Evaluation of protocol biopsy utility 12 months after renal transplantation: a multicenter observational analysis

High levels of dd-cfDNA identify patients with TCMR 1A and borderline allograft rejection at elevated risk of graft injury

The clinical importance of subclinical, early T cell-mediated rejection (Banff TCMR 1A and borderline lesions) remains unclear, due, in part to the fact that histologic lesions used to characterize early TCMR can be nonspecific. Donor-derived cell-free DNA (dd-cfDNA) is an important molecular marker of active graft injury. Over a study period from June 2017 to May 2019, we assessed clinical outcomes in 79 patients diagnosed with TCMR 1A/borderline rejection across 11 US centers with a simultaneous measurement of dd-cfDNA. Forty-two patients had elevated dd-cfDNA (≥0.5%) and 37 patients had low levels (<0.5%). Elevated levels of dd-cfDNA predicted adverse clinical outcomes: among patients with elevated cfDNA, estimated glomerular filtration rate declined by 8.5% (interquartile rate [IQR] -16.22% to -1.39%) (-3.50 mL/min/1.73 m2 IQR -8.00 to -1.00) vs 0% (-4.92%, 4.76%) in low dd-cfDNA patients (P = .004), de novo donor-specific antibody formation was seen in 40% (17/42) vs 2.7% (P < .0001), and future or persistent rejection occurred in 9 of 42 patients (21.4%) vs 0% (P = .003). The use of dd-cfDNA may complement the Banff classification and to risk stratify patients with borderline/TCMR 1A identified on biopsy.

Low-dose Rituximab and Thymoglobulin Induction With Steroid-free Maintenance Immunosuppression and Protocol Biopsies Improves Long-term Patient and Graft Survival After Kidney Transplantation: Survival and Safety Outcomes in More Than 1100 Patients From a Single Center

BACKGROUND

Steroid-free maintenance immunosuppression after kidney transplantation provides acceptable patient and graft survival and minimizes steroid-associated side effects among recipients with a low immunological risk. However, the long-term outcomes of such protocols, incorporating low-dose rituximab and thymoglobulin induction along with protocol biopsies, in non-European populations remains underreported.

METHODS

We retrospectively analyzed 1142 consecutive kidney transplantations conducted at our center from July 2005 to October 2017. Immunosuppression protocol included induction with thymoglobulin and low-dose preoperative rituximab. Maintenance immunosuppression consisted of tacrolimus and mycophenolate mofetil; prednisolone was discontinued on postoperative day 5. Protocol biopsies were carried out at 3 months and at 1, 5, and 10 years after transplantation-in addition to the indicated biopsies. The 12-year patient and graft survival and posttransplantation complications were studied.

RESULTS

The analysis of outcomes was conducted for 1111 transplant recipients. Patients (70.59%) remained steroid-free at 12 years after transplantation. The patient survival rates at 1, 5, and 12 years were 97.7%, 94.8%, and 92.4%, respectively. The corresponding graft survival rates were 97.2%, 90.9%, and 86.1%, respectively. Biopsy-proven acute rejection occurred in 12.7% of recipients, including 3.5% subclinical rejections. The cumulative incidence of graft loss was 6.56% at 12.3 years. The overall incidence of death was 5.3%.

CONCLUSIONS

Steroid-free maintenance immunosuppression was associated with excellent long-term patient and graft survival rates and reduced incidence of prednisolone-related side effects, despite acceptable rejection rates. Low-dose rituximab with thymoglobulin induction with immediate steroid withdrawal and surveillance biopsies resulted in excellent long-term outcomes in our single-center experience.

The 1-year Renal Biopsy Index: a scoring system to drive biopsy indication at 1-year post-kidney transplantation

Surveillance biopsies after renal transplantation remain debatable. To drive the decision of such intervention, we propose a predictive score of abnormal histology at 1-year post-transplantation, named 1-year Renal Biopsy Index (1-RBI). We studied 466 kidney recipients from the DIVAT cohort alive with a functioning graft and a surveillance biopsy at 1-year post-transplantation. Patients displaying abnormal histology (49%) (borderline, acute rejection, interstitial fibrosis and tubular atrophy [IFTA] grade 2 or 3, glomerulonephritis) were compared to the normal or subnormal (IFTA grade 1) histology group. Obtained from a lasso penalized logistic regression, the 1-RBI was composed of recipient gender, serum creatinine at 3, 6, and 12 month post-transplantation and anticlass II immunization at transplantation (internal validation: AUC = 0.71, 95% CI [0.53-0.83]; external validation: AUC = 0.62, 95% CI [0.58-0.66]). While we could not determinate a threshold able to identify patients at high chance of normal or subnormal histology, we estimated and validated a discriminating threshold capable of identifying a subgroup of 15% of the patients with a risk of abnormal histology higher than 80%. The 1-RBI is computable online at www.divat.fr. The 1-RBI could be a useful tool to standardize 1-year biopsy proposal and may for instance help to indicate one in case of high risk of abnormal histology.

The significance of histological diagnosis in renal allograft biopsies in 2014

In 2014, the renal allograft biopsy still represents the best available diagnostic 'gold' standard to assess reasons for allograft dysfunction. However, it is well recognized that histological lesion observed in the biopsy is of limited diagnostic specificity and that the Banff classification as the international diagnostic standard represents mere expert consensus. Here, we review the role of the renal allograft biopsy in different clinical and diagnostic settings. To increase diagnostic accuracy and to compensate for lack of specificity, the interpretation of biopsy pathology needs to be within the clinical context, primarily defined by time post-transplantation and patient-specific risk profile. With this in mind, similar histopathological patterns will lead to different conclusions with regard to diagnosis, disease grading and staging and thus to patient-specific clinical decision-making. Consensus generation for such integrated diagnostic approach, preferably including new molecular tools, represents the next challenge to the transplant community on its way to precision medicine in transplantation.

Regulatory T cells in the immunodiagnosis and outcome of kidney allograft rejection

Acute rejection (AR) is responsible for up to 12% of graft loss with the highest risk generally occurring during the first six months after transplantation. AR may be broadly classified into humoral as well as cellular rejection. Cellular rejection develops when donor alloantigens, presented by antigen-presenting cells (APCs) through class I or class II HLA molecules, activate the immune response against the allograft, resulting in activation of naive T cells that differentiate into subsets including cytotoxic CD8⁺ and helper CD4⁺ T cells type 1 (TH1) and TH2 cells or into cytoprotective immunoregulatory T cells (Tregs). The immune reaction directed against a renal allograft has been suggested to be characterized by two major components: a destructive one, mediated by CD4⁺ helper and CD8⁺ cytotoxic T cells, and a protective response, mediated by Tregs. The balance between these two opposite immune responses can significantly affect the graft survival. Many studies have been performed in order to define the role of Tregs either in the immunodiagnosis of transplant rejection or as predictor of the clinical outcome. However, information available from the literature shows a contradictory picture that deserves further investigation.