Human leukocyte antigen compatibility and lymphocyte cross-matching play no significant role in the current adult-to-adult living donor liver transplantation

Liver paired exchange: A US single-center experience-Pairs, chains, and use of compatible pairs

In the United States, the discrepancy between organ availability and need has persisted despite changes in allocation, innovations in preservation, and policy initiatives. Living donor liver transplant remains an underutilized means of improving access to timely liver transplantation and decreasing waitlist mortality. Liver paired exchange (LPE) represents an opportunity to overcome living donor liver transplant pair incompatibility due to size, anatomy, or blood type. LPE was adopted as a strategy to augment access to liver transplantation at our institution. Specific educational materials, consent forms, and selection processes were developed to facilitate LPE. From 2019 through October 2023, our center performed 11 LPEs, resulting in 23 living donor liver transplant pairs. The series included several types of LPE: those combining complementary incompatible pairs, the inclusion of compatible pairs to overcome incompatibility, and the use of altruistic nondirected donors to initiate chains. These exchanges facilitated transplantation for 23 recipients, including 1 pediatric patient. LPE improved access to liver transplantation at our institution. The ethical application of LPE includes tailored patient education, assessment and disclosure of exchange balance, mitigation of risk, and maximization of benefit for donors and recipients.

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.

Immunology of simultaneous liver and kidney transplants with identification and prevention of rejection

Simultaneous liver and kidney (SLK) transplantation is considered the best treatment modality among selected patients with both chronic kidney disease (CKD) and end-stage liver disease (ESLD). Since the first SLK transplant in 1983, the number of SLK transplants has increased worldwide, and particularly in the United States since the implementation of the MELD system in 2002. SLK transplants are considered a relatively low immunological risk procedure evidenced by multiple studies displaying the immunomodulatory properties of the liver on the immune system of SLK recipients. SLK recipients demonstrate lower rates of both cellular and antibody-mediated rejection on the kidney allograft when compared to kidney transplant-alone recipients. Therefore, SLK transplants in the setting of preformed donor-specific HLA antibodies (DSA) are a common practice, at many centers. Acceptance and transplantation of SLKs are based solely on ABO compatibility without much consideration of crossmatch results or DSA levels. However, some studies suggest an increased risk for rejection for SLK recipients transplanted across high levels of pre-formed HLA DSA. Despite this, there is no consensus regarding acceptable levels of pre-formed DSA, the role of pre-transplant desensitization, splenectomy, or immunosuppressive management in this unique population. Also, the impact of post-transplant DSA monitoring on long-term outcomes is not well-studied in SLK recipients. In this article, we review recent and relevant past articles in this field with a focus on the immunological risk factors among SLK recipients, and strategies to mitigate the negative outcomes among them.

The Impact of Donor and Recipient Genetic Variation on Outcomes After Solid Organ Transplantation: A Scoping Review and Future Perspectives

At the outset of solid organ transplantation, genetic variation between donors and recipients was recognized as a major player in mechanisms such as allograft tolerance and rejection. Genome-wide association studies have been very successful in identifying novel variant-trait associations, but have been difficult to perform in the field of solid organ transplantation due to complex covariates, era effects, and poor statistical power for detecting donor-recipient interactions. To overcome a lack of statistical power, consortia such as the International Genetics and Translational Research in Transplantation Network have been established. Studies have focused on the consequences of genetic dissimilarities between donors and recipients and have reported associations between polymorphisms in candidate genes or their regulatory regions with transplantation outcomes. However, knowledge on the exact influence of genetic variation is limited due to a lack of comprehensive characterization and harmonization of recipients' or donors' phenotypes and validation using an experimental approach. Causal research in genetics has evolved from agnostic discovery in genome-wide association studies to functional annotation and clarification of underlying molecular mechanisms in translational studies. In this overview, we summarize how the recent advances and progresses in the field of genetics and genomics have improved the understanding of outcomes after solid organ transplantation.

Donor-recipient human leukocyte antigen A mismatching is associated with hepatic artery thrombosis, sepsis, graft loss, and reduced survival after liver transplant

Human leukocyte antigen (HLA) matching is not routinely performed for liver transplantation as there is no consistent evidence of benefit; however, the impact of HLA mismatching remains uncertain. We explored the effect of class I and II HLA mismatching on graft failure and mortality. A total of 1042 liver transplants performed at a single center between 1999 and 2016 with available HLA typing data were included. The median follow-up period was 9.38 years (interquartile range 4.9-14) and 350/1042 (33.6%) transplants resulted in graft loss and 280/1042 (26.9%) in death. Graft loss and mortality were not associated with the overall number of mismatches at HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ loci. However, graft failure and mortality were both increased in HLA mismatching on graft failure and mortality the presence of one (p = 0.004 and p = 0.01, respectively) and two (p = 0.01 and p = 0.04, respectively) HLA-A mismatches. Elevated hazard ratios for graft failure and death were observed with HLA-A mismatches in univariate and multivariate Cox proportional hazard models. Excess graft loss with HLA-A mismatch (138/940 [14.7%] mismatched compared with 6/102 [5.9%] matched transplants) occurred within the first year following transplantation (odds ratio 2.75; p = 0.02). Strikingly, transplants performed at a single all grafts lost due to hepatic artery thrombosis were in HLA-A-mismatched transplants (31/940 vs. 0/102), as were those lost due to sepsis (35/940 vs. 0/102). In conclusion, HLA-A mismatching was associated with increased graft loss and mortality. The poorer outcome for the HLA-mismatched group was due to hepatic artery thrombosis and sepsis, and these complications occurred exclusively with HLA-A-mismatched transplants. These data suggest that HLA-A mismatching is important for outcomes following liver transplant. Therefore, knowledge of HLA-A matching status may potentially allow for enhanced surveillance, clinical interventions in high-risk transplants or stratified HLA-A matching in high-risk recipients.

Immunosuppression in liver and intestinal transplantation

Immunosuppression handling plays a key role in the early and long-term results of transplantation. The development of multiple immunosuppressive drugs led to numerous clincial trials searching to reach the ideal regimen. Due to heterogeneity of the studied patient cohorts and flaws in many, even randomized controlled, study designs, the answer still stands out. Nowadays triple-drug immunosuppression containing a calcineurin inhibitor (preferentially tacrolimus), an antimetabolite (using mycophenolate moffettil or Azathioprine) and short-term steroids with or without induction therapy (using anti-IL2 receptor blocker or anti-lymphocytic serum) is the preferred option in both liver and intestinal transplantation. This chapter aims, based on a critical review of the definitions of rejection, corticoresistant rejection and standard immunosuppression to give some reflections on how to reach an optimal immunosuppressive status and to conduct trials allowing to draw solid conclusions. Endpoints of future trials should not anymore focus on biopsy proven, acute and chronic, rejection but also on graft and patient survival. Correlation between early- and long-term biologic, immunologic and histopathologic findings will be fundamental to reach in much more patients the status of operational tolerance.

Rituximab Desensitization in Liver Transplant Recipients With Preformed Donor-specific HLA Antibodies: A Japanese Nationwide Survey

Background.

The significance of preformed donor-specific anti-HLA antibodies (DSAs) in liver transplant recipients is controversial. Moreover, there has been no established desensitization protocol for DSA-positive recipients.

Methods.

A Japanese nationwide survey was performed to investigate the clinical practice among preformed DSA-positive patients with special reference to rituximab desensitization.

Results.

There was a total of 47 cases, including 2 pediatric cases, in which rituximab (287 ± 159 mg [319 (50–916)/m²]) was administered to desensitize preformed DSA. The decision for the indication of rituximab desensitization was based on a single-antigen assay in the majority of cases (83%, 39/47), and the most frequent protocol was rituximab monotherapy (n = 12) followed by quadruple treatment with rituximab tacrolimus, mycophenolate mofetil, and plasmapheresis (n = 11). The overall 1-, 3-, and 5-y graft and patient survival rates among adult patients were 85%, 83%, 83%, and 81%, 77%, 74%, respectively, while neither graft loss nor death was observed in the 2 pediatric cases. The 1-, 3-, and 12-mo cumulative incidence of antibody-mediated rejection (AMR) was 11%, 13%, and 13%, respectively. The incidence of AMR was significantly higher in the lower rituximab dose group than in the higher rituximab dose group (cutoff 300 mg/m², 4% versus 24%, P = 0.041). The rate of infusion-related adverse drug reactions (ADRs) was 4.4%, and all ADRs were mild and self-limiting. A total of 99 ADRs among 27 patients were reported, none of which were severe adverse events associated with rituximab.

Conclusions.

The rituximab induction was well tolerated among DSA-positive liver transplant recipients with a satisfactory outcome. A rituximab dose >300 mg/m² was observed to achieve less incidence of the development of AMR.

Impact of human leukocyte antigen compatibility on outcomes of living donor liver transplantation: Experience from a tertiary care center

INTRODUCTION

The role of HLA compatibility in kidney, heart, and stem cell transplantation is well known, but with regard to living donor liver transplantation (LDLT), there is a different scenario. In the present study, we aim to examine the effects of donor-recipient HLA mismatches at A, B, and DR loci on various outcomes of LDLT-like graft survival, early allograft dysfunction (EAD), acute rejection, length of hospital (LOH) stay, sepsis, and cytomegalovirus (CMV) reactivation.

METHODS

This is a retrospective single center study of a cohort of adult patients who underwent first time ABO-compatible (ABOc) LDLT between January 2010 and December 2018. Transplants with incomplete records or without HLA typing data were excluded. Donor-recipient HLA-A, B, and DR mismatches were assessed in the host versus graft (HVG) direction and were correlated with various post-transplant outcomes.

RESULTS

Among 140 transplants being evaluated, approximately two third had total HLA mismatches between 2 and 3. HLA mismatches at each locus as well as cumulative HLA mismatches did not show any association with overall graft survival, EAD, acute rejection episodes, and LOH stay. However, the presence of minimum one mismatch at HLA-A and DR loci was associated with the development of CMV reactivation (P = .03) and sepsis (P = .02) post-LDLT respectively.

CONCLUSION

HLA mismatch is not associated with acute rejection, early graft dysfunction, and overall survival in LDLT. Its impact on CMV reactivation and sepsis needs further evaluation.

Autoantibodies to LG3 are associated with poor long-term survival after liver retransplantation

Autoantibodies are detrimental to the survival of organ transplantation. We demonstrated that Angiotensin II Type I Receptor agonistic autoantibodies (AT1R-AA) were associated with poor outcomes after liver retransplantation. To examine the effect of other autoantibodies, we studied a retrospective cohort of 93 patients who received a second liver transplant. Pre-retransplant sera were tested with Luminex-based solid-phase assays. Among 33 tested autoantibodies, 15 were significantly higher in 48 patients who lost their regrafts than 45 patients whose regrafts were still functioning. Specifically, patients with autoantibodies to the C-terminal laminin-like globular domain of Perlecan (LG3) experienced significantly worse regraft survival (p = .002) than those with negative LG3 autoantibodies (LG3-A). In multivariate analysis, LG3-A (HR = 2.35 [1.11-4.98], p = .027) and AT1R-AA (HR = 2.09 [1.07-4.10], p = .032) remained significant predictors of regraft loss after adjusting for recipient age and sex. There were synergistic deleterious effects on regraft survival in patients who were double-positive for LG3-A and donor-specific antibody (DSA) (HR = 5.26 [2.15-12.88], p = .001), or LG3-A and AT1R-AA (HR = 3.23 [1.37-7.66], p = .008). All six double-positive patients lost their liver regrafts. In conclusion, LG3-A is associated with inferior long-term outcomes of a second liver transplant. Screening anti-HLA antibodies and autoantibodies such as LG3-A/AT1R-AA identifies patients with a higher risk for liver transplantation.

Vascularized composite allotransplantation in the United States: A retrospective analysis of the Organ Procurement and Transplantation Network data after 5 years of the Final Rule

On July 3, 2014, the Organ Procurement and Transplantation Network (OPTN) began overseeing vascularized composite allotransplantation/allografts (VCA) in the United States. For the past 6 years, centers performing VCAs have been requested to submit data into a biometric repository, in parallel with systems used by solid organ transplant centers. Currently, 62 VCAs are reported in the entire OPTN database, with 36 of these transplants reported as performed after VCA was added to the OPTN Final Rule. Of these 36 recipients, 16 received uterus transplants, most of which (11) occurred from living donors. Ten patients received hand transplants and 6 received face transplants. Two patients received abdominal wall transplants, 1 patient received a scalp transplant, and 1 patient received a penile transplant. The present manuscript represents the query of a nationalized database for VCA type, immunosuppression treatment, and clinical outcomes for VCAs. This manuscript provides a report of the current VCA data reported to the OPTN after the Final Rule.

Donor-dominant one-way matching of human leukocyte antigen-A/B/DR alleles predicts graft-versus-host disease following living donor liver transplantation

AIM

Graft-versus-host disease (GVHD) following liver transplantation is rare but fatal. Therefore, it is important to identify possible risk factors before transplantation. Although it has been suggested that donor-dominant one-way human leukocyte antigen (HLA) matching of three loci (HLA-A/B/DR) is associated with the occurrence of GVHD, the precise significance of HLA matching including HLA-C/DQ/DP remains unclear.

METHODS

We retrospectively analyzed the impact of donor-dominant one-way HLA matching at six HLA loci at the allele level on GVHD using clinical registry data from 1759 cases who underwent living donor liver transplantation between June 1990 and June 2019. We extracted cases with donor-dominant one-way HLA matching at the antigen level and reconfirmed them at the allele level using preserved DNA samples.

RESULTS

Three of four cases (75%) who developed GVHD showed donor-dominant one-way HLA matching at three HLA-A/B/DR loci. These cases also showed donor-dominant one-way HLA matching at HLA-C/DQ/DP. Three of six cases (50%) with donor-dominant one-way HLA matching at three loci of HLA-A/B/DR developed GVHD. Notably, none of the cases with donor-dominant one-way HLA matching at one or two HLA-A/B/DR loci developed GVHD, irrespective of matching status at HLA-C/DQ/DP. The HLA matching status at the antigen level was revised in 22 of 56 cases, following reconfirmation at the allele level.

CONCLUSIONS

Pairing of donors and recipients with donor-dominant one-way HLA matching at three HLA-A/B/DR loci should be avoided to prevent GVHD. No impact of HLA-C/DQ/DP on GVHD was identified. For liver transplantation, HLA genotypes should be determined at the allele level.