BACKGROUND The problem of AMR remains unsolved because standardized schemes for diagnosis and treatment remains contentious. Therefore, a consensus conference was organized to discuss the current status of antibody-mediated rejection (AMR) in heart transplantation. METHODS The conference included 83 participants (transplant cardiologists, surgeons, immunologists and pathologists) representing 67 heart transplant centers from North America, Europe, and Asia who all participated in smaller break-out sessions to discuss the various topics of AMR and attempt to achieve consensus. RESULTS A tentative pathology diagnosis of AMR was established, however, the pathologist felt that further discussion was needed prior to a formal recommendation for AMR diagnosis. One of the most important outcomes of this conference was that a clinical definition for AMR (cardiac dysfunction and/or circulating donor-specific antibody) was no longer believed to be required due to recent publications demonstrating that asymptomatic (no cardiac dysfunction) biopsy-proven AMR is associated with subsequent greater mortality and greater development of cardiac allograft vasculopathy. It was also noted that donor-specific antibody is not always detected during AMR episodes as the antibody may be adhered to the donor heart. Finally, recommendations were made for the timing for specific staining of endomyocardial biopsy specimens and the frequency by which circulating antibodies should be assessed. Recommendations for management and future clinical trials were also provided. CONCLUSIONS The AMR Consensus Conference brought together clinicians, pathologists and immunologists to further the understanding of AMR. Progress was made toward a pathology AMR grading scale and consensus was accomplished regarding several clinical issues.

In an open-label, 24-month trial, 721 de novo heart transplant recipients were randomized to everolimus 1.5 mg or 3.0 mg with reduced-dose cyclosporine, or mycophenolate mofetil (MMF) 3 g/day with standarddose cyclosporine (plus corticosteroids ± induction). Primary efficacy endpoint was the 12-month composite incidence of biopsy-proven acute rejection, acute rejection associated with hemodynamic compromise, graft loss/retransplant, death or loss to follow-up. Everolimus 1.5 mg was noninferior to MMF for this endpoint at month 12 (35.1% vs. 33.6%; difference 1.5% [97.5% CI: -7.5%, 10.6%]) and month 24. Mortality to month 3 was higher with everolimus 1.5 mg versus MMF in patients receiving rabbit antithymocyte globulin (rATG) induction, mainly due to infection, but 24-month mortality was similar (everolimus 1.5 mg 10.6% [30/282], MMF 9.2% [25/271]). Everolimus 3.0 mg was terminated prematurely due to higher mortality. The mean (SD) 12-month increase in maximal intimal thickness was 0.03 (0.05) mm with everolimus 1.5 mg versus 0.07 (0.11) mm with MMF (p < 0.001). Everolimus 1.5 mg was inferior to MMF for renal function but comparable in patients achieving predefined reduced cyclosporine trough concentrations. Nonfatal serious adverse events were more frequent with everolimus 1.5 mg versus MMF. Everolimus 1.5 mg with reduced-dose cyclosporine offers similar efficacy to MMF with standard-dose cyclosporine and reduces intimal proliferation at 12 months in de novo heart transplant recipients.

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Identification of biomarkers that assess post-transplant risk is needed to improve long-term outcomes following heart transplantation. The Clinical Trials in Organ Transplantation (CTOT)-05 protocol was an observational, multicenter, cohort study of 200 heart transplant recipients followed for the first post-transplant year. The primary endpoint was a composite of death, graft loss/re-transplantation, biopsy proven acute rejection (BPAR) and cardiac allograft vasculopathy (CAV) as defined by intravascular ultrasound (IVUS). We serially measured anti-HLA- and auto-antibodies, angiogenic proteins, peripheral blood allo-reactivity and peripheral blood gene expression patterns. We correlated assay results and clinical characteristics with the composite endpoint and its components. The composite endpoint was associated with older donor allografts (p<0.03) and with recipient anti-HLA antibody (p<0.04). Recipient CMV-negativity (regardless of donor status) was associated with BPAR p<0.001), and increases in plasma vascular endothelial growth factor-C (OR 20; 95%CI:1.9–218) combined with decreases in endothelin-1: (OR 0.14; 95%CI:0.02–0.97) associated with CAV. The remaining biomarkers showed no relationships with the study endpoints. While suboptimal endpoint definitions and lower than anticipated event rates were identified as potential study limitations, the results of this multicenter study do not yet support routine use of the selected assays as noninvasive approaches to detect BPAR and/or CAV following heart transplantation.

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