Immunosuppression overcomes insulin- and vector-specific immune responses that limit efficacy of AAV2/8-mediated insulin gene therapy in NOD mice.

We report the restoration of euglycaemia in chemically induced diabetic C57BL/6 mice and spontaneously diabetic Non Obese Diabetic (NOD) mice by intravenous systemic administration of a single-stranded adeno-associated virus (ssAAV2/8) codon optimised (co) vector encoding furin cleavable human proinsulin under a liver-specific promoter. There were no immunological barriers to efficacy of insulin gene therapy in chemically induced C57BL/6 mice, which enjoyed long-lasting correction of hyperglycaemia after therapy, up to 250 days. Euglycaemia was also restored in spontaneously diabetic NOD mice, although these mice required a 7-10-fold higher dose of vector to achieve similar efficacy as the C57BL/6 mice and the immunodeficient NODscid mice. We detected CD8+ T cell reactivity to insulin and mild inflammatory infiltration in the livers of gene therapy recipient NOD mice, neither of which were observed in the treated C57BL/6 mice. Efficacy of the gene therapy in NOD mice was partially improved by targeting the immune system with anti-CD4 antibody treatment, while transfer of NOD mouse AAV2/8-reactive serum to recipients prevented successful restoration of euglycaemia in AAV2/8-HLP-hINSco-treated NODscid mice. Our data indicate that both immune cells and antibodies form a barrier to successful restoration of euglycaemia in autoimmune diabetic recipient mice with insulin gene therapy, but that this barrier can be overcome by increasing the dose of vector and by suppressing immune responses.

Development of a liver-specific Tet-off AAV8 vector for improved safety of insulin gene therapy for diabetes.

BACKGROUND: Diabetes mellitus is caused by a partial or complete lack of insulin production in the body. We have previously shown that a single injection of an adeno-associated virus serotype 8 (AAV8) vector carrying a modified and codon optimized human insulin gene induced hepatic production of insulin and corrected streptozotocin (STZ)-induced diabetes in mice for more than 1 year. Insulin production was constitutive, analogous to long-acting insulin therapy. METHODS: We have developed a single AAV8 vector with a Tet-Off regulatable system as a safety mechanism to turn off insulin secretion should hypoglycaemia develop in vector-treated diabetic mice. We first transfected HepG2 cells or freshly isolated rat hepatocytes in vitro with the Tet-Off system (pAAV-Tetoffbidir -Alb-luc) regulating a luciferase reporter gene. We subsequently incorporated a furin-cleavable codon-optimised human proinsulin cDNA into pAAV-Tetoffbidir backbone to form the doxycycline inducible pAAV-Tetoffbidir -Alb-hINSco. RESULTS: Using STZ-induced diabetic mice, we were able to switch off insulin secretion repeatedly with doxycycline administration, and showed full restoration of insulin secretion on withdrawing doxycycline. CONCLUSIONS: The present study provides proof of concept that, under circumstances when inappropriate basal insulin secretion is a safety concern, insulin secretion from AAV8 gene therapy can be turned off reversibly with doxycycline.

Promoter optimisation of lentiviral vectors for efficient insulin gene expression in canine mesenchymal stromal cells: potential surrogate beta cells.

BACKGROUND: The lack of an ideal cell type that can be easily acquired, modified to produce insulin, and re-implanted has been a limitation for ex vivo insulin gene therapy. Canine diabetes is currently treated with human insulin and is a good model for human diabetes. Mesenchymal stromal cells (MSCs) are a promising candidate cell type for gene therapy. In the present study, we optimised insulin production using lentiviral transduced canine MSCs (cMSCs), aiming to evaluate their ability for use as surrogate beta cells. METHODS: Canine MSCs were derived from bone marrow and validated by measuring the expression of MSC lineage specific markers. Lentivirus vectors encoding the proinsulin gene (with or without a Kozak sequence) under the control of spleen focus forming virus, cytomegalovirus, elongation factor 1α and simian virus 40 promotors were generated and used to transduce primary cMSCs and a hepatocyte cell line. The insulin-producing capacity of transduced primary cMSCs was assessed by measuring the concentration of C-peptide produced. RESULTS: Primary cMSC could be readily expanded in culture and efficiently transduced using lentiviral vectors encoding proinsulin. Increasing the multiplicity of infection from 3 to 20 led to an increase in C-peptide secretion (from 1700 to 4000 pmol/l). The spleen focus forming virus promoter conferred the strongest transcriptional ability. CONCLUSIONS: The results of the present study suggest that optimised lentiviral transduction of the insulin gene into primary cMSCs renders these cells capable of secreting insulin over both the short- and long-term, in sufficient quantities in vitro to support their potential use in insulin gene therapy.

Some observations on prope tolerance.

PURPOSE OF REVIEW: To outline the rationale of powerful depleting induction therapy with alemtuzumab and minimal maintenance immunosuppression after organ transplantation. RECENT FINDINGS: The original observations in principle have been confirmed by many independent centres. SUMMARY: Follow-up of the 'prope tolerance' protocol has confirmed a low incidence of rejection, infection and post transplant lymphoproliferative disorder (PTLD). Especially, encouraging results were obtained in African-Americans. There were few side effects and the regimen was well tolerated by patients. Treg cells were observed in the circulation, which could be an important factor in the mechanisms of graft acceptance using a prope tolerance regimen. There was a considerable reduction in the costs of the transplantation procedure. It is suggested that this minimalisation of maintenance immunosuppression is the best therapy currently available that we can offer to our patients.

Organ transplantation has come of age.

Organ transplantation started in the mid-1950s with a kidney transplant between identical twins, demonstrating the surgical technique could provide successful therapy. The immunological barrier to be overcome, however proved to be far more difficult to deal with. The introduction of immunosuppressive agents produced some success but it was not until Cyclosporin became available in the 1980s that results became sufficiently good for widespread acceptance and rapid development of organ grafting. Now with more powerful and selective agents, although there is still much room for improvement in immunosuppression, one of the main problems in organ transplantation is a result of its success, namely a shortage of organ donors. In this review, I summarise these matters.

Modification of a Constitutive to Glucose-Responsive Liver-Specific Promoter Resulted in Increased Efficacy of Adeno-Associated Virus Serotype 8-Insulin Gene Therapy of Diabetic Mice.

We have previously used a hepatotropic adeno-associated viral (AAV) vector with a modified human insulin gene to treat diabetic mice. The HLP (hybrid liver-specific promoter) used was constitutively active and non-responsive to glucose. In this study, we examined the effects of addition of glucose responsive elements (R3G) and incorporation of a 3' albumin enhancer (3'iALB) on insulin expression. In comparison with the original promoter, glucose responsiveness was only observed in the modified promoters in vitro with a 36 h lag time before the peak expression. A 50% decrease in the number of viral particles at 5 × 109 vector genome (vg)/mouse was required by AAV8-R3GHLP-hINSco to reduce the blood sugar level to near normoglycemia when compared to the original AAV8-HLP-hINSco that needed 1 × 1010 vg/mouse. The further inclusion of an 860 base-pairs 3'iALB enhancer component in the 3' untranslated region increased the in vitro gene expression significantly but this increase was not observed when the packaged virus was systemically injected in vivo. The addition of R3G to the HLP promoter in the AAV8-human insulin vector increased the insulin expression and secretion, thereby lowering the required dosage for basal insulin treatment. This in turn reduces the risk of liver toxicity and cost of vector production.

Transplantation: current developments and future directions.

An historical overview of transplantation is presented in which the medical, legal, ethical, physiological and immunological issues are reviewed in the context of the definition of death. A discussion of the benefits of minimal immunosuppression is presented as an attractive proposal compared with conventional immunosuppression. Prope tolerance was first used with the powerful lympholytic monoclonal antibody Campath 1H. The five-year follow-up of the first renal transplant patients treated with Campath induction and maintenance low-dose cyclosporine has been satisfactory, thus indicating considerable experience of the use of induction followed by steroid-free minimal maintenance immunosuppression. It appears likely that this will become a favoured method of recipient management.

Transplantation: current developments and future directions.

Organ transplantation has emerged from a few sporadic failed attempts to one of the most successful branches of surgery in the course of 50 years since the first identical twin transplant was performed in Boston. In this article I will attempt to portray the historical background and the recent shift of attitude regarding immunosuppression for solid organ transplants. Previously a culture of increasing immunosuppression and incorporating new and powerful agents into an already effective regimen has resulted in over-immunosuppression and more sepsis without an improvement in long-term graft survival. Over-immunosuppression is probably detrimental in preventing the natural control and "switching off" of the immune response as a vital function of the immune system and as a consequence any attempts to produce immunological tolerance are likely to be impaired by excessive immunosuppressive regimens. I will therefore,, explain and advocate a minimalistic approach to immunosuppression, a background on tissue typing and a summary of clinical results. Now that the procedure is perceived worldwide as an excellent therapy for previously doomed patients, there is an increasing mismatch between the number of donor organs available and patients in need of a graft. This has produced ethical dilemmas previously unknown in the medical profession. These are extremely important considerations as they can undermine the Hippocratic tradition and the high ethical standing previously enjoyed by our profession.

[Allogenic islet transplantation on the rat liver after allogenic nonparenchymal cells injection in the thymus]. / Alotransplante de ilhotas de Langerhans no fígado de ratos submetidos a manipulação tímica com células não-parenquimatosas.

BACKGROUND: [corrected] The major indication for pancreas or islet transplantation is diabetes mellitus type I. This process has to supply the insulin necessity keeping glucose under control AIM: We studied allogenic islet transplantation on the rat liver, Wistar (RT1u) to Lewis (RT1(1)) as a recipient. Control group (n = 8) and nonparenchymal cell group (n = 8) respectively with injection of Hanks solution and nonparenchymal cells in the thymus before islet transplantation. MATERIAL AND METHODS: With the method of isolation and purification of the islets we obtained both in the control group 3.637 +/-783,3 islets with purity of 85 +/- 3,52% and nonparenchymal cell group 3.270 +/- 770 islets with purity of 84,25 +/- 2,76%. The nonparenchymal cells were retrieved from the liver and we obtained 2 x 106 cells. Diabetes was induced by i.v. streptozotocin RESULTS: Control group the transplantation of 3.637 +/- 783,3 islets in the rat liver normalized glucose test, 7,21 +/- 0,57 mmol/L in the 2nd postoperative day. Acute rejection came in the 6th postoperative day with significantly increase of glucose test in nonparenchymal cell group, the transplantation of 3.270 +/- 770 islets in the rat liver, almost normalized the glucose test was 17,95 +/- 5,33 mmol/L in the 2nd postoperative day. From the 4th postoperative day to 10th postoperative day. The glucose test increase significantly showing an early acute rejection CONCLUSION: The injection of nonparenchymal cells in the thymus before allogenic islet transplantation in the rat liver lead to an early acute rejection.

Correction of Murine Diabetic Hyperglycaemia With A Single Systemic Administration of An AAV2/8 Vector Containing A Novel Codon Optimized Human Insulin Gene.

We report the correction of hyperglycemia of STZ induced diabetic mice using one intravenous systemic administration of a single stranded serotype 8 pseudotyped adeno-associated virus (ssAAV2/8) vector encoding the human proinsulin gene under a constitutive liver specific promoter. In vivo dose titration experiments were carried out and we identified an optimal range that achieved maintenance of euglycaemia or a mild diabetic condition for at least 9 months and ongoing to beyond 1 year for some animals, accompanied by human C-peptide secretion and weight gain. Further DNA codon optimization of the insulin gene construct resulted in approximately 3-10 times more human C-peptide secreted in the blood of codon optimized treated animals thereby reducing the number of vector particles required to achieve the same extent of reduction in blood glucose levels as the non-codon optimized vector. The constitutive secretion of insulin achieved with a single administration of the vector could be of therapeutic value for some diabetic patients.

Possible advantages of stem cell transfusion into the peripheral circulation, as opposed to localized transplantation in situ.

Studies to date have overlooked the possible limitations of transplanting stem cells locally (in situ), directly at the site of tissue or organ damage. This approach is contrary to the intrinsic physiological process of tissue and organ regeneration in vivo, which is thought to involve the activation of stem cells resident within the transplanted tissues or their mobilization from ectopic sites, in particular the bone marrow. Signaling pathways and other molecular processes within stem cells transplanted in situ may not be primed to achieve optimal tissue regeneration and may even be confused by the sudden rapid transition in the cellular microenvironment encountered during transplantation. Moreover, there is a risk of the transplanted cells giving rise to undesired lineages at the transplantation site. A novel alternative would be to transfuse stem cells into the peripheral blood circulation, followed by induced homing to the site of tissue damage. This could better replicate the natural physiological process of tissue repair in vivo. Transfusion into the peripheral blood circulation could be a strategy to augment the inadequate mobilization of endogenous adult stem cells from ectopic sites for tissue repair, which may be the case for older patients. The transfused stem cells can then be induced to home in on a damaged tissue or organ, via the controlled release of specific cytokines or chemokines (i.e., stromal cell derived factor-1) emanating from that particular tissue or organ. The gradient of released cytokines/ chemokines within the peripheral blood circulation would then direct the chemotactic migration and homing of the transfused stem cells to the target tissue or organ.

Randomized trial of Alemtuzumab for prevention of graft rejection and preservation of renal function after kidney transplantation.

BACKGROUND: A randomized, multicenter, controlled trial was undertaken to evaluate the safety and efficacy of Alemtuzumab, a powerful lytic agent for both T and B lymphocytes, in the prophylaxis of rejection in renal transplantation (RTx). METHODS: Thirty patients were randomized to receive Alemtuzumab together with low-dose cyclosporine (CsA) monotherapy (CAMPATH, n = 20) or to full doses of CsA with azathioprine and corticosteroids (Standard, n = 10). CsA was administered at doses to achieve whole-blood trough CsA levels of 90 to 110 ng/mL and 180 to 225 ng/mL in CAMPATH and Standard groups, respectively. RESULTS: Per protocol, CsA trough levels were lower in patients assigned to CAMPATH post-RTx (median trough level of 119 vs. 166 ng/mL at 6 months, CAMPATH vs. Standard; 95% confidence interval, -92 to -34). At 6 months post-RTx, serum creatinine, graft and patient survivals, incidence of biopsy proven acute rejection (25% vs. 20%, CAMPATH vs. Standard), overall treatment failure, and severe and moderate infections were comparable. Whereas all patients receiving Standard therapy required maintenance corticosteroids at 6 months, of the 17 of 20 patients with functioning grafts in CAMPATH, 15 (88%, 95% confidence interval, 53%-97%) were steroid free. CONCLUSION: These results suggest that Alemtuzumab is an effective induction agent that permits low-dose steroid-free immunosuppression in RTx.

Insulin-secreting cells derived from stem cells: clinical perspectives, hypes and hopes.

Diabetes is a degenerative disease that results from the selective destruction of pancreatic beta-cells. These cells are responsible for insulin production and secretion in response to increases in circulating concentrations of nutrients, such as glucose, fatty acids and amino acids. This degenerative disease can be treated by the transplantation of differentiated islets obtained from cadaveric donors, according to a new surgical intervention developed as Edmonton protocol. Compared to the classical double transplant kidney-pancreas, this new protocol presents several advantages, concerning to the nature of the implant, immunosuppressive drug regime and the surgical procedure itself. However, the main problem to face in any islet transplantation program is the scarcity of donor pancreases and the low yield of islets isolated (very often around 50%) from each pancreas. Nevertheless, transplanted patients presented no adverse effects and no progression of diabetic complications. In the search of new cell sources for replacement trials, stem cells from embryonic and adult origins represent a key alternative. In order to become a realistic clinical issue transplantation of insulin-producing cells derived from stem cells, it needs to overcome multiple experimental obstacles. The first one is to develop a protocol that may allow obtaining a pure population of functional insulin-secreting cells as close as possible to the pancreatic beta-cell. The second problem should concern to the transplantation itself, considering issues related to immune rejection, tumour formation, site for implant, implant survival, and biosafety mechanisms. Although transplantation of bioengineered cells is still far in time, experience accumulated in islet transplantation protocols and in experiments with appropriate animal models will give more likely the clues to address this question in the future.

[Alogenic islet transplantation on the rat liver after alogenic dendritic cells injection in the thymus]. / Alotransplante de ilhotas de Langerhans no fígado de ratos submetidos a manipulação tímica com células dendríticas.

BACKGROUND: The major indication for pancreas or islet transplantation is diabetes mellitus type I. This process has to supply the insulin necessity keeping glucose under control. AIM: We studied alogenic islet transplantation on the rat liver, Wistar (RT1u) to Lewis (RT1(1)) as a recipient. Control group (n = 8) and dendritic cell group (n = 9) respectively with injection of Hanks solution and dendritic cells in the thymus before islet transplantation. MATERIAL AND METHODS: With the method of isolation and purification of the islets we obtained both in the control group 3637 +/- 783,3 islets with purity of 85 +/- 3,52% and dendritic cell group 3268 +/- 378 islets with purity of 87 +/- 4,47%. The dendritic cells were retrieved from the spleen and we obtained 3,34 x 105+/-1,16 cells. Diabetes was induced by i.v. streptozotocin. RESULTS: Control group the transplantation of 3637 +/- 783,3 islets in the rat liver normalized glucose test, 7,21 +/- 0,57 mmol/L in the second post-operative day. Acute rejection came in the 10 postoperative day with significantly increase of glucose test. Dendritic cell group, the transplantation of 3258 +/- 378 islets in the rat liver, normalized the glucose test was 9,3 +/- 2,85 mmoL/L in the second postoperative day. From the 4th postoperative day to 10th postoperative day the glucose test increase significantly showing an early acute rejection. CONCLUSION: The injection of dendritic cells in the thymus before alogenic islet transplantation in the rat liver lead to an early acute rejection.

Characterization of Insulin-Secreting Porcine Bone Marrow Stromal Cells Ex Vivo and Autologous Cell Therapy In Vivo.

Cell therapy could potentially meet the need for pancreas and islet transplantations in diabetes mellitus that far exceeds the number of available donors. Bone marrow stromal cells are widely used in clinical trials mainly for their immunomodulatory effects with a record of safety. However, less focus has been paid to developing these cells for insulin secretion by transfection. Although murine models of diabetes have been extensively used in gene and cell therapy research, few studies have shown efficacy in large preclinical animal models. Here we report optimized conditions for ex vivo expansion and characterization of porcine bone marrow stromal cells and their permissive expression of a transfected insulin gene. Our data show that these cells resemble human bone marrow stromal cells in surface antigen expression, are homogeneous, and can be reproducibly isolated from outbred Yorkshire-Landrace pigs. Porcine bone marrow stromal cells were efficiently expanded in vitro to >10(10) cells from 20 ml of bone marrow and remained karyotypically normal during expansion. These cells were electroporated with an insulin expression plasmid vector with high efficiency and viability, and secreted human insulin and C-peptide indicating appropriate processing of proinsulin. We showed that autologous insulin-secreting bone marrow stromal cells implanted and engrafted in the liver of a streptozotocin-diabetic pig that modeled type 1 diabetes resulted in partial, but significant, improvement in hyperglycemia that could not be ascribed to regeneration of endogenous ß-cells. Glucose-stimulated insulin secretion in vivo from implanted cells in the treated pig was documented by a rise in serum human C-peptide levels during intravenous glucose tolerance tests. Compared to a sham-treated control pig, this resulted in significantly reduced fasting hyperglycemia, a slower rise in serum fructosamine, and prevented weight loss. Taken together, this study suggests that bone marrow stromal cells merit further development as autologous cell therapy for diabetes.

Long-term kidney graft survival by delayed T cell ablative treatment in rhesus monkeys.

BACKGROUND: Tolerance to organ allografts in primates including man has been elusive, although in rodents and pigs tolerance can be achieved to organ allografts with relatively short courses of immunosuppressive treatment. In all varieties of graft acceptance that do not require full-dose maintenance immunosuppression, immunological engagement of donor and recipient and an early unstable period have been observed. On the basis of the hypothesis that elimination of aggressive T cell function should tip the balance in favor of an operationally tolerant state, experiments have been performed in monkeys allowing recipient-donor interaction before T-cell ablation and a short course of immunosuppression. METHODS: Rhesus monkeys received an allogeneic kidney graft from a MHC-mismatched donor. The animals either received anti-CD3 immunotoxin (FN18-CRM9) alone, started 2 days after transplantation, or in combination with a short course of cyclosporine (CsA) and/or rapamycin (RAPA), started at 5 days after transplantation. Kidney function was followed by monitoring serum creatinine levels and regular biopsies. Humoral and cellular antidonor immunity was tested in vitro before and at several time points after transplantation. RESULTS: Graft survival of monkeys that received CsA alone (mean survival time (MST)=29.3) was significantly prolonged compared with the controls (MST=6). FN18-CRM9 treatment alone also resulted in prolonged graft survival (MST=29.4). The combined treatment of FN18-CRM9 and CsA and/or RAPA resulted in prolonged graft survival after all immunosuppression was stopped (MST=207.8). CONCLUSIONS: It seems feasible to postpone immunosuppression posttransplantation and yet prevent allograft rejection without the need of permanent immunosuppression.

Immunosupression, tolerance and cell transplantation.

This paper gives a brief overview of part of a life's work in the field of transplantation science, that formed the basis of a lecture on the occasion of the Prince Mahidol Award in Bangkok in January 2003.