In pediatric transplantation, acute rejection is a major contributor of graft failure. Current approaches include kidney biopsy in response to graft dysfunction and/or the emergence of donor‐specific HLA antibodies (DSA). However, biopsy is associated with potential complications. Thus, there is a need for non‐invasive diagnostics. Detection of donor‐derived cell‐free DNA (dd‐cfDNA, AlloSure) > 1% is associated with rejection in adult kidney transplants. Here, we evaluate the utility of dd‐cfDNA for identifying allograft rejection in pediatric patients. Between 10/2017 and 10/2019, 67 patients, who underwent initial testing with dd‐cfDNA as part of routine monitoring or in response to clinical suspicion for rejection, were included. Biopsies were performed when dd‐cfDNA > 1.0% or where clinical suspicion was high. Demographics, dd‐cfDNA, antibody status, and biopsies were collected prospectively. Data were analyzed to determine predictive value of dd‐cfDNA for identifying grafts at risk for rejection. 19 of 67 patients had dd‐cfDNA testing as part of routine monitoring with a median dd‐cfDNA score of 0.37 (IQR: 0.19‐1.10). 48 of 67 patients who had clinical suspicion of rejection had median dd‐cfDNA score of 0.47 (0.24‐2.15). DSA‐positive recipients had higher dd‐cfDNA scores than those who were negative or had AT1R positivity alone (P = .003). There was no association between dd‐cfDNA score and strength of DSA positivity. 7 of 48 recipients had a biopsy with a dd‐cfDNA score <1%; two showed evidence of rejection. Neither DSA nor AT1R positivity was statistically associated with biopsy‐proven rejection. However, dd‐cfDNA >1% was diagnostic of rejection with sensitivity of 86% and specificity of 100% (AUC: 0.996, 0.98‐1.00; P = .002). dd‐cfDNA represents a non‐invasive method for early detection of rejection in pediatric renal transplants. Our study shows dd‐cfDNA to be highly predictive of histological rejection and superior to other indicators such as graft dysfunction or antibody positivity alone. Further studies are necessary to refine these initial observations.

Background: Detection of donor-derived cell-free DNA (dd-cfDNA) reliably identifies allograft rejection in pediatric and adult kidney transplant (KT) recipients. Here, we evaluate the utility of dd-cfDNA for monitoring response to treatment among pediatric renal transplant recipients suffering graft rejection.Methods: 58 pediatric transplant recipients were enrolled between April 2018 and March 2020 and underwent initial dd-cfDNA testing to monitor for rejection.Allograft biopsy was performed for dd-cfDNA scores >1.0%. Patients with histologically proven rejection formed the study cohort and underwent appropriate treatment. Results of dd-cfDNA, serum creatinine (SCr), biopsy findings, and treatment outcomes were evaluated. Standard statistical analyses were applied.Results: Nineteen of 58 (31%) patients had dd-cfDNA score >1.0%, of which 18 (94.7%) had biopsy-proven rejection. Median dd-cfDNA value was 1.90% (interquartile range 1.43%-3.23%), and biopsy results showed 11 patients (61.1%) with antibody-mediated rejection (AMR), 2 patients (11.1%) with T-cell mediated rejection (TCMR), and 5 patients (27.7%) with mixed AMR/TCMR. SCr at time of biopsy was 1.28 ± 1.09 mg/dl. Following treatment, dd-cfDNA scores decreased for all types of rejection but still remained >1.0% in both AMR (1.50% [0.90%-3.10%]) and mixed (1.40% [0.95%-4.15%]) groups. Repeat dd-cfDNA values were <1.0% for patients with TCMR (0.20%-0.28%). SCr showed minimal change from pre-treatment levels regardless of rejection subtype. Conclusions:Patients with TCMR may be reliably followed by dd-cfDNA; however, it remains unclear whether persistently elevated dd-cfDNA levels in AMR is a reflection of ongoing subclinical rejection or an inherent limitation of the assay's utility.

Background: Treatment options for antibody-mediated rejection (AMR) are limited. Recent studies have shown that inhibition of interleukin-6 (IL-6)/interleukin-6 receptor (IL-6R) signaling can reduce inflammation and slow AMR progression. Methods: We report our experience using monthly tocilizumab (anti-IL6R) in 25 pediatric renal transplant recipients with AMR, refractory to IVIg/Rituximab. From January 2013 to June 2019, a median (IQR) of 12 (6.019.0) doses of tocilizumab were given per patient. Serial assessments of renal function, biopsy findings, and HLA DSA (by immunodominant HLA DSA [iDSA] and relative intensity score [RIS]) were performed.Results: Median (IQR) time from transplant to AMR was 41.4 (24.367.7) months, and time from AMR to first tocilizumab was 10.6 (8.317.6) months. At median (IQR) follow up of 15.8 (8.435.7) months post-tocilizumab initiation, renal function was stable except for 1 allograft loss. There was no significant decrease in iDSA or RIS. Follow up biopsies showed reduction in peritubular capillaritis (p = .015) and C4d scoring (p = .009). The most frequent adverse events were cytopenias.

Background The role of angiotensin II type 1 receptor antibodies (AT1R‐Ab) in pediatric renal transplantation is unclear. Here, we evaluated pre‐transplant AT1R‐Ab on transplant outcomes in the first 5 years. Secondary analysis compared pre‐transplant AT1R‐Ab levels by age. Methods Thirty‐six patients, 2–20 years old, were divided into two groups: pre‐transplant AT1R‐Ab− (<17 U/ml; n = 18) and pre‐transplant AT1R‐Ab+ (≥17 U/ml; n = 18). eGFR was determined at 6‐month, 1‐, 2‐, and 4‐year post‐transplant. Allograft biopsies were performed in the setting of strong HLA‐DSA (MFI > 10 000), AT1R‐Ab ≥17 U/ml, and/or elevated creatinine. Results Mean age in pre‐transplant AT1R‐Ab− was 13.3 years vs. 11.0 in pre‐transplant AT1R‐Ab+ (p = 0.16). At 6 months, mean eGFR was 111.3 ml/min/1.73 m2 in pre‐transplant AT1R‐Ab− vs. 100.2 in pre‐transplant AT1R‐Ab + at 1 year, 103.6 ml/min/1.73 m2 vs. 100.5; at 2 years, 98.9 ml/min/1.73 m2 vs. and 93.7; at 4 years, 72.6 ml/min/1.73 m2 vs. 80.9. 11/36 patients had acute rejection (6 in pre‐transplant AT1R‐Ab−, 5 in pre‐transplant AT1R‐Ab + ). There was no difference in rejection rates. All 6 subjects with de novo HLA‐DSA and AT1R‐Ab ≥17 U/ml at the time of biopsy experienced rejection. Mean age in those with the AT1R‐Ab ≥40 U/ml was 10.0 years vs. 13.2 in those <40 U/ml (p = 0.07). Conclusion In our small cohort, pre‐transplant AT1R‐Ab ≥17 U/ml was not associated with reduced graft function or rejection. The pathogenicity of pre‐transplant AT1R‐Ab in pediatric kidney transplantation requires further investigation.

Background As COVID‐19‐positive donors are becoming more common, there is an increasing need for the transplant community to evaluate the safety and efficacy of organ transplant from a SARS‐CoV‐2‐infected donor. Methods Here we describe outcomes of two pediatric kidney transplant recipients who were vaccinated against COVID‐19 and received their allograft from a SARS‐CoV‐2‐positive donor. Results Both donors did not die from a COVID‐19‐related illness; the first donor had 1 week of COVID‐19 symptoms 4 weeks prior to donation and the second was asymptomatic. Donor 1 had a Ct of 33.4 at 3 days and Donor 2 with a Ct of 37.2 at 16 days prior to donation. The first recipient was positive for SARS‐CoV‐2 anti‐spike IgG on the day of transplant, but the second patient was negative and both patients received IVIg perioperatively. There was no evidence of SARS‐CoV‐2 transmission or compromised renal function at 86‐ and 80‐day post‐transplant, respectively. Conclusions This case series suggests favorable short‐term outcomes with accepting SARS‐CoV‐2‐positive donors for pediatric renal transplantation, after thorough evaluation of the donor's risk for transmission, assessing the recipient's serologic status to SARS‐CoV‐2, and considering pre‐emptive measures to mitigate the risk for severe COVID‐19 should the recipient acquire donor‐derived SARS‐CoV‐2.