Analysis of Linear Antibody Epitopes on Factor H and CFHR1 Using Sera of Patients with Autoimmune Atypical Hemolytic Uremic Syndrome

Introduction: In autoimmune atypical hemolytic uremic syndrome (aHUS), the complement regulator factor H (FH) is blocked by FH autoantibodies, while 90% of the patients carry a homozygous deletion of its homolog complement FH-related protein 1 (CFHR1). The functional consequence of FH-blockade is widely established; however, the molecular basis of autoantibody binding and the role of CFHR1 deficiency in disease pathogenesis are still unknown. We performed epitope mapping of FH to provide structural insight in the autoantibody recruitment on FH and potentially CFHR1. Methods: Eight anti-FH positive aHUS patients were enrolled in this study. With overlapping synthetic FH and CFHR1 peptides, we located the amino acids (aa) involved in binding of acute and convalescence stage autoantibodies. We confirmed the location of the mapped epitopes using recombinant FH domains 19-20 that carried single-aa substitutions at the suspected antibody binding sites in three of our patients. Location of the linear epitopes and the introduced point mutations was visualized using crystal structures of the corresponding domains of FH and CFHR1. Results: We identified three linear epitopes on FH (aa1157-1171; aa1177-1191; and aa1207-1226) and one on CFHR1 (aa276-290) that are recognized both in the acute and convalescence stages of aHUS. We observed a similar extent of autoantibody binding to the aHUS-specific epitope aa1177-1191 on FH and aa276-290 on CFHR1, despite seven of our patients being deficient for CFHR1. Epitope mapping with the domain constructs validated the location of the linear epitopes on FH with a distinct autoantibody binding motif within aa1183-1198 in line with published observations. Summary: According to the results, the linear epitopes we identified are located close to each other on the crystal structure of FH domains 19-20. This tertiary configuration contains the amino acids reported to be involved in C3b and sialic acid binding on the regulator, which may explain the functional deficiency of FH in the presence of auto antibodies. The data we provide identify the exact structures involved in autoantibody recruitment on FH and confirm the presence of an autoantibody binding epitope on CFHR1.Peer reviewe

Adult Height in Patients with Advanced CKD Requiring Renal Replacement Therapy during Childhood.

BACKGROUND AND OBJECTIVES: Growth and final height are of major concern in children with ESRD. This study sought to describe the distribution of adult height of patients who started renal replacement therapy (RRT) during childhood and to identify determinants of final height in a large cohort of RRT children. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A total of 1612 patients from 20 European countries who started RRT before 19 years of age and reached final height between 1990 and 2011 were included. Linear regression analyses were performed to calculate adjusted mean final height SD score (SDS) and to investigate its potential determinants. RESULTS: The median final height SDS was -1.65 (median of 168 cm in boys and 155 cm in girls). Fifty-five percent of patients attained an adult height within the normal range. Adjusted for age at start of RRT and primary renal diseases, final height increased significantly over time from -2.06 SDS in children who reached adulthood in 1990-1995 to -1.33 SDS among those reaching adulthood in 2006-2011. Older age at start of RRT, more recent period of start of RRT, cumulative percentage time on a functioning graft, and greater height SDS at initiation of RRT were independently associated with a higher final height SDS. Patients with congenital anomalies of the kidney and urinary tract and metabolic disorders had a lower final height than those with other primary renal diseases. CONCLUSIONS: Although final height remains suboptimal in children with ESRD, it has consistently improved over time

Aldosterone Antagonists in Monotherapy Are Protective against Streptozotocin-Induced Diabetic Nephropathy in Rats

Angiotensin converting enzyme inhibitors (ACEi) and angiotensin II receptor blockers (ARB) are the standard clinical therapy of diabetic nephropathy (DN), while aldosterone antagonists are only used as adjuncts. Previously in experimental DN we showed that Na/K ATPase (NKA) is mislocated and angiotensin II leads to superimposed renal progression. Here we investigated the monotherapeutic effect of aldosterone blockers on the progression of DN and renal NKA alteration in comparison to ACEi and ARBs. Streptozotocin-diabetic rats developing DN were treated with aldosterone antagonists; ACEi and ARB. Renal function, morphology, protein level and tubular localization of NKA were analyzed. To evaluate the effect of high glucose per se; HK-2 proximal tubular cells were cultured in normal or high concentration of glucose and treated with the same agents. Aldosterone antagonists were the most effective in ameliorating functional and structural kidney damage and they normalized diabetes induced bradycardia and weight loss. Aldosterone blockers also prevented hyperglycemia and diabetes induced increase in NKA protein level and enzyme mislocation. A monotherapy with aldosterone antagonists might be as, or more effective than ACEi or ARBs in the prevention of STZ-induced DN. Furthermore the alteration of the NKA could represent a novel pathophysiological feature of DN and might serve as an additional target of aldosterone blockers

Renal Ultrafiltration Changes Induced by Focused US1

US bursts combined with microbubbles can temporarily enhance glomerular ultrafiltration and temporarily enable the passage of large-molecule agents that normally are not filtered by the kidneys

Prevalence and predictors of the sub-target Hb level in children on dialysis

Background Anaemia is a common and potentially treatable co-morbidity of end-stage renal disease. We aimed to determine the prevalence of the sub-target haemoglobin (Hb) level among European children on dialysis and to identify factors associated with a low Hb level. Methods From the European Society for Paediatric Nephrology (ESPN)/European Renal Association-European Dialysis Transplant Association (ERA-EDTA) registry, data were available on 2351 children between 1 month and 18 years of age, totalling 5546 measurements from 19 countries. Results The mean Hb level was 10.8 g/dL (5th–95th percentiles, 7.4–13.9). Among those above 2 years of age, the mean Hb level was 10.9 g/dL (11.4% below 8.5 g/dL), while it was 10.3 g/dL among those below 2 years (11.2% below 8.0 g/dL). A total of 91.2% of the patients were on an erythropoiesis-stimulating agent (ESA). Hb levels increased with age and were higher in peritoneal dialysis compared with haemodialysis patients. Patients with congenital anomalies of the kidney and urinary tract showed the highest Hb levels, and those with cystic kidney diseases or metabolic disorders the lowest ones. Ferritin levels between 25 and 50 ng/mL were associated with the highest Hb levels. We found a weak inverse association between parathyroid hormone (PTH) and Hb. Whereas standardized blood pressure (BP) was not elevated in patients with above-target Hb, elevated systolic BP z-score was noted in those with sub-target Hb levels. Conclusions Sub-target Hb levels remain common in children on dialysis, in spite of virtually all children being treated with ESA; although we cannot exclude under-dosing. Optimal ferritin levels seemed to be slightly lower in children (25–50 ng/mL) than those in adults. Other risk factors for sub-target Hb are dialysis modality and a high PTH level

Neurocognitive functions of pediatric kidney transplant recipients

BACKGROUND: End-stage renal disease (ESRD) in children is associated with impaired neurocognitive function and development. However, data on factors associated with neurocognitive dysfunctions in children with kidney transplants are limited. METHODS: We conducted a cross-sectional analysis comparing cognitive functions (using the Woodcock-Johnson International Edition, WJIE) in 35 kidney transplant and 35 healthy control children. Data on laboratory measurements, comorbidities, and social characteristics were collected. RESULTS: Transplant children had significantly worse scores on the intelligence quotient (IQ) test compared with controls [Full Scale IQ score 85 (26) vs 107 (10), p 9 months) were associated with lower test scores. Age-standardized duration of hospitalization was inversely correlated with IQ (r = -0.46, p <0.01) and was an independent significant predictor (Beta = -0.38, p = 0.02) of IQ scores in transplanted children. CONCLUSIONS: Child kidney transplant recipients have neurocognitive function impairments that are associated with markers of socioeconomic status (SES) and factors related to disease severity