Impact of pretransplant antibodies on outcomes after heart transplantation

Increase of Cardiac Autoantibodies Against Beta-2-adrenergic Receptor During Acute Cellular Heart Transplant Rejection

BACKGROUND

Acute cellular rejection (ACR) in heart transplant (HTx) recipients may be accompanied by cardiac cell damage with subsequent exposure to cardiac autoantigens and the production of cardiac autoantibodies (aABs). This study aimed to evaluate a peptide array screening approach for cardiac aABs in HTx recipients during ACR (ACR-HTx).

METHODS

In this retrospective single-center observational study, sera from 37 HTx recipients, as well as age and sex-matched healthy subjects were screened for a total of 130 cardiac aABs of partially overlapping peptide sequences directed against structural proteins using a peptide array approach.

RESULTS

In ACR-HTx, troponin I (TnI) serum levels were found to be elevated. Here, we could identify aABs against beta-2-adrenergic receptor (β-2AR: EAINCYANETCCDFFTNQAY) to be upregulated in ACR-HTx (intensities: 0.80 versus 1.31, P = 0.0413). Likewise, patients positive for β-2AR aABs showed higher TnI serum levels during ACR compared with aAB negative patients (10.0 versus 30.0 ng/L, P = 0.0375). Surprisingly, aABs against a sequence of troponin I (TnI: QKIFDLRGKFKRPTLRRV) were found to be downregulated in ACR-HTx (intensities: 3.49 versus 1.13, P = 0.0025). A comparison in healthy subjects showed the same TnI sequence to be upregulated in non-ACR-HTx (intensities: 2.19 versus 3.49, P = 0.0205), whereas the majority of aABs were suppressed in non-ACR-HTx.

CONCLUSIONS

Our study served as a feasibility analysis for a peptide array screening approach in HTx recipients during ACR and identified 2 different regulated aABs in ACR-HTx. Hence, further multicenter studies are needed to evaluate the prognostic implications of aAB testing and diagnostic or therapeutic consequences.

Differences in Donor Heart Acceptance by Race and Gender of Patients on the Transplant Waiting List

Importance

Barriers to heart transplant must be overcome prior to listing. It is unclear why Black men and women remain less likely to receive a heart transplant after listing than White men and women.

Objective

To evaluate whether race or gender of a heart transplant candidate (ie, patient on the transplant waiting list) is associated with the probability of a donor heart being accepted by the transplant center team with each offer.

Design, Setting, and Participants

This cohort study used the United Network for Organ Sharing datasets to identify organ acceptance with each offer for US non-Hispanic Black (hereafter, Black) and non-Hispanic White (hereafter, White) adults listed for heart transplant from October 18, 2018, through March 31, 2023.

Exposures

Black or White race and gender (men, women) of a heart transplant candidate.

Main Outcomes and Measures

The main outcome was heart offer acceptance by the transplant center team. The number of offers to acceptance was assessed using discrete time-to-event analyses, nonparametrically (stratified by race and gender) and parametrically. The hazard probability of offer acceptance for each offer was modeled using generalized linear mixed models adjusted for candidate-, donor-, and offer-level variables.

Results

Among 159 177 heart offers with 13 760 donors, there were 14 890 candidates listed for heart transplant; 30.9% were Black, 69.1% were White, 73.6% were men, and 26.4% were women. The cumulative incidence of offer acceptance was highest for White women followed by Black women, White men, and Black men (P < .001). Odds of acceptance were less for Black candidates than for White candidates for the first offer (odds ratio [OR], 0.76; 95% CI, 0.69-0.84) through the 16th offer. Odds of acceptance were higher for women than for men for the first offer (OR, 1.53; 95% CI, 1.39-1.68) through the sixth offer and were lower for the 10th through 31st offers.

Conclusions and Relevance

The cumulative incidence of heart offer acceptance by a transplant center team was consistently lower for Black candidates than for White candidates of the same gender and higher for women than for men. These disparities persisted after adjusting for candidate-, donor-, and offer-level variables, possibly suggesting racial and gender bias in the decision-making process. Further investigation of site-level decision-making may reveal strategies for equitable donor heart acceptance.

The role of lung-restricted autoantibodies in the development of primary and chronic graft dysfunction

Lung transplantation is a life-saving treatment for both chronic end-stage lung diseases and acute respiratory distress syndrome, including those caused by infectious agents like COVID-19. Despite its increasing utilization, outcomes post-lung transplantation are worse than other solid organ transplants. Primary graft dysfunction (PGD)-a condition affecting more than half of the recipients post-transplantation-is the chief risk factor for post-operative mortality, transplant-associated multi-organ dysfunction, and long-term graft loss due to chronic rejection. While donor-specific antibodies targeting allogenic human leukocyte antigens have been linked to transplant rejection, the role of recipient's pre-existing immunoglobulin G autoantibodies against lung-restricted self-antigens (LRA), like collagen type V and k-alpha1 tubulin, is less understood in the context of lung transplantation. Recent studies have found an increased risk of PGD development in lung transplant recipients with LRA. This review will synthesize past and ongoing research-utilizing both mouse models and human subjects-aimed at unraveling the mechanisms by which LRA heightens the risk of PGD. Furthermore, it will explore prospective approaches designed to mitigate the impact of LRA on lung transplant patients.

Expanding heart transplantation in 2022 and beyond

PURPOSE OF REVIEW

Despite advances in the technology of mechanical circulatory support, the need for heart transplantation continues to grow. The longevity of heart transplants continues to be superior to mechanical solutions, though the short-term differences are shrinking. In this review, we cover three timely developments and summarize the recent literature.

RECENT FINDINGS

After stagnant rates of heart transplant activity for some years, recently, transplant volume has increased. The developments that have ignited interest have been the use of hepatitis C infected donors, which can now be safely transplanted with the advent of curative oral regimens, and the worldwide use of donors following withdrawal of life support as opposed to traditional brain death donors. In addition, the recent experience of human cardiac xenotransplantation has been very exciting, and though it is not of clinical utility yet, it holds the promise for a virtually unlimited supply of organs at some time in the future.

SUMMARY

Much work remains to be done, but together, all three of these developments are exciting and important to be aware of in the future. Each will contribute to additional donors for human heart transplantation and hopefully will alleviate suffering and death on the waiting list.

Pre-existing Ab against vimentin leads to false-positive HLA Ab results in two pediatric heart transplant candidates

BACKGROUND

HLA Ab analysis is carried out as a routine assay both pre- and post-heart transplantation to identify Abs directed against HLA with a focus post-transplant on those Abs that are donor-specific. While virtual crossmatching has decreased the requirement for prospective crossmatching in many cases, the management of highly sensitized children on the heart transplant waitlist remains challenging and can delay the ability to successfully identify a suitable organ.

METHODS

This report describes the histocompatibility assessment and management of identical twin boys with familial restrictive cardiomyopathy serially listed for transplant. The boys presented with HLA Ab testing that demonstrated broad pan-DR reactivity which included Abs directed against SAgs.

RESULTS

Our team began investigating the initial Ab results soon after listing the first child; the brother was listed 8 days later and had the same broad Ab profile. The clinical lab ran multiple investigative crossmatches using donor samples with known antigen typing and continued to see broad reactivity. We then partnered with an affiliated research lab where we identified high-level Abs directed against vimentin along with vimentin-positive exosomes in both boys.

CONCLUSIONS

While Abs directed against the self-antigen vimentin has been described to cause false-positive tissue crossmatches, this is the first report of these Abs being associated with false-positive Ab screens using solid-phase assays. This finding informed our management and surveillance in these two vulnerable pediatric heart transplant candidates.

De novo human leukocyte antigen allosensitization patterns in patients bridged to heart transplantation using left ventricular assist devices

INTRODUCTION

We examined the impact and time course of de novo human leukocyte antigen (HLA) allosensitization following left ventricular assist device (LVAD) implantation.

METHODS AND RESULTS

Forty patients had a calculated panel reactive antibody (cPRA) prior to LVAD surgery between January 2014 and December 2018. Of these patients, we retrospectively studied 33 patients who had pre-LVAD cPRA <10%. De novo allosensitization was defined as cPRA ≥10% within 3 months following LVAD surgery, and "persistent allosensitization" was defined as cPRA ≥10% at time of heart transplant or death. One-third (11/33) of our cohort developed de novo allosensitization within 3-months post-LVAD. Median duration of follow-up during LVAD support was 588 days (IQR 337-1071 days), or approximately 19 months. In an adjusted, multivariable analysis, female sex remained associated with de novo allosensitization (adjusted odds ratio [95%CI]: 11 (1.4-85), P = 0.026). De novo allosensitization was subsequently associated with persistent allosensitization (P = 0.024). Both axial-flow and centrifugal-flow LVADs had similar rates of allosensitization. Compared to those with no allosensitization, patients with de novo allosensitization did not appear to have inferior post-transplant outcomes of death or treated rejection.

CONCLUSION

In our single-center experience, one-third of patients developed de novo allosensitization which did not appear to associate with inferior post-transplant outcomes. Female sex was associated with de novo allosensitization.

Pathways to Clinical Cardiac Xenotransplantation

Heart transplantation is the only long-lasting lifesaving option for patients with terminal cardiac failure. The number of available human organs is however far below the actual need, resulting in substantial mortality of patients while waiting for a human heart. Mechanical assist devices are used to support cardiac function but are associated with a high risk of severe complications and poor quality of life for the patients. Consistent success in orthotopic transplantation of genetically modified pig hearts into baboons indicates that cardiac xenotransplantation may become a clinically applicable option for heart failure patients who cannot get a human heart transplant. In this overview, we project potential paths to clinical cardiac xenotransplantation, including the choice of genetically modified source pigs; associated requirements of microbiological, including virological, safety; optimized matching of source pig and recipient; and specific treatments of the donor heart after explantation and of the recipients. Moreover, selection of patients and the regulatory framework will be discussed.

Set Up for Failure: Pre-Existing Autoantibodies in Lung Transplant

Lung transplant patients have the lowest long-term survival rates compared to other solid organ transplants. The complications after lung transplantation such as primary graft dysfunction (PGD) and ultimately chronic lung allograft dysfunction (CLAD) are the main reasons for this limited survival. In recent years, lung-specific autoantibodies that recognize non-HLA antigens have been hypothesized to contribute to graft injury and have been correlated with PGD, CLAD, and survival. Mounting evidence suggests that autoantibodies can develop during pulmonary disease progression before lung transplant, termed pre-existing autoantibodies, and may participate in allograft injury after transplantation. In this review, we summarize what is known about pulmonary disease autoantibodies, the relationship between pre-existing autoantibodies and lung transplantation, and potential mechanisms through which pre-existing autoantibodies contribute to graft injury and rejection.

Heart transplantation candidacy

PURPOSE OF REVIEW

Timely referral of eligible candidates for consideration of advanced therapies, such as a heart transplantation or mechanical circulatory support is essential. The characteristics of heart transplantation candidates have changed significantly over the years, leading to a more complex evaluation process. The present review summarizes recent advances in the evaluation process for heart transplantation eligibility.

RECENT FINDINGS

The heart transplantation allocation policy was recently reviewed in the USA in an effort to reduce waitlist mortality and to ensure fair geographic allocation of organs to the sickest patients. Moreover, patients with chronic infectious diseases, as well as malignancies, are being currently considered acceptable candidates for transplantation. Listing practices for heart transplantation vary between programmes, with a greater willingness to consider high-risk candidates at higher-volume centres.

SUMMARY

The ultimate decision to place high-risk candidates on the heart transplantation waitlist should be based on a combination of quantitative and qualitative data analysis informed by clinical judgement, and the chronic shortage of organ donors makes this process an important ethical concern for any society. Future guidelines should discuss approaches to achieve fair organ allocation while preserving improved outcomes after transplantation.

Heart transplant candidate with medical complexity in the era of prolonged left ventricular assist device support - A case report

Heart transplantation improves quality of life and survival in patients with advanced heart failure. However, the shortage of available heart donors and technological advances for left ventricular assist devices (LVAD) have led to longer waiting times for transplantation, and long-term use of LVAD may increase the medical complexity of subsequent transplantation. We present the case of a 35-year-old man who underwent heart transplantation after being supported by an LVAD for 1490 days (∼4 years). He was sensitized with kidney dysfunction and recurrent infections, including candidemia, at the time of transplantation. He underwent a successful heart transplantation with pretransplant plasma exchange, intravenous immunoglobulin administration, early initiation of everolimus, and prompt management of infections. <Learning objective: With a growing number of heart transplant candidates who are supported by left ventricular assist devices for long duration, managing such candidates is becoming increasingly complex and difficult to standardize. The present case had three problems that were linked to each other: (1) anti-HLA antibodies, (2) fungal infection, and (3) pre-transplantation renal dysfunction. Management of heart transplant candidates, including desensitization and immunosuppressive therapies, should be tailored to the individual and the clinical presentation to improve the survival and quality of life.>.