Applying rigor and reproducibility standards to assay donor-derived cell-free DNA as a non-invasive method for detection of acute rejection and graft injury after heart transplantation

BACKGROUND

Use of new genomic techniques in clinical settings requires that such methods are rigorous and reproducible. Previous studies have shown that quantitation of donor-derived cell-free DNA (%ddcfDNA) by unbiased shotgun sequencing is a sensitive, non-invasive marker of acute rejection after heart transplantation. The primary goal of this study was to assess the reproducibility of %ddcfDNA measurements across technical replicates, manual vs automated platforms, and rejection phenotypes in distinct patient cohorts.

METHODS

After developing and validating the %ddcfDNA assay, we subjected the method to a rigorous test of its reproducibility. We measured %ddcfDNA in technical replicates performed by 2 independent laboratories and verified the reproducibility of %ddcfDNA patterns of 2 rejection phenotypes: acute cellular rejection and antibody-mediated rejection in distinct patient cohorts.

RESULTS

We observed strong concordance of technical-replicate %ddcfDNA measurements across 2 independent laboratories (slope = 1.02, R² > 0.99, p < 10^-6), as well as across manual and automated platforms (slope = 0.80, R² = 0.92, p < 0.001). The %ddcfDNA measurements in distinct heart transplant cohorts had similar baselines and error rates. The %ddcfDNA temporal patterns associated with rejection phenotypes were similar in both patient cohorts; however, the quantity of ddcfDNA was significantly higher in samples with severe vs mild histologic rejection grade (2.73% vs 0.14%, respectively; p < 0.001).

CONCLUSIONS

The %ddcfDNA assay is precise and reproducible across laboratories and in samples from 2 distinct types of heart transplant rejection. These findings pave the way for larger studies to assess the clinical utility of %ddcfDNA as a marker of acute rejection after heart transplantation.

Ventricular assist device elicits serum natural IgG that correlates with the development of primary graft dysfunction following heart transplantation

BACKGROUND

Pre-transplant sensitization is a limiting factor in solid-organ transplantation. In heart transplants, ventricular assist device (VAD) implantation has been associated with sensitization to human leukocyte antigens (HLA). The effect of VAD on non-HLA antibodies is unclear. We have previously shown that polyreactive natural antibodies (Nabs) contribute to pre-sensitization in kidney allograft recipients. Here we assessed generation of Nabs after VAD implantation in pre-transplant sera and examined their contribution to cardiac allograft outcome.

METHODS

IgM and IgG Nabs were tested in pre-transplant serum samples collected from 206 orthotopic heart transplant recipients, including 128 patients with VAD (VAD patients) and 78 patients without VAD (no-VAD patients). Nabs were assessed by testing serum reactivity to apoptotic cells by flow cytometry and to the generic oxidized epitope, malondialdehyde, by enzyme-linked immunosorbent assay.

RESULTS

No difference was observed in serum levels of IgM Nabs between VAD and no-VAD patients. However, serum IgG Nabs levels were significantly increased in VAD compared with no-VAD patients. This increase was likely due to the presence of the VAD, as revealed by lower serum IgG Nabs levels before implantation. Elevated pre-transplant IgG Nabs level was associated with development of primary graft dysfunction (PGD).

CONCLUSIONS

Our study demonstrates that VAD support elicits IgG Nabs reactive to apoptotic cells and oxidized epitopes. These findings further support broad and non-specific B-cell activation by VAD, resulting in IgG sensitization. Moreover, the association of serum IgG Nabs levels with development of PGD suggests a possible role for these antibodies in the inflammatory reaction accompanying this complication.

Early risk prognosis of free-flap transplant failure by quantitation of the macrophage colony-stimulating factor in patient plasma using 2-dimensional liquid-chromatography multiple reaction monitoring-mass spectrometry

Although great success of microvascular free-flap transplantation surgery has been achieved in recent years, between 1.5% and 15% of flaps are still lost due to vascular occlusion. The clinical challenge remains to salvage a transplant in the case of vascular complications. Since flap loss is devastating for the patient, it is of utmost importance to detect signs of complications or of conspicuities as soon as possible. Rescue success rates highly depend on early revision. In this study, we collected blood samples during transplantation surgery from either the contributory artery or the effluent vein of the flap and applied a targeted mass spectrometry-based approach to quantify 24 acute phase proteins, cytokines, and growth factors in 63 plasma samples from 21 hospitalized patients, generating a dataset with 9450 protein concentration values. Biostatistical analyses of the targeted plasma protein concentrations in all 63 plasma samples showed that venous concentrations of macrophage colony-stimulating factor (M-CSF) provided the highest accuracy for discriminating patients with either clinical conspicuities or complications from control individuals. Using 21.33 ng/mL of M-CSF as the diagnostic threshold when analyzing venous blood plasma samples, the assay obtained a sensitivity of 0.93 and a specificity of 0.85 with an area under the curve value of 0.902 in the receiver operating characteristic analysis. Overall, our results indicate that M-CSF is a potential molecular marker for early risk prognosis of free-flap transplant failure.

Predictive factors of short term outcome after liver transplantation: A review

Liver transplantation represents a fundamental therapeutic solution to end-stage liver disease. The need for liver allografts has extended the set of criteria for organ acceptability, increasing the risk of adverse outcomes. Little is known about the early postoperative parameters that can be used as valid predictive indices for early graft function, retransplantation or surgical reintervention, secondary complications, long intensive care unit stay or death. In this review, we present state-of-the-art knowledge regarding the early post-transplantation tests and scores that can be applied during the first postoperative week to predict liver allograft function and patient outcome, thereby guiding the therapeutic and surgical decisions of the medical staff. Post-transplant clinical and biochemical assessment of patients through laboratory tests (platelet count, transaminase and bilirubin levels, INR, factor V, lactates, and Insulin Growth Factor 1) and scores (model for end-stage liver disease, acute physiology and chronic health evaluation, sequential organ failure assessment and model of early allograft function) have been reported to have good performance, but they only allow late evaluation of patient status and graft function, requiring days to be quantified. The indocyanine green plasma disappearance rate has long been used as a liver function assessment technique and has produced interesting, although not univocal, results when performed between the 1^th and the 5^th day after transplantation. The liver maximal function capacity test is a promising method of metabolic liver activity assessment, but its use is limited by economic cost and extrahepatic factors. To date, a consensual definition of early allograft dysfunction and the integration and validation of the above-mentioned techniques, through the development of numerically consistent multicentric prospective randomised trials, are necessary. The medical and surgical management of transplanted patients could be greatly improved by using clinically reliable tools to predict early graft function.

Serum Neutrophil Gelatinase-Associated Lipocalin and Cystatin C for Assessing Recovery of Graft Function in Patients Undergoing Living-Donor Kidney Transplantation

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) can be used as an early indicator of acute kidney injury (AKI), and cystatin C is also suggested to be an ideal marker of glomerular filtration rate (GFR), but they were not sufficiently studied in recipients without delayed graft function (DGF) after living-donor kidney transplant (LDKT). The aim of the study is to investigate whether serum NGAL and cystatin C can assess the recovery of renal function after LDKT.

METHODS

49 adult patients that had undergone LDKT between January 2012 and March 2014 were prospectively enrolled. Serum creatinine, NGAL, and cystatin C were measured on day 0-7, day 10, day 14 and month 9 after transplant. Recovery of graft function was evaluated by the time needed to reach eGFR > or = 60 mL/min/1.73 in2 Poor long-term graft outcome was defined as eGFR < 60 mL/min/1.73 M2 at 9 months.

RESULTS

No DGF was recorded. Serum NGAL level decreased to normal earlier than creatinine after transplant. Cystatin C declined rapidly, but still stayed above the normal range. Serum NGAL on day 0 (p = 0.028) and cystatin C on day 2 (p < 0.001) were independent predictors of the time for graft function recovery in multivariate analysis. Compared to recipients with fair long-term graft outcome (eGFR > 60 mL/min/1.73 m2 at 9 months), recipients with poor long-term graft outcome (eGFR < 60 mL/min/1.73 m2 at 9 months) displayed higher serum NGAL on day 2 (p = 0.045), older age (p = 0.002), longer time on dialysis (p = 0.02), and lower donor eGFR (p = 0.045). There were correlations between serum NGAL and eGFR on day 0 and day 2. Correlations between serum cystatin C and eGFR on day 0, day 2, and month 9 were all significant.

CONCLUSIONS

Serum NGAL may be used as an early predictor of recovery of post-transplant graft function after LDKT, but may not be used for real-time assessment of GFR. At the same time, the predictive ability of serum cystatin C needs to be further assessed.

High levels of procalcitonin in the early phase after pediatric liver transplantation indicate poor postoperative outcome

BACKGROUND/AIMS

To date, no data is available about procalcitonin (PCT) levels and its relevance to morbidity and graft function in the early phase after pediatric liver transplantation (pLTx). The aim of this study was to analyse the prognostic relevance of early postoperative PCT elevations in pediatric liver recipients.

METHODOLOGY

Thirty pediatric patients who underwent 32 liver transplantations were included into this observational single-center study.

RESULTS

Patients with high PCT levels on postoperative day (POD) 2 had higher International Normalized Ratio values on POD 5 (p<0.05) and suffered more often from primary graft non-function (p<0.05). They also had a longer stay in the pediatric intensive care unit (p<0.01) and on mechanical ventilation (p=0.001). There was no correlation between PCT elevation and systemic infection. However, PCT levels were correlated with peak serum lactate levels immediately after graft reperfusion and elevation of serum aminotransferases on POD 1 (r2=0.61, p<0.001).

CONCLUSIONS

High levels of PCT after pLTx are an early indicator of poor postoperative outcome and may reflect ischemia induced liver cell injury within the context of an ischemia- reperfusion injury.

Elevated plasma angiopoietin-2 levels and primary graft dysfunction after lung transplantation

INTRODUCTION

Primary graft dysfunction (PGD) is a significant contributor to early morbidity and mortality after lung transplantation. Increased vascular permeability in the allograft has been identified as a possible mechanism leading to PGD. Angiopoietin-2 serves as a partial antagonist to the Tie-2 receptor and induces increased endothelial permeability. We hypothesized that elevated Ang2 levels would be associated with development of PGD.

METHODS

We performed a case-control study, nested within the multi-center Lung Transplant Outcomes Group cohort. Plasma angiopoietin-2 levels were measured pre-transplant and 6 and 24 hours post-reperfusion. The primary outcome was development of grade 3 PGD in the first 72 hours. The association of angiopoietin-2 plasma levels and PGD was evaluated using generalized estimating equations (GEE).

RESULTS

There were 40 PGD subjects and 79 non-PGD subjects included for analysis. Twenty-four PGD subjects (40%) and 47 non-PGD subjects (59%) received a transplant for the diagnosis of idiopathic pulmonary fibrosis (IPF). Among all subjects, GEE modeling identified a significant change in angiopoietin-2 level over time in cases compared to controls (p = 0.03). The association between change in angiopoietin-2 level over the perioperative time period was most significant in patients with a pre-operative diagnosis of IPF (p = 0.02); there was no statistically significant correlation between angiopoietin-2 plasma levels and the development of PGD in the subset of patients transplanted for chronic obstructive pulmonary disease (COPD) (p = 0.9).

CONCLUSIONS

Angiopoietin-2 levels were significantly associated with the development of PGD after lung transplantation. Further studies examining the regulation of endothelial cell permeability in the pathogenesis of PGD are indicated.