Gene expression profiling scores in dual organ transplant patients are similar to those in heart-only recipients

Diagnostic Performance of Gene Expression and dd-cfDNA in Multiorgan Transplant Recipients

Background

The aim of this analysis was to evaluate early signals of the utility of gene expression profile (GEP) and donor-derived cell-free DNA (dd-cfDNA) for ruling out subclinical rejection in multiorgan transplant recipients.

Methods

This was a prospective, single-center, observational pilot study that began enrolling patients in September 2022. Participants were enrolled after providing informed consent and had biomarker samples drawn before surveillance or for-cause biopsy. GEP result of TX was considered negative and a dd-cfDNA of ≤0.69% was considered negative, regardless of a nonrenal organ.

Results

There were 49 participants with 55 surveillance and/or for-cause biopsies. After exclusion of biopsies not paired with biomarkers, 51 biopsies were evaluated with at least 1 biomarker. Fifty-one biopsies had paired GEP results, whereas 47 biopsies had paired dd-cfDNA results. Overall, there were 12 biopsy-proven acute rejections (24%), 5 of which were T cell-mediated rejections (4-1A and 1-1B), 2 were antibody-mediated rejections, and 5 were borderline for T cell-mediated rejections. GEP by itself in 51 biopsies demonstrated a sensitivity of 17%, specificity of 74%, positive predictive value of 17%, negative predictive value of 74%, and balanced accuracy of 61%. Among 47 paired biopsies, dd-cfDNA demonstrated a sensitivity of 67% and specificity of 37%. Median dd-cfDNA was above the positivity threshold for both participants with rejection on biopsy and without (1.86% versus 1.35%, respectively). When evaluating GEP, specifically in surveillance biopsies and patients with liver transplants, diagnostic performance was maintained.

Conclusions

In this pilot analysis, GEP maintained a high negative predictive value in a multiorgan cohort, regardless of the nonrenal organ. dd-cfDNA did not have good performance when using the kidney threshold cutoff, which was expected and driven by the liver component of multiorgan recipients. Further technological advances with dd-cfDNA to differentiate organs and multiple donors could be impactful. The results support the use of GEP for ruling out kidney rejection in a multiorgan population, including those with a liver transplant. Further evaluation is necessary to confirm the results.

Advancements in noninvasive techniques for transplant rejection: from biomarker detection to molecular imaging

Transplant rejection remains a significant barrier to the long-term success of organ transplantation. Biopsy, although considered the gold standard, is invasive, costly, and unsuitable for routine monitoring. Traditional biomarkers, such as creatinine and troponin, offer limited predictive value owing to their low specificity, and conventional imaging techniques often fail to detect early organ damage, increasing the risk of undiagnosed rejection episodes. Considering these limitations, emerging noninvasive biomarkers and molecular imaging techniques hold promise for the early and accurate detection of transplant rejection, enabling personalized management strategies. This review highlights noninvasive biomarkers that predict, diagnose, and assess transplant prognosis by reflecting graft injury, inflammation, and immune responses. For example, donor-derived cell-free DNA (dd-cfDNA) is highly sensitive in detecting early graft injury, whereas gene expression profiling effectively excludes moderate-to-severe acute rejection (AR). Additionally, microRNA (miRNA) profiling enhances the diagnostic specificity for precise AR detection. Advanced molecular imaging techniques further augment the monitoring of rejection. Fluorescence imaging provides a high spatiotemporal resolution for AR grading, ultrasound offers real-time and portable monitoring, and magnetic resonance delivers high tissue contrast for anatomical assessments. Nuclear imaging modalities such as single photon emission computed tomography and positron emission tomography, enable dynamic visualization of immune responses within transplanted organs. Notably, dd-cfDNA and nuclear medicine imaging have already been integrated into clinical practice, thereby demonstrating the translational potential of these techniques. Unlike previous reviews, this work uniquely synthesizes advancements in both noninvasive biomarkers and molecular imaging, emphasizing their complementary strengths. Biomarkers deliver molecular-level insights, whereas imaging provides spatial and temporal resolution. Together, they create a synergistic framework for comprehensive and precise transplant monitoring. By bridging these domains, this review underscores their individual contributions and collective potential to enhance diagnostic accuracy, improve patient outcomes, and guide future research and clinical applications in transplant medicine.

Transcriptional responses define dysregulated immune activation in Hepatitis C (HCV)-naïve recipients of HCV-infected donor kidneys

Renal transplantation from hepatitis C (HCV) nucleic acid amplification test-positive (NAAT-positive) donors to uninfected recipients has greatly increased the organ donation pool. However, there is concern for adverse outcomes in these recipients due to dysregulated immunologic activation secondary to active inflammation from acute viremia at the time of transplantation. This includes increased rates of cytomegalovirus (CMV) DNAemia and allograft rejection. In this study, we evaluate transcriptional responses in circulating leukocytes to define the character, timing, and resolution of this immune dysregulation and assess for biomarkers of adverse outcomes in transplant patients. We enrolled 67 renal transplant recipients (30 controls, 37 HCV recipients) and performed RNA sequencing on serial samples from one, 3-, and 6-months post-transplant. CMV DNAemia and allograft rejection outcomes were measured. Least absolute shrinkage and selection operator was utilized to develop gene expression classifiers predictive of clinical outcomes. Acute HCV incited a marked transcriptomic response in circulating leukocytes of renal transplant recipients in the acute post-transplant setting, despite the presence of immunosuppression, with 109 genes significantly differentially expressed compared to controls. These HCV infection-associated genes were reflective of antiviral immune pathways and generally resolved by the 3-month timepoint after sustained viral response (SVR) for HCV. Differential gene expression was also noted from patients who developed CMV DNAemia or allograft rejection compared to those who did not, although transcriptomic classifiers could not accurately predict these outcomes, likely due to sample size and variable time-to-event. Acute HCV infection incites evidence of immune activation and canonical antiviral responses in the human host even in the presence of systemic immunosuppression. After treatment of HCV with antiviral therapy and subsequent aviremia, this immune activation resolves. Changes in gene expression patterns in circulating leukocytes are associated with some clinical outcomes, although larger studies are needed to develop accurate predictive classifiers of these events.

Heart transplant Recipients' perspectives on invasive versus Non-invasive graft failure surveillance Methods

BACKGROUND

Heart transplant recipients must regularly be assessed for graft rejection; however, endomyocardial biopsy (EMB), can be stressful, painful, and inconvenient. AlloMap® is the only commercially available non-invasive test for graft rejection. Current guidelines include AlloMap® testing in low-risk patients OBJECTIVES: To examine the patients' perspective, this study compared patients' experiences of AlloMap® and EMB surveillance at our center.

METHODS

We enrolled consecutive heart transplant recipients who were to undergo routine EMB and AlloMap® testing (on different visits) to quantify their anxiety on the GAD-7 scale and their pain level on the Polyclinic Pain Scale. We assessed paired differences of anxiety and pain within patients according to surveillance method.

RESULTS

We studied 43 participants (median age 60.5[54, 66] years; 35(81%) men; 27(63%) Caucasian). The median GAD-7 scores were 1[0, 4] and 2[0, 5] prior to EMB and AlloMap®, respectively (paired difference: 0[-1, 1],P = 0.323). The median pain scores were 1[0, 1] and 0[0, 0] for EMB and AlloMap®, respectively. Patients experienced less pain with AlloMap® testing compared to EMB (EMB-AlloMap;1[0, 1],P = 0.006). Seven (16%) participants experienced a total of 9 adverse events (pain, bruising, bleeding, swelling) from EMB vs 2(5%) participants who experienced a total of 3 adverse events (pain, bruising) from AlloMap®(P = 0.059).

CONCLUSION

Heart transplant recipients had less pain and fewer adverse events while undergoing graft rejection surveillance with AlloMap® testing compared to EMB. An additional benefit of AlloMap® testing is that it may be performed at home and reduce these high-risk patients' infectious exposures.

Serum biomarkers of acute rejection: Towards precision medicine in heart transplant

Despite the important changes in the management of heart transplantation in the recent decades, the use of endomyocardial biopsy is still necessary for the follow-up of these patients. However, this technique has several limitations, the most important being the substantial interobserver variability. In the last years multiple attempts have been made to find non-invasive assays for cardiac allograft surveillance, such as imaging modalities and serum biomarkers. This state-of-the-art review focuses on describing the different serum biomarkers that have been proposed for non-invasive diagnosis of acute rejection and that are paving the way towards precision medicine in the field of heart transplantation.

The evolution of patient-specific precision biomarkers to guide personalized heart-transplant care

Introduction

In parallel to the clinical maturation of heart transplantation over the last 50 years, rejection testing has been revolutionized within the systems biology paradigm triggered by the Human Genome Project.

Areas Covered

We have co-developed the first FDA-cleared diagnostic and prognostic leukocyte gene expression profiling biomarker test in transplantation medicine that gained international evidence-based medicine guideline acceptance to rule out moderate/severe acute cellular cardiac allograft rejection without invasive endomyocardial biopsies. This work prompted molecular re-classification of intragraft biology, culminating in the identification of a pattern of intragraft myocyte injury, in addition to acute cellular rejection and antibody-mediated rejection. This insight stimulated research into non-invasive detection of myocardial allograft injury. The addition of a donor-organ specific myocardial injury marker based on donor-derived cell-free DNA further strengthens the non-invasive monitoring concept, combining the clinical use of two complementary non-invasive blood-based measures, host immune activity-related risk of acute rejection as well as cardiac allograft injury.

Expert Opinion

This novel complementary non-invasive heart transplant monitoring strategy based on leukocyte gene expression profiling and donor-derived cell-free DNA that incorporates longitudinal variability measures provides an exciting novel algorithm of heart transplant allograft monitoring. This algorithm's clinical utility will need to be tested in an appropriately designed randomized clinical trial which is in preparation.

Risk evaluation using gene expression screening to monitor for acute cellular rejection in heart transplant recipients

BACKGROUND

Gene expression profiling (GEP) was developed for non-invasive surveillance of acute cellular rejection. Despite its widespread use, there has been a paucity in outcome data for patients managed with GEP outside of clinical trials.

METHODS

The Outcomes AlloMap Registry (OAR) is an observational, prospective, multicenter study including patients aged ≥ 15 years and ≥ 55 days post-cardiac transplant. Primary outcome was death and a composite outcome of hemodynamically significant rejection, graft dysfunction, retransplantation, or death. Secondary outcomes included readmission rates and development of coronary allograft vasculopathy and malignancies.

RESULTS

The study included 1,504 patients, who were predominantly Caucasian (69%), male (74%), and aged 54.1 ± 12.9 years. The prevalence of moderate to severe acute cellular rejection (≥2R) was 2.0% from 2 to 6 months and 2.2% after 6 months. In the OAR there was no association between higher GEP scores and coronary allograft vasculopathy (p = 0.25), cancer (p = 0.16), or non-cytomegalovirus infection (p = 0.10). Survival at 1, 2, and 5 years post-transplant was 99%, 98%, and 94%, respectively. The composite outcome occurred in 103 patients during the follow-up period. GEP scores in dual-organ recipients (heart-kidney and heart-liver) were comparable to heart-alone recipients.

CONCLUSIONS

This registry comprises the largest contemporary cohort of patients undergoing GEP for surveillance. Among patients selected for GEP surveillance, survival is excellent, and rates of acute rejection, graft dysfunction, readmission, and death are low.