Anti-Hla donor-specific antibody monitoring in pancreas transplantation: Role of protocol biopsies

Pancreas rejection: quieting the storm to preserve graft function

PURPOSE OF REVIEW

Allograft rejection remains enigmatic and elusive following pancreas transplantation. In the absence of early technical pancreas graft failure, pancreas allograft rejection is the major cause of death-censored pancreas graft loss both short- and long-term. Despite this circumstance, there are variations in the diagnosis and treatment of pancreas rejection. In this article, we summarize recent literature, review common practices, and discuss various management algorithms.

RECENT FINDINGS

Although pancreas allograft biopsy is the gold standard for the diagnosis of rejection, not all transplant centers have the capability to perform pancreas allograft biopsy. Some centers depend on clinical or laboratory parameters exclusively or rely on dysfunction or biopsy of a simultaneous kidney allograft as a marker for pancreas allograft rejection. New biomarkers are evolving to assess the risk for rejection and may help to diagnose early rejection. In the future, the use of machine learning algorithms and artificial intelligence may play a role identifying patients at risk and detecting pancreas rejection without performing a pancreas allograft biopsy.

SUMMARY

Despite decades of experience in pancreas transplantation, the diagnosis and management of pancreas rejection remains challenging. Emerging biomarkers and machine learning algorithms are needed to mitigate immunological complications and guide immunosuppression in these patients.

The Use of Long-Term Monthly Basiliximab Infusions as Rescue Maintenance Immunosuppression in Pancreas Transplant Recipients

This single-center retrospective study was designed to evaluate the use of basiliximab as an alternative rescue maintenance immunosuppression in situations where standard maintenance immunosuppression is not tolerated after a pancreas transplant. All pancreas transplants performed between January 11, 2006, and January 6, 2022, were reviewed. All recipients received rabbit antithymocyte globulin (rATG) induction with tacrolimus + sirolimus maintenance for simultaneous pancreas and kidney (SPK) and additional low-dose mycophenolic acid for pancreas transplant alone (PTA). Basiliximab 40mg IV q 4 weeks was either added to or in replacement of adjunct immunosuppression in cases of medication intolerance. All recipients who received ≥3 months of basiliximab with ≥1 year follow-up were included. 29/557 (5.2%) recipients (5 SPK and 24 PTA) were identified. Median time to switch was 13 months. When compared 1:2 to matched controls on standard immunosuppression, there was no difference in pancreas rejection, allograft loss, or mortality. Eleven recipients had 13 episodes of pancreas rejection at a median of 28 months post conversion. Eight pancreas allografts failed at a median of 28 months post conversion, and there were five deaths-all occurring in PTA, 4/5 occurring ≥1 year after discontinuation of basiliximab. Renal allograft rejection occurred in one SPK and there was one renal allograft loss. Five PTA developed renal failure. Ten remain on basiliximab (2/5 SPK, 8/24 PTA) at a median of 44 months with good pancreas and kidney function; 4 pts > 4 years. Basiliximab can be considered an alternative rescue maintenance strategy in pancreas transplant recipients who failed other conventional agents.

Analysis of Rejection, Infection and Surgical Outcomes in Type I Versus Type II Diabetic Recipients After Simultaneous Pancreas-Kidney Transplantation

Given the increasing frequency of simultaneous pancreas-kidney transplants performed in recipients with Type II diabetes and CKD, we sought to evaluate possible differences in the rates of allograft rejection, infection, and surgical complications in 298 Type I (T1D) versus 47 Type II (T2D) diabetic recipients of simultaneous pancreas-kidney transplants between 2006-2017. There were no significant differences in patient or graft survival. The risk of biopsy-proven rejection of both grafts was not significantly different between T2D and T1D recipients (HRpancreas = 1.04, p = 0.93; HRkidney = 0.96; p = 0.93). Rejection-free survival in both grafts were also not different between the two diabetes types (ppancreas = 0.57; pkidney = 0.41). T2D had a significantly lower incidence of de novo DSA at 1 year (21% vs. 39%, p = 0.02). There was no difference in T2D vs. T1D recipients regarding readmissions (HR = 0.77, p = 0.25), infections (HR = 0.77, p = 0.18), major surgical complications (HR = 0.89, p = 0.79) and thrombosis (HR = 0.92, p = 0.90). In conclusion, rejection, infections, and surgical complications after simultaneous pancreas-kidney transplant are not statistically significantly different in T2D compared to T1D recipients.

Banff 2022 pancreas transplantation multidisciplinary report: Refinement of guidelines for T cell-mediated rejection, antibody-mediated rejection and islet pathology. Assessment of duodenal cuff biopsies and noninvasive diagnostic methods

The Banff pancreas working schema for diagnosis and grading of rejection is widely used for treatment guidance and risk stratification in centers that perform pancreas allograft biopsies. Since the last update, various studies have provided additional insight regarding the application of the schema and enhanced our understanding of additional clinicopathologic entities. This update aims to clarify terminology and lesion description for T cell-mediated and antibody-mediated allograft rejections, in both active and chronic forms. In addition, morphologic and immunohistochemical tools are described to help distinguish rejection from nonrejection pathologies. For the first time, a clinicopathologic approach to islet pathology in the early and late posttransplant periods is discussed. This update also includes a discussion and recommendations on the utilization of endoscopic duodenal donor cuff biopsies as surrogates for pancreas biopsies in various clinical settings. Finally, an analysis and recommendations on the use of donor-derived cell-free DNA for monitoring pancreas graft recipients are provided. This multidisciplinary effort assesses the current role of pancreas allograft biopsies and offers practical guidelines that can be helpful to pancreas transplant practitioners as well as experienced pathologists and pathologists in training.

BSHI and BTS UK guideline on the detection of alloantibodies in solid organ (and islet) transplantation

Solid organ transplantation represents the best (and in many cases only) treatment option for patients with end-stage organ failure. The effectiveness and functioning life of these transplants has improved each decade due to surgical and clinical advances, and accurate histocompatibility assessment. Patient exposure to alloantigen from another individual is a common occurrence and takes place through pregnancies, blood transfusions or previous transplantation. Such exposure to alloantigen's can lead to the formation of circulating alloreactive antibodies which can be deleterious to solid organ transplant outcome. The purpose of these guidelines is to update to the previous BSHI/BTS guidelines 2016 on the relevance, assessment, and management of alloantibodies within solid organ transplantation.

Comparison of long-term outcomes in simultaneous pancreas-kidney transplant versus simultaneous deceased donor pancreas and living donor kidney transplant

Simultaneous deceased donor pancreas and living donor kidney transplant (SPLK) has certain advantages over conventional simultaneous pancreas-kidney transplant (SPK) and may be beneficial for overcoming the paucity of organs needed for diabetic patients requiring transplant. We compared the clinical outcomes of patients who underwent either SPK (n = 149) or SPLK (n = 46) in terms of pre- and post-transplantation variables, development of de novo DSA, occurrence of biopsy-proven acute rejection (BPAR), and graft survival rates. There were no significant differences in the baseline characteristics between the SPK and SPLK groups except for the shorter cold ischemic time of kidney grafts, shorter duration of diabetes, older age of pancreas graft-donors, and younger age of kidney graft-donors in the SPLK group. Our results showed that the death-censored pancreas graft survival rate was lower in the SPLK group. In addition, the incidence of BPAR of the pancreas graft was higher in the SPLK group. There was no significant difference in the presence of de novo DSA and the rates of kidney graft failure, kidney BPAR, and mortality. Our results show that SPLK can be considered an alternative option for SPK although higher incidences of BPAR and graft failure of pancreas after SPLK need to be overcome.

Immune Profiling of Peripheral Blood Mononuclear Cells at Pancreas Acute Rejection Episodes in Kidney-Pancreas Transplant Recipients

Profiling of circulating immune cells provides valuable insight to the pathophysiology of acute rejection in organ transplantation. Herein we characterized the peripheral blood mononuclear cells in simultaneous kidney-pancreas transplant recipients. We conducted a retrospective analysis in a biopsy-matched cohort (n = 67) and compared patients with biopsy proven acute rejection (BPAR; 41%) to those without rejection (No-AR). We observed that CD3+ T cells, both CD8+ and CD4+, as well as CD19+ B cells were increased in patients with BPAR, particularly in biopsies performed in the early post-transplant period (<3 months). During this period immune subsets presented a good discriminative ability (CD4+ AUC 0.79; CD8+ AUC 0.80; B cells AUC 0.86; p < 0.05) and outperformed lipase (AUC 0.62; p = 0.12) for the diagnosis of acute rejection. We further evaluated whether this could be explained by differences in frequencies prior to transplantation. Patients presenting with early post-transplant rejection (<3 months) had a significant increase in T-cell frequencies pre-transplant, both CD4+ T cells and CD8+ T cells (p < 0.01), which were associated with a significant inferior rejection-free graft survival. T cell frequencies in peripheral blood correlated with pancreas acute rejection episodes, and variations prior to transplantation were associated with pancreas early acute rejection.

Donor-derived Cell-free DNA Shows High Sensitivity for the Diagnosis of Pancreas Graft Rejection in Simultaneous Pancreas-kidney Transplantation

BACKGROUND

Pancreas graft status in simultaneous pancreas-kidney transplant (SPKTx) is currently assessed by nonspecific biochemical markers, typically amylase or lipase. Identifying a noninvasive biomarker with good sensitivity in detecting early pancreas graft rejection could improve SPKTx management.

METHODS

Here, we developed a pilot study to explore donor-derived cell-free DNA (dd-cfDNA) performance in predicting biopsy-proven acute rejection (P-BPAR) of the pancreas graft in a cohort of 36 SPKTx recipients with biopsy-matched plasma samples. dd-cfDNA was measured using the Prospera test (Natera, Inc.) and reported both as a fraction of the total cfDNA (fraction; %) and as concentration in the recipient's plasma (quantity; copies/mL).

RESULTS

In the absence of P-BPAR, dd-cfDNA was significantly higher in samples collected within the first 45 d after SPKTx compared with those measured afterward (median, 1.00% versus 0.30%; median, 128.2 versus 35.3 cp/mL, respectively with both; P  = 0.001). In samples obtained beyond day 45, P-BPAR samples presented a significantly higher dd-cfDNA fraction (0.83 versus 0.30%; P  = 0.006) and quantity (81.3 versus 35.3 cp/mL; P  = 0.001) than stable samples. Incorporating dd-cfDNA quantity along with dd-cfDNA fraction outperformed dd-cfDNA fraction alone to detect active rejection. Notably, when using a quantity cutoff of 70 cp/mL, dd-cfDNA detected P-BPAR with a sensitivity of 85.7% and a specificity of 93.7%, which was more accurate than current biomarkers (area under curve of 0.89 for dd-cfDNA (cp/ml) compared with 0.74 of lipase and 0.46 for amylase).

CONCLUSIONS

dd-cfDNA measurement through a simple noninvasive blood test could be incorporated into clinical practice to help inform graft management in SPKTx patients.

Antibody-Mediated Rejection and Recurrent Primary Disease: Two Main Obstacles in Abdominal Kidney, Liver, and Pancreas Transplants

The advances in acute phase care have firmly established the practice of organ transplantation in the last several decades. Then, the next issues that loom large in the field of transplantation include antibody-mediated rejection (ABMR) and recurrent primary disease. Acute ABMR is a daunting hurdle in the performance of organ transplantation. The recent progress in desensitization and preoperative monitoring of donor-specific antibodies enables us to increase positive outcomes. However, chronic active ABMR is one of the most significant problems we currently face. On the other hand, recurrent primary disease is problematic for many recipients. Notably, some recipients, unfortunately, lost their vital organs due to this recurrence. Although some progress has been achieved in these two areas, many other factors remain largely obscure. In this review, these two topics will be discussed in light of recent discoveries.

Working towards an ERAS Protocol for Pancreatic Transplantation: A Narrative Review

Enhanced recovery after surgery (ERAS) initially started in the early 2000s as a series of protocols to improve the perioperative care of surgical patients. They aimed to increase patient satisfaction while reducing postoperative complications and postoperative length of stay. Despite these protocols being widely adopted in many fields of surgery, they are yet to be adopted in pancreatic transplantation: a high-risk surgery with often prolonged length of postoperative stay and high rate of complications. We have analysed the literature in pancreatic and transplantation surgery to identify the necessary preoperative, intra-operative and postoperative components of an ERAS pathway in pancreas transplantation.