In situ induction of dendritic cell-based T cell tolerance in humanized mice and nonhuman primates

Anti-intercellular adhesion molecule 1 monomaintenance therapy induced long-term liver allograft survival without chronic rejection

Calcineurin inhibitors (CNIs) are essential in liver transplantation (LT); however, their long-term use leads to various adverse effects. The anti-intercellular adhesion molecule (ICAM)-1 monoclonal antibody MD3 is a potential alternative to CNI. Despite its promising results with short-term therapy, overcoming the challenge of chronic rejection remains important. Thus, we aimed to investigate the outcomes of long-term MD3 therapy with monthly MD3 monomaintenance in nonhuman primate LT models. Rhesus macaques underwent major histocompatibility complex-mismatched allogeneic LT. The conventional immunosuppression group (Con-IS, n = 4) received steroid, tacrolimus, and sirolimus by 4 months posttransplantation. The induction MD3 group (IN-MD3, n = 5) received short-term MD3 therapy for 3 months with Con-IS. The maintenance MD3 group (MA-MD3, n = 4) received MD3 for 3 months, monthly doses by 2 years, and then quarterly. The MA-MD3 group exhibited stable liver function without overt infection and had significantly better liver allograft survival than the IN-MD3 group. Development of donor-specific antibody and chronic rejection were suppressed in the MA-MD3 group but not in the IN-MD3 group. Donor-specific T cell responses were attenuated in the MA-MD3 group. In conclusion, MD3 monomaintenance therapy without maintenance CNI provides long-term liver allograft survival by suppressing chronic rejection, offering a potential breakthrough for future human trials.

Clinically available immunosuppression averts rejection but not systemic inflammation after porcine islet xenotransplant in cynomolgus macaques

A safe, efficacious, and clinically applicable immunosuppressive regimen is necessary for islet xenotransplantation to become a viable treatment option for diabetes. We performed intraportal transplants of wild-type adult porcine islets in 25 streptozotocin-diabetic cynomolgus monkeys. Islet engraftment was good in 21, partial in 3, and poor in 1 recipient. Median xenograft survival was 25 days with rapamycin and CTLA4Ig immunosuppression. Adding basiliximab induction and maintenance tacrolimus to the base regimen significantly extended median graft survival to 147 days (p < .0001), with three animals maintaining insulin-free xenograft survival for 265, 282, and 288 days. We demonstrate that this regimen suppresses non-Gal anti-pig antibody responses, circulating effector memory T cell expansion, effector function, and infiltration of the graft. However, a chronic systemic inflammatory state manifested in the majority of recipients with long-term graft survival indicated by increased neutrophil to lymphocyte ratio, IL-6, MCP-1, CD40, and CRP expression. This suggests that this immunosuppression regimen fails to regulate innate immunity and resulting inflammation is significantly associated with increased incidence and severity of adverse events making this regimen unacceptable for translation. Additional studies are needed to optimize a maintenance regimen for regulating the innate inflammatory response.

Short-term therapy with anti-ICAM-1 monoclonal antibody induced long-term liver allograft survival in nonhuman primates

Tolerance induction remains challenging following liver transplantation and the long-term use of immunosuppressants, especially calcineurin inhibitors, leads to serious complications. We aimed to test an alternative immunosuppressant, a chimeric anti-ICAM-1 monoclonal antibody, MD-3, for improving the outcomes of liver transplantation. We used a rhesus macaque liver transplantation model and monkeys were divided into three groups: no immunosuppression (n = 2), conventional immunosuppression (n = 4), and MD-3 (n = 5). Without immunosuppression, liver allografts failed within a week by acute rejection. Sixteen-week-long conventional immunosuppression that consisted of prednisolone, tacrolimus, and an mTOR inhibitor prolonged liver allograft survival; however, recipients died of acute T cell-mediated rejection (day 52), chronic rejection (days 62 and 66), or adverse effects of mTOR inhibitor (day 32). In contrast, 12-week-long MD-3 therapy with transient conventional immunosuppression in the MD-3 group significantly prolonged the survival of liver allograft recipients (5, 96, 216, 412, 730 days; p = .0483). MD-3 effectively suppressed intragraft inflammatory cell infiltration, anti-donor T cell responses, and donor-specific antibody with intact anti-cytomegalovirus antibody responses. However, this regimen ended in chronic rejection. In conclusion, short-term therapy with MD-3 markedly improved liver allograft survival to 2 years without maintenance of immunosuppressant. MD-3 is therefore a promising immune-modulating agent for liver transplantation.

Dendritic Cells: Versatile Players in Renal Transplantation

Dendritic cells (DCs) induce and regulate adaptive immunity through migrating and maturing in the kidney. In this procedure, they can adopt different phenotypes—rejection-associated DCs promote acute or chronic injury renal grafts while tolerogenic DCs suppress the overwhelmed inflammation preventing damage to renal functionality. All the subsets interact with effector T cells and regulatory T cells (Tregs) stimulated by the ischemia–reperfusion procedure, although the classification corresponding to different effects remains controversial. Thus, in this review, we discuss the origin, maturation, and pathological effects of DCs in the kidney. Then we summarize the roles of divergent DCs in renal transplantation: taking both positive and negative stages in ischemia–reperfusion injury (IRI), switching phenotypes to induce acute or chronic rejection, and orchestrating surface markers for allograft tolerance via alterations in metabolism. In conclusion, we prospect that multidimensional transcriptomic analysis will revolute researches on renal transplantation by addressing the elusive mononuclear phagocyte classification and providing a holistic view of DC ontogeny and subpopulations.

Immunoglobulin M and Immunoglobulin G Subclass Distribution of Anti-galactose-Alpha-1,3-Galactose and Anti-N-Glycolylneuraminic Acid Antibodies in Healthy Korean Adults

BACKGROUND

Human preformed antibodies (Abs), anti-galactose-alpha-1,3-galactose (Gal) and anti-N-glycolylneuraminic acid (Neu5Gc), can react with porcine antigens of wild-type pigs. To provide basic population data of the Abs for potential application in clinical xenotransplantation, we developed enzyme-linked immunosorbent assay methods and investigated the serum titers of anti-Gal and anti-Neu5Gc Abs, including immunoglobulin (Ig) M and IgG along with its subclasses, in humans.

METHODS

Anti-Gal and anti-Neu5Gc Abs serum titers were measured in 380 healthy Korean adults using the in-house enzyme-linked immunosorbent assays. The frequency and median values of anti-Gal and anti-Neu5Gc were measured, and their class and subclass distribution were evaluated.

RESULTS

The detection frequencies of anti-Gal were 99.2%, 95.0%, 23.2%, 94.5%, 12.4%, and 3.4% for IgM, IgG, IgG1, IgG2, IgG3, and IgG4, respectively. The detection frequencies of anti-Neu5Gc Abs were 87.4%, 96.6%, 1.6%, 46.3%, 0.0%, and 0.0% for IgM, IgG, IgG1, IgG2, IgG3, and IgG4, respectively. The median values of anti-Gal IgM (1001.6 ng/mL) and IgG (1198.3 ng/mL) were significantly higher than those of anti-Neu5Gc Abs (IgM, 328.4 ng/mL; IgG, 194.7 ng/mL; P < .001). IgG2 titers of both anti-Gal and anti-Neu5Gc Abs correlated better with the IgG class than the titers of other IgG subclasses.

CONCLUSIONS

The titers of anti-Gal Abs were higher than those of anti-Neu5Gc Abs. IgG2 was the main IgG subclass in both anti-Gal and anti-Neu5Gc Abs. Variation in the titers of anti-Gal or anti-Neu5Gc Abs may partly explain the biological and immunologic changes that occur in recipients of xenotransplants.

Distinct Roles of LFA-1 and ICAM-1 on ILC2s Control Lung Infiltration, Effector Functions, and Development of Airway Hyperreactivity

Asthma is a heterogeneous airway inflammatory disease characterized by increased airway hyperreactivity (AHR) to specific and unspecific stimuli. Group 2 innate lymphoid cells (ILC2)s are type-2 cytokine secreting cells capable of inducing eosinophilic lung inflammation and AHR independent of adaptive immunity. Remarkably, reports show that ILC2s are increased in the blood of human asthmatics as compared to healthy donors. Nevertheless, whether ILC2 expression of adhesion molecules regulates ILC2 trafficking remains unknown. Our results show that IL-33-activated ILC2s not only express LFA-1 but also strikingly LFA-1 ligand ICAM-1. Both LFA-1^-/- and ICAM-1^-/- mice developed attenuated AHR in response to IL-33 intranasal challenge, associated with a lower airway inflammation and less lung ILC2 accumulation compared to controls. Our mixed bone marrow chimera studies however revealed that ILC2 expression of LFA-1 - but not ICAM-1 - was required for their accumulation in the inflamed lungs. Importantly, we found that LFA-1 remarkably controlled ILC2 homing to the lungs, suggesting that LFA-1 is involved in ILC2 trafficking to the lungs. Our exploratory transcriptomic analysis further revealed that ICAM-1 deficiency on ILC2s significantly affects their effector functions. While it downregulated pro-inflammatory cytokines such as Il5, Il9, Il13, and Csf2, it however notably also upregulated cytokines including Il10 both at the transcriptomic and protein levels. These findings provide novel avenues for future investigations, as modulation of LFA-1 and/or ICAM-1 represents an unappreciated regulatory mechanism for ILC2 trafficking and cytokine production respectively, potentially serving as therapeutic target for ILC2-dependent diseases such as allergic asthma.

Functional Human CD141+ Dendritic Cells in Human Immune System Mice

BACKGROUND

For the purpose of studying functional human dendritic cells (DCs) in a humanized mouse model that mimics the human immune system (HIS), a model referred to as HIS mice was established.

METHODS

Human immune system mice were made by engrafting NOD/SCID/IL2Rgammanull (NSG) mice with human hematopoietic stem cells (HSCs) following the transduction of genes encoding human cytokines and human leukocyte antigen (HLA)-A2.1 by adeno-associated virus serotype 9 (AAV9) vectors.

RESULTS

Our results indicate that human DC subsets, such as CD141+CD11c+ and CD1c+CD11c+ myeloid DCs, distribute throughout several organs in HIS mice including blood, bone marrow, spleen, and draining lymph nodes. The CD141+CD11c+ and CD1c+CD11c+ human DCs isolated from HIS mice immunized with adenoviruses expressing malaria/human immunodeficiency virus (HIV) epitopes were able to induce the proliferation of malaria/HIV epitopes-specific human CD8+ T cells in vitro. Upregulation of CD1c was also observed in human CD141+ DCs 1 day after immunization with the adenovirus-based vaccines.

CONCLUSIONS

Establishment of such a humanized mouse model that mounts functional human DCs enables preclinical assessment of the immunogenicity of human vaccines in vivo.

Tolerogenic dendritic cells in organ transplantation

Dendritic cells (DCs) are specialized cells of the innate immune system that are characterized by their ability to take up, process and present antigens (Ag) to effector T cells. They are derived from DC precursors produced in the bone marrow. Different DC subsets have been described according to lineage-specific transcription factors required for their development and function. Functionally, DCs are responsible for inducing Ag-specific immune responses that mediate organ transplant rejection. Consequently, to prevent anti-donor immune responses, therapeutic strategies have been directed toward the inhibition of DC activation. In addition however, an extensive body of preclinical research, using transplant models in rodents and nonhuman primates, has established a central role of DCs in the negative regulation of alloimmune responses. As a result, DCs have been employed as cell-based immunotherapy in early phase I/II clinical trials in organ transplantation. Together with in vivo targeting through use of myeloid cell-specific nanobiologics, DC manipulation represents a promising approach for the induction of transplantation tolerance. In this review, we summarize fundamental characteristics of DCs and their roles in promotion of central and peripheral tolerance. We also discuss their clinical application to promote improved long-term outcomes in organ transplantation.

CD4+ /CD8+ T-cell ratio correlates with the graft fate in pig-to-non-human primate islet xenotransplantation

BACKGROUND

Xenogeneic islet transplantation using porcine pancreata has been a promising option for substituting human islet transplantation. Moreover, recent advances in pre-clinical results have put islet xenotransplantation closer to the possibility of clinical application. While preparing for the era of clinical xenotransplantation, developing non-invasive immune monitoring method which could predict the graft fate could benefit the patient. However, there are few reports showing predictive immune parameters associated with the fate of the graft in islet xenotransplantation.

METHODS

The absolute number and ratio of T-cell subsets have been measured via flow cytometry from the peripheral blood of 16 rhesus monkeys before and after porcine islet xenotransplantation. The correlation between the graft survival and the absolute number or ratio of T cells was retrospectively analyzed.

RESULTS

The ratio of CD4⁺ versus CD8⁺ T cells was significantly reduced due to CD8⁺ effector memory cells' increase. Correlation analyses revealed that CD4⁺ /CD8⁺ , CD4⁺ /CD8⁺ naïve, CD4⁺ naïve/CD8⁺ naïve, and CD4⁺ central memory/CD8⁺ naïve cell ratios negatively correlated with the duration of graft survival. Conversely, further analyses discovered strong, positive correlation of CD4⁺ /CD8⁺ cell ratios within the early graft-rejected monkeys (≤60 days).

CONCLUSIONS

This retrospective study demonstrated that CD4⁺ /CD8⁺ ratios correlated with graft survival, especially in recipients which rejected the graft in early post-transplantation periods. CD4⁺ /CD8⁺ ratios could be used as a surrogate marker to predict the graft fate in pig-to-NHP islet xenotransplantation.

UVB-induced depletion of donor-derived dendritic cells prevents allograft rejection of immune-privileged hair follicles in humanized mice

Dendritic cells (DCs) are key targets for immunity and tolerance induction; they present donor antigens to recipient T cells by donor- and recipient-derived pathways. Donor-derived DCs, which are critical during the acute posttransplant period, can be depleted in graft tissue by forced migration via ultraviolet B light (UVB) irradiation. Here, we investigated the tolerogenic potential of donor-derived DC depletion through in vivo and ex vivo UVB preirradiation (UV) combined with the injection of anti-CD154 antibody (Ab) into recipients in an MHC-mismatched hair follicle (HF) allograft model in humanized mice. Surprisingly, human HF allografts achieved long-term survival with newly growing pigmented hair shafts in both Ab-treated groups (Ab-only and UV plus Ab) and in the UV-only group, whereas the control mice rejected all HF allografts with no hair regrowth. Perifollicular human CD3⁺ T cell and MHC class II⁺ cell infiltration was significantly diminished in the presence of UV and/or Ab treatment. HF allografts in the UV-only group showed stable maintenance of the immune privilege in the HF epithelium without evidence of antigen-specific T cell tolerance, which is likely promoted by normal HFs in vivo. This immunomodulatory strategy targeting the donor tissue exhibited novel biological relevance for clinical allogeneic transplantation without generalized immunosuppression.

CD4hiCD8low Double-Positive T Cells Are Associated with Graft Rejection in a Nonhuman Primate Model of Islet Transplantation

Peripheral CD4/CD8 double-positive (DP) T cells are associated with autoimmune disorders, cancer, and viral infection. However, the relationship between organ transplantation and DP T cells is unclear. Here, we examined the functional characteristics of peripheral DP T cells and analyzed their significance with respect to islet graft rejection in a nonhuman primate model of islet transplantation. DP T cells were functionally equivalent to conventional CD4 and CD8 T cells in terms of helper and cytotoxic activity, respectively. DP T cells expressed high levels of CXCR5 and PD-1 and secreted IFN-γ, IL-4, and IL-21 in amounts equivalent to those secreted by CD4 or CD8 T cells; also, they produced large amounts of granzyme B and perforin. In addition, under steady-state conditions, DP T cells expressed eomesodermin (Eomes) and promyelocytic leukemia zinc finger (PLZF) proteins, both of which act as transcription factors in innate/memory-like T cells. The number of peripheral DP T cells in the islet transplantation model was high in the group that experienced graft rejection; this was not the case in the long-term survival group. Interestingly, numbers of effector memory T cells (TEM) within the DP T cell population increased significantly during islet graft rejection, as did those of TEM within the cytotoxic CD8 T cells. Furthermore, the most conspicuous of which was the increase of CD4^hiCD8^low T cell subpopulation at that point. Taken together, the data suggest that peripheral DP T cells showing an innate/memory-like phenotype have both helper and cytotoxic activity in vitro and that they may act as a novel biomarker for graft rejection after islet transplantation.

Executive Summary of IPITA-TTS Opinion Leaders Report on the Future of β-Cell Replacement

The International Pancreas and Islet Transplant Association (IPITA), in conjunction with the Transplantation Society (TTS), convened a workshop to consider the future of pancreas and islet transplantation in the context of potential competing technologies that are under development, including the artificial pancreas, transplantation tolerance, xenotransplantation, encapsulation, stem cell derived beta cells, beta cell proliferation, and endogenous regeneration. Separate workgroups for each topic and then the collective group reviewed the state of the art, hurdles to application, and proposed research agenda for each therapy that would allow widespread application. Herein we present the executive summary of this workshop that focuses on obstacles to application and the research agenda to overcome them; the full length article with detailed background for each topic is published as an online supplement to Transplantation.

Porcine antigen-specific IFN-γ ELISpot as a potentially valuable tool for monitoring cellular immune responses in pig-to-non-human primate islet xenotransplantation

BACKGROUND

Recent progress in xenotransplantation of porcine islets to non-human primates (NHPs) gives hope for human clinical trials in the near future. Thus, implementation of an appropriate monitoring method to detect the development of detrimental porcine antigen-specific cellular immune responses is necessary. The enzyme-linked immunospot (ELISpot) assay has been widely used to monitor antigen-specific alloreactive T-cell responses in humans; however, the utility of porcine islet-specific ELISpot assay has not yet been thoroughly evaluated for pig-to-NHPs intraportal islet xenotransplantation.

METHODS

The optimal ELISpot assay conditions, including the number of responder and stimulator cells and the provision of costimulation, were determined. Then, ELISpot assays were conducted on serial stocks of peripheral blood mononuclear cell (PBMC) samples previously isolated from NHP recipients transplanted with porcine islets. Either splenocytes from donor pigs or pancreatic islets from third-party pigs were used for antigen stimulation. At the same time, the ratio of CD4(+) /CD8(+) T cells and the percentage of CD4(+) FoxP3(+) T cells in the peripheral blood were evaluated. Finally, liver biopsy samples were evaluated to assess the immunopathology of the grafts.

RESULTS

The optimal conditions for the ELISpot assay were defined as 2.5 × 10(5) responder cells incubated with 5.0 × 10(5) stimulator cells in 96-well, flat-bottom plates without further costimulation. Using donor splenocytes as stimulators, a serial interferon-gamma (IFN-γ) ELISpot assay with PBMCs from the monkeys with prolonged porcine islet grafts (>180 days) demonstrated that the number of donor antigen-specific IFN-γ-producing cells significantly increased upon overt graft rejection. However, use of third-party porcine islets as stimulators did not reflect graft rejection, suggesting that the use of donor-specific PBMCs, and not tissue (porcine islet)-specific cells, as stimulators could better serve the purpose of this assay in adult porcine islet transplantation. IFN-γ spot number was neither influenced by the peripheral blood CD4(+) /CD8(+) T-cell ratio nor the percentage of CD4(+) FoxP3(+) T cells. Finally, in cases of overt graft rejection, the number of IFN-γ spots and the graft-infiltrating T cells in biopsied liver samples increased simultaneously.

CONCLUSION

Use of PBMCs in a porcine antigen-specific IFN-γ ELISpot assay is a reliable method for monitoring T-cell-mediated rejection in pig-to-NHP islet xenotransplantation.

First update of the International Xenotransplantation Association consensus statement on conditions for undertaking clinical trials of porcine islet products in type 1 diabetes--Chapter 6: patient selection for pilot clinical trials of islet xenotransplantation

Patients in whom type 1 diabetes is complicated by impaired awareness of hypoglycemia and recurrent episodes of severe hypoglycemia are candidates for islet or pancreas transplantation if severe hypoglycemia persists after completion of a structured stepped care approach or a formalized medical optimization run-in period that provides access to hypoglycemia-specific education including behavioral therapies, insulin analogs, and diabetes technologies under the close supervision of a specialist hypoglycemia service. Patients with type 1 diabetes and end-stage renal failure who cannot meet clinically appropriate glycemic goals or continue to experience severe hypoglycemia after completion of a formalized medical optimization program under the guidance of an expert diabetes care team are candidates for islet or pancreas transplantation either simultaneously with or after a previous kidney transplant. Similarly, patients with type 2 diabetes and problematic hypoglycemia or renal failure who meet these criteria are considered candidates for islet replacement. Likewise, patients with pancreatectomy-induced diabetes in whom an islet autograft was not available or deemed inappropriate are candidates for islet or pancreas transplantation if extreme glycemic lability persists despite best medical therapy. To justify participation of these transplant candidates in early-phase trials of porcine islet cell products, lack of timely access to islet or pancreas allotransplantation due to allosensitization, high islet dose requirements, or other factors, or alternatively, a more favorable benefit-risk determination associated with the xenoislet than the alloislet or allopancreas transplant must be demonstrated. Additionally, in non-uremic xenoislet recipients, the risks associated with diabetes must be perceived to be more serious than the risks associated with the xenoislet product and the rejection prophylaxis, and in xenoislet recipients with renal failure, the xenoislet product and immunosuppression must not impact negatively on renal transplant outcomes. The most appropriate patient group for islet xenotransplantation trials will be defined by the specific characteristics of each investigational xenoislet product and related technologies applied for preventing rejection. Selecting recipients who are more likely to experience prolonged benefits associated with the islet xenograft will help these patients comply with lifelong monitoring and other public health measures.

Combination strategy of multi-layered surface camouflage using hyperbranched polyethylene glycol and immunosuppressive drugs for the prevention of immune reactions against transplanted porcine islets

This study suggests a novel method of stabilizing fragile porcine islets to prevent the dissociation after isolation and reducing immune cell invasion in a combination therapy of 'surface camouflaging' and immunosuppressive drugs (FK506, Rapamycin, MR-1, anti-CD19 mAb, and Clodrosome(®)) to effectively alleviate overall immune reactions against xenotransplanted porcine islets. The surface camouflage of pancreatic islets using biocompatible materials improved stabilization of pancreatic islet and prevented the infiltration of immune cells. Firstly, the surface of porcine islets was camouflaged by SH-6-arm-PEG-lipid and gelatin-catechol (artificial extracellular matrix) in order to stabilize the fragile isolated islets. Secondly, three different PEG layers (6-arm-PEG-SH, 6-arm-PEG-catechol, and linear PEG-SH) were chemically conjugated onto the surface of the stabilized porcine islets. Both artificial extracellular matrix (artificial ECM) and PEGylation effectively covered the surface of porcine islets without increasing the size of the whole islet. In addition, the viability and functionality of the islets were not affected by this multi-layer surface modification. The multi-layer modification significantly reduced the attachment of human serum albumin, fibronectin, and immunoglobulin G in comparison to the control collagen surface. The combination effect of multi-layer PEGylation and cocktailed immunosuppressive drugs on the survival time of the transplanted islets was assessed in a xenogeneic porcine-to-mouse model. The median survival time (MST) of 'artificial ECM + PEGylation' group was 4-fold increased compared to that of control group. In addition, the MST of 'artificial ECM + PEGylation + drug' group was 2.16-fold increased, compared to the 'control + drug' group. In conclusion, we proposed a novel porcine islet transplantation protocol using surface multi-layer modification and cocktailed immunosuppressive drugs, for stabilization and immunoprotection against xenogeneic immune reactions.

The Introduction of Human Heme Oxygenase-1 and Soluble Tumor Necrosis Factor-α Receptor Type I With Human IgG1 Fc in Porcine Islets Prolongs Islet Xenograft Survival in Humanized Mice

Apoptosis during engraftment and inflammation induce poor islet xenograft survival. We aimed to determine whether overexpression of human heme oxygenase-1 (HO-1) or soluble tumor necrosis factor-α receptor type I with human IgG1 Fc (sTNF-αR-Fc) in porcine islets could improve islet xenograft survival. Adult porcine islets were transduced with adenovirus containing human HO-1, sTNF-αR-Fc, sTNF-αR-Fc/HO-1 or green fluorescent protein (control). Humanized mice were generated by injecting human cord blood-derived CD34(+) stem cells into NOD-scid-IL-2Rγ(null) mice. Both HO-1 and sTNF-αR-Fc reduced islet apoptosis under in vitro hypoxia or cytokine stimuli and suppressed RANTES induction without compromising insulin secretion. Introduction of either gene into islets prolonged islet xenograft survival in pig-to-humanized mice transplantation. The sTNF-αR-Fc/HO-1 group showed the best glucose tolerance. Target genes were successfully expressed in islet xenografts. Perigraft infiltration of macrophages and T cells was suppressed with decreased expression of RANTES, tumor necrosis factor-α and IL-6 in treatment groups; however, frequency of pig-specific interferon-γ-producing T cells was not decreased, and humoral response was not significant in any group. Early apoptosis of islet cells was suppressed in the treatment groups. In conclusion, overexpression of HO-1 or sTNF-αR-Fc in porcine islets improved islet xenograft survival by suppressing both apoptosis and inflammation. HO-1 or sTNF-αR-Fc transgenic pigs have potential for islet xenotransplantation.

Long-term control of diabetes in immunosuppressed nonhuman primates (NHP) by the transplantation of adult porcine islets

Pig islets are an alternative source for islet transplantation to treat type 1 diabetes (T1D), but reproducible curative potential in the pig-to-nonhuman primate (NHP) model has not been demonstrated. Here, we report that pig islet grafts survived and maintained normoglycemia for >6 months in four of five consecutive immunosuppressed NHPs. Pig islets were isolated from designated pathogen-free (DPF) miniature pigs and infused intraportally into streptozotocin-induced diabetic rhesus monkeys under pretreatment with cobra venom factor (CVF), anti-thymocyte globulin (ATG) induction and maintenance with anti-CD154 monoclonal antibody and low-dose sirolimus. Ex vivo expanded autologous regulatory T cells were adoptively transferred in three recipients. Blood glucose levels were promptly normalized in all five monkeys and normoglycemia (90-110 mg/dL) was maintained for >6 months in four cases, the longest currently up to 603 days. Intravenous glucose tolerance tests during the follow-up period showed excellent glucose disposal capacity and porcine C-peptide responses. Adoptive transfer of autologous regulatory T cells was likely to be associated with more stable and durable normoglycemia. Importantly, the recipients showed no serious adverse effects. Taken together, our results confirm the clinical feasibility of pig islet transplantation to treat T1D patients without the need for excessive immunosuppressive therapy.

Therapeutic effect of anti CEACAM6 monoclonal antibody against lung adenocarcinoma by enhancing anoikis sensitivity

Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) plays a crucial role in tumorigenesis of lung cancer. However, the therapeutic potential for anti CEACAM6 monoclonal antibody (mAb) has only been limitedly explored. Here, we evaluate the therapeutic potential of naked anti CEACAM6 mAb against lung adenocarcinoma. Clone 8F5, recognizing B domain of CEACAM6, is established by immunizing A549 cells and screening for clones double positive for A549 and CEACAM6-Fc recombinant protein. We found that 85.7% of 70 resected lung adenocarcinoma tissue sections were positive for CEACAM6, whereas all squamous cell carcinoma examined were negative. A549 cells with high levels of CEACAM6 demonstrated more aggressive growth nature and showed increased paclitaxel chemosensitivity upon 8F5 binding. Treatment with 8F5 to A549 decreased cellular CEACAM6 expression and reversed anoikis resistance. 8F5 also decreased cellular status of Akt phosphorylation and increased apoptosis via caspase activation. In a mouse model of lung adenocarcinoma with xenotransplanted A549 cells, 8F5 treatment alone demonstrated 40% tumor growth inhibition. When combined with paclitaxel treatment, 8F5 markedly enhanced tumor growth inhibition, up to 80%. In summary, we demonstrate that anti CEACAM6 mAb is an effective therapeutic treatment for lung adenocarcinoma whose effect is further enhanced by combined treatment with paclitaxel.

Application of Humanized Mice in Immunological Research

During the past decade, the development of humanized mouse models and their general applications in biomedical research greatly accelerated the translation of outcomes obtained from basic research into potential diagnostic and therapeutic strategies in clinic. In this chapter, we firstly present an overview on the history and current progress of diverse humanized mouse models and then focus on those equipped with reconstituted human immune system. The update advancement in the establishment of humanized immune system mice and their applications in the studies of the development of human immune system and the pathogenesis of multiple human immune-related diseases are intensively reviewed here, while the shortcoming and perspective of these potent tools are discussed as well. As a valuable bridge across the gap between bench work and clinical trial, progressive humanized mouse models will undoubtedly continue to play an indispensable role in the wide area of biomedical research.

Orchestration of transplantation tolerance by regulatory dendritic cell therapy or in-situ targeting of dendritic cells

PURPOSE OF REVIEW

Extensive research in murine transplant models over the past two decades has convincingly demonstrated the ability of regulatory dendritic cells (DCregs) to promote long-term allograft survival. We review important considerations regarding the source of therapeutic DCregs (donor or recipient) and their mode of action, in-situ targeting of DCregs, and optimal therapeutic regimens to promote DCreg function.

RECENT FINDINGS

Recent studies have defined protocols and mechanisms whereby ex-vivo-generated DCregs of donor or recipient origin subvert allogeneic T-cell responses and promote long-term organ transplant survival. Particular interest has focused on how donor antigen is acquired, processed and presented by autologous dendritic cells, on the stability of DCregs, and on in-situ targeting of dendritic cells to promote their tolerogenic function. New evidence of the therapeutic efficacy of DCregs in a clinically relevant nonhuman primate organ transplant model and production of clinical grade DCregs support early evaluation of DCreg therapy in human graft recipients.

SUMMARY

We discuss strategies currently used to promote dendritic cell tolerogenicity, including DCreg therapy and in-situ targeting of dendritic cells, with a view to improved understanding of underlying mechanisms and identification of the most promising strategies for therapeutic application.

Minimizing immunosuppression in islet xenotransplantation

Pancreatic islet transplantation is a promising treatment option for Type 1 diabetes, but organ supply shortage limits its wide adoption. Pig islets are the most promising alternative source and many important measures such as donor animal selection, pig islet production release criteria, preclinical data and zoonosis surveillance prior to human clinical trials have been put forward as a consensus through the efforts of the International Xenotransplantation Association. To bring pig islet transplantation to clinical reality, the development of clinically applicable immunosuppression regimens and methods to minimize immunosuppression to reduce side effects should be established. This review encompasses immune rejection mechanisms in islet xenotransplantation, immunosuppression regimens that have enabled long-term graft survival in pig-to-nonhuman primate experiments and strategies for minimizing immunosuppression in islet xenotransplantation. By thoroughly examining the drugs that are currently available and in development and their individual targets within the immune response, the best strategy for enabling clinical trials of pig islets for Type 1 diabetes will be proposed.

Establishment of major histocompatibility complex homozygous gnotobiotic miniature swine colony for xenotransplantation

To overcome shortages of human donor organs for organ failure patients, we made a commitment to develop gnotobiotic miniature swine as an alternative organ donor source for xenotransplantation. For this, we have constructed an absolute barrier-sustained gnotobiotic facility. Pregnant sows of gnotobiotic miniature swine, were procured and germfree piglets were obtained by hysterectomy. These were maintained in germfree isolators for about 4 weeks, deprived of colostrum and were fed sterilized soybean milk. They were associated with di-flora, anaerobic Lactobacillus sp. and Streptococcus sp. After confirmation of successful associations, gnotobiotic piglets were transferred into the facility aseptically. The piglets are maintained on high-efficiency particle air-filtered air in and out; maintaining constant room air pressure of 33 ± 3 mmAq, and sterile water and diet. In 10 sessions of hysterectomy, 18 male and 32 female piglets were obtained of which piglets (M six, F eight) died within 5 days. Among live piglets, piglets (M eight, F 12) were confirmed to be germfree by microbiological monitoring. For research of xenotransplantation, one consistent experimental result was essential. Therefore, major histocompatibility complex class II which related innate immunity, homozygotic gnotobiotic miniature swine was developed. As a result, genotyping revealed 14 individuals to be homozygous for major histocompatibility complex class II (DRB, DQB) as 0301, three individuals were homozygous as 0201 and each of two were homozygous for DQB as 0701 and DRB as 0404, respectively. Genetic modifications and immunological research for ideal alternative organ sources are in progress.

Tolerogenic dendritic cells and their applications in transplantation

In transplantation immunology, the ultimate goal is always to successfully and specifically induce immune tolerance of allografts. Tolerogenic dendritic cells (tol-DCs) with immunoregulatory functions have attracted much attention as they play important roles in inducing and maintaining immune tolerance. Here, we focused on tol-DCs that have the potential to promote immune tolerance after solid-organ transplantation. We focus on their development and interactions with other regulatory cells, and we also explore various tol-DC engineering protocols. Harnessing tol-DCs represents a promising cellular therapy for promoting long-term graft functional survival in transplant recipients that will most likely be achieved in the future.

A mechanistic role for leptin in human dendritic cell migration: differences between ileum and colon in health and Crohn's disease

Dendritic cells (DC) migrate to lymph nodes on expression of C-C motif chemokine receptor 7 (CCR7) and control immune activity. Leptin, an immunomodulatory adipokine, functions via leptin receptors, signaling via the long isoform of receptor, LepRb. Leptin promotes DC maturation and increases CCR7 expression on blood DC. Increased mesenteric fat and leptin occur early in Crohn's disease (CD), suggesting leptin-mediated change in intestinal CCR7 expression on DC as a pro-inflammatory mechanism. We have demonstrated CCR7 expression and capacity to migrate to its ligand macrophage inflammatory protein 3β in normal human ileal DC but not colonic or blood DC. In CD, functional CCR7 was expressed on DC from all sites. Only DC populations containing CCR7-expressing cells produced LepRb; in vitro exposure to leptin also increased expression of functional CCR7 in intestinal DC in a dose-dependent manner. In conclusion, leptin may regulate DC migration from gut, in homeostatic and inflammatory conditions, providing a link between mesenteric obesity and inflammation.

Fundamental immunology of skin transplantation and key strategies for tolerance induction

Transplantation of allogeneic or xenogeneic skin grafts can evoke strong immune responses that lead to acute rejection of the graft tissues. In this process, donor-derived dendritic cells play crucial roles in the triggering of such immune responses. Both the innate and acquired host immune systems participate in graft rejection. At present, the rejection of skin grafts cannot be well-controlled by ordinary systemic immunosuppression therapy. Although several strategies for the long-term survival of allogeneic or xenogeneic skin grafts have been demonstrated in animal models, the induction of long-term tolerance to skin grafts is still a great challenge in clinical settings. In this article, we review the progress in the understanding of immune responses to skin grafts and discuss the possible methods that can decrease the immunogenicity of graft tissues and improve the survival of skin grafts, especially those included in preoperative pre-treatments.

Human hemato-lymphoid system mice: current use and future potential for medicine

To directly study complex human hemato-lymphoid system physiology and respective system-associated diseases in vivo, human-to-mouse xenotransplantation models for human blood and blood-forming cells and organs have been developed over the past three decades. We here review the fundamental requirements and the remarkable progress made over the past few years in improving these systems, the current major achievements reached by use of these models, and the future challenges to more closely model and study human health and disease and to achieve predictive preclinical testing of both prevention measures and potential new therapies.

In situ application of hydrogel-type fibrin-islet composite optimized for rapid glycemic control by subcutaneous xenogeneic porcine islet transplantation

Maximum engraftment of transplanted islets is essential for the clinical application of a subcutaneous site. Significant barriers to the current approaches are associated with their low effectiveness, complexity and unproven biosafety. Here, we evaluated and optimized a fibrin-islet composite for effective glycemic control in a subcutaneous site whose environment is highly hypoxic due to low vascularization potential. In the setting of xenogeneic porcine islet transplantation into the subcutaneous space of a diabetic mouse, the in vivo islet functions were greatly affected by the concentrations of fibrinogen and thrombin. The optimized hydrogel-type fibrin remarkably reduced the marginal islet mass to approximately one tenth that of islets without fibrin. This marginal islet mass was comparable to that in the setting of the subcapsular space of the kidney, which is a highly vascularized organ. Highly vascularized structures were generated inside and on the outer surface of the grafts. A hydrogel-type fibrin-islet composite established early diabetic control within an average of 3.4days after the transplantation. In the mechanistic studies, fibrin promoted local angiogenesis, enhanced islet viability and prevented fragmentation of islets into single cells. In conclusion, in situ application of hydrogel-type fibrin-islet composite may be a promising modality in the clinical success of subcutaneous islet transplantation.