Monitoring tolerance after human liver transplantation

Cell Therapy as a Tool for Induction of Immunological Tolerance after Liver Transplantation

Transplantation of solid organs, including liver, induces a number of serious complications related to immune incompatibility and requiring long-term use of immunosuppressive drugs. Finding the ways to inducing recipient immunological tolerance to the grafts is a top priority in organ transplantation and immunology. Along with the search for immunosupressive therapy, the development of alternative approaches to induction of immunological tolerance based on cell technologies is now in progress. In this regard, studies of the so-called spontaneous operational tolerance observed in ~20% patients after orthotopic liver transplantation is a promising trend. Understanding of this phenomenon can shed light on the mechanisms of immunological tolerance to allografts and will help to identify specific tolerance biomarkers and cell types with the aptitude for the induction of tolerance to liver allografts.

Immunologic Monitoring to Personalize Immunosuppression After Liver Transplant

Although immunosuppressive drugs have enhanced patient outcomes in transplantation, the liver transplant community has made significant research efforts into the discovery of more accurate and precise methods of posttransplant monitoring and diagnosing. Current research in biomarkers reveals many promising approaches.

Epstein-Barr virus DNA monitoring in serum and whole blood in pediatric liver transplant recipients who do or do not discontinue immunosuppressive therapy

The rate of PTLD can be reduced by weaned IS guided by monitoring of EBV DNA. In this single-center retrospective case series study, we analyzed how reduction in IS influenced EBV DNA levels in whole blood and serum in 30 children during the first year after liver transplantation, and how these levels were related to symptoms putatively due to EBV. Primary and reactivated EBV infection was seen in 18 (60%) and eight patients (27%), respectively. Thirteen patients (42%) developed chronic high load the first year post-transplant. IS was successfully discontinued in six patients the first year post-transplant and in another two patients within 3 years. EBV DNA levels were reduced, but persisted long term in all the eight patients who had IS completely withdrawn. There was no case of PTLD. In summary, EBV DNAemia and chronic high load were very common after pediatric liver transplantation. Liver graft tolerance facilitates radical reduction in IS treatment, which may prevent PTLD, but EBV DNAemia may persist long term after discontinued IS.

Tolerance in liver transplantation: Biomarkers and clinical relevance

Transplantation is the optimal treatment for end-stage organ failure, and modern immunosuppression has allowed important progress in short-term outcomes. However, immunosuppression poorly influences chronic rejection and elicits chronic toxicity in current clinical practice. Thus, a major goal in transplantation is to understand and induce tolerance. It is well established that human regulatory T cells expressing the transcription factor FoxP3 play important roles in the maintenance of immunological self-tolerance and immune homeostasis. The major regulatory T cell subsets and mechanisms of expansion that are critical for induction and long-term maintenance of graft tolerance and survival are being actively investigated. Likewise, other immune cells, such as dendritic cells, monocyte/macrophages or natural killer cells, have been described as part of the process known as "operational tolerance". However, translation of these results towards clinical practice needs solid tools to identify accurately and reliably patients who are going to be tolerant. In this way, a plethora of genetic and cellular biomarkers is raising and being validated worldwide in large multi-center clinical trials. Few of the studies performed so far have provided a detailed analysis of the impact of immunosuppression withdrawal on pre-existing complications derived from the long-term administration of immunosuppressive drugs and the side effects associated with them. The future of liver transplantation is aimed to develop new therapies which increase the actual low tolerant vs non-tolerant recipients ratio.

Pediatric transplantation and tolerance: past, present, and future

Solid organ transplantation is the treatment of choice in children with end-stage organ failure. With improving methods of transplant surgery and post-transplant care, transplantation is more frequently performed worldwide. However, lifelong and non-specific suppression of the recipient's immune system is a cause of significant morbidity in children, including infection, diabetes, and cancer. There is a great need to develop IS minimization/withdrawal and tolerance induction approaches.

Elevated blood eosinophil count is a valuable biomarker for predicting late acute cellular rejection after liver transplantation

BACKGROUND

Recent studies have indicated the value of increased blood eosinophil counts for the diagnosis of acute cellular rejection (ACR) after orthotopic liver transplantation (OLT). However, the relationship between eosinophil count and late ACR at more than 6 months after OLT is still unclear.

METHODS

We sought to retrospectively analyzed the ACR predictive value of eosinophil counts. In the day before or the day of biopsy among 40 biopsies performed on 37 patients beyond 6 months after OLT.

RESULTS

Relative eosinophil count was significantly higher in the ACR (n = 24) than the non-ACR cohort, albeit with no significant difference in absolute eosinophil count. Receiver operating characteristic (ROC) analysis showed an absolute eosinophil count of 0.145 × 10(9)/L and a relative eosinophil count of 2.3% to show the highest Youden index with area under the ROC curves of 0.746 and 0.813, respectively. When absolute eosinophil count ≥ 0.145 × 10(9)/L or relative eosinophil count ≥ 2.3% was defined to be elevated, the sensitivity and specificity to predict ACR were 45.8% and 87.5%, and 75% and 87.5%, respectively. When the absolute eosinophil count ≥ 0.285 × 10(9)/L or relative eosinophil count ≥ 3% was defined as elevated, the sensitivity and specificity were 25% and 100%, and 50% and 100%, respectively. All patients with an absolute eosinophil count ≥ 0.285 × 10(9)/L showed a relative eosinophil count ≥ 3%.

CONCLUSIONS

Elevated blood eosinophil count was a valuable biomarker to predict late ACR after OLT.

Living related liver transplant following bone marrow transplantation from same donor: long-term survival without immunosuppression

We report long-term (seven yr) immunological tolerance in a 16-yr-old boy, to a liver allograft donated by his father following a bone marrow transplant at age 2.5 yr from the same donor. The bone marrow transplant was complicated by severe GVHD leading to liver failure and the ensuing need for a liver transplant, performed under planned avoidance of immunosuppression. At one wk post-transplant, although a liver biopsy was histologically compatible with acute rejection, favorable clinical and biochemical evolution precluded initiating immunosuppressive therapy, thus highlighting the need for caution when interpreting early histological changes so that administration of unnecessary immunosuppression can be avoided. Induction of tolerance in transplant recipients remains an elusive goal. In those patients who had received conventional bone marrow transplants and had endured the consequences of GVHD, development of macrochimerism may allow immunosuppression-free solid organ transplantation from the same donor.

Immunology of uterine transplantation: a review

The idea of using organ transplantation to solve quality-of-life issues was first introduced a century ago, with cornea transplants and thrusted before the world again in 1998, following a controversial hand transplant. Uterus transplantation (UTn) has been proposed as another quality-of-life transplant for the cure of permanent uterine factor infertility. In order to proceed in humans, a greater appreciation of the immunological mechanisms that underlie UTn is desirable. Allogeneic UTn (animal model) was first described by 2 studies in 1969. The first and only human UTn, performed in 2000, was an early attempt with limited use of animal model experiments prior to moving onto the human setting. Since then, work using rat, mouse, ovine, goat, and nonhuman primate models has demonstrated that the uterus is a very different but manageable organ immunologically compared to other transplanted organs. Therefore, specifically exploring immunological issues relating to UTn is a valuable and necessary part of the inevitable scientific process leading to successful human UTn.

Circulating cytokines are associated with human islet graft function in type 1 diabetes

Islet cell transplantation has considerable potential as a cure for type 1 diabetes, but recurrent autoimmunity and allograft rejection in which both cytokines play an important role are major obstacles. Using a new approach considering confounders by regression analysis, we investigated circulating cytokines and their association with graft function in type 1 diabetes patients who underwent either simultaneous islet kidney (SIK) or islet after kidney (IAK) transplantation. After transplantation, interleukin (IL)-10 was lower in SIK recipients with subsequent loss of graft function in comparison to recipients maintaining graft function. Before transplantation, high IL-13 and IL-18 concentrations were prospectively associated for subsequent loss of graft function in IAK recipients, whereas in SIK recipients, high macrophage migration inhibitory factor (MIF) concentrations were associated with subsequent loss of graft function. Circulating cytokines are associated with islet graft function in patients with long-standing type 1 diabetes when considering confounders.

FoxP3 in peripheral blood is associated with operational tolerance in liver transplant patients during immunosuppression withdrawal

BACKGROUND

Human liver allografts do sometimes survive in a recipient after withdrawal of immunosuppression (IS), commonly referred to as "operational tolerance." Preliminary clinical data have suggested an increase in the frequency of regulatory T cells (Treg) CD4+CD25 high and FoxP3 expression in operationally tolerant liver transplant recipients (Gr-T). In the context of human liver transplantation, the dynamics of Treg have not been studied. We designed a prospective study to ascertain the profile of the Treg population and FoxP3 expression during IS withdrawal.

METHODS

To identify such parameters, we analyzed peripheral blood mononuclear cell populations and FoxP3 mRNA expression in 12 liver allograft recipients under cyclosporine A-based IS, who showed stable function of the allograft for more than 2 years.

RESULTS

An increase was observed in the frequency of CD4+CD25 high cells when the IS was withdrawn in Gr-T patients (n=5). These patients exhibited a 3.5-fold increase for relative mRNA FoxP3 expression before the complete IS withdrawal and this continued when IS therapy was stopped. In patients who suffered rejection (n=7) there was no increase in the CD4+CD25 high cells or FoxP3 expression.

CONCLUSIONS

With the present study, the first evidence is provided that the increase of CD4+CD25 high T cells and FoxP3 transcripts is associated with operational tolerance in liver transplanted patients during IS withdrawal.