ABO-incompatible heart transplantation: an alternative to improve the donor shortage in infants:

New Answers to Old Conundrums: What Antibodies, Exosomes and Inflammasomes Bring to the Conversation. Canadian National Transplant Research Program International Summit Report

Antibody-mediated injury is a major cause of allograft dysfunction and loss. Antibodies to ABH(O) blood group antigens are classic mediators of ABO-incompatible graft rejection, whereas donor-specific anti-HLA antibodies and, more recently, autoantibodies are appreciated as important contributors to allograft inflammation and dysfunction. In August 2016, the International Summit of the Canadian National Transplant Research Program focused on recent advances in the field of antibody-mediated rejection. Here, we describe work presented and discussed at the meeting, with a focus on 3 major themes: the importance of (1) natural antibodies and autoantibodies, (2) tissue injury-derived exosomes and autoimmunity, (3) inflammasome activation and innate immune responses in regulating allograft inflammation and dysfunction. Finally, we explore novel areas of therapeutic intervention that have recently emerged from these 3 major and overlapping fields of transplantation research.

Successful ABO-incompatible heart transplantation in a child despite blood-group sensitization after ventricular assist device support

In the first two yr of life blood-group incompatible (ABO-incompatible) heart transplantation can be performed leading to immune tolerance to donor blood group. Antibody titers should be below 1:4. VAD use is correlated with sensitization toward blood-group antigens. A boy was diagnosed with dilated cardiomyopathy at nine months of age and listed for 0-compatible transplantation. Progressive heart failure required implantation of a left VAD. His listing was extended for ABO-incompatible transplantation despite antibody titers of 1:32 anti-A and 1:8 anti-B. After 26 days on VAD, he was transplanted with a B donor heart. No hyperacute or acute rejection occurred in 12 months post-transplant. Anti-B antibodies rose to a maximum of 1:2. No use of rituximab or plasmapheresis was required. There are no signs of graft vasculopathy. This indicates that inclusion criteria for ABO-incompatible transplantation may be extended to immediate cases. This is the first case with a healthy immune system to show signs of tolerance development after ABO-incompatible heart transplantation with increased prior antibody titers and without specific treatment.

Waiting before birth: outcomes after fetal listing for heart transplantation

Following fetal diagnosis of a profound heart defect, transplantation (HTx) is an alternative to pregnancy termination or neonatal surgical palliation. Retrospective review of the cardiac and transplant databases of fetal listings for HTx between 1990 and July 2006 was undertaken to describe outcomes after listing. We identified 26 fetal listings (of 269 total listings). Diagnoses included congenital heart disease (n = 24) and cardiomyopathy (n = 2). Seven patients were delisted after birth: in five cases parents opted for surgical palliation, two clinically improved. One patient died wait-listed (stillborn). Time wait-listed as a fetus ranged from 1-41 days (median 19 days). Eighteen patients underwent HTx (median weight 2.8 kg, range 2.1-10.9 kg); median days wait-listed after birth was 22 (4 h-123 days). Two fetuses were surgically delivered at 36 weeks gestation when a donor organ became available; 11 were transplanted as neonates (<30 days). The median age at HTx was 1 month (4 h-2.6 months). Fetal listing for HTx increases the potential window of opportunity for a donor organ to become available; patients had low wait-list mortality and a fair intermediate-term outcome. Well-defined criteria for eligibility for fetal listing and priority allocation to infants over fetuses seem rational approaches for centers that offer fetal listing.