Tom Blydt-Hansen

Evolution and clinical pathologic correlations of de novo donor-specific HLA antibody post kidney transplant.

The natural history for patients with de novo donor‐specific antibodies (dnDSA) and the risk factors for its development have not been well defined. Furthermore, clinical and histologic correlation with serologic data is limited. We studied 315 consecutive renal transplants without pretransplant DSA, with a mean follow‐up of 6.2 ± 2.9 years. Protocol (n = 215) and for cause (n = 163) biopsies were analyzed. Solid phase assays were used to screen for dnDSA posttransplant. A total of 47 out of 315 (15%) patients developed dnDSA at a mean of 4.6 ± 3.0 years posttransplant. Independent predictors of dnDSA were HLA‐DRβ1 MM > 0 (OR 5.66, p < 0.006); and nonadherence (OR 8.75, p < 0.001); with a strong trend toward clinical rejection episodes preceding dnDSA (OR 1.57 per rejection episode, p = 0.061). The median 10‐year graft survival for those with dnDSA was lower than the No dnDSA group (57% vs. 96%, p < 0.0001). Pathology consistent with antibody‐mediated injury can occur and progress in patients with dnDSA in the absence of graft dysfunction and furthermore, nonadherence and cellular rejection contribute to dnDSA development and progression to graft loss.

Masked Hypertension Associates with Left Ventricular Hypertrophy in Children with CKD

Left ventricular hypertrophy (LVH) associates with increased risk for cardiovascular disease. Hypertension leads to LVH in adults, but its role in the pathogenesis of LVH in children is not as well established. To examine left ventricular mass and evaluate factors associated with LVH in children with stages 2 through 4 chronic kidney disease (CKD), we analyzed cross-sectional data from children who had baseline echocardiography (n = 366) and underwent ambulatory BP monitoring (n = 226) as a part of the observational Chronic Kidney Disease in Children (CKiD) cohort study. At baseline, 17% of children had LVH (11% eccentric and 6% concentric) and 9% had concentric remodeling of the left ventricle. On the basis of a combination of ambulatory and casual BP assessment (n = 198), 38% of children had masked hypertension (normal casual but elevated ambulatory BP) and 18% had confirmed hypertension (both elevated casual and ambulatory BP). There was no significant association between LVH and kidney function. LVH was more common in children with either confirmed (34%) or masked (20%) hypertension compared with children with normal casual and ambulatory BP (8%). In multivariable analysis, masked (odds ratio 4.1) and confirmed (odds ratio 4.3) hypertension were the strongest independent predictors of LVH. In conclusion, casual BP measurements alone are insufficient to predict the presence of LVH in children with CKD. The high prevalence of masked hypertension and its association with LVH supports early echocardiography and ambulatory BP monitoring to evaluate cardiovascular risk in children with CKD.

Class II HLA Epitope Matching—A Strategy to Minimize De Novo Donor‐Specific Antibody Development and Improve Outcomes

De novo donor‐specific antibody (dnDSA) develops in 15–25% of renal transplant recipients within 5 years of transplantation and is associated with 40% lower graft survival at 10 years. HLA epitope matching is a novel strategy that may minimize dnDSA development. HLAMatchmaker software was used to characterize epitope mismatches at 395 potential HLA‐DR/DQ/DP conformational epitopes for 286 donor–recipient pairs. Epitope specificities were assigned using single antigen HLA bead analysis and correlated with known monoclonal alloantibody epitope targets. Locus‐specific epitope mismatches were more numerous in patients who developed HLA‐DR dnDSA alone (21.4 vs. 13.2, p < 0.02) or HLA‐DQ dnDSA alone (27.5 vs. 17.3, p < 0.001). An optimal threshold for epitope mismatches (10 for HLA‐DR, 17 for HLA‐DQ) was defined that was associated with minimal development of Class II dnDSA. Applying these thresholds, zero and 2.7% of patients developed dnDSA against HLA‐DR and HLA‐DQ, respectively, after a median of 6.9 years. Epitope specificity analysis revealed that 3 HLA‐DR and 3 HLA‐DQ epitopes were independent multivariate predictors of Class II dnDSA. HLA‐DR and DQ epitope matching outperforms traditional low‐resolution antigen‐based matching and has the potential to minimize the risk of de novo Class II DSA development, thereby improving long‐term graft outcome.

Gene Transfer-Induced Local Heme Oxygenase-1 Overexpression Protects Rat Kidney Transplants From Ischemia/Reperfusion Injury

Heme oxygenase-1 (HO-1) overexpression using gene transfer protects rat livers against ischemia/reperfusion (I/R) injury. This study evaluates the effects of Ad-HO-1 gene transfer in a rat renal isograft model. Donor LEW kidneys were perfused with Ad-HO-1, Ad-beta-gal, or PBS, stored at 4 degrees C for 24 h, and transplanted orthotopically into LEW recipients, followed by contralateral native nephrectomy. Serum creatinine, urine protein/creatinine ratios, severity of histologic changes, HO-1 mRNA/protein expression, and HO enzymatic activity were analyzed. Ad-HO-1 gene transfer conferred a survival advantage when compared with PBS- and Ad-beta-gal-treated controls, with median survival of 100, 7, and 7 d, respectively (P < 0.01). Serum creatinine levels were elevated at day 7 in all groups (range, 2.2 to 5.8 mg/dl) but recovered to 1.0 mg/dl by day 14 (P < 0.01) in Ad-HO-1 group, which was sustained thereafter. Urine protein/creatinine ratio at day 7 was elevated in both PBS and Ad-beta-gal, as compared with the Ad-HO-1 group (12.0 and 9.8 versus 5.0; P < 0.005); histologically, ATN and glomerulosclerosis was more severe in Ad-beta-gal group at all time points. Reverse transcriptase-PCR-based HO-1 gene expression was significantly increased before reperfusion (P < 0.001) and remained increased in the Ad-HO-1-treated group for 3 d after transplantation. Concomitantly, HO enzymatic activity was increased at transplantation and at 3 d posttransplant in the Ad-HO-1 group, compared with Ad-beta-gal controls (P < 0.05); tubular HO-1 expression was discernible early posttransplant in the Ad-HO-1 group alone. These findings are consistent with protective effects of HO-1 overexpression using a gene transfer approach against severe renal I/R injury, with reduced mortality and attenuation of tissue injury.

Effect of sirolimus on malignancy and survival after kidney transplantation: systematic review and meta-analysis of individual patient data.

Objective To examine risk of malignancy and death in patients with kidney transplant who receive the immunosuppressive drug sirolimus. Design Systematic review and meta-analysis of individual patient data. Data sources Medline, Embase, and the Cochrane Central Register of Controlled Trials from inception to March 2013. Eligibility Randomized controlled trials comparing immunosuppressive regimens with and without sirolimus in recipients of kidney or combined pancreatic and renal transplant for which the author was willing to provide individual patient level data. Two reviewers independently screened titles/abstracts and full text reports of potentially eligible trials to identify studies for inclusion. All eligible trials reported data on malignancy or survival. Results The search yielded 2365 unique citations. Patient level data were available from 5876 patients from 21 randomized trials. Sirolimus was associated with a 40% reduction in the risk of malignancy (adjusted hazard ratio 0.60, 95% confidence interval 0.39 to 0.93) and a 56% reduction in the risk of non-melanoma skin cancer (0.44, 0.30 to 0.63) compared with controls. The most pronounced effect was seen in patients who converted to sirolimus from an established immunosuppressive regimen, resulting in a reduction in risk of malignancy (0.34, 0.28 to 0.41), non-melanoma skin cancer (0.32, 0.24 to 0.42), and other cancers (0.52, 0.38 to 0.69). Sirolimus was associated with an increased risk of death (1.43, 1.21 to 1.71) compared with controls. Conclusions Sirolimus was associated with a reduction in the risk of malignancy and non-melanoma skin cancer in transplant recipients. The benefit was most pronounced in patients who converted from an established immunosuppressive regimen to sirolimus. Given the risk of mortality, however, the use of this drug does not seem warranted for most patients with kidney transplant. Further research is needed to determine if different populations, such as those at high risk of cancer, might benefit from sirolimus.

Rates and Determinants of Progression to Graft Failure in Kidney Allograft Recipients With De Novo Donor-Specific Antibody

Understanding rates and determinants of clinical pathologic progression for recipients with de novo donor‐specific antibody (dnDSA), especially subclinical dnDSA, may identify surrogate endpoints and inform clinical trial design. A consecutive cohort of 508 renal transplant recipients (n = 64 with dnDSA) was studied. Recipients (n = 388) without dnDSA or dysfunction had an eGFR decline of −0.65 mL/min/1.73 m2/year. In recipients with dnDSA, the rate eGFR decline was significantly increased prior to dnDSA onset (−2.89 vs. −0.65 mL/min/1.73 m2/year, p < 0.0001) and accelerated post‐dnDSA (−3.63 vs. −2.89 mL/min/1.73 m2/year, p < 0.0001), suggesting that dnDSA is both a marker and contributor to ongoing alloimmunity. Time to 50% post‐dnDSA graft loss was longer in recipients with subclinical versus a clinical dnDSA phenotype (8.3 vs. 3.3 years, p < 0.0001). Analysis of 1091 allograft biopsies found that dnDSA and time independently predicted chronic glomerulopathy (cg), but not interstitial fibrosis and tubular atrophy (IFTA). Early T cell–mediated rejection, nonadherence, and time were multivariate predictors of IFTA. Independent risk factors for post‐dnDSA graft survival available prior to, or at the time of, dnDSA detection were delayed graft function, nonadherence, dnDSA mean fluorescence intensity sum score, tubulitis, and cg. Ultimately, dnDSA is part of a continuum of mixed alloimmune‐mediated injury, which requires solutions targeting T and B cells.

Pediatric kidney transplant practice patterns and outcome benchmarks, 1987–2010: A report of the North American Pediatric Renal Trials and Collaborative Studies

The NAPRTCS transplant registry has collected clinical information on children undergoing kidney transplantation since 1987 and now includes information on 11 603 kidney transplants in 10 632 patients. Since the first data analysis in 1989, NAPRTCS reports have documented marked improvements in outcome after kidney transplantation in addition to identifying factors associated with both favorable and poor outcomes. Patient demographics have changed over the course of the registry with a decrease in the percentage of white recipients from a high of 72% in 1987 to less than 43% in 2007. The percentage of living donors decreased to its lowest point in 2007 at 37%. Acute rejection rates continue to decline with improvements in short‐ and long‐term graft survival. Recently, NAPRTCS data have been used as a source of benchmark data for pediatric kidney transplant centers.

The use of immunoglobulin therapy for patients undergoing solid organ transplantation: an evidence-based practice guideline.

This guideline for the use of immunoglobulin (IG) for sensitized patients undergoing solid organ transplantation (SOT) is an initiative of the Canadian Blood Services and the National Advisory Committee on Blood and Blood Products of Canada to (1) provide guidance for Canadian practitioners involved in the care of patients undergoing SOT and transfusion medicine specialists on the use of IG and (2) standardize care, limit adverse events, and optimize patient care. A systematic expert and bibliography literature search up to July 2008 was conducted, with 791 literature citations and 45 reports reviewed. To validate the recommendations, the guideline was sent to physicians involved in SOT in Canada and a patient representative. The recommendations identify (1) sensitized patients undergoing SOT that would have a better survival and decreased morbidity by receiving IG preoperatively, postoperatively, and for the treatment of organ rejection; (2) patients who may not have any benefit from receiving IG; and (3) potential adversities to IG.

Surveillance biopsies are superior to functional studies for the diagnosis of acute and chronic renal allograft pathology in children

Abstract:  In this report of our 3‐yr protocol biopsy program, we describe the evolution of acute rejection (AR) and chronic renal allograft nephropathy (CAN) in a cohort of 21 children treated with antibody induction, tacrolimus, mycophenolate mofetil, and prednisone. The aims of this study were to compare the pathogenicity of clinical acute rejection (CAR) and subclinical acute rejection (SAR), and to determine whether functional studies accurately represent acute and chronic renal allograft pathology in pediatric recipients with disproportionately large grafts. Using concurrent biopsies, we evaluated: (i) the utility of changes in the baseline sCr (ΔsCr) to predict both the onset of AR and the response to immunosuppressive therapy; and (ii) the relationship of the calculated creatinine clearance and the presence of pathologic proteinuria to the severity of CAN. We performed 112 biopsies: 11 donor, 73 protocol, 16 acute graft dysfunction and 12 1‐month follow‐up AR therapy. CAR and SAR were similar in incidence, timing and histologic severity. Progression of CAN was associated with the first episode of CAR (p < 0.02) and the cumulative number of episodes of CAR (p < 0.01), SAR (p < 0.05), CAR plus SAR (p < 0.002) and borderline SAR (B‐SAR) (p < 0.006). One‐month post‐treatment ΔsCrs could not distinguish 1‐month follow‐up biopsies with histologically confirmed worsened or unchanged AR from those with improved histology (35.2 ± 74.8% vs. 23.8 ± 24.9%, p = NS). These findings led to the addition of anti‐lymphocyte antibody therapy in five of 10 (50%) cases. Despite 100% 3‐yr actuarial graft survival and excellent function (GFR = 111 ± 36 mL/min/1.73 m2), 18 of 21 (86%) patients had grade I CAN or greater chronic histology at a mean ± sd follow‐up period of 18.2 ± 13.1 months. Thirteen of 21 (62%) patients progressed to grade I CAN at 5.2 ± 3.6 months and five (38%) of these patients progressed to grade II CAN at 17.8 ± 11.3 months. Schwartz GFR did not differ between patients with or without CAN (108 ± 38 mL/min/1.73 m2 vs. 127 ± 8 mL/min/1.73 m2, p = NS). In biopsies with CAN and no associated AR, neither the Banff chronic tubulointerstitial (Banff ci) score nor the Banff chronic grade correlated with the GFR. Proteinuria was not associated with CAN. Clinical AR and SAR are similar histologic lesions with a capacity for CAN progression. In pediatric renal transplant recipients, longitudinal protocol biopsies are superior to functional studies for the diagnosis and post‐therapeutic monitoring of AR and for the surveillance of CAN.

PHEX expression in parathyroid gland and parathyroid hormone dysregulation in X-linked hypophosphatemia

Abstract X-linked hypophosphatemia (XLH), a renal phosphate (Pi) wasting disorder with defective bone mineralization, is caused by mutations in the PHEX gene (a Pi-regulating gene with homology to endopeptidases on the X chromosome). Parathyroid hormone (PTH) status in XLH has been controversial, with the prevailing belief that hyperparathyroidism develops in response to Pi therapy. We report a 5-year-old girl with XLH (patient 1) who had significant hyperparathyroidism at presentation, prior to initiation of therapy. We examined her response to a single oral Pi dose, in combination with calcitriol, and demonstrated a rise in serum concentration of intact PTH, which peaked at 4 h and paralleled the rise in serum Pi concentration. We also present two other patients whose parathyroid glands were analyzed for PHEX mRNA expression following parathyroidectomy. Patient 2 had autonomous hyperparathyroidism associated with chronic renal insufficiency, and patient 3, with XLH, developed autonomous hyperparathyroidism after 8 years of therapy with Pi and calcitriol. Following parathyroidectomy, patient 3 exhibited an increase in both serum Pi concentration and renal Pi reabsorption. The abundance of PHEX mRNA, relative to β-actin mRNA, in parathyroid glands from patients 2 and 3 was several-fold greater than that in human fetal calvaria, as estimated by ribonuclease protection assay. In summary, we have shown that hyperparathyroidism can be a primary manifestation of XLH and that PHEX is abundantly expressed in the parathyroid gland. Given that PHEX has homology to endopeptidases, we propose that PHEX may have a role in the normal regulation of PTH.