Manel Perello

The reproducibility and predictive value on outcome of renal biopsies from expanded criteria donors

Reproducibility and predictive value on outcome are the main criteria to evaluate the utility of histological scores. Here we analyze the reproducibility of donor biopsy assessment by different on-call pathologists and the retrospective evaluation by a single renal pathologist blinded to clinical outcomes. We also evaluate the predictive value on graft outcome of both evaluations. A biopsy was performed in donors with any of the following: age≥55 years, hypertension, diabetes, creatinine>1.5 mg/dl, or stroke. Glomerulosclerosis, interstitial fibrosis, tubular atrophy, intimal thickening, and arteriolar hyalinosis evaluated according to the Banff criteria were added to obtain a chronic score. Biopsies were classified as mild (≥3), intermediate (4-5), or advanced (6-7) damage, and unacceptable (≥8) for transplantation of 127 kidneys biopsied. Weighted κ value between both readings was 0.41 (95% CI: 0.28-0.54). Evaluation of biopsies by the renal pathologist was significantly and independently associated with estimated 12-month glomerular filtration rate and a significant composite outcome variable, including death-censored graft survival and time to reach an estimated glomerular filtration rate<30 ml/min per 1.73 m2. Thus, there was no association between readings of on-call pathologists and outcome. The lack of association between histological scores obtained by the on-call pathologists and graft outcome suggests that a specific training on renal pathology is recommended to optimize the use of kidneys retrieved from expanded criteria donors.

Gene expression signature of tolerance and lymphocyte subsets in stable renal transplants: Results of a cross-sectional study

BACKGROUND In kidney transplants operational tolerance has been associated with up-regulation of B cell differentiation genes and an increased number of total, naive and transitional peripheral B cells. The aim is to evaluate tolerance biomarkers in different cohorts of stable renal transplants under immunosuppression. METHODS This is a cross-sectional study conducted in renal transplants. We evaluate genetic tolerance signature and lymphocyte subsets in stable transplants treated with calcineurin inhibitors (CNI) at 1 (n=15), 5 (n=14) and 10 (n=16) years, and azathioprine-treated transplants followed 30 years (n=8). Healthy volunteers (n=10) and patients with chronic rejection (n=15) served as controls. RESULTS We confirm that peripheral expression of IGKV1D-13 and IGKV4-1 genes by RT-PCR distinguish tolerant (n=10) from stable transplants (n=10) provided by the International Tolerance Network. Tolerance signature was defined as the lowest expression for both genes in tolerant patients. In CNI-treated patients, genetic signature of tolerance and B cells showed a time-dependent increase not observed in azathioprine-treated patients (p<0.01). Genetic tolerance signature was observed in 0% at 1, 7% at 5 and 25% at 10-years while it was not observed in azathioprine-treated and chronic rejection patients. Fifteen out of 16 CNI-treated transplants at 10 years were revaluated 3 months apart. Nine did not show the tolerance signature in any determination, 4 in one and 2 in both determinations. Genetic signature of tolerance was associated with an increase of total, naive and transitional B cells (p<0.05). CONCLUSIONS IGKV1D-13 and IGKV4-1 gene expression and its linked B cell populations increase during follow up in CNI-treated patients. At 10 years, 2 out of 15 CNI treated patients consistently express biomarkers associated with true tolerance. In azathioprine-treated patients these biomarkers were down-regulated.

Comparing transplant glomerulopathy in the absence of C4d deposition and donor-specific antibodies to chronic antibody-mediated rejection

Transplant glomerulopathy (TG) is the characteristic lesion of chronic antibody‐mediated rejection (AMR). However, in some patients presents with no circulating HLA antibodies or C4d positivity.

Estimation of renal allograft half-life: fact or fiction?

INTRODUCTION Renal allograft half-life time (t½) is the most straightforward representation of long-term graft survival. Since some statistical models overestimate this parameter, we compare different approaches to evaluate t½. PATIENTS AND METHODS Patients with a 1-year functioning graft transplanted in Spain during 1990, 1994, 1998 and 2002 were included. Exponential, Weibull, gamma, lognormal and log-logistic models censoring the last year of follow-up were evaluated. The goodness of fit of these models was evaluated according to the Cox-Snell residuals and the Akaikes information criterion (AIC) was employed to compare these models. RESULTS We included 4842 patients. Real t½ in 1990 was 14.2 years. Median t½ (95% confidence interval) in 1990 and 2002 was 15.8 (14.2-17.5) versus 52.6 (35.6-69.5) according to the exponential model (P < 0.001). No differences between 1990 and 2002 were observed when t½ was estimated with the other models. In 1990 and 2002, t½ was 14.0 (13.1-15.0) versus 18.0 (13.7-22.4) according to Weibull, 15.5 (13.9-17.1) versus 19.1 (15.6-22.6) according to gamma, 14.4 (13.3-15.6) versus 18.3 (14.2-22.3) according to the log-logistic and 15.2 (13.8-16.6) versus 18.8 (15.3-22.3) according to the lognormal models. The AIC confirmed that the exponential model had the lowest goodness of fit, while the other models yielded a similar result. CONCLUSIONS The exponential model overestimates t½, especially in cohorts of patients with a short follow-up, while any of the other studied models allow a better estimation even in cohorts with short follow-up.

Treatment of chronic antibody mediated rejection with intravenous immunoglobulins and rituximab: A multicenter, prospective, randomized, double-blind clinical trial

There are no approved treatments for chronic antibody mediated rejection (ABMR). We conducted a multicenter, prospective, randomized, placebo‐controlled, double‐blind clinical trial to evaluate efficacy and safety of intravenous immunoglobulins (IVIG) combined with rituximab (RTX) (EudraCT 2010‐023746‐67). Patients with transplant glomerulopathy and anti‐HLA donor‐specific antibodies (DSA) were eligible. Patients with estimated glomerular filtration rate (eGFR) <20 mL/min per 1.73m2 and/or severe interstitial fibrosis/tubular atrophy were excluded. Patients were randomized to receive IVIG (4 doses of 0.5 g/kg) and RTX (375 mg/m2) or a wrapped isovolumetric saline infusion. Primary efficacy variable was the decline of eGFR at one year. Secondary efficacy variables included evolution of proteinuria, renal lesions, and DSA at 1 year. The planned sample size was 25 patients per group. During 2012‐2015, 25 patients were randomized (13 to the treatment and 12 to the placebo group). The planned patient enrollment was not achieved because of budgetary constraints and slow patient recruitment. There were no differences between the treatment and placebo groups in eGFR decline (−4.2 ± 14.4 vs. −6.6 ± 12.0 mL/min per 1.73 m2, P‐value = .475), increase of proteinuria (+0.9 ± 2.1 vs. +0.9 ± 2.1 g/day, P‐value = .378), Banff scores at one year and MFI of the immunodominant DSA. Safety was similar between groups. These data suggest that the combination of IVIG and RTX is not useful in patients displaying transplant glomerulopathy and DSA.

Tacrolimus and mycophenolate regimen and subclinical tubulo-interstitial inflammation in low immunological risk renal transplants

The aim was to evaluate the relationship between maintenance immunosuppression, subclinical tubulo‐interstitial inflammation and interstitial fibrosis/tubular atrophy (IF/TA) in surveillance biopsies performed in low immunological risk renal transplants at two transplant centers. The Barcelona cohort consisted of 109 early and 66 late biopsies in patients receiving high tacrolimus (TAC‐C0 target at 1‐year 6–10 ng/ml) and reduced MMF dose (500 mg bid at 1‐year). The Oslo cohort consisted of 262 early and 237 late biopsies performed in patients treated with low TAC‐C0 (target 3–7 ng/ml) and standard MMF dose (750 mg bid). Subclinical inflammation, adjusted for confounders, was associated with low TAC‐C0 in the early (OR: 0.75, 95% CI: 0.61–0.92; P = 0.006) and late biopsies (OR: 0.69, 95% CI: 0.50–0.95; P = 0.023) from Barcelona. In the Oslo cohort, it was associated with low MMF in early biopsies (OR: 0.90, 95% CI: 0.83–0.98; P = 0.0101) and with low TAC‐C0 in late biopsies (OR: 0.77, 95% CI: 0.61–0.97; P = 0.0286). MMF dose was significantly reduced in Oslo between early and late biopsies. IF/TA was not associated with TAC‐C0 or MMF dose in the multivariate analysis. Our data suggest that in TAC‐ and MMF‐based regimens, TAC‐C0 levels are associated with subclinical inflammation in patients receiving reduced MMF dose.

Subclinical Inflammation in Early Surveillance Biopsies is Associated with Immunosuppression Exposure and HLA-DR Mismatch

Background Subclinical inflammation in stable renal allografts observed in surveillance biopsies is associated with IF/TA progression and de novo HLA donor specific antibodies (DSA). Maintenance immunosuppression has been associated with subclinical inflammation being lower in patients treated with tacrolimus and MMF. However, the relationship between tacrolimus/MMF exposure and sublcinical inflammation has not been widely explored. Patients and Methods We analyze a prospective cohort of early surveillance biopsies (3-6 months) performed in 131 low immunological risk renal transplants treated with tacrolimus and MMF. Surveillance biopsies were evaluated according to the last update of Banff classification. We analyze the relationship between subclinical inflammation (i-Banff score >1) and clinical variables. To evaluate exposure to tacrolimus, time-concentration area under the curve (AUC; ng/mL/day) at different time points before performing the biopsy (AUC-TAC_0-1 month, AUC-TAC_1-2 months; AUC-TAC_2-3 months and AUC-TAC_3 months-biopsy) and the coefficient of variation of tacrolimus trough levels until biopsy were estimated. To evalaute exposure to MMF, AUC of MMF dose at the same time periods was estimated. Results Sublcinical inflammation was observed in 34 out of 131 biopsies (25.9%). In the univariate analysis subclinical inflammation was associated with patient age, HLA-DR mismatches, early steroid withdrawal, time of biopsy, AUC-TAC_2-3 months, AUC-TAC_3 months-Bx and coefficient of variation of TAC levels until biopsy. By logistic regression analysis independent variables associated with subclinical inflammation were: AUC-TAC_3 months-Bx (OR:0.64, p=0.005), HLA-DR mismatches (OR:2.09, p=.043) and early steroid withdrawal (OR:21, p=0.004). Figure. No caption available. Conclusions Subclinical inflammation in early surveillance biopsies is associated with low TAC exposure few weeks before biopsy, steroid free regimens and in high HLA-DR mismatches. I Beca Sociedad Española de Trasplantes-Novartis para Investigación Clínica.