Tolerance and Long-Lasting Peripheral Chimerism After Allogeneic Intestinal Transplantation in MGH Miniature Swine

Development of a large animal orthotopic intestinal transplantation model with long-term survival for study of immunologic outcomes

Introduction

Intestinal transplantation (ITx) is the last remaining therapy for patients with intestinal failure once parenteral nutrition is no longer an option, however its use is limited by immunological complications, including high rates of rejection and morbidity associated with immunosuppression, such as infection and malignancy. We aimed to develop a large animal model of ITx with which to study the immune response to ITx and to design and test tolerance induction regimens.

Methods

Learning from prior complications, we developed and progressively improved both surgical methods for the donor and recipient as well as postoperative management strategies. Methods of stoma generation, bowel positioning, vessel preparation, and fluid management were optimized. The immunosuppression strategy mirrored our clinical regimen.

Results

As a result of our modifications, results improved from survival less than 1 month to consistent long-term survival with good graft function. We review several techniques that were developed to avoid pitfalls that were encountered, which can be used to optimize outcomes in this model.

Discussion

Achieving long-term survival after swine orthotopic ITx permits immunological analysis and pre-clinical trials in a large animal model of ITx.

Lack of antidonor alloantibody does not indicate lack of immune sensitization: studies of graft loss in a haploidentical hematopoietic cell transplantation swine model

Loss of chimerism is an undesirable outcome of allogeneic hematopoietic cell transplantation (HCT) after reduced-intensity conditioning. Understanding the nature of cellular and humoral immune responses to HCT after graft loss could lead to improved retransplantation strategies. We investigated the immunologic responses after graft loss in miniature swine recipients of haploidentical HCT that received reduced-intensity conditioning. After the loss of peripheral blood chimerism, antidonor cellular responses were present without detectable antidonor antibody. Reexposure to donor hematopoietic cells after graft loss induced a sensitized antidonor cellular response. No induced antidonor antibody response could be detected despite evidence of cellular sensitization to donor cells. In contrast, unconditioned animals exposed repeatedly to similar doses of haploidentical donor cells developed antidonor antibody responses. These results could have important implications for the design of treatment strategies to overcome antidonor responses in HCT and improve the outcome of retransplantation after graft loss.