Immunosuppression preventing concordant xenogeneic islet graft rejection is not sufficient to prevent recurrence of autoimmune diabetes in nonobese diabetic mice

Endogenous expansion of regulatory T cells leads to long-term islet graft survival in diabetic NOD mice

Donor pancreatic lymph node cells (PLNC) protect islet transplants in Non-obese diabetic (NOD) mice. We hypothesized that induced FoxP3(+) regulatory T cells (Tregs) were required for long-term islet engraftment. NOD or NOD.NON mice were treated with ALS (antilymphocyte serum) and transplanted with NOR islets +/-PLNC (5 × 10(7) ). In vivo proliferation and expansion of FoxP3(+) Tregs was monitored in spleen and PLN from ALS- and ALS/PLNC-treated recipient mice. Anti-CD25 depletion was used to determine the necessity of Tregs for tolerance. FoxP3(+) numbers significantly increased in ALS/PLNC-treated recipients compared to ALS-treated mice. In ALS/PLNC-treated mice, recipient-derived Tregs localized to the transplanted islets, and this was associated with intact, insulin-producing β cells. Proliferation and expansion of FoxP3(+) Tregs was markedly increased in PLNC-treated mice with accepted islet grafts, but not in diabetic mice not receiving PLNC. Deletion of Tregs with anti-CD25 antibodies prevented islet graft tolerance and resulted in rejection. Adoptive transfer of Tregs to secondary NOD.scid recipients inhibited autoimmunity by cotransferred NOD effector T cells. Treg expansion induced by ALS/PLNC-treatment promoted long term islet graft survival. Strategies leading to Treg proliferation and localization to the transplant site represent a therapeutic approach to controlling recurrent autoimmunity.

Combination of anti-CD4 with anti-LFA-1 and anti-CD154 monoclonal antibodies promotes long-term survival and function of neonatal porcine islet xenografts in spontaneously diabetic NOD mice

Type 1 diabetes mellitus (T1DM) is caused by the autoimmune destruction of pancreatic islet beta-cells, which are required for the production of insulin. Islet transplantation has been shown to be an effective treatment option for TIDM; however, the current shortage of human islet donors limits the application of this treatment to patients with brittle T1DM. Xenotransplantation of pig islets is a potential solution to the shortage of human donor islets provided xenograft rejection is prevented. We demonstrated that a short-term administration of a combination of anti-LFA-1 and anti-CD154 monoclonal antibodies (mAbs) was highly effective in preventing rejection of neonatal porcine islet (NPI) xenografts in non-autoimmune-prone B6 mice. However, the efficacy of this therapy in preventing rejection of NPI xenografts in autoimmune-prone nonobese diabetic (NOD) mice is not known. Given that the current application of islet transplantation is for the treatment of T1DM, we set out to determine whether a combination of anti-LFA-1 and anti-CD154 mAbs could promote long-term survival of NPI xenografts in NOD mice. Short-term administration of a combination of anti-LFA-1 and anti-CD154 mAbs, which we found highly effective in preventing rejection of NPI xenografts in B6 mice, failed to promote long-term survival of NPI xenografts in NOD mice. However, addition of anti-CD4 mAb to short-term treatment of a combination of anti-LFA-1 and anti-CD154 mAbs resulted in xenograft function in 9/12 animals and long-term graft (>100 days) survival in 2/12 mice. Immunohistochemical analysis of islet grafts from these mice identified numerous insulin-producing beta-cells. Moreover, the anti-porcine antibody as well as autoreactive antibody responses in these mice was reduced similar to those observed in naive nontransplanted mice. These data demonstrate that simultaneous targeting of LFA-1, CD154, and CD4 molecules can be effective in inducing long-term islet xenograft survival and function in autoimmune-prone NOD mice.

Increasing donor chimerism and inducing tolerance to islet allografts by post-transplant donor lymphocyte infusion

Inducing donor chimerism is the most consistently successful approach to achieve transplant tolerance. We found that a low level of donor chimerism, which was induced by a relatively non-toxic approach, induced donor-specific tolerance to islet allografts in chemically induced diabetic mice. However, a similar level of donor chimerism could not protect donor islet allografts in non-obese diabetic (NOD) mice that spontaneously developed autoimmune diabetes. Rejection of donor islet allografts in diabetic NOD mice with a low level of donor chimerism was mediated by recurrent autoimmunity. We used post-transplant donor lymphocyte infusion (DLI) to increase donor chimerism and to induce tolerance to islet allografts. DLI significantly increased donor chimerism and promoted donor-specific tolerance to islet allografts in diabetic NOD mice. Self-tolerance to islet autoantigens was restored and restoring self-tolerance is mediated by immunoregulation. Thus, our data showed that adoptive immunotherapy with post-transplant DLI after establishing a low level of donor chimerism as a platform enhances donor chimerism, induces donor-specific tolerance to islet allografts and restores self-tolerance in the setting of autoimmune diabetes. Our data also showed that central tolerance is not sufficient to induce tolerance and peripheral tolerance through immunoregulation for restoring self-tolerance is required in the setting of autoimmune diabetes.

CD8+ T Cell Tolerance in Nonobese Diabetic Mice Is Restored by Insulin-Dependent Diabetes Resistance Alleles

Although candidate genes controlling autoimmune disease can now be identified, a major challenge that remains is defining the resulting cellular events mediated by each locus. In the current study we have used NOD-InsHA transgenic mice that express the influenza hemagglutinin (HA) as an islet Ag to compare the fate of HA-specific CD8+ T cells in diabetes susceptible NOD-InsHA mice with that observed in diabetes-resistant congenic mice having protective alleles at insulin-dependent diabetes (Idd) 3, Idd5.1, and Idd5.2 (Idd3/5 strain) or at Idd9.1, Idd9.2, and Idd9.3 (Idd9 strain). We demonstrate that protection from diabetes in each case is correlated with functional tolerance of endogenous islet-specific CD8+ T cells. However, by following the fate of naive, CFSE-labeled, islet Ag-specific CD8+ (HA-specific clone-4) or CD4+ (BDC2.5) T cells, we observed that tolerance is achieved differently in each protected strain. In Idd3/5 mice, tolerance occurs during the initial activation of islet Ag-specific CD8+ and CD4+ T cells in the pancreatic lymph nodes where CD25+ regulatory T cells (Tregs) effectively prevent their accumulation. In contrast, resistance alleles in Idd9 mice do not prevent the accumulation of islet Ag-specific CD8+ and CD4+ T cells in the pancreatic lymph nodes, indicating that tolerance occurs at a later checkpoint. These results underscore the variety of ways that autoimmunity can be prevented and identify the elimination of islet-specific CD8+ T cells as a common indicator of high-level protection.

NKG2D Blockade Prevents Autoimmune Diabetes in NOD Mice

NKG2D is an activating receptor on CD8(+) T cells and NK cells that has been implicated in immunity against tumors and microbial pathogens. Here we show that RAE-1 is present in prediabetic pancreas islets of NOD mice and that autoreactive CD8(+) T cells infiltrating the pancreas express NKG2D. Treatment with a nondepleting anti-NKG2D monoclonal antibody (mAb) during the prediabetic stage completely prevented disease by impairing the expansion and function of autoreactive CD8(+) T cells. These findings demonstrate that NKG2D is essential for disease progression and suggest a new therapeutic target for autoimmune type I diabetes.

A substantial level of donor hematopoietic chimerism is required to protect donor-specific islet grafts in diabetic NOD mice

BACKGROUND

Mixed chimerism can induce tolerance to alloantigens and restore self-tolerance to autoantigens, thereby permitting islet transplantation. However, the minimal level of donor chimerism that is required to prevent islet allograft rejection and recurrence of autoimmune diabetes has not been established.

METHODS

We investigated whether allogeneic Balb/c donor chimerism can be induced in C57BL/6 mice, in prediabetic NOD mice, and in diabetic NOD mice after transplantation of a modest dose of bone marrow by using purine nucleoside analogue, fludarabine phosphate and cyclophosphamide conditioning therapy, followed by short-term anti-CD40 ligand monoclonal antibody and rapamycin posttransplant treatment. We also investigated whether the induced donor chimerism is sufficient to prevent the onset of diabetes in prediabetic NOD mice and protect donor islet grafts in diabetic NOD mice.

RESULTS

Allogeneic donor chimerism could be induced under the authors' approach that is nonmyeloablative and radiation-free. Diabetes onset was prevented in chimeric prediabetic NOD mice. The induction of mixed chimerism protected donor-specific islet grafts in diabetic NOD mice. At 60 days after islet transplantation, all donor Balb/c islet grafts survived in diabetic NOD mice whose level of donor-derived lymphocytes was higher than 30% at the time of islet transplantation (n=8). In contrast, Balb/c islet grafts were rejected in five of seven diabetic NOD mice whose level was lower than 30%.

CONCLUSIONS

Our data demonstrate that a donor lymphocyte chimerism (>30%) at the time of islet transplantation is required to protect donor-specific islet grafts, and indicate that a strictly non-irradiation-based protocol can be used to achieve this goal.

Prolonged islet allograft survival in diabetic NOD mice by targeting CD45RB and CD154

Clinical islet transplantation is a successful procedure that can improve the quality of life in recipients with diabetes. A drawback of the procedure is the need for chronic administration of immunosuppressive drugs that, among other side effects, are potentially diabetogenic. Definition of immunosuppressive protocols that utilize nondiabetogenic compounds could further improve islet transplantation outcome. We used the NOD mouse to assess the effect of targeting the T-lymphocyte surface receptors CD45RB and CD154 in preventing loss of allogeneic islet grafts as a result of recurrence of autoimmunity and allorejection. Administration of the two antibodies led to significantly prolonged allograft survival, with a percentage of grafts surviving long-term. The therapeutic efficacy of the treatment was paralleled by a shift in CD45RB isoform expression on T-lymphocytes, increased in vitro responsiveness to interleukin-7, and increased in vitro gamma-interferon production after anti-CD3 antibody stimulation. Furthermore, graft infiltration by CD8+ T-cells was remarkably reduced. Recipient mice bearing functioning allografts were otherwise immunocompetent, as assessed in vivo and in vitro by numerous tests, including intragraft cytokine production, responsiveness to polyclonal stimulation and alloantigens, and analysis of cell subset phenotype. These data show that nondiabetogenic regimens of immunomodulation can lead to prolonged islet allograft survival in the challenging NOD mouse model.

Pig islet xenografts are resistant to autoimmune destruction by non-obese diabetic recipients after anti-CD4 treatment

In addition to providing a large source of donor tissue, xenogeneic islet transplantation might avoid recurrent autoimmunity in patients with type 1 diabetes. To examine this possibility further, xenogeneic pig islets were transplanted into recipient mice in the presence or absence of autoimmunity. Spontaneously, non-obese diabetic (NOD) recipients rejected isografts rapidly whether or not the recipients were depleted of CD4+ T-cells. Young NOD mice made diabetic with streptozotocin accepted islet isografts without immunosuppression, indicating that destructive autoimmunity did not develop in these recipients. Pig xenografts were rejected equally quickly in the two types of NOD recipients in the absence of immunosuppression and survived for up to 9 weeks in both types of NOD recipients after CD4 depletion. BALB/c mice often accepted pig xenografts indefinitely after anti-CD4 antibody treatment. These results suggest that pig islets are resistant to recurrent autoimmunity when CD4+ T-cells are depleted. The difficulty in obtaining indefinite islet xenograft survival in NOD recipients occurs independently from the development of destructive autoimmunity.

Inducing tolerance to MHC-matched allogeneic islet grafts in diabetic NOD mice by simultaneous islet and bone marrow transplantation under nonirradiative and nonmyeloablative conditioning therapy

BACKGROUND

Human type 1 diabetes is associated with defects in the hematopoietic stem cells. Simultaneous donor islet and bone marrow transplantation may be an ideal therapeutic approach for inducing tolerance to islet allogeneic antigens and restoring self-tolerance to islet autoimmune antigens.

METHODS

Using a nonobese diabetic (NOD) mouse model of human type 1 diabetes, we investigated whether tolerance to MHC-matched allogeneic islet grafts from male nonobese diabetes-resistant (NOR) donors can be induced in female NOD recipients by simultaneous islet and bone marrow transplantation under fludarabine phosphate-based nonmyeloablative and irradiation-free conditioning therapy. Donor-specific chimerism in the peripheral blood of tolerant mice (n=7) was measured by semiquantitative polymerase chain reaction for a male-specific marker (SRY).

RESULTS

Donor-specific tolerance to NOR islet grafts was induced in all diabetic NOD mice after simultaneous islet and bone marrow transplantation and treated with fludarabine phosphate, cyclophosphamide, anti-mouse lymphocyte serum, and rapamycin. At 100 days and 200 days after transplantation, the average percentage of male NOR marker in DNA derived from the peripheral blood of NOD recipients that had long-term islet graft survival was over 10%.

CONCLUSION

Our data suggest that this approach may induce donor-specific tolerance in clinical islet transplantation and living-related donor solid organ transplantation.

Immunotherapy with nondepleting anti-CD4 monoclonal antibodies but not CD28 antagonists protects islet graft in spontaneously diabetic nod mice from autoimmune destruction and allogeneic and xenogeneic graft rejection

BACKGROUND

T-cell activation and the subsequent induction of effector functions require not only the recognition of antigen peptides bound to MHC molecules by T-cell receptor (TCR) for antigen but also a costimulatory signal provided by antigen presenting cells. CD4 T-cell activation and function require the CD4 molecule as a coreceptor of TCR. The CD28/B7 pathway is a major costimulatory signal for T-cell activation and differentiation.

METHODS

The effect of targeting CD4 by nondepleting anti-CD4 monoclonal antibodies (mAbs) versus blocking CD28/B7 by CTLA4Ig, anti-CD80 mAbs, and anti-CD86 mAbs on the prevention of recurrence of autoimmune diabetes after MHC-matched nonobese diabetes-resistant (NOR) islet transplantation in nonobese diabetic (NOD) mice were compared. Whether nondepleting anti-CD4 mAbs prolong allogeneic islet graft survival and xenogeneic pig islet graft survival in diabetic NOD mice were studied. Furthermore, the effect of nondepleting anti-CD4 mAbs combined with CTLA4Ig on allogeneic islet graft survival in NOD mice was investigated.

RESULTS

Recurrence of autoimmune diabetes can be prevented by nondepleting anti-CD4 mAbs. Blocking the CD28/B7 costimulatory pathway by CTLA4Ig or by anti-CD80 mAbs and anti-CD86 mAbs cannot prevent recurrence of autoimmune diabetes after islet transplantation. Short-term treatment with nondepleting anti-CD4 mAbs significantly prolongs allogeneic islet graft survival and xenogeneic pig islet graft survival in diabetic NOD mice. But nondepleting anti-CD4 mAbs combined with CTLA4Ig decreased allogeneic islet graft survival.

CONCLUSIONS

Nondepleting anti-CD4 mAbs but not CD28 antagonists protect islet grafts in diabetic NOD mice from autoimmune destruction and allogeneic and xenogeneic graft rejection. The efficacy of nondepleting anti-CD4 mAbs is compromised when it combines with CTLA4Ig.

Ingested interferon-alpha prevents allograft islet transplant rejection

BACKGROUND

Ingested interferon (IFN)-alpha is a biological response modifier in experimental autoimmune encephalomyelitis and multiple sclerosis, and prevents type 1 diabetes in nonobese diabetic mice. Islet transplantation possesses significant potential advantages over whole-gland transplantation because it is simple, may achieve insulin independence, and has clear advantages over exogenous insulin therapy. Therefore, we examined whether ingested IFN-alpha, administered to islet allograft recipients, could prevent islet allograft rejection.

METHODS

Recipient C3H mice (H2k) were made diabetic and either untreated or treated with 10-1000 international units (IU) of ingested murine IFN-alpha daily from day -7 through day +14 after transplantation for a total of 21 days. Seven days after diabetes induction, recipients received allograft islets isolated from C57BL.10 donors (H2b) under the kidney capsule and were followed for overt diabetes via elevated blood glucose.

RESULTS

Control recipients and recipients fed 1000 IU all became diabetic by day 13, whereas mice ingesting IFN-alpha had delayed rejection for up to 27 (10 IU) to 29 days (100 IU) after islet transplantation. Treatment of recipients of islet allografts with ingested IFN-alpha doubles the time period before rejection compared with control mice. The feeding period with daily IFN-alpha was doubled from 21 days to 42 days in total, 7 days before transplantation and 35 days after transplantation.

CONCLUSION

Treatment of recipients of islet allografts with prolonged ingested IFN-alpha prevents rejection in a subset of recipients. Ingested IFN-alpha may prevent rejection if given continuously after transplantation.

Efficient gene transfer and expression in islets by an adenoviral vector that lacks all viral genes

Although adenoviral vector-mediated gene transfer has significant potential for gene therapy, host immune responses to virally expressed proteins and small insert capacity may limit its clinical application. In order to overcome these disadvantages, a new adenoviral vector that lacks all viral genes has been developed. Using the green fluorescent (GFP) gene as a reporter gene, we investigated the efficiency of gene transfer by this all-viral-genes-deleted and minimal cis-element remaining adenoviral vector (miniAd-GFP) in islets in vitro and ex vivo, and compared it with the E1-deleted adenoviral vector (E1-GFP). One day after in vitro infection, GFP was expressed in both miniAd-GFP- and E1-GFP-infected islets. The percentage of GFP-positive single cells was not significantly different between miniAd-GFP-infected islets and E1-GFP-infected islets. When these islets were transplanted into syngeneic diabetic mice, both miniAd-GFP- and E1-GFP-infected islet grafts reversed diabetes, and normal blood glucose levels were maintained for over 20 weeks posttransplantation. Mild lymphocyte infiltration was found in all E1-GFP-infected islet grafts at all time points. However, this was not seen in most miniAd-GFP-infected islet grafts. Our results indicate that gene transfer by an adenoviral vector that lacks all viral genes is as efficient as E1-deleted adenoviral vector-mediated gene transfer in islets. Furthermore, this adenoviral vector might be less immunogeneic than the E1-deleted adenoviral vector.