Objective
Allogeneic cell therapy is emerging as a cure for Type 1 Diabetes, yet the long-term function of these allogeneic cells is currently dependent upon immunosuppression. Immunosuppression protocols attempt to balance the risk of rejection with the risks of neoplasia and infection. Protocol monitoring of the graft has begun, and includes assessing body weight, fasting glucose/C-peptide, hemoglobin A1c, and presence donor-specific antibodies, with adjunctive strategies being developed in the setting of suspected rejection. However, these surveillance modalities identify graft injury as a lagging indicator of rejection. The delayed identification of graft injury precludes the ability to deliver interventions to rescue the graft.
We propose a novel strategy to monitor the immune system and predict graft rejection that avoids invasive biopsies, enables characterization of the immune response, and creates a therapeutic window for personalized immune suppression that extends graft function. The foundation of this technology began in cancer metastasis, in which we reported that subcutaneous scaffold implants sample immune cells and identify immune cell phenotypes within tissues that are characteristic of cancer metastasis, with the immune cells recruiting metastatic cancer cells. We have extended this technology for monitoring immune responses to predict immune injury of allogeneic heart transplants, and for early identification of immune responses prior to initiation of autoimmune destruction of islets. Here, we propose to translate the diagnostic potential of this immunosurveillance technology to clinically relevant islet transplantation scenarios. We propose to employ scaffolds that support the formation of surrogate tissue, from which immune cells can be isolated and analyzed to identify predictive biomarkers of effective or insufficient immune suppression in allograft recipients with underlying autoimmune disease. This analysis approach has the potential to identify the early signs of rejection, allowing for personalization of immune interventions that protect the graft.
Background Rationale
Solid organ and cell transplantation are life-saving procedures for many end-stage organ dysfunction. Solid organ transplants (SOT), which have been performed for decades, have an estimated cost of $30B, with cell transplant therapies emerging as an exciting clinical opportunity for treating Type 1 Diabetes. Most transplants are allogeneic, and patients must receive immunosuppression, which is aggressively applied in a one-size-fits-all approach. Graft rejection remains a major challenge, yet strategies for monitoring organ or cell transplants are limited. No current method can predict transplant rejection to rescue a graft before significant injury. Also, immunosuppression substantially increases risk of infections, neoplasia, and renal damage. Effectively all late graft losses are attributed to immunosuppression, either over-suppression (e.g., infection or malignancy) or under-suppression (by acute or chronic rejection). These risks are exacerbated for young transplant recipients who must undergo decades of immunosuppression. For example, non-Hodgkin’s lymphoma risk is >200 fold greater in pediatric transplant recipients than for other children. Personalized immunosuppression protocols could reduce graft failure in transplant recipients, yet we lack the tools to personalize immune suppression. A minimally-invasive system that identifies biomarkers of active immune responses would predict rejection and transform the transplantation field by enabling personalized immunosuppression with consequently minimized comorbidities. We have developed an implantable device that remotely monitors immune biomarkers of graft rejection, which would enable preservation of transplant health through personalizing immune suppression.
Monitoring of graft health has been a key component of clinical practice for solid organ transplantation, and is emerging for islet transplantation. In heart and kidney transplantation, graft health is monitored with frequent biopsies for diagnosing rejection, with many limitations. This invasive procedure is a patient stressor, with a risk of serious complication. Also, graft biopsy has high incidence of sampling errors and variability. In heart transplantation, biopsy measures damage, a lagging indicator of allograft rejection. Histological evidence lags behind molecular signs of rejection, and the actionable importance of mild graft rejection as identified by histology is unclear. Alternatively, blood-based surveillance methods measure T cell responses and graft injury, but can only rule out graft damage rather than diagnose rejection. Gene expression profiling (GEP, such as the AlloMap test) is influenced by common immune suppression. Cell-free donor-derived DNA (cfDNA, such as the AlloSure test) assesses graft cell death. Novel blood-based biomarkers such as miRNAs and extracellular vesicles also show low sensitivity and specificity for rejection. In islet transplantation, protocol monitoring of the graft has begun, and includes assessing body weight, fasting glucose/C-peptide, hemoglobin A1c, and presence donor-specific antibodies, with adjunctive strategies being developed in the setting of suspected rejection. Collectively, these assays for monitoring in organ and cell transplantation are limited to lagging indicators of rejection for irreversible graft injury and lack predictive power. A novel assay is needed to identify early rejection to create a personalized therapeutic window for rescuing the graft.
Description of Project
Type 1 diabetes (T1D) affects an estimated 1.25 million people in the US, and the most common treatment is life-long exogenous insulin. Although insulin therapy has been successful, hypoglycemic events and vascular complications persist. Intraportal allogeneic islet transplantation has had successful clinical results, yet is limited by a shortage of donor islets, for which allogeneic human pluripotent stem cells represent an unlimited source of functional β-cells. The long-term function of these allogeneic cells is currently dependent upon immunosuppression, with the immunosuppression protocol attempting to balance the risk of rejection with the risks of neoplasia and infection. Protocol monitoring of the graft has begun, and includes assessing body weight, fasting glucose/C-peptide, hemoglobin A1c, and presence donor-specific antibodies, with adjunctive strategies being developed in the setting of suspected rejection. However, these surveillance modalities identify graft injury as a lagging indicator of rejection. The delayed identification of graft injury precludes the ability to deliver interventions to rescue the graft, similar to how T1D onset results in a critical loss of β-cell mass prior to diagnosis, eliminating the possibility for preventative treatment. Graft injury and rejection further exacerbates the shortage of donor islets, as a single patient would need multiple transplants over the course of their lifetime. Immune suppression to prevent rejection is thus applied aggressively, resulting in susceptibility to infections and renal impairment. Enhanced immune monitoring is needed to identify grafts pre-rejection to enable intervention, as well as to monitor the efficacy of more personalized immune suppression regimens. We propose to employ scaffolds that support the formation of surrogate tissue, from which immune cells can be isolated and analyzed to identify predictive biomarkers of effective or insufficient immune suppression in allograft recipients with underlying autoimmune disease. This analysis approach has the potential to identify the early signs of rejection, allowing for personalization of immune interventions that protect the graft.
Anticipated Outcome
Our preliminary data identify the scaffold-based immune dynamics which provide a specific molecular signature correlating with solid organ transplant rejection, which we anticipate can be adapted for allogeneic islet transplantation. We anticipate that analysis of the scaffolds can distinguish recipients with graft rejection from recipients with operational transplant tolerance prior to the onset of significant graft injury. We anticipate that core biopsy of the scaffold will sample sufficient numbers of multiple immune cell types for analysis, including monocytes, macrophages, T cells, B cells and NK cells, all of which are involved in transplant rejection. An additional outcome will be the cellular and molecular composition in the scaffold as a measure of transplant health following immune suppression, along with a dynamic analysis of T cell phenotypes that are present with graft acceptance relative to graft rejection. We anticipate rejection will be associated with greater T cell activation, whereas graft operational tolerance will have decreased T cell activation and increased regulatory T cell function. Additional rejection mechanisms can also be evaluated, such as decreased T cell motility or NK cell responses. We anticipate identifying distinct cell phenotypes at the scaffold that influence T cell responses underlying rejection or operational tolerance. We anticipate gene expression sequencing will provide a more comprehensive and unbiased strategy relative to other experimental and clinical approaches.
The scaffold, since it is not a vital tissue, allows for regular sampling of immune cells that is not possible with analysis of the graft itself. The studies will thus determine how early we can identify signs of rejection, which we anticipate, based on our previous studies, will be on the order of several weeks. A key component of this determination will be the development of the computational methods for characterization of immune responses in graft rejection. We anticipate that our computational methods will lead to novel methods for characterizing the immune dynamics present with graft acceptance and graft rejection. In graft rejection, we anticipate an early signature that have gene expression that is more representative of innate immune cells relative to adaptive immune cells, and at time closer to rejection the signature will be more representative of adaptive immune cell relative to innate immune cells. Collectively, we anticipate that the analysis of the scaffold will identify immune responses prior to significant graft injury, and identify the immune responses that should be targeted to prevent progression of graft rejection.
Relevance to T1D
Type 1 diabetes (T1D) affects an estimated 1.25 million people in the US, and the most common treatment is life-long exogenous insulin. Although insulin therapy has been successful, hypoglycemic events and vascular complications persist. Intraportal allogeneic islet transplantation has had successful clinical results, yet is limited by a shortage of donor islets, for which human pluripotent stem cells represent an unlimited source of functional β-cells. The long-term function of these allogeneic cells is currently dependent upon immunosuppression, with the immunosuppression protocol attempting to balance the risk of rejection with the risks of neoplasia and infection. Protocol monitoring of the graft has begun, and includes assessing body weight, fasting glucose/C-peptide, hemoglobin A1c, and donor-specific antibody, with adjunctive strategies being developed in the setting of suspected rejection. These surveillance modalities identify graft injury as a lagging indicator of rejection, however, and cannot predict risk of graft damage nor enable interventions to rescue the graft. Immune suppression to prevent rejection is thus applied aggressively, resulting in susceptibility to infections and renal impairment. We propose to employ scaffolds that support the formation of surrogate tissue, from which immune cells can be isolated and analyzed to identify predictive biomarkers of effective or insufficient immune suppression in allograft recipients with underlying autoimmune disease. This analysis approach has the potential to identify the early signs of rejection, allowing for personalization of immune interventions that protect the graft and prolong graft function.