In pediatric renal transplantation, sirolimus and tacrolimus CV % is a potential tool for monitoring patients at risk for allograft rejection and donor-specific antibodies secondary to medication nonadherence.

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.

Steroid avoidance in pediatric kidney transplants was found effective with extended daclizumab induction. Upon discontinuation of daclizumab, lymphocyte‐depleting agents became used, with little comparative data. We assessed outcomes in children undergoing low immunologic‐risk deceased donor (DD) kidney transplants using induction with antithymocyte globulin (ATG) compared to alemtuzumab. We reviewed consecutive DD kidney transplants from January 2015 to September 2017 at two pediatric centers that used different lymphocyte‐depleting agents in steroid‐avoidance protocols: ATG (Center A) and alemtuzumab (Center B), with tacrolimus and MMF as maintenance immunosuppression. Anti‐infective prophylaxis was based on center protocol. Over the first year post‐tx, there were similar rates of infections. EBV and BK viremia were comparable though Center A manifested more low‐grade CMV viremia (A 46% vs B 0%; P = .0009) at median onset 1.8 months, followed by early seroconversion. Reduction of immunosuppression did not differ between groups. DSA at 1 year was similar (A 8% vs 13%) with low rates of BPAR. Need for steroid‐based conversion was low. There were no graft losses and no differences in median eGFR at 30, 90, 180, and 365 days. (a) 1‐year graft outcomes are excellent in steroid‐avoidance regimens using ATG or alemtuzumab induction; (b) conversion to steroid‐based therapy is low; (c) alemtuzumab/high‐dose MMF is associated with lower WBC and more GCSF use; (d) alemtuzumab/higher dose MMF results in more diarrhea and azathioprine conversion than ATG/lower dose MMF; (e) CMV viremia is seen more often with ATG use with infection prophylaxis reduction; however, seroconversion occurs promptly.

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.

Preformed and de novo donor specific antibodies (pDSA and dnDSA) are risk factors for ABMR. This study compares the effects of pDSA vs dnDSA in pediatric kidney transplant recipients. Sixteen pediatric patients with biopsy-proven ABMR were evaluated. Strong DSA (MFI >10 000) was recorded at transplant, rejection, and follow-up. DSAs with the highest MFI were termed iDSAs. Allograft biopsies were scored according to Banff 2013 criteria. Seven of 16 (44%) patients had pDSA at transplant; 9 (56%) developed dnDSA. Patients with pDSA developed ABMR earlier (median = 63 vs 1344 days, P = .017), while patients with dnDSA were more likely to have strong Class II iDSA (100% vs 28%, P = .009). Viral infection or non-adherence was more common in patients developing dnDSA (88.8% vs 28.6%, P < .01). Pathology in those with pDSAs demonstrated worse transplant glomerulitis (g score 1.57 ± 0.98 vs 0.56 ± 0.73, P = .031); however, those with dnDSAs exhibited higher C4d+ ABMR (P = .013). Patients developing dnDSAs showed ABMR later post-transplant with predominance of HLA-Class II iDSAs. Inadequate immunosuppression likely contributes to dnDSA formation. Patients with no DSA who have unprotocolized decreases in immunosuppression should be screened for dnDSA as it could lead to early intervention and potentially better outcomes.

ABMR remains a significant concern for early graft loss, especially for those who are HS against HLA antigens. We sought to determine the risk factors leading to ABMR in HS pediatric kidney transplant recipients. From January 2009 to December 2015, 16 HS pediatric kidney transplant patients at our center (age range 2-21) were retrospectively reviewed for outcomes and risk factors for ABMR. All HS patients received desensitization with high-dose IVIG/rituximab prior to transplant. Two groups were examined: ABMR (n = 7) and ABMR (n = 9). Patient survival was 100%; however, one patient in the ABMR group suffered graft loss from ABMR 16 months post-transplant. ABMR patients had higher Class I PRA at the time of transplant (Class I: 73.1 ± 19.1 vs 49.1 ± 28.3, P = .075), although not statistically significant. ABMR patients were more likely to have a history of transplant nephrectomy (P = .013). The characteristic that most strongly correlated with ABMR was the DSA-RIS (P = .045), a scoring system used to quantify cumulative intensity of all DSA. In conclusion, DSA, as quantified by the RIS at the time of transplant, should be considered as part of the initial allocation strategy and patients with high RIS monitored closely for ABMR post-transplant.

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.