Complement C5-inhibiting therapy for the thrombotic microangiopathies: accumulating evidence, but not a panacea.
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SUBMITTER: Brocklebank V
PROVIDER: S-EPMC5622895 | biostudies-literature | 2017 Oct
REPOSITORIES: biostudies-literature
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Complement C5-inhibiting therapy for the thrombotic microangiopathies: accumulating evidence, but not a panacea.
Brocklebank Vicky V Kavanagh David D
Clinical kidney journal 20170508 5
Thrombotic microangiopathy (TMA), characterized by organ injury occurring consequent to severe endothelial damage, can manifest in a diverse range of diseases. In complement-mediated atypical haemolytic uraemic syndrome (aHUS) a primary defect in complement, such as a mutation or autoantibody leading to over activation of the alternative pathway, predisposes to the development of disease, usually following exposure to an environmental trigger. The elucidation of the pathogenesis of aHUS resulted ...[more]
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Project description:Background and objectives: Atypical hemolytic uremic syndrome is a form of thrombotic microangiopathy caused by dysregulation of the alternative complement pathway. There is evidence showing complement activation in other thrombotic microangiopathies. The aim of this study was to evaluate complement activation in different thrombotic microangiopathies and to monitor treatment response.Design, setting, participants, & measurements: Complement activation was assessed by exposing endothelial cells to sera or activated-patient plasma-citrated plasma mixed with a control sera pool (1:1)-to analyze C5b-9 deposits by immunofluorescence. Patients with atypical hemolytic uremic syndrome (n=34) at different stages of the disease, HELLP syndrome (a pregnancy complication characterized by hemolysis, elevated liver enzymes, and low platelet count) or severe preeclampsia (n=10), and malignant hypertension (n=5) were included.Results: Acute phase atypical hemolytic uremic syndrome-activated plasma induced an increased C5b-9 deposition on endothelial cells. Standard and lower doses of eculizumab inhibited C5b-9 deposition in all patients with atypical hemolytic uremic syndrome, except in two who showed partial remission and clinical relapse. Significant fibrin formation was observed together with C5b-9 deposition. Results obtained using activated-plasma samples were more marked and reproducible than those obtained with sera. C5b-9 deposition was also increased with samples from patients with HELLP (all cases) and preeclampsia (90%) at disease onset. This increase was sustained in those with HELLP after 40 days, and levels normalized in patients with both HELLP and preeclampsia after 6-9 months. Complement activation in those with malignant hypertension was at control levels.Conclusions: The proposed methodology identifies complement overactivation in patients with atypical hemolytic uremic syndrome at acute phase and in other diseases such as HELLP syndrome and preeclampsia. Moreover, it is sensitive enough to individually assess the efficiency of the C5 inhibition treatment.
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Project description:UNLABELLED:ESSENTIALS: Molecular diagnostics has improved the differentiation of acute thrombotic microangiopathys (TMAs). Atypical hemolytic uremic syndrome may have features mimicking thrombotic thrombocytopenic purpura. We identified novel complement mutations and a high incidence of CD46, with favorable long term outcomes. Complement mutation analysis in TMA where the diagnosis is unclear and ADAMTS-13 activity is >10%. BACKGROUND:Differentiation of acute thrombotic microangiopathy (TMA) at presentation has historically been dependent on clinical parameters. Confirmation of thrombotic thrombocytopenic purpura (TTP) is increasingly reliant on demonstrating deficient ADAMTS-13 activity. The identification of alternative complement pathway abnormalities in atypical hemolytic uremic syndrome (aHUS), along with the proven efficacy of terminal complement inhibitors in treatment, has increased the need for rapid differentiation of TTP from aHUS. OBJECTIVES:We describe the clinical phenotype and nature of complement mutations in a cohort of aHUS patients referred as acute TMAs. PATIENTS/METHODS:Fourteen consecutive aHUS patients were screened for mutations in C3, CD46, CFH, CFI, and CFB, as well as factor H (FH) antibodies. All aHUS patients had ADAMTS-13 activity > 10%. RESULTS:Of 14 aHUS patients, 11 (79%) had platelet counts < 30 × 10(9) /L during the acute phase. Median presenting creatinine level was 295 ?mol L(-1) , while five (36%) of 14 presented with a serum creatinine level < 200 ?mol L(-1) . Alternative complement pathway mutations were detected in 9 (64%) of 14 patients, including CD46 mutations in five (36%) of 14 patients. Patients were identified with novel mutations in CFB and C3 that have not been previously reported. CONCLUSIONS:We demonstrate that diagnostic differentiation based on platelet count and renal function is insufficient to predict an underlying complement mutation in some aHUS cases. Specifically, we demonstrate a high frequency of functionally significant CD46 mutations which may mimic TTP. ADAMTS-13 activity > 10% in a patient with a TMA should necessitate genetic screening for complement abnormalities.
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Project description:Pentraxin-3 (PTX3) and C-reactive protein (CRP) have been shown to regulate complement activation in vitro, but their role has not been investigated in complement consumption in vivo. Thrombotic microangiopathies (TMA) are often accompanied by complement overactivation and consumption, therefore we analyzed the relation of the systemic pentraxin levels to the complement profile, laboratory parameters and clinical outcome of TMA patients. We determined the PTX3 and CRP levels, complement factor and activation product concentrations in blood samples of 171 subjects with the diagnosis of typical hemolytic uremic syndrome (STEC-HUS) (N = 34), atypical HUS (aHUS) (N = 44), secondary TMA (N = 63), thrombotic thrombocytopenic purpura (TTP) (N = 30) and 69 age-matched healthy individuals. Clinical data, blood count and chemistry were collected from medical records. To determine the in vitro effect of PTX3 on alternative pathway (AP) activation, sheep red blood cell-based hemolytic assay and AP activity ELISA were used. We found that PTX3 levels were elevated in the acute phase of STEC-HUS, aHUS and secondary TMA, whereas PTX3 elevation was exceptional is TTP. Conversely, a significantly higher median CRP was present in all patient groups compared to controls. PTX3, but not CRP was associated with signs of complement consumption in vivo, and PTX3 significantly decreased the AP hemolytic activity in vitro. Our results provide a detailed description of acute phase-TMA patients' complement profile linked to changes in the systemic pentraxin levels that may support further molecular studies on the function of PTX3 in disease pathogenesis and add to the laboratory assessment of complement consumption in TMA.
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Project description:BackgroundThe 2 main forms of thrombotic microangiopathy (TMA) are thrombotic thrombocytopenic purpura (TTP) and atypical hemolytic uremic syndrome (aHUS). Deficiency of ADAMTS13 and dysregulation of the complement pathway result in TTP and aHUS, respectively; however, overlap of their clinical characteristics makes differential diagnosis challenging.Objectives and methodsWe aimed to develop a TMA diagnosis workflow based on ADAMTS13 activity and screening of ADAMTS13 and complement genes using a custom next-generation sequencing (NGS) gene panel.PatientsFor this, from a cohort of 154 Portuguese patients with acute TMA, the genotype-phenotype correlations were analyzed in 7 hereditary TTP (ADAMTS13 activity <10%, no inhibitor), 36 acquired TTP (ADAMTS13 activity <10%, presence of an inhibitor), and in 34 presumable aHUS.ResultsIn total, 37 different rare variants, 8 of which novel (in ADAMTS13,CFH, and CD46), were identified across 7 genes. Thirteen TTP patients were homozygous (n=6), compound heterozygous (n=2), and heterozygous (n=5) for 11 ADAMTS13 variants (6 pathogenic mutations). Among the 34 aHUS patients, 17 were heterozygous for 23 variants in the different complement genes with distinct consequences, ranging from single pathogenic mutations associated with complete disease penetrance to benign variants that cause aHUS only when combined with other variants and/or CFH and CD46 risk haplotypes or CFHR1-3 deletion.ConclusionsOur study provides evidence of the usefulness of the NGS panel as an excellent technology that enables more rapid diagnosis of TMA, and is a valuable asset in clinical practice to discriminate between TTP and aHUS.
| S-EPMC6058207 | biostudies-literature