Dynamics of Donor-Derived Cell-Free DNA at the Early Phase After Pediatric Kidney Transplantation: A Prospective Cohort Study

Detection of Subclinical Rejection in Pediatric Kidney Transplantation: Current and Future Practices

INTRODUCTION

The successes in the field of pediatric kidney transplantation over the past 60 years have been extraordinary. Year over year, there have been significant improvements in short-term graft survival. However, improvements in longer-term outcomes have been much less apparent. One important contributor has been the phenomenon of low-level rejection in the absence of clinical manifestations-so-called subclinical rejection (SCR).

METHODS

Traditionally, rejection has been diagnosed by changes in clinical parameters, including but not limited to serum creatinine and proteinuria. This review examines the shortcomings of this approach, the effects of SCR on kidney allograft outcome, the benefits and drawbacks of surveillance biopsies to identify SCR, and new urine and blood biomarkers that define the presence or absence of SCR.

RESULTS

Serum creatinine is an unreliable index of SCR. Surveillance biopsies are the method most utilized to detect SCR. However, these have significant drawbacks. New biomarkers show promise. These biomarkers include blood gene expression profiles and donor derived-cell free DNA; urine gene expression profiles; urinary cytokines, chemokines, and metabolomics; and other promising blood and urine tests.

CONCLUSION

Specific emphasis is placed on studies carried out in pediatric kidney transplant recipients.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT03719339.

Immune monitoring in pediatric kidney transplant

BACKGROUND

Long-term outcomes in pediatric kidney transplantation remain suboptimal, largely related to chronic rejection. Creatinine is a late marker of renal injury, and more sensitive, early markers of allograft injury are an active area of current research.

METHODS

This is an educational review summarizing existing strategies for monitoring for rejection in kidney transplant recipients.

RESULTS

We summarize supporting currently available clinical tests, including surveillance biopsy, donor specific antibodies, and donor-derived cell free DNA, as well as the potential limitations of these studies. In addition, we review the current avenues of active research, including transcriptomics, proteomics, metabolomics, and torque tenovirus levels.

CONCLUSION

Advancing the use of noninvasive immune monitoring will depend on well-designed multicenter trials that include patients with stable graft function, include biopsy results on all patients, and can demonstrate both association with a patient-relevant clinical endpoint such as graft survival or change in glomerular filtration rate and a potential timepoint for intervention.

Single center study investigating the clinical association of donor-derived cell-free DNA with acute outcomes in lung transplantation

Background

Circulating donor-derived cell-free DNA (dd-cfDNA) levels have been proposed as a potential tool for the diagnosis of graft injury. In this study, we prospectively investigated dd-cfDNA plasma levels and their association with severe primary graft dysfunction (PGD) and graft rejection after lung transplant.

Methods

A total of 40 subjects undergoing de-novo lung transplants at our institution were recruited in this study. Blood samples were collected at various time points before and after lung transplant for 1 year. Dd-cfDNA in samples was determined using AlloSure assay (CareDx Inc.). The correlation of the value of %dd-cfDNA was investigated with the incidence of PGD, acute cellular rejection (ACR), and donor-specific antibody.

Results

We observed a rapid increase of %dd-cfDNA in the blood of recipients after lung transplantation compared to baseline. The levels of dd-cfDNA decreased during the first two weeks. The peak was observed within 72 h after transplantation. The peak values of %dd-cfDNA varied among subjects and did not correlate with severe PGD incidence. We observed an association between levels of %dd-cfDNA from blood collected at the time of transbronchial biopsy and the histological diagnosis of ACR at 3 weeks.

Conclusion

Our data show that circulating dd-cfDNA levels are associated with ACR early after transplantation but not with severe PGD. Plasma levels of dd-cfDNA may be a less invasive tool to estimate graft rejection after lung transplantation however larger studies are still necessary to better identify thresholds.

Longitudinal Evaluation of Donor-Derived Cellfree DNA in Pediatric Kidney Transplantation

BACKGROUND AND OBJECTIVES

Donor-derived cellfree DNA (cfDNA) is a less-invasive marker of allograft injury compared with kidney biopsy. However, donor-derived cfDNA has not yet been extensively tested in children, where the test may have different characteristics.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We assayed donor-derived cfDNA (AlloSure; CareDx) from 290 stored plasma samples from a prospective biobank at our center, collected from 57 children monthly in the first year postkidney transplant between January 2013 and December 2019. We assessed the kinetic changes in donor-derived cfDNA levels within the first year post-transplant. We analyzed donor-derived cfDNA levels for associations with biopsy-proven acute rejection using area under the receiver operating characteristic curve to longitudinal plasma and urine BK viral loads using linear mixed models. We analyzed the prognostic effect of an elevated donor-derived cfDNA level on the eGFR 30 days after the assay via Kolmogorov-Smirnov two-sample tests or on measured GFR or interstitial fibrosis at 12 months post-transplant.

RESULTS

The donor-derived cfDNA levels in children remained persistently elevated for at least 4 months post-transplant, more so if there is greater disparity in size between the donor and the recipient, before reaching a steady low level. A donor-derived cfDNA level of >1% discriminated between biopsy-proven acute rejection with a receiver operating characteristic area under the curve of 0.82 (95% confidence interval, 0.71 to 0.93). During BK viruria or viremia, patients had a significantly higher median donor-derived cfDNA than before or after and a significant rise within the same patient. A donor-derived cfDNA of >0.5% predicted a wider spread in the eGFR over the next 30 days but not the 12-month outcomes.

CONCLUSIONS

In children, donor-derived cfDNA is a valuable, less invasive biomarker for assessment of allograft rejection and injury.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2022_10_27_CJN03840322.mp3.