Multicenter Analysis of Immune Biomarkers and Heart Transplant Outcomes: Results of the Clinical Trials in Organ Transplantation-05 Study

Abstract

Identification of biomarkers that assess posttransplant 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 posttransplant year. The primary endpoint was a composite of death, graft loss/retransplantation, 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.

Keywords: Biomarker; heart transplantation/cardiology; monitoring: immune; rejection: acute; translational research/science; vasculopathy.

Conflict of interest statement

Disclosure

The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation.

© Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.

Figures

Figure 1. Overview of study outcomes

Consort diagram illustrating the outcomes of subjects throughout the course of the study including numbers and results of biopsies performed and numbers of subjects who reached the 12-month endpoint. 0f 200 transplanted subjects (and of 180 who completed the study), 64 were not evaluable for the primary composite endpoint because IVUS data were missing (not evaluable for the CAV component) and the subject did not have an episode of BPAR >2R. Subjects without IVUS data but who had an episode of BPAR component were considered evaluable because they met the BPAR component of the composite endpoint.

Figure 2. Relationships between serum anti-HLA or anti-CM antibodies and study outcomes

A. Percentages of study subjects with any serum anti-HLA antibodies (left), antibodies reactive to class I HLA (middle) and antibodies reactive to class II HLA (right), stratified by meeting (gray) or not meeting (white) the composite endpoint. B-C. Percentages of study subjects with serum anti-CM antibodies at baseline (B) or at 12-months (C) who met (gray) or did not meet (white) the composite endpoint (left), BPAR endpoint (middle), CAV endpoint (right). Anti-VM antibodies were also tested baseline and 12-months, and no relationships were observed with any of the endpoints at either time point (not shown).

Figure 3. Panel of reactive T cell (PRT) and study outcomes

Frequencies of alloreactive IFNγ-producing PBMCs at baseline, 6-weeks, 6-months and 12-months post-transplant who met (grey) or did not meet (white) the composite endpoint (A), the BPAR endpoint (B) or CAV endpoint (C). The values (n) below each bar represent the number of subjects with available ELISPOT results who were evaluable for each endpoint. There were no statistically significant differences among groups.

Figure 4. Gene expression profiling and study outcomes

A. Absolute copy numbers for each of the listed genes normalized to the copy number of 18S–rRNA in peripheral blood cell samples obtained up to the first episode of BPAR in each individual, stratified by meeting (gray) or not meeting (white) the BPAR endpoint. The values (n) below each bar represent the number of evaluable subjects with available PCR results. B. Absolute copy numbers for each of the listed genes normalized to the copy number of 18S–rRNA in endomyocardial tissue samples obtained at the time of protocol or for-cause biopsy

Figure 5. Plasma angiogenesis-related proteins and CAV

Change in plasma concentration by ELISA for each of the listed proteins between the pre-transplant and 1 year post-transplant visit stratified by meeting (gray) or not meeting (white) the CAV endpoint. The values (n) below each bar represent the number of IVUS evaluated subjects with available paired ELISA results.