proliferation and cytotoxic T lymphocyte generation.

RESULTS

Retrovirally transduced DC expressed both vIL-10 and EGFP gene products. Approximately 20% of unsorted cells expressed EGFP, as determined by flow cytometry. vIL-10 was produced at a mean rate of 31 ng/40 hr/10(6) cells. After sorting, the incidence of EGFP+ DC was increased dramatically to at least 95%, and the production of vIL-10 was increased approximately three- to fourfold, to a mean of 107 ng/40 hr/10(6) cells. These highly purified, vIL-10-secreting DC exhibited markedly diminished capacity to induce allogeneic T-cell proliferative and cytotoxic responses.

CONCLUSIONS

DCp retrovirally transduced to express both vIL-10 and EGFP can be rapidly identified and sorted to high levels of purity. The availability of highly enriched preparations of vIL-10-transduced DC facilitates studies of their immunoregulatory function and may enhance their therapeutic potential in transplantation or autoimmune disease.