Kata Kelen

The role of complement in Streptococcus pneumoniae-associated haemolytic uraemic syndrome

BACKGROUND Atypical forms of haemolytic uraemic syndrome (aHUS) include HUS caused by defects in the regulation of alternative complement pathway and HUS linked to neuraminidase-producing pathogens, such as Streptococcus pneumoniae. Increasing data support a pathogenic role of neuraminidase in the development of S. pneumoniae-associated haemolytic uraemic syndrome (SP-HUS), but the role of complement has never been clarified in detail. Therefore, we aimed to investigate whether the pathologic complement profile and genetic risk factors of aHUS are present in patients with SP-HUS. METHODS Enrolling five patients with SP-HUS classical and alternative pathway activity, besides C3, C4, factors H, B, I and anti-factor H autoantibody levels were determined. The coding regions of CFH, CFI, CD46 (MCP), THBD, C3 and CFB genes were sequenced and the copy number of CFI, CD46, CFH and related genes were also analyzed. RESULTS We found that in the acute phase samples of SP-HUS patients, complement components C4, C3 and activity of the classical and alternative pathways were decreased, indicating severe activation and complement consumption, but most of these alterations normalized later in remission. Three of the patients carried mutations and risk haplotypes in complement-mediated aHUS associated genes. The identified mutations include a previously published CFI variant (P50A) and two novel ones in CFH (R1149X) and THBD (T44I) genes. CONCLUSIONS Our results suggest that severe complement dysregulation and consumption accompany the progress of invasive pneumococcal disease (IPD)-associated SP-HUS and genetic variations of complement genes may contribute to the development of this complication in a proportion of the affected patients.

Genetic analysis and functional characterization of novel mutations in a series of patients with atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome (aHUS) is a rare disorder caused by dysregulation of the complement alternative pathway, and associated with mutations in genes of complement components and regulators. In the recent years several studies have been published describing these mutations, however, no data is available from the Central and Eastern European region. In this study we present a detailed genetic analysis of our 30 patients, hospitalized with the diagnosis of aHUS in the past 7 years. We analyzed the genetic variants of genes CFH, CFI, CD46, THBD, CFB and C3; furthermore the possible effect of mutations that may alter the function or level of factor H protein was also investigated. We identified 27 (12 novel and 15 previously described) potentially disease-causing mutations in the candidate genes in 23 patients. Genetic analysis of family members revealed that in most cases the disease develops in individuals with multiple genetic risk factors, which may explain the low penetrance of the mutations. Here we showed that two novel mutations (p.W198R, p.P1161T) and a previously reported one (p.R1215Q) in CFH caused impaired regulation as indicated by increased lysis in hemolytic test, while four CFH mutations (p.V609D, p.S722X, p.T1216del and p.C448Y) were associated with decreased factor H protein level in serum as determined by allele-specific immunoassay. These results further point to the necessity of complete genetic workup of patients with aHUS and to the importance of functional characterization of novel variations.

Decreased neutrophil extracellular trap degradation in shiga toxin-associated haemolytic uraemic syndrome

Background: Neutrophil extracellular traps (NETs) can stimulate thrombosis, and their degradation is decreased in several autoimmune disorders. It was recently reported that some patients with haemolytic uraemic syndrome (HUS) also fail to degrade NETs and that neutrophils from Shiga toxin-associated HUS are primed to form NETs. Method: We used a well-characterized cohort of 74 thrombotic microangiopathy (TMA) patients, with a subset also providing follow-up samples, and 112 age-matched controls to investigate NET degradation and serum nuclease activity in TMA before, during and after treatment. Results: We identified that in the cohort of TMA patients, 50% of patients with Shiga toxin-associated HUS displayed a decreased ability to degrade NETs. NET degradation correlated with serum nuclease activity, but not with autoantibodies against double-stranded DNA, which has been previously observed in some autoimmune disorders. Further, NET degradation negatively correlated with serum creatinine levels, suggesting that kidney function was negatively impacted by the low NET degradation ability. Conclusions: We revealed that decreased NET degradation is a common feature of Shiga toxin-associated HUS and that it is associated with decreased kidney function in these patients. It remains to be clarified whether improving NET degradation would be beneficial for the patient.

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 autoantibodies. 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.

Peritonealis dialízis gyermekkorban. A Semmelweis Egyetem I. Gyermekgyógyászati Klinikájának eredményei

Absztrakt: Bevezetes, celkitűzes, modszer: A Semmelweis Egyetem I. Gyermekgyogyaszati Klinikaja hazank legnagyobb, kronikus veseelegtelen gyermekeket ellato centruma, ahol kiemelt szerepet kap a peritonealis dializis alkalmazasa. 2010 es 2017 kozott a Nemzetkozi Gyermek Peritonealis Dializis Regiszter kereteben prospektiv adatgyűjtes kapcsan elemeztuk kezelesi gyakorlatunkat. Eredmenyek: A fenti időszak 39 betegenek atlageletkora a kezeles inditasakor 9,3 ± 6,6 ev, a dializiskezelesen toltott idő 1,3 ± 1,3 ev. Veseelegtelenseguk hattereben allo vezető okok a glomerulopathiak es a vese/hugyutak fejlődesi rendellenessegei voltak. Centrumunkban magas aranyban megfigyelhetők komorbiditasok, szindromak. 18 betegunknel diagnosztizaltunk peritonitist. Laborertekeinkben elterest az ajanlott tartomanyoktol parathormon- es foszfatertekekben tapasztaltunk. Gyogyszerelesi statisztikaink megfeleltek az ajanlasoknak, bar bizonyos szerek hazankban gyermek betegek szamara nem elerhetőek. Betegeink rovid dializisen toltot...