ABSTRACT
Donor specific anti-HLA antibodies (DSA) and donor-derived cell-free DNA (dd-cfDNA) have lead to substantial progress in the non-invasive monitoring of the renal allograft by being able to detect or rule out subclinical rejection and guide immunosuppressive changes. In this study we sought to analyze the clinical, de novo DSA (dnDSA) and histological determinants of dd-cfDNA levels. The study included a cohort of stable renal function kidney transplant (KT) recipients who underwent anti-HLA dnDSA and dd-cfDNA testing between September 2017-December 2019. Statistical models were constructed to detect association with predictors of dd-cfDNA levels and other clinical characteristics. 171 renal allograft recipients were tested for dd-cfDNA and dnDSA at a median 1.06 years posttransplant (IQR: 0.37-4.63). Median dd-cfDNA was 0.25% (IQR: 0.19-0.51), 18.7% of patients having a dd-cfDNA ≥ 1%. In a multivariate linear regression model the presence of dnDSA MFI ≥ 2500 was the best independent determinant of dd-cfDNA level (p < 0.001). Among patients tested, 54 had concurrent dd-cfDNA determination at the time of an allograft biopsy. dd-cfDNA had an AUC of 0.82 (95% CI 0.69-0.91; p < 0.001) and of 0.96 (95% CI 0.87-0.99) to discriminate any rejection and ABMR, respectively. After multivariate adjustment, the models that included ABMR (R = 0.82, R2 = 0.67, p < 0.001), or ptc (R = 0.79, R2 = 0.63, p < 0.001) showed the best correlation with dd-cfDNA level. We are confirming a strong association of dd-cfDNA with dnDSA and underlying alloimmune-mediated injury in renal allograft recipients in a cohort of patients with unsuspecting clinical characteristics for rejection and excellent allograft function. Our findings support the need for noninvasive biomarker surveillance in KT recipients and we propose that dd-cfDNA may complement dnDSA screening.
Subject(s)
Cell-Free Nucleic Acids , Kidney Transplantation , Antibodies , Biomarkers , Cell-Free Nucleic Acids/genetics , Graft Rejection , Humans , Kidney Transplantation/adverse effects , Tissue DonorsABSTRACT
We sought to evaluate the association between de novo donor-specific antibodies (dnDSAs) class and their mean fluorescence intensity (MFI) with donor-derived cell-free DNA (dd-cfDNA), aiming to further clarify the biomarker utility of these noninvasive tests in relation to renal allograft function and histology. METHODS: The study included kidney transplant recipients (n = 171) who underwent surveillance testing with DSA and dd-cfDNA as part of their clinical care between September 2017 and December 2019 at our center. RESULTS: We identified dnDSA in 43 patients (25%) at a median of 4.63 y (IQR, 1.5-7) posttransplant. The presence of DSA with MFI >2500 was associated with a median dd-cfDNA of 0.96% (IQR, 0.26-2.95) significantly higher than in patients with DSA MFI <2500 (0.28%; IQR, 0.19-0.39) or without detectable DSA (0.22%; IQR, 0.17-0.37; P < 0.001). Class II dnDSAs were the most prevalent dnDSA (88.3%), the majority with MFI >2500 (82.9%). Patients with DQ-dnDSAs (47.4%) had higher MFI and dd-cfDNA levels than other class II dnDSAs. By comparison, all patients that developed only class I DSAs had MFI <2500 and a low dd-cfDNA. In addition, the serum creatinine was 1.55 ± 0.48 mg/dL in those dnDSA-negative, 1.15 ± 0.37 mg/dL in those with dnDSA MFI <2500, and 1.53 ± 0.66 mg/dL in those with dnDSA MFI >2500 (P = 0.05). After multivariate adjustment, an elevated dd-cfDNA was independently associated with the presence of dnDSA with MFI ≥2500. We identified that both dd-cfDNA and dnDSAs were strongly associated with antibody-mediated rejection, whereas for individual Banff histological lesions, DSA MFIs ≥2500 had the strongest association with C4d staining score and dd-cfDNA >1% with microvascular inflammation. CONCLUSIONS: Our study identifies class II dnDSA as being strongly associated with late alloimmune injury post kidney transplant independent of allograft dysfunction and shows that dd-cfDNA may complement the clinical significance of dnDSAs.