Giuseppina Spartà

Integrin α3 mutations with kidney, lung, and skin disease.

Integrin α(3) is a transmembrane integrin receptor subunit that mediates signals between the cells and their microenvironment. We identified three patients with homozygous mutations in the integrin α(3) gene that were associated with disrupted basement-membrane structures and compromised barrier functions in kidney, lung, and skin. The patients had a multiorgan disorder that included congenital nephrotic syndrome, interstitial lung disease, and epidermolysis bullosa. The renal and respiratory features predominated, and the lung involvement accounted for the lethal course of the disease. Although skin fragility was mild, it provided clues to the diagnosis.

Neuropsychologic side‐effects of tacrolimus in pediatric renal transplantation

Calcineurin inhibition with tacrolimus has been used after renal transplantation (RTPL) as rescue therapy for insufficient immunological control or if cyclosporin A (CSA) toxicity occurred. Neurologic side‐effects occur but are rare in children, usually presenting as tremor; however, serious complications, e.g. the posterior leukoencephalopathy syndrome are also documented. Twenty children (10 girls) were switched to tacrolimus: 11 (55%) for immunological reasons (n = 9: steroid‐resistant rejection; n = 2: recurrent rejections) and nine for CSA side‐effects. Tacrolimus was started at a median of 8 wk (range 10 d to 8.7 yr) after RTPL and was continued for a median of 2.5 yr (range 5 wk to 4.6 yr). Renal function significantly improved over a period of 12 months following conversion to tacrolimus (glomerular filtration rate 56 ± 19 vs. 66 ± 16 mL/min/1.73 m2; p < 0.03; n = 13). Fifteen of 20 (75%) patients tolerated tacrolimus well.

Clinical and Molecular Characterization of Patients with Heterozygous Mutations in Wilms Tumor Suppressor Gene 1

BACKGROUND AND OBJECTIVES The Wilms tumor suppressor gene 1 (WT1) plays an essential role in urogenital and kidney development. Genotype/phenotype correlations of WT1 mutations with renal function and proteinuria have been observed in world-wide cohorts with nephrotic syndrome or Wilms tumor (WT). This study analyzed mid-European patients with known constitutional heterozygous mutations in WT1, including patients without proteinuria or WT. DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS Retrospective analysis of genotype, phenotype, and treatment of 53 patients with WT1 mutation from all pediatric nephrology centers in Germany, Austria, and Switzerland performed from 2010 to 2012. RESULTS Median age was 12.4 (interquartile range [IQR], 6-19) years. Forty-four of 53 (83%) patients had an exon mutation (36 missense, eight truncating), and nine of 53 (17%) had an intronic lysine-threonine-serine (KTS) splice site mutation. Fifty of 53 patients (94%) had proteinuria, which occurred at an earlier age in patients with missense mutations (0.6 [IQR, 0.1-1.5] years) than in those with truncating (9.7 [IQR, 5.7-11.9]; P<0.001) and splice site (4.0 [IQR, 2.6-6.6]; P=0.004) mutations. Thirteen of 50 (26%) were treated with steroids and remained irresponsive, while three of five partially responded to cyclosporine A. Seventy-three percent of all patients required RRT, those with missense mutations significantly earlier (at 1.1 [IQR, 0.01-9.3] years) than those with truncating mutations (16.5 [IQR, 16.5-16.8]; P<0.001) and splice site mutations (12.3 [IQR, 7.9-18.2]; P=0.002). Diffuse mesangial sclerosis was restricted to patients with missense mutations, while focal segmental sclerosis occurred in all groups. WT occurred only in patients with exon mutations (n=19). Fifty of 53 (94%) patients were karyotyped: Thirty-one (62%) had XY and 19 (38%) had XX chromosomes, and 96% of male karyotypes had urogenital malformations. CONCLUSIONS Type and location of WT1 mutations have predictive value for the development of proteinuria, renal insufficiency, and WT. XY karyotype was more frequent and associated with urogenital malformations in most cases.

Binding of vitronectin and Factor H to Hic contributes to immune evasion of Streptococcus pneumoniae serotype 3.

Streptococcus pneumoniae serotype 3 strains are highly resistant to opsonophagocytosis due to recruitment of the complement inhibitor Factor H via Hic, a member of the pneumococcal surface protein C (PspC) family. In this study, we demonstrated that Hic also interacts with vitronectin, a fluid-phase regulator involved in haemostasis, angiogenesis, and the terminal complement cascade as well as a component of the extracellular matrix. Blocking of Hic by specific antiserum or genetic deletion significantly reduced pneumococcal binding to soluble and immobilised vitronectin and to Factor H, respectively. In parallel, ectopic expression of Hic on the surface of Lactococcus lactis conferred binding to soluble and immobilised vitronectin as well as Factor H. Molecular analyses with truncated Hic fragments narrowed down the vitronectin-binding site to the central core of Hic (aa 151-201). This vitronectin-binding region is separate from that of Factor H, which binds to the N-terminus of Hic (aa 38-92). Binding of pneumococcal Hic was localised to the C-terminal heparin-binding domain (HBD3) of vitronectin. However, an N-terminal region to HBD3 was further involved in Hic-binding to immobilised vitronectin. Finally, vitronectin bound to Hic was functionally active and inhibited formation of the terminal complement complex. In conclusion, Hic interacts with vitronectin and simultaneously with Factor H, and both human proteins may contribute to colonisation and invasive disease caused by serotype 3 pneumococci.

Interaction between Multimeric von Willebrand Factor and Complement: A Fresh Look to the Pathophysiology of Microvascular Thrombosis

von Willebrand factor (VWF), a multimeric protein with a central role in hemostasis, has been shown to interact with complement components. However, results are contrasting and inconclusive. By studying 20 patients with congenital thrombotic thrombocytopenic purpura (cTTP) who cannot cleave VWF multimers because of genetic ADAMTS13 deficiency, we investigated the mechanism through which VWF modulates complement and its pathophysiological implications for human diseases. Using assays of ex vivo serum-induced C3 and C5b-9 deposits on endothelial cells, we documented that in cTTP, complement is activated via the alternative pathway (AP) on the cell surface. This abnormality was corrected by restoring ADAMTS13 activity in cTTP serum, which prevented VWF multimer accumulation on endothelial cells, or by an anti-VWF Ab. In mechanistic studies we found that VWF interacts with C3b through its three type A domains and initiates AP activation, although assembly of active C5 convertase and formation of the terminal complement products C5a and C5b-9 occur only on the VWF-A2 domain. Finally, we documented that in the condition of ADAMTS13 deficiency, VWF-mediated formation of terminal complement products, particularly C5a, alters the endothelial antithrombogenic properties and induces microvascular thrombosis in a perfusion system. Altogether, the results demonstrated that VWF provides a platform for the activation of the AP of complement, which profoundly alters the phenotype of microvascular endothelial cells. These findings link hemostasis-thrombosis with the AP of complement and open new therapeutic perspectives in cTTP and in general in thrombotic and inflammatory disorders associated with endothelium perturbation, VWF release, and complement activation.

Erratum to: Health-related quality of life and mental health in parents of children with hemolytic uremic syndrome.

Background Little is known about health-related quality of life (HRQoL) and mental health of parents having children with a history of hemolytic uremic syndrome (HUS).

Membranoproliferative glomerulonephritis and C3 glomerulopathy in children: change in treatment modality? A report of a case series

Abstract Background Membranoproliferative glomerulonephritis (MPGN) with immune complexes and C3 glomerulopathy (C3G) in children are rare and have a variable outcome, with some patients progressing to end-stage renal disease (ESRD). Mutations in genes encoding regulatory proteins of the alternative complement pathway and of complement C3 (C3) have been identified as concausative factors. Methods Three children with MPGN type I, four with C3G, i.e. three with C3 glomerulonephritis (C3GN) and one with dense deposit disease (DDD), were followed. Clinical, autoimmune data, histological characteristics, estimated glomerular filtration rate (eGFR), proteinuria, serum C3, genetic and biochemical analysis were assessed. Results The median age at onset was 7.3 years and the median eGFR was 72 mL/min/1.73 m2. Six children had marked proteinuria. All were treated with renin–angiotensin–aldosterone system (RAAS) blockers. Three were given one or more immunosuppressive drugs and two eculizumab. At the last median follow-up of 9 years after diagnosis, three children had normal eGFR and no or mild proteinuria on RAAS blockers only. Among four patients without remission of proteinuria, genetic analysis revealed mutations in complement regulator proteins of the alternative pathway. None of the three patients with immunosuppressive treatment achieved partial or complete remission of proteinuria and two progressed to ESRD and renal transplantation. Two patients treated with eculizumab revealed relevant decreases in proteinuria. Conclusions In children with MPGN type I and C3G, the outcomes of renal function and response to treatment modality show great variability independent from histological diagnosis at disease onset. In case of severe clinical presentation at disease onset, early genetic and biochemical analysis of the alternative pathway dysregulation is recommended. Treatment with eculizumab appears to be an option to slow disease progression in single cases.