Prevention of autoimmune recurrence and rejection by adenovirus-mediated CTLA4Ig gene transfer to the pancreatic graft in BB rat

Pancreas-specific immune-related adverse events in patients with lung cancer: a case series study

Immune-related adverse events (irAEs) are one of the key concerns in cancer patients treated with immune checkpoint inhibitors (ICIs). Among the various irAEs, pancreas-specific irAE is a rare but special one with a variety of manifestations, such as pancreatic enzymes elevation, pancreatitis as well as diabetes. The current study reported 22 pancreas-specific irAEs in 21 patients with lung cancer, including pancreatic injury in 13 patients, pancreatitis in four patients and diabetes mellitus in five patients.

Impact of GAD65 and IA2 autoantibodies on islet allograft survival

Introduction

Islet transplantation (ITx) shows promise in treating T1D, but the role of islet autoantibodies on graft survival has not been clearly elucidated. We aimed to analyze the effect of GAD65 and IA2 autoantibody status on graft survival and attainment of insulin independence in subjects with T1D who underwent ITx.

Method

We conducted a retrospective cohort study on 47 ITx recipients from 2000 to 2018. Islet infusion was performed via intrahepatic portal (n=44) or onto the omentum via laparoscopic approach (n=3). Immunosuppression involved anti-IL2 receptor antibody, anti-TNF, and dual combinations of sirolimus, tacrolimus, or mycophenolate mofetil (Edmonton-like) in 38 subjects (80.9%). T-cell depletion induction with Edmonton-like maintenance was used in 9 subjects (19%). GAD65 and IA2 autoantibodies were assessed pre-transplant and post-transplant (monthly) until graft failure, and categorized as persistently negative, persistently positive, or seroconverters. Graft survival was analyzed using U-Mann-Whitney test, and Quade's nonparametric ANCOVA adjusted for confounders. Kaplan-Meier and Log-Rank tests were employed to analyze attainment of insulin independence. P value <0.05 indicated statistical significance.

Results

ITx recipients with persistent autoantibody negativity (n = 21) showed longer graft function (98 [61 - 182] months) than those with persistent autoantibody positivity (n = 18; 38 [13 - 163] months), even after adjusting for immunosuppressive induction protocol (P = 0.027). Seroconverters (n=8) had a median graft survival time of 73 (7.7 - 167) months, which did not significantly differ from the other 2 groups. Subjects with persistently single antibody positivity to GAD65 (n = 8) had shorter graft survival compared to negative islet autoantibody (GAD65/IA2) subjects (n = 21; P = 0.016). Time of graft survival did not differ in subjects with single antibody positivity to IA2. The proportion of insulin independence attainment was similar irrespective of autoantibody status.

Conclusion

The persistence of islet autoantibodies, as markers of islet autoimmunity, may represent an underappreciated contributing factor to the failure of transplanted β cells. Whether induction with T-cell depletion may lead to improved graft survival, independent of islet autoantibody status, could not be evaluated in our cohort. Larger prospective studies are needed to further address the role of islet autoantibody status on islet graft survival.

Immune-related pancreatitis secondary to nivolumab in a patient with recurrent lung adenocarcinoma: A case report

Immune checkpoint inhibitor is a verified standard of care as a second-line chemotherapy for non-small cell lung cancer. Management of immune-related adverse effects (irAEs) is crucial for ensuring patient safety. However, less frequent irAEs may result in complications. Here, we report a patient with recurrent lung adenocarcinoma who was treated with nivolumab and developed immune-related pancreatitis. A 66-year-old Japanese female with recurrent lung adenocarcinoma and metastatic lymph nodes presented with anorexia, vomiting, and back pain on day 18 of two cycles of nivolumab. Laboratory data demonstrated a grade 3 elevation of serum amylase and lipase levels. Initially, no abnormality could be detected on computed tomography (CT), magnetic resonance cholangiopancreatography (MRCP), or the Gallium scan. The patient was treated with high-dose prednisone, resulting in gradual improvement of symptoms and laboratory data. A follow-up MRCP revealed a swollen pancreas and pancreatic inflammation. Immune-related pancreatitis is a rare type of nivolumab-induced irAE that shows no significant changes on radiologic imaging, except for a swollen pancreas on CT, and can be suppressed using high-dose prednisone.

Cellular islet autoimmunity associates with clinical outcome of islet cell transplantation

Background

Islet cell transplantation can cure type 1 diabetes (T1D), but only a minority of recipients remains insulin–independent in the following years. We tested the hypothesis that allograft rejection and recurrent autoimmunity contribute to this progressive loss of islet allograft function.

Methodology/Principal Findings

Twenty-one T1D patients received cultured islet cell grafts prepared from multiple donors and transplanted under anti-thymocyte globulin (ATG) induction and tacrolimus plus mycophenolate mofetil (MMF) maintenance immunosuppression. Immunity against auto- and alloantigens was measured before and during one year after transplantation. Cellular auto- and alloreactivity was assessed by lymphocyte stimulation tests against autoantigens and cytotoxic T lymphocyte precursor assays, respectively. Humoral reactivity was measured by auto- and alloantibodies. Clinical outcome parameters - including time until insulin independence, insulin independence at one year, and C-peptide levels over one year- remained blinded until their correlation with immunological parameters. All patients showed significant improvement of metabolic control and 13 out of 21 became insulin-independent. Multivariate analyses showed that presence of cellular autoimmunity before and after transplantation is associated with delayed insulin-independence (p = 0.001 and p = 0.01, respectively) and lower circulating C-peptide levels during the first year after transplantation (p = 0.002 and p = 0.02, respectively). Seven out of eight patients without pre-existent T-cell autoreactivity became insulin-independent, versus none of the four patients reactive to both islet autoantigens GAD and IA-2 before transplantation. Autoantibody levels and cellular alloreactivity had no significant association with outcome.

Conclusions/Significance

In this cohort study, cellular islet-specific autoimmunity associates with clinical outcome of islet cell transplantation under ATG-tacrolimus-MMF immunosuppression. Tailored immunotherapy targeting cellular islet autoreactivity may be required. Monitoring cellular immune reactivity can be useful to identify factors influencing graft survival and to assess efficacy of immunosuppression.

Trial Registration

Clinicaltrials.gov NCT00623610

Genetic modification of cells for transplantation

Progress in gene therapy has produced promising results that translate experimental research into clinical treatment. Gene modification has been extensively employed in cell transplantation. The main barrier is an effective gene delivery system. Several viral vectors were utilized in end-stage differentiated cells. Recently, successful applications were described with adenovirus-associated vectors. As an alternative, embryonic stem cell- and stem cell-like systems were established for generation of tissue-specified gene-modified cells. Owing to the feasibility for genetic manipulations and the self-renewing potency of these cells they can be used in a way enabling large-scale in vitro production. This approach offers the establishment of in vitro cell culture systems that will deliver sufficient amounts of highly purified, immunoautologous cells suitable for application in regenerative medicine. In this review, the current technology of gene delivery systems to cells is recapitulated and the latest developments for cell transplantation are discussed.

Ex vivo gene transfer of viral interleukin-10 to BB rat islets: no protection after transplantation to diabetic BB rats

Allogeneic and autoimmune islet destruction limits the success of islet transplantation in autoimmune diabetic patients. This study was designed to investigate whether ex vivo gene transfer of viral interleukin-10 (vIL-10) protects BioBreeding (BB) rat islets from autoimmune destruction after transplantation into diabetic BB recipients. Islets were transduced with adenoviral constructs (Ad) expressing the enhanced green fluorescent protein (eGFP), α-1 antitrypsin (AAT) or vIL-10. Transduction efficiency was demonstrated by eGFP-positive cells and vIL-10 production. Islet function was determined in vitro by measuring insulin content and insulin secretion and in vivo by grafting AdvIL-10-transduced islets into syngeneic streptozotocin (SZ)-diabetic, congenic Lewis (LEW.1 W) rats. Finally, gene-modified BB rat islets were grafted into autoimmune diabetic BB rats. Ad-transduction efficiency of islets increased with virus titre and did not interfere with insulin content and insulin secretion. Ad-transduction did not induce Fas on islet cells. AdvIL-10-transduced LEW.1 W rat islets survived permanently in SZ-diabetic LEW.1 W rats. In diabetic BB rats AdvIL-10-transduced BB rat islets were rapidly destroyed. Prolongation of islet culture prior to transplantation improved the survival of gene-modified islets in BB rats. Several genes including those coding for chemokines and other peptides associated with inflammation were down-regulated in islets after prolonged culture, possibly contributing to improved islet graft function in vivo. Islets transduced ex vivo with vIL-10 are principally able to cure SZ-diabetic rats. Autoimmune islet destruction in diabetic BB rats is not prevented by ex vivo vIL-10 gene transfer to grafted islets. Graft survival in autoimmune diabetic rats may be enhanced by improvements in culture conditions prior to transplantation.

Lessons on autoimmune diabetes from animal models

T1DM (Type I diabetes mellitus) results from selective destruction of the insulin-producing beta-cells of the pancreas by the immune system, and is characterized by hyperglycaemia and vascular complications arising from suboptimal control of blood glucose levels. The discovery of animal models of T1DM in the late 1970s and early 1980s, particularly the NOD (non-obese diabetic) mouse and the BB (BioBreeding) diabetes-prone rat, had a fundamental impact on our ability to understand the genetics, aetiology and pathogenesis of this disease. NOD and BB diabetes-prone rats spontaneously develop a form of diabetes that closely resembles the human counterpart. Early studies of these animals quickly led to the realization that T1DM is caused by autoreactive T-lymphocytes and revealed that the development of T1DM is controlled by numerous polymorphic genetic elements that are scattered throughout the genome. The development of transgenic and gene-targeting technologies during the 1980s allowed the generation of models of T1DM of reduced genetic and pathogenic complexity, and a more detailed understanding of the immunogenetics of T1DM. In this review, we summarize the contribution of studies in animal models of T1DM to our current understanding of four fundamental aspects of T1DM: (i) the nature of genetic elements affording T1DM susceptibility or resistance; (ii) the mechanisms underlying the development and recruitment of pathogenic autoreactive T-cells; (iii) the identity of islet antigens that contribute to the initiation and/or progression of islet inflammation and beta-cell destruction; and (iv) the design of avenues for therapeutic intervention that are rooted in the knowledge gained from studies of animal models. Development of new animal models will ensure continued progress in these four areas.

Avenues for immunomodulation and graft protection by gene therapy in transplantation

Organ transplantation represents the only definitive therapy for many causes of end-organ failure. However, the universal success of this therapy is limited by chronic allograft rejection, the side effects of chronic immunosuppressive therapy, and a severe shortage of donor organs. Presently, the success of solid-organ transplantation depends on the continuous administration of toxic and nonspecific immunosuppressive agents, therapies that present risks for opportunistic infection, malignancy, and a variety of agent-specific side effects. To promote the use of transplantation with limited risk of long-term sequelae, three dominant research challenges emerge: (i) elimination of the need for exogenous immunosuppression by immunological tolerance induction; (ii) prevention of chronic rejection/graft dysfunction; and (iii) expansion of available organs for transplantation. Gene therapy may provide significant advances and solutions in each of these areas. Rejection of the graft in the immediate post-transplant period has been attacked through the transfer of immunomodulatory molecules in addition to tolerance inducing approaches. Chronic graft rejection may be similarly addressed through permanent tolerance induction or alternatively through the introduction of molecules to resist chronic graft damage. Genetic manipulation of stem cells may ultimately produce transgenic animals to serve as tissue donors to overcome the limited donor organ supply. This review will highlight ongoing developments in the translation of gene therapy approaches to the challenges inherent in transplantation.

Intrapatient dose escalation of anti-CTLA-4 antibody in patients with metastatic melanoma

We previously reported our experience in treating 56 patients with metastatic melanoma using a human anti-cytotoxic T-lymphocyte antigen 4 (CTLA-4) antibody. Durable tumor regressions were seen that correlated with the induction of autoimmune toxicities. In this study, we treated 46 additional patients using an intrapatient dose escalation schema to test whether higher doses of anti-CTLA-4 antibody would induce increased autoimmunity and concomitant tumor regression. Twenty-three patients started anti-CTLA-4 antibody administration at 3 mg/kg and 23 patients started treatment at 5 mg/kg, receiving doses every 3 weeks. Patients were dose-escalated every other dose to a maximum of 9 mg/kg or until objective clinical responses or grade III/IV autoimmune toxicity were seen. Escalating doses of antibody resulted in proportionally higher plasma concentrations. Sixteen patients (35%) experienced a grade III/IV autoimmune toxicity. Five patients (11%) achieved an objective clinical response. Two of the responses are ongoing at 13 and 16 months, respectively. Flow cytometric analysis of peripheral blood revealed significant increases in both T-cell surface markers of activation and memory phenotype. Thus, higher serum levels and prolonged administration of anti-CTLA-4 antibody resulted in a trend toward a greater incidence of grade III/IV autoimmune toxicity than previously reported, but did not seem to increase objective response rates.

Gene therapy for type 1 diabetes

The most intensively studied autoimmune disorder, type 1 diabetes mellitus (DM1), has attracted perhaps the greatest interest for gene-based therapeutic and prophylactic interventions. The final clinical manifestation of this immunologically and genetically complex disease, the absence of insulin, is the major starting point for almost all the gene therapy modalities attempted to date. Insulin replacement by transplantation of islets of Langerhans or surrogate beta cells is the obvious choice, but the allogeneic nature of the transplants activates potent antidonor immunoreactivity necessitating gene and cell-based immunosuppressive strategies as an alternative to the toxic pharmacologic immunosuppressives indicated for classic solid organ transplants. Accumulating knowledge of the cellular mechanisms involved in onset, however, have yielded promising tolerance induction prophylactic approaches using genes and cells. Despite the early successes in a number of animal models, the true test of efficacy in humans remains to be demonstrated.

Viral IL-10-mediated immune regulation in pancreatic islet transplantation

Protection of transplanted pancreatic islet grafts in recipients with autoimmune diabetes depends on the suppression of autoimmune recurrence and allogeneic rejection. The aim of this study was to investigate the efficiency of viral IL-10 gene delivery in the prevention of autoimmune recurrence following islet transplantation. We evaluated the effectiveness of a systemically delivered adeno-associated viral vector (AAV vIL-10) carrying viral IL-10 in protecting islet engraftment. We observed significant prolongation of graft survival after treatment with AAV vIL-10 when using islets from donors lacking autoimmunity. We found that the mechanism of vIL-10-mediated protection was associated with suppression of T cell activation and that donor immune cells that were simultaneously transferred with the islet grafts could induce autoimmune recurrence. AAV vIL-10 gene transfer suppressed previously activated T cells and protected grafted islets from autoimmune-mediated destruction. We conclude that vIL-10 can regulate autoimmune activity and that transfer of its gene may have potential for therapeutic islet transplantation.

Development of islet-like cell clusters after pancreas transplantation in the spontaneously diabetic Torri rat

Pancreas transplantation (PTx) has evolved as a clinical therapy to achieve sustained euglycemia. However, it remains unclear if naive diseased islets of the pancreas benefit from the avoidance of glucose toxicity by PTx. In the present study, using an animal model of type 2 diabetes, the Spontaneously Diabetic Torii (SDT; RT1a) rat, we syngeneically transplanted nondiabetic 10-week-old pancreaticduodenal grafts into diabetic 25-week-old recipients. In the control SDT rats that received no treatment, hyperglycemia developed with a mean onset time of 25 +/- 3.9 weeks of age. Few normal islet cells were found from 25 weeks and none at 40 weeks. However, in the PTx rats, the onset age (graft age) of diabetes was significantly prolonged (47 +/- 18.2 weeks). Moreover, we found that the beta-cell mass was significantly increased in the naive pancreases of 40-week-old PTx recipients (PTx40-naive). Interestingly, islet-like cell clusters of varying size were found close to ductal structures of PTx40-naive pancreases, suggesting that these cells are derived from ductal cells. Furthermore, pancreatic and duodenal homeobox factor-1 (PDX-1) was more clearly expressed in the nuclei of PTx40-naive pancreatic islet-like cell clusters. Our results demonstrate the development of duct-derived beta cells in the pancreas of type 2 diabetic recipients after PTx.

Autoimmunity correlates with tumor regression in patients with metastatic melanoma treated with anti-cytotoxic T-lymphocyte antigen-4

PURPOSE

Previously, we reported our experience treating 14 patients with metastatic melanoma using a fully human antibody to cytotoxic T-lymphocyte antigen-4 (anti-CTLA-4) in conjunction with peptide vaccination. We have now treated 56 patients to evaluate two different dose schedules of anti-CTLA-4 and to explore the relationship between autoimmunity and tumor regression.

PATIENTS AND METHODS

A total of 56 patients with progressive stage IV melanoma were enrolled onto the study. All had Karnofsky performance status > or = 60% with no prior history of autoimmunity. Twenty-nine patients received 3 mg/kg anti-CTLA-4 every 3 weeks, whereas 27 received 3 mg/kg as their initial dose with subsequent doses reduced to 1 mg/kg every 3 weeks. In both cohorts patients received concomitant vaccination with two modified HLA-A*0201-restricted peptides from the gp100 melanoma-associated antigen, gp100:209-217(210M) and gp100:280-288(288V).

RESULTS

Two patients achieved a complete response (ongoing at 30 and 31 months, respectively) and five patients achieved a partial response (durations of 4, 6, 25+, 26+, and 34+ months, respectively), for an overall objective response rate of 13%. Tumor regression was seen in lung, liver, brain, lymph nodes, and subcutaneous sites. Of 14 patients with grade 3/4 autoimmune toxicity, five (36%) experienced a clinical response compared with only two responses in the 42 patients (5%) with no autoimmune toxicity (P = .008). There were no significant differences in response rate or toxicity between the two dose schedules.

CONCLUSION

Administration of anti-CTLA-4 monoclonal antibody plus peptide vaccination can cause durable objective responses, which correlate with the induction of autoimmunity, in patients with metastatic melanoma.

Synthesis and evaluation of fluorine-18 labeled glyburide analogs as beta-cell imaging agents

Glyburide is a prescribed hypoglycemic drug for the treatment of type 2 diabetic patients. We have synthesized two of its analogs, namely N-[4-[beta-(2-(2'-fluoroethoxy)-5-chlorobenzenecarboxamido)ethyl]benzenesulfonyl]-N'-cyclohexylurea (2-fluoroethoxyglyburide, 8b) and N-[4-[beta-(2-(2'-fluoroethoxy)-5-iodobenzenecarboxamido)ethyl]benzenesulfonyl]-N'-cyclohexylurea (2-fluoroethoxy-5-deschloro-5-iodoglyburide, 8a), and their fluorine-18 labeled analogs as beta-cell imaging agents. Both F-18 labeled compound 8a and compound 8b were synthesized by alkylation of the corresponding multistep synthesized hydroxy precursor 4a and 4b with 2-[(18)F]fluoroethyl tosylate in DMSO at 120 degrees C for 20 minutes followed by HPLC purification in an overall radiochemical yield of 5-10% with a synthesis time of 100 minutes from EOB. The octanol/water partition coefficients of compounds 8a and 8b were 141.21 +/- 27.77 (n = 8) and 124.33 +/- 21.61 (n = 8), respectively. Insulin secretion experiments of compounds 8a and 8b on rat islets showed that both compounds have a similar stimulating effect on insulin secretion as that of glyburide. In vitro binding studies showed that approximately 2% of compounds 8a and 8b bound to beta TC3 and Min6 cells and that the binding was saturable. Preliminary biodistribution studies in mice showed that the uptake of both compounds 8a and 8b in liver and small intestine were high, whereas the uptake in other organs studied including pancreas were low. Additionally, the uptake of compound 8b in vivo was nonsaturable. These results tend to suggest that compounds 8a and 8b may not be the ideal beta-cell imaging agents.

Development of Donor-Specific Immunoregulatory T-Cells After Local CTLA4Ig Gene Transfer to Pancreatic Allograft

BACKGROUND

CTLA4Ig gene transfer directly to graft tissue might have the potential to avoid the need for systemic immunosuppression. In our previous studies of bio-breeding (BB) rats, local adenovirus-mediated CTLA4Ig gene transfer protected the pancreas from autoimmune and alloimmune responses. This study investigated the potency of local CD28/B7 costimulatory blockade for induction of donor-specific tolerance and further examined the existing mechanisms.

METHODS

Brown Norway (BN; RT1)-pancreaticoduodenal grafts transfected with Ad.CTLA4Ig via intraarterial ex vivo perfusion were transplanted into streptozotocin-induced diabetic Lewis (LEW; RT1) rats.

RESULTS

Ad.CTLA4Ig transduced grafts combined with a short course of FK506 resulted in indefinitely prolonged survival (>156 days vs. 19.5 days with FK506 alone). CTLA4Ig was predominantly expressed in grafts on day 4. The expression was gradually diminished and was only slightly detectable at day >100. The proliferative responses against BN antigen were remarkably enhanced among recipients with rejected grafts, but the T-cells from tolerant recipients (>100 days) showed poor cytotoxic responses. On adoptive transfer assay, the splenic T-cells of tolerant recipients were able to suppress the rejection of BN, but not third-party Wistar Furth (WF; RT1) hearts in irradiated (480 cGy) LEW recipients. The percentage of CD4CD25 splenic T-cells was significantly increased in tolerant recipients (13.53 +/- 4.06% vs. 6.06 +/- 0.56% in naive rats).

CONCLUSION

CTLA4Ig gene transfer to the pancreaticoduodenal allograft combined with a short course of FK506 induces donor-specific tolerance. The mechanism of maintaining tolerance could be explained by development of splenic T suppressor cells.

The novel anti-inflammatory agent lisofylline prevents autoimmune diabetic recurrence after islet transplantation1

BACKGROUND

Pancreatic islet transplantation has become a promising treatment for type 1 diabetes. However, autoimmune reactivity destroys engrafted islets in type 1 diabetic recipients. The authors' previous studies demonstrated that a novel anti-inflammatory agent, lisofylline (LSF), suppressed autoimmune reactivity and protected nonobese diabetic (NOD) mice from diabetes. In this study, the authors investigated the potential of LSF in preventing autoimmune diabetes recurrence after islet transplantation.

METHODS

Spontaneously diabetic NOD mice received NOD severe combined immunodeficiency islet transplants and were treated with daily LSF injections at 50 mg/kg for 3 weeks. Blood glucose levels were monitored. Serum cytokine levels were measured at 1 and 3 weeks after engraftment. Nephrectomy of the islet-implanted kidney was performed in LSF-treated recipients. Histology of islet grafts was assessed at the end of the study. The effect of LSF on beta-cell function was studied in vitro.

RESULTS

Without immunosuppressants and insulin, the LSF-treated recipient mice maintained euglycemia significantly longer than the saline-treated recipients (mean, >65 days in the LSF-treated group vs. 6 days in saline controls; P=0.0004). Serum levels of interferon-gamma were markedly reduced in LSF-treated recipients at 1 and 3 weeks posttransplant. Diabetes recurred in the LSF-treated recipients after removing the islet-implanted kidneys. Immunohistochemistry showed retention of insulin-positive cells in the grafts of the LSF-treated recipients. LSF preserved beta-cell insulin secretory function in the presence of inflammatory cytokines in vitro.

CONCLUSIONS

This study demonstrates that autoimmune diabetes recurrence after islet transplantation could be prevented by treatment with LSF. LSF and its analogues may have the potential to prevent islet autoimmune destruction in clinical transplantation.

Optimal modes and targets of gene therapy in transplantation

Genetic modification strategies have the potential to improve outcome following cell/organ transplantation. A unique opportunity in transplantation is that gene therapies need not be restricted to in vivo approaches and that ex vivo genetic modification of cell and/or organs can be of value. Improvements in vector design, production, and delivery should enhance transfection efficiency and optimize gene expression. Herein, we discuss potential modes of gene therapy, focusing on viral, liposome, or naked DNA-based systems for gene delivery. We suggest gene therapy targets taking into consideration the essential constituents of anti-allograft repertory. In addition to strategies that may have salutary effects in mitigating the threat of acute rejection, we suggest genetic strategies for minimizing ischemia/reperfusion injury as well as for the perennial problem of progressive functional loss of the transplanted organ. Data from pre-clinical transplant models support the idea that gene therapy may improve allograft function and survival. We are optimistic that gene therapy will be of clinical value in the near future in the management of recipients of allografts; we believe that genetic strategies would be essential for successful breaching of the formidable challenge of xenotransplantation.

Toward cell replacement therapy: promises and caveats

Studies in animal models have suggested a role for stem cells in repair and regeneration of the nervous system. Human equivalents of stem and precursor cells have been isolated and their efficacy is being evaluated in rodent and primate models. Difficulties exist in translating results of these preclinical models to therapy in humans. Evolutionary differences among rodents, primates, and humans; fundamental differences in the anatomy and physiology; differences in immune responses in xenotransplant models; the paucity of good transplant models of chronic disease; and allelic variability in the cells themselves make any study evaluating the efficacy of cells in transplant models difficult to interpret. As no better alternatives to testing in animals exist, we suggest that at this early stage a considered step-by-step approach to testing and comparison of different transplant strategies in isolation will prepare us better for clinical trials than simple evaluation of functional outcomes in various models of disease. We emphasize that we do not recommend delaying or abandoning clinical trials; rather, we suggest that one anticipate failures and design experiments and data collection such that we learn from these failures to ensure future success in as rapid a time frame as possible.

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.

Ex vivo and systemic transfer of adenovirus-mediated CTLA4Ig gene combined with a short course of FK506 therapy prolongs islet graft survival

Adenovirus-mediated CTLA4Ig gene transfer has been reported to enhance graft survival in several rodent transplantation models. In this study, we investigated the efficacy of ex vivo and systemic transfer of the CTLA4Ig gene by adenoviral vectors in pancreatic islet allo-transplantation. Islet grafts from BN rats were transplanted to chemically induced diabetic LEW rats. First, ex vivo CTLA4Ig gene transfer into isolated islets was performed prior to transplantation. Survival of transduced grafts under the kidney capsule was slightly prolonged (8.6+/-1.3 days) compared with survival of untransduced grafts (6.7+/-1.2 days); when combined with a short course of FK506, graft survival was further extended (32.6+/-10.7 days vs. 13.7+/-1.0 days with FK506 alone). Secondly, systemic gene transfer was accomplished by intravenous administration immediately after the transplantation procedure. In these animals, islet grafts under the kidney capsule survived longer (15.2+/-3.3 days) than in controls (6.7+/-1.2 days), and when FK506 was administered perioperatively, all the islet grafts survived for more than 100 days. In systemically transduced recipients, the survival of islet grafts transplanted into the liver was not significantly different from that of the grafts placed under the kidney capsule. In order to examine organ-specific immunogenicity, heterotopic BN cardiac grafts were transplanted to LEW rats intra-abdominally, with the virus transferred systemically as in the islet model. In contrast to the islet grafts, all the cardiac grafts were accepted for longer than 100 days, even without FK506 therapy. Finally, the LEW recipients with long-surviving islet or cardiac grafts were re-transplanted with islet grafts from the same donor strain (BN) on day 100. The second islet grafts survived longer than 100 days in half of the cardiac recipients, but consistently failed in the islet recipients. We conclude that in this transplant model, CTLA4Ig gene transfer and FK506 treatment synergistically improved islet graft survival, systemic transfer of the gene was more effective than ex vivo transfer to the islets, and donor-specific tolerance could not be achieved for islet transplantation but was achieved for cardiac transplantation.

Immunomodulation with CTLA4-Ig in islet transplantation

The need for permanent, nonspecific, and potentially harmful immunosuppression remains a major obstacle for islet transplantation. The response of a type 1 diabetic recipient to an islet graft includes a specific allogenic immune response and the recurrence of autoimmunity. Free or encapsulated in an immunoisolation device, islet cells are exposed to immune aggression, initiated by donor antigen-presenting cells or by indirect, host antigen-presenting cell-mediated antigen presentation. CTLA4-Ig is a genetically engineered fusion protein of human CTLA4 and the IgG 1 Fc region. It prevents T-cell activation by binding to human B7, which costimulates T cells through CD28. Interesting data were reported in experimental islet transplantation, suggesting that CTLA4-Ig may be slightly but significantly beneficial to islet allograft survival, although studies in autoimmune diabetes are scarce. The main limitations include transient and low levels of expression when CTLA4-Ig is delivered locally, a predominant effect on the direct recognition pathway, and the lack of effect on memory cells. Clinical trials in islet transplantation could be discussed in nonuremic patients, with steroid-free and anticalcineurin-free regimens, in combination with another costimulation blocker, rapamycin, and an anti-interleukin 2 receptor antibody, and with a strategy directed against the recurrence of autoimmunity.

Neonatal porcine pancreatic cell clusters as a potential source for transplantation in humans: characterization of proliferation, apoptosis, xenoantigen expression and gene delivery with recombinant AAV

Neonatal porcine islets are characterized by reproducible isolation success and high yields, sizable advantages over adult islets. In this work we have analyzed selected phenotypic and functional characteristics of porcine neonatal islets relevant to their possible use for transplant in humans. We show that porcine islet cells proliferate in culture, and synthesize and store islet-specific hormones. Proliferating beta cells can be easily identified. Implant of cultured neonatal islets in immunodeficient rodents results in the reversal of diabetes, albeit with delay. We also show that measurable apoptosis occurs in cultured neonatal porcine islets. Further, antigens recognized by human natural antibodies are expressed in a dynamic fashion over the culture period analyzed and are not limited to the alpha-Gal epitope. Lastly, we demonstrate that a recombinant Adeno-Associated virus can be used to efficiently deliver a reporter gene in porcine islets. This characterization might be helpful in the definition of the potential use of neonatal porcine islets for human transplantation.

Molecular organization of the nodal region is not altered in spontaneously diabetic BB-Wistar rats

We examined the organization of the molecular components of the nodal region in spontaneously diabetic BB-Wistar rats. Frozen sections and teased fibers from the sciatic nerves were immunostained for nodal (voltage-gated Na(+) channels, ankyrin(G), and ezrin), paranodal (contactin, Caspr, and neurofascin 155 kDa), and juxtaparanodal (Caspr2, the Shaker-type K(+) channels Kv1.1 and Kv1.2, and their associated subunit Kvbeta2) proteins. All of these proteins were properly localized in myelinated fibers from rats that had been diabetic for 15-44 days, compared to age-matched, nondiabetic animals. These results demonstrate that the axonal membrane is not reorganized, so nodal reorganization is not likely to be the cause of nerve conduction slowing in this animal model of acute diabetes.

CTLA4 gene polymorphisms are associated with, and linked to, insulin-dependent diabetes mellitus in a Russian population

BACKGROUND

The association between the human cytotoxic T lymphocyte-associated antigen-4 (CTLA4) gene and insulin-dependent diabetes mellitus (IDDM) is unclear in populations. We therefore investigated whether the gene conferred susceptibility to IDDM in a Russian population. We studied two polymorphic regions of the CTLA4 gene, the codon 17 dimorphism and the (AT)n microsatellite marker in the 3' untranslated region in 56 discordant sibling pairs and in 33 identical by descent (IBD) affected sibships.

RESULTS

The Alal7 allele of the CTLA4 gene was preferentially transmitted from parents to diabetic offspring (p<0.0001) as shown by the combined transmission/disequlibrium test (TDT) and sib TDT (S-TDT) analysis. A significant difference between diabetic and non-diabetic offspring was also observed for the transmission of alleles 17, 20, and 26 of the dinucleotide microsatellite. Allele 17 was transmitted significantly more frequently to affected offspring than to other children (p=0.0112) whereas alleles 20 and 26 were transmitted preferentially to non-diabetic sibs (p=0.045 and 0.00068 respectively). A nonrandom excess of the Ala17 CTLA4 molecular variant (maximum logarithm of odds score (MLS) of 3.26) and allele 17 of the dinucleotide marker (MLS=3.14) was observed in IBD-affected sibling pairs.

CONCLUSION

The CTLA4 gene is strongly associated with, and linked to IDDM in a Russian population.

Regulation of gene expression of murine MD-1 regulates subsequent T cell activation and cytokine production

The immunoadhesin (OX2:Fc) comprising the extracellular domain of murine OX2 linked to IgG2aFc, inhibits production of IL-2 and IFN-gamma by activated T cells and increases allograft and xenograft survival in vivo. Increased expression of OX2 on dendritic cells (DC) in vivo following preimmunization via the portal vein is also associated with elevated expression of MD-1. We have used antisense oligodeoxynucleotides (ODNs) to MD-1 to investigate the effect of inhibition of expression of MD-1 by DC on their function as allostimulatory cells. We also investigated by FACS analysis the cell surface expression of OX2, CD80, and CD86 on DC incubated with ODN-1 blocking MD-1 expression. Blocking MD-1 gene expression inhibits surface expression of CD80 and CD86, but not of OX2. DC incubated with ODN-1 to MD-1 did not stimulate IL-2 or IFN-gamma production, but generated cells able to suppress, in a second culture of fresh DC plus allogeneic T cells, production of IL-2 and IFN-gamma. This inhibition was blocked by anti-OX2 mAb. Infusion of DC preincubated with ODN-1 prolonged renal allograft survival, an effect also reversed by anti-OX2 mAb. By FACS, incubation of DC with anti-MD-1 Ab to promote capping eliminated cell surface expression of MD-1 and CD14 without altering DEC205, DC26, CD80, CD86, or OX2 expression. Thus OX2 and MD-1 are independent surface molecules on DC that may reciprocally regulate T cell stimulation. MD-1 is linked to CD14, a "danger receptor complex," and activation of this complex can regulate cell surface expression of CD80/CD86, which signal T cells.

The role of costimulatory molecules as targets for new immunosuppressives in transplantation

T-cell costimulation is critical for all T-cell-mediated immune responses that are responsible for endpoints such as allograft rejection or autoimmune disease. Recent experimental data elucidate specific pathways for T-cell activation and negative regulatory mechanisms via unique costimulatory molecules. These data have implications for the development of novel therapeutic strategies to prevent graft rejection and improve long-term graft survival in transplant patients, and to treat autoimmune diseases in humans.

Gene therapy strategies to facilitate organ transplantation

Organ transplantation is now the definitive therapy for many forms of end-organ disease, but chronic allograft rejection, the side effects of chronic immunosuppressive therapy and the severe donor organ shortage continue to limit its success. Gene therapy has the potential to prevent graft rejection by manipulating the immune response in the microenvironment of the graft or by facilitating the induction of tolerance. Genetic manipulation of stem cells to create transgenic and/or knockout animals that could serve as organ or cell donors could be combined with gene therapy approaches to overcome the problem of limited allogeneic donor organ supply.