Search

Aim: To investigate the serum circulating DPP4 activity in patients with COVID-19 disease. Materials & methods: Serum samples from 102 hospitalized COVID-19 patients and 43 post-COVID-19 plasma donors and 39 SARS-CoV-2 naive controls and their medical data were used. Circulating DPP4 activities according to different COVID-19 disease peak severity (WHO) groups at sampling and at peak were assessed. Results: A significant decrease (p [area = 0.5] < 0.0001) as single predictor and 83.45% (p[area = 0.5] < 0.0001) in combination with age among hospitalized patients with COVID-19. Conclusion: Decreased circulating DPP4 activity is associated with severe COVID-19 disease and is a strong prognostic biomarker of mortality.

Autologous hematopoietic stem cell transplantation (HSCT) is often complicated by hemostatic and thrombotic events associated with endothelial cell injury. Thrombotic complications are affected by a disturbed balance between platelets, circulating von Willebrand factor (VWF), and its specific protease, ADAMTS13. HSCT-associated endothelial dysfunction, impaired hemostasis, and inflammation are interrelated processes, and research on the complex interplay of conditioning regimens from engraftment to bone marrow regeneration remains intensive. This prospective observational study comparing lymphoma and multiple myeloma (MM) patients who underwent autologous HSCT explored how platelet count, VWF level, ADAMTS13 activity, and C-reactive protein (CRP) level as potential markers (1) vary in response to therapy, (2) differ between the 2 groups, and (3) correlate with the remission state at 100 days after HSCT. We correlated the quantitative changes in platelet count and levels of VWF, ADAMTS13, and CRP with one another during HSCT and in the remission state in 45 patients with lymphoma and 59 patients with MM who underwent autologous HSCT between 2010 and 2013 at the University of Debrecen. Samples were collected at the start of conditioning chemotherapy, on the day of stem cell transplantation, and at 5, 11, and 100 days following HSCT. CRP levels peaked when platelet counts dropped to a minimum, and these changes were much more pronounced in the lymphoma group. VWF level was the highest, with lower ADAMTS13 activity, at platelet engraftment in both patient groups equally. Diagnostic evidence indicative of thrombotic complications was not found. In the lymphoma group, VWF level prior to conditioning had statistically significant correlations with platelet count, CRP level, and hemoglobin concentration at the time of bone marrow regeneration (P.001) and during the remission state (P = .034). In the MM group, platelet count before conditioning was correlated with platelet count (P.001) and white blood cell count (P = .012) at the time of bone marrow regeneration. The statistically significant correlation of the markers at the time of bone marrow regeneration with the preconditioning VWF levels in lymphoma and with the preconditioning platelet counts in MM might indicate the clinical significance of the bone marrow niches of arterioles and megakaryocytes, respectively, where the stem cells are located and regulated. Because preconditioning VWF levels are associated with remission after HSCT in lymphoma patients, VWF should be screened before conditioning, along with the markers used in HSCT protocols, to optimize personalized treatment and reduce therapeutic risks.

Hereditary thrombotic thrombocytopenic purpura (hTTP) is a rare thrombotic microangiopathy characterized by severe congenital ADAMTS13 deficiency and recurring acute episodes causing morbidity and premature death. Information on the annual incidence and severity of acute episodes in patients with hTTP is largely lacking. This study reports prospective data on 87 patients from the Hereditary TTP Registry (clinicaltrials.gov #NCT01257269) for survival, frequency, and severity of acute episodes from enrollment until December 2019. The 87 patients, followed up for a median of 4.2 years (range, 0.01-15 years), had a median age at overt disease onset and at clinical diagnosis of 4.6 years and 18 years (range, 0.0-70 years for both), respectively. Forty-three patients received regular plasma prophylaxis, whereas 22 did not, and treatment changed over time or was unknown in the remaining 22. Forty-three patients experienced 131 acute episodes, of which 91 (69%) occurred in patients receiving regular prophylaxis. This resulted in an annual incidence of acute episodes of 0.36 (95% confidence interval [CI], 0.29-0.44) with regular plasma treatment and of 0.41 (95% CI, 0.30-0.56) without regular plasma treatment. More than one-third of acute episodes (n = 51) were documented in children 40 years (1.18 [95% CI, 0.88-1.55] vs 0.14 [95% CI, 0.08-0.23]). The prophylactic plasma infusion regimens used were insufficient to prevent acute episodes in many patients. Such regimens are burdensome, and caregivers, patients, and their guardians are reluctant to start regular plasma infusions, from which children particularly would benefit.

International audience; Background Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is caused by anti-ADAMTS13 autoantibodies inducing a severe deficiency of ADAMTS13. Epitope mapping studies on samples obtained during acute iTTP episodes have shown that the iTTP immune response is polyclonal, with almost all patients having autoantibodies targeting the spacer domain of ADAMTS13.Objectives To identify the immunogenic hotspots in the spacer domain of ADAMTS13.Patients/methods A library of 11 full-length ADAMTS13 spacer hybrids was created in which amino acid regions of the spacer domain of ADAMTS13 were exchanged by the corresponding region of the spacer domain of ADAMTS1. Next, the full-length ADAMTS13 spacer hybrids were used in enzyme-linked immunosorbent assay to epitope map anti-spacer autoantibodies in 138 samples from acute and remission iTTP patients.Results Sixteen different anti-spacer autoantibody profiles were identified with a similar distribution in acute and remission patients. There was no association between the anti-spacer autoantibody profiles and disease severity. Almost all iTTP samples contained anti-spacer autoantibodies against the following three regions: amino acid residues 588-592, 602-610, and 657-666 (hybrids E, G, and M). Between 31% and 57% of the samples had anti-spacer autoantibodies against amino acid regions 572-579, 629-638, 667-676 (hybrids C, J, and N). In contrast, none of the samples had anti-spacer autoantibodies against amino acid regions 556-563, 564-571, 649-656, and 677-685 (hybrids A, B, L, and O).Conclusion We identified three hotspot regions (amino acid regions 588-592, 602-610, and 657-666) in the spacer domain of ADAMTS13 that are targeted by anti-spacer autoantibodies found in a large cohort of iTTP patients.

Background: Type 2 diabetes mellitus (T2DM) and obesity are risk factors of COVID-19 disease course. Retrospective observational analyses reported improvement in COVID-19 severe outcomes and mortality in T2DM patients using a DPP4 inhibitor. However, little is known about the prognostic value of circulating soluble DPP4 activity in patients with SARS-CoV-2 infection. Methods: We conducted an observational, retrospective cohort study with 184 Hungarian adults. Hospitalized patients with acute COVID-19 disease (n=102) and plasma donors (n=43) recovered from prior SARS-CoV-2 infection were enrolled from April to July, 2020 at two institutions in Budapest. “Non-COVID-19 controls” (n=39) were employed with serum sDPP4 activity determined from samples taken before September, 2019. Duplicate serum sDPP4 activity determinations by microplate base enzyme kinetic assay were successful in 182 individuals from different COVID-19 disease severity groups (acute COVID-19 patients were classified into 4 and plasma donors into 2 categories based on peak severity). Findings: A significant difference in sDPP4 activity was found among study groups (p

Anti-A Disintegrin and Metalloproteinase with a ThromboSpondin type 1 motif, member 13 (ADAMTS13) autoantibodies cause a severe ADAMTS13 deficiency in immune-mediated thrombotic thrombocytopenic purpura (iTTP). ADAMTS13 consists of a metalloprotease (M), a disintegrin-like (D) domain, 8 thrombospondin type 1 repeats (T1-T8), a cysteine-rich (C), a spacer (S), and 2 CUB domains (CUB1-2). We recently developed a high-throughput epitope mapping assay based on small, nonoverlapping ADAMTS13 fragments (M, DT, CS, T2-T5, T6-T8, CUB1-2). With this assay, we performed a comprehensive epitope mapping using 131 acute-phase samples and for the first time a large group of remission samples (n = 50). Next, samples were stratified according to their immunoprofiles, a field that is largely unexplored in iTTP. Three dominant immunoprofiles were found in acute-phase samples: profile 1: only anti-CS autoantibodies (26.7%); profile 2: both anti-CS and anti-CUB1-2 autoantibodies (12.2%); and profile 3: anti-DT, anti-CS, anti-T2-T5, anti-T6-T8, and anti-CUB1-2 autoantibodies (8.4%). Interestingly, profile 1 was the only dominant immunoprofile in remission samples (52.0%). Clinical data were available for a relatively small number of patients with acute iTTP (>68), and no correlation was found between immunoprofiles and disease severity. Nevertheless, profile 1 was linked with younger and anti-T2-T5 autoantibodies with older age and the absence of anti-CUB1-2 autoantibodies with cerebral involvement. In conclusion, identifying acute phase and remission immunoprofiles in iTTP revealed that anti-CS autoantibodies seem to persist or reappear during remission providing further support for the clinical development of a targeted anti-CS autoantibody therapy. A large cohort study with acute iTTP samples will validate possible links between immunoprofiles or anti-domain autoantibodies and clinical data. ispartof: BLOOD ADVANCES vol:5 issue:17 pages:3427-3435 ispartof: location:United States status: published

Hematopoietic stem cell transplantation (HSCT)-associated thrombotic microangiopathy (TA-TMA) is a multifactorial complication. Complement dysregulation may play an important role in the pathogenesis of TA-TMA. Our previous observations suggested that early increase of soluble C5b-9 (sC5b-9), before the development of other complications, can predict the development of later TA-TMA. The present study aims to validate our earlier findings in an independent cohort enrolling 67 pediatric patients who underwent allogeneic HSCT during the study period (October 2015–January 2019). Five different TA-TMA diagnostic criteria were applied, and all important clinical and laboratory parameters of TA-TMA activity were registered. Complement pathway activities, components and sC5b-9 levels were systematically measured before transplantation and on days 28, 56, and 100 after HSCT. A strong and remarkable association still have been found between early increase of sC5b-9 (10 of 10 patients with TA-TMA vs. 27 of 57 without TA-TMA; P = 0.002) and the development of TA-TMA during 100 days post-transplantation. An increase in sC5b-9 concentration had 100% sensitivity and 53% specificity for TA-TMA in the cohort. All TA-TMA cases have been observed during cyclosporine immunosuppression, no TA-TMA was diagnosed during tacrolimus or mycophenolat mofetil therapy. In the majority of patients TA-TMA was mild and self-limiting, without any signs of organ damage. No additional complement parameters were closely associated with the development of TA-TMA. Early raise of the sC5b-9 activation marker was predictive for later development of TA-TMA throughout the whole study period. In patients with a marked increase, early and frequent monitoring of TA-TMA activity markers should be attempted, to facilitate subsequent therapy decisions in time. However, patients with TA-TMA were only identified during or after cyclosporine immunosuppression. Further studies enrolling higher number of patients are necessary to determine the role of immunosuppression in the pathogenesis of TA-TMA.

Hematopoietic stem cell transplantation (HSCT)–associated thrombotic microangiopathy (TA-TMA) is a multifactorial complication, and its prediction is largely unresolved. Our aim was to analyze changes of complement profile after HSCT to identify potential markers of TA-TMA development. Thirty-three consecutive pediatric patients (9.6 ± 4.4 years old) who underwent allogeneic HSCT due to malignant (n = 17) or nonmalignant (n = 16) indications were included in this study. Graft-versus-host disease (GVHD) was diagnosed using Glucksberg criteria, viral reactivation was monitored, 5 different TA-TMA diagnostic criteria were applied, and all important clinical and laboratory parameters of TA-TMA activity were registered. Complement pathway activities, components and terminal pathway activation marker (sC5b-9) levels were systematically measured before transplantation and on days 28, 56, and 100 after HSCT. During the first 100 days after HSCT, 1 of 33 patients died (day 50, multiple organ failure), whereas 10 subjects met the criteria for TA-TMA, typically on day 61 (range, 16 to 98 days). TA-TMA was preceded by acute GVHD in 3 of 10 patients, by viral reactivation in 2 of 10, or by both in 4 of 10 cases. Baseline sC5b-9 levels did not differ in patients without (200 [interquartile range, 144 to 266] ng/mL), or with (208 [interquartile range, 166 to 271] ng/mL) subsequent TA-TMA; however, on day 28 significant differences were observed (201 [interquartile range, 185 to 290] ng/mL versus 411 [interquartile range, 337 to 471] ng/mL; P = .004). Importantly, all 10 patients with TMA showed increase in sC5b-9 level from baseline level to day 28, whereas in patients without TMA the same tendency was observed for only 9 of 23 patients (P = .031). No additional complement parameters were closely associated with the development of TA-TMA. Development of TA-TMA occurred in 30% of our patients, typically after GVHD and/or viral reactivation. However, early raise of sC5b-9 activation marker was predictive for later development of TA-TMA, and should therefore be considered as an alarming sign necessitating a careful monitoring of all TA-TMA activity markers. Further studies enrolling a higher number of patients are necessary to determine if terminal pathway activation is an independent predictor of TA-TMA.

Thrombotic microangiopathies (TMAs) are rare but life-threatening disorders characterized by microvascular hemolytic anemia and acute thrombocytopenia with or without organ damage. The term TMA covers various subgroups of diseases, the pathogenesis of which is briefly summarized in this review. As highlighted here, complement activation may represent an important amalgamating process in all of these conditions, since it is able to link together activation and damage of multiple involved cell types, such as endothelial cells, platelets, and neutrophils.

The acquired form of idiopathic thrombotic thrombocytopenic purpura (TTP) is an autoimmune disease, in which the underlying ADAMTS13-deficiency is caused by inhibitory autoantibodies against the protease. Human leukocyte antigens (HLA), responsible for antigen presentation, play an important role in the development of antibodies. The loci coding HLA DR and DQ molecules are inherited in linkage as haplotypes. The c.1858C>T polymorphism of the PTPN22 gene, which codes a protein tyrosine phosphatase important in lymphocyte activation, predisposes to a number of autoimmune diseases. We determined the HLA-DRB1-DQB1 haplotypes and the PTPN22 c.1858C>T genotypes in 75 patients with acquired idiopathic TTP and in healthy controls, in order to assess the role of these genetic factors and their interactions in the susceptibility to TTP. We found that the carrier frequencies of the DRB1∗11-DQB1∗03 and DRB1∗15-DQB1∗06 haplotypes were higher, while those of the DRB1∗07-DQB1∗02 and DRB1∗13-DQB1∗06 haplotypes were lower in TTP patients. There was no difference in the overall frequency of the PTPN22 c.1858T allele between TTP patients and controls. In conclusion, we identified four HLA-DRB1-DQB1 haplotypes associated with an increased (DRB1∗11-DQB1∗03 and DRB1∗15-DQB1∗06) or a decreased (DRB1∗07-DQB1∗02 and DRB1∗13-DQB1∗06) susceptibility to acquired idiopathic TTP.

Recently, we showed that ADAMTS13 circulates in an open conformation during the acute phase of immune-mediated thrombotic thrombocytopenic purpura (iTTP). Although the cause of this conformational change remains elusive, ADAMTS13 is primarily closed in iTTP patients in remission with ADAMTS13 activity >50% and undetectable anti-ADAMTS13 autoantibodies, as well as after rituximab treatment, suggesting a role for anti-ADAMTS13 autoantibodies. Therefore, immunoglobulin G from 18 acute iTTP patients was purified and added to closed ADAMTS13 in healthy donor plasma. This resulted in open ADAMTS13 in 14 of 18 (78%) samples, proving that anti-ADAMTS13 autoantibodies can induce an open ADAMTS13 conformation. To further elucidate the conformation of ADAMTS13 in iTTP patients, we studied a novel iTTP patient cohort (n = 197) that also included plasma samples from iTTP patients in remission in whom ADAMTS13 activity was 50%, although free anti-ADAMTS13 autoantibodies were not always detected. Thus, open ADAMTS13 is a hallmark of acute iTTP, as well as a novel biomarker that can be used to detect subclinical iTTP in patients in remission. Finally, a long-term follow-up study in 1 iTTP patient showed that the open conformation precedes a substantial drop in ADAMTS13 activity. In conclusion, we have shown that anti-ADAMTS13 autoantibodies from iTTP patients induce an open ADAMTS13 conformation. Most importantly, an open ADAMTS13 conformation is a biomarker for subclinical iTTP and could become an important tool in TTP management. ispartof: BLOOD vol:136 issue:3 pages:353-361 ispartof: location:United States status: published

SummaryThrombotic thrombocytopenic purpura (TTP) is characterised by the deficiency of the von Willebrand factor (VWF) cleaving protease (ADAMTS-13). Although several observations indicate an important role of endothelial activation in the pathogenesis of TTP, no reliable endothelial activation markers are available in the clinical management of TTP. Our aim was to investigate the presence of endothelial activation in TTP and to determine its connections with disease activity, therapy and complement activation. We enrolled 54 patients (median age 40.5; 44 females) and 57 healthy controls (median age 34; 30 females),VWF antigen, carboxiterminal-pro-endothelin-1 (CT-proET-1), complement Factor H and complement activation products (C3bBbP and SC5b-9) were measured. In both the acute and remission phase of TTP we found increased CT-proET-1 and VWF levels, while Factor H levels decreased compared with healthy controls. In remission, however, the elevated CT-proET-1 levels showed 22 % decrease when compared with the acute phase in paired samples (p=0.0031), whereas no changes for VWF and Factor H levels were observed. We also found positive correlations between CT-proET-1 levels and alternative pathway activation markers (C3bBbP; p=0.0360; r=0.4299). The data we present here demonstrate a role of endothelium activation in patients with acute TTP. The finding that CT-proET-1 levels decreased in remission compared with the acute phase further supports endothelial involvement. In addition, we show that endothelial activation also correlated with the activation of the alternative complement pathway. The data suggest that complement and endothelium activation jointly contribute to the development of TTP episodes in patients with predisposition to TTP.Supplementary Material to this article is available online at www.thrombosis-online.com.

Distant metastasis is a major cause of colorectal cancer–related death, but the mechanism of tumour progression is not fully understood. There is growing evidence of an interaction between tumour cells and platelets which may influence tumour progression and metastasis formation. Quality and quantity of von Willebrand factor may regulate the interaction between tumour cells and platelets. Our aim was to measure the platelet count, von Willebrand factor antigen (VWF:Ag) levels and ADAMTS13 activity in a large (n = 232) cohort of colorectal cancer patients and to examine their relationships with the stage of the disease and 5-year survival without thrombotic complications using multivariable models. Significantly higher platelet counts (p = 0.005), VWF:Ag levels (p = 0.008) and decreased ADAMTS13 activity (p = 0.006) were observed in patients with metastatic disease. Results of the Kaplan–Meier analysis showed that lower platelet counts (p 1.7, p

Background. Deficient ADAMTS13 activity (TS13:act 50%. However, also iTTP patients in remission with a persistent ( Aim. Determine ADAMTS13 conformation in plasma of iTTP patients during acute TTP and remission when TS13:act is 50% and investigate if anti-ADAMTS13 autoAbs induce conformational changes in ADAMTS13. Methods. TS13:act was determined in 120 iTTP plasma samples from 4 different centers (Marseille, Milan, Budapest, Utrecht). Samples were categorized according to the presence of clinical symptoms (acute versusremission) and their TS13:act in remission (>50%, 10-50%, Results. Of the 120 iTTP plasma samples, 46 were obtained during the acute (clinical signs present) and 74 during the remission phase (clinical signs absent). Further subdividing remission samples showed that TS13:act was >50% in 41, 10-50% in 14 and 50%, confirming our previous results. Interestingly, ADAMTS13 was open in 93% and 89% of remission samples with TS13:act 10-50% and Conclusion. We show that ADAMTS13 is not only in the open conformation in iTTP patient plasma during the acute phase but also in remission when TS13:act is Disclosures Peyvandi: Octapharma US: Honoraria; Kedrion: Consultancy; Ablynx: Other: Member of Advisory Board, Speakers Bureau; Grifols: Speakers Bureau; Sobi: Speakers Bureau; Shire: Speakers Bureau; Novo Nordisk: Speakers Bureau; Octapharma US: Honoraria; Octapharma US: Honoraria; Novo Nordisk: Speakers Bureau; Kedrion: Consultancy; Roche: Speakers Bureau; Novo Nordisk: Speakers Bureau; Ablynx: Other: Member of Advisory Board, Speakers Bureau; Ablynx: Other: Member of Advisory Board, Speakers Bureau; Shire: Speakers Bureau; Sobi: Speakers Bureau; Roche: Speakers Bureau; Roche: Speakers Bureau; Shire: Speakers Bureau; Ablynx: Other: Member of Advisory Board, Speakers Bureau; Octapharma US: Honoraria; Roche: Speakers Bureau; Roche: Speakers Bureau; Grifols: Speakers Bureau; Sobi: Speakers Bureau; Ablynx: Other: Member of Advisory Board, Speakers Bureau; Sobi: Speakers Bureau; Shire: Speakers Bureau; Sobi: Speakers Bureau; Novo Nordisk: Speakers Bureau; Shire: Speakers Bureau; Kedrion: Consultancy; Novo Nordisk: Speakers Bureau; Grifols: Speakers Bureau; Grifols: Speakers Bureau; Kedrion: Consultancy; Kedrion: Consultancy; Grifols: Speakers Bureau; Octapharma US: Honoraria. Coppo:Ablynx: Consultancy. Veyradier:LFB: Other: Investigator. Vanhoorelbeke:Shire: Consultancy; Ablynx: Consultancy.

Introduction Genetic and autoimmune risk factors contribute to the development of thrombotic thrombocytopenic purpura (TTP) but triggers are needed to bring about acute disease. The aim of the study was to investigate the association of neutrophil activation with acute TTP, to assess whether neutrophil activation changes during plasma exchange therapy and to show if complement- and neutrophil activation are parallel, characteristic processes in acute TTP. Materials and Methods Altogether 49 EDTA-plasma samples of 21 TTP patients with acute disease and 17 in remission were investigated along with 20 healthy controls. A stable complex of PMNE-proteinase-inhibitor was measured by ELISA (Calbiochem, Merck-Millipore, Darmstadt, Germany). Results Acute disease was associated with significantly increased PMNE levels, the group medians were similarly low in TTP patients in remission and in healthy controls. Increased PMNE levels were characteristic for hematologically active and ADAMTS13 deficient form of TTP. PMNE concentration inversely correlated to disease activity markers platelet count (r = − 0.349, p = 0.032) and hemoglobin levels (p = − 0.382 p = 0.018). Achievement of remission was associated with significant reduction of plasma PMNE levels (p = 0.031, Wilcoxon test). There was positive correlation between PMNE levels and complement activation markers C3a and Bb. Conclusions We report increased PMNE levels in acute TTP and showed its association to activity markers of acute TTP and complement activation. Effective treatment of an acute TTP episode resulted in marked decrease in PMNE levels. Our data support and extend previous observations that neutrophil extracellular traps may be released in acute TTP and potentially contribute to the pathophysiology of this disease.

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.

INTRODUCTION: Low ADAMTS13 activity is associated with an increased risk of thrombotic thrombocytopenic purpura (TTP). This may be caused by the presence of inhibitory autoantibody (immune-mediated TTP) or genetic deficiency of the enzyme. The latter condition is also known as Upshaw-Schulman syndrome (USS), the extremely rare congenital form of TTP. The clinical picture typically presents during infancy or early childhood but an increasing number of late-onset cases are detected. OBJECTIVE: Clinical and laboratory characterization of the first 5 Hungarian cases with ADAMTS13 mutations. PATIENTS: During the last 4 years, 5 cases with ADAMTS13 gene mutations were recognized in Hungary. All were adults, 4 females and 1 male. Two patients (Pts) showed an immune-mediated TTP like clinical picture, while 3 Pts were examined in conjunction with their pregnancies. The first Pt was an 18 years old girl, initially presenting with stroke and isolated cerebral vasculitis. She responded promptly to plasma exchange (PE) combined with immunosuppressive treatment (ISU) and acetylsalicylate (AS). However, severe headache with progressively decreasing platelet (PLT) count into the low normal range and repeatedly deficient ADAMTS13 activity returned after one week of PE cessation necessitating further treatment. ISU was stopped when cerebral vasculitis was excluded. There were several, plasma (PE/infusion) responsive severe headache+bradycardia episodes without hematologic manifestation in the follow-up period. The first TTP episode of the only male Pt occurred at age of 25 and the later clinical course highly resembled autoimmune relapsing (intermittent type) TTP. The Pt received several series of PEs, ISU, even splenectomy, before having the correct diagnosis. Interestingly, this Pt had unclassified HUS in the childhood. The 3rd case was a 40 years old woman with HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count) needing an immediate cesarean section (CS) in the 25th week of gestation. She achieved a spontaneous remission and remained symptom-free. The fourth Pt a 29 years old female had typical HUS at 3 years of age. Her kidney function slowly declined without HUS flares to end-stage kidney failure necessitating kidney transplantation. She had deep venous thrombosis (DVT) and intrauterine fetal death at 20 weeks of gestation. The workup showed decreased but not severely deficient ADAMTS13 activity. She received AS + low molecular weight heparin (LMWH) and increasing dose of plasma treatment starting at the 10th week of gestation of her next pregnancy. CS was done due to progressive hypertension and worsening placental circulation at the 30th week of gestation. The last Pt was a 41-year-old pregnant woman with recurrent abortions in her history. She received AS and LMWH only. The pregnancy was terminated by CS due to severe vaginal bleeding at the 30th week of gestation. RESULTS: Pts 1 and 2 with TTP clinical phenotype and Pt 3 with HELLP syndrome had deficient ADAMTS13 activity (0-0-8%, respectively). The activity was decreased but not deficient in Pts 4 and 5 (13-35%). All deficient Pts were compound heterozygous for ADAMTS13 mutations: c.3178C>T and c.4143-4144dupA (Pt1), c.1016_1017delCA and c.3199T>A (Pt2), c.1261C>T and c.3283C>T (Pt3). Three of these mutations were described in patients with USS, 1 in Pts with DVT, whereas 2 mutations are novel. By family study, we could demonstrate the association of c.1261C>T mutation described in DVT and one USS Pts with reduced ADAMTS13 activity. The two non-deficient cases were heterozygous for one of the following mutations: c.3178C>T and c.2839C>T. The previous was identified in late-onset USS, the latter has not yet been described, its association with reduced ADAMTS13 activity was also proven by family study. CONCLUSIONS: Clinical and molecular characterization of the first 5 Hungarian cases with ADAMTS13 mutations was presented. Compound heterozygous, damaging ADAMTS13 mutations with deficient plasma ADAMTS13 activity were associated with serious clinical consequences. In case of thrombotic microangiopathy in young patients with stroke, or HELLP syndrome, complete workup for ADAMTS13 activity and inhibitors is necessary, and genetic analysis should be considered. Three new ADAMTS13 mutations (c.1016_1017delCA, c.3199T>A , c.2839C>T) were identified and shown to be associated with decreased plasma ADAMTS13 activity. Disclosures Kremer Hovinga: Ablynx: Other: Member of Advisory Board; Shire: Other: Member of Advisory Board, Research Funding. Masszi:AbbVie: Consultancy; Novartis: Consultancy; Takeda: Consultancy; Janssen-Cilag: Consultancy; BMS: Consultancy; Pfizer: Consultancy.

In thrombotic microangiopathies (TMA) pathological changes of the small vessels are present, which lead to ischaemia of the affected tissues, low platelet-count and intravascular haemolytic anaemia with fragmentocytes. Two main clinical syndromes belong to the group of TMAs: the haemolytic uraemic syndrome (HUS) with kidney failure, mainly affecting children, and the thrombotic thrombocytopenic purpura (TTP), starting primarily in adulthood. HUS can be clinically classified into two forms: typical and atypical HUS, the latter being caused by defective regulation of the complement system. However, acccording to recent studies, complement activation is also present in other TMAs. Complement activation products (C3a, C5a, MAC) are able to activate endothelial cells, which results in loss of their antiinflammatory and antithrombotic potential. Activation of the complement system can also lead to direct activation of platelets and granulocytes. The consequent endothelial damage and thrombosis forms the pathological basis of the TMAs. Exploring the exact pathogenetic role of the complement system in these diseases makes the development of new therapeutic methods possible.

Background Endothelial and complement activation were both associated with immunothrombosis, a key determinant of COVID-19 severity, but their interrelation has not yet been investigated. Objectives We aimed to determine von Willebrand factor (VWF) antigen (VWF:Ag) concentration, VWF collagen binding activity (VWF:CBA), a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) activity (ADAMTS13:Ac), and their ratios in hospitalized COVID-19 patients, and to investigate how these parameters and their constellation with complement activation relate to disease severity and in-hospital mortality in COVID-19. Methods Samples of 102 hospitalized patients with polymerase chain reaction-confirmed severe acute respiratory syndrome coronavirus 2 positivity were included in our observational cohort study. Patients were stratified according to the peak severity of COVID-19 disease in agreement with the World Health Organization ordinal scale. Twenty-six convalescent plasma donors with previous COVID-19 disease formed the control group. VWF:Ag concentration and VWF:CBA were determined by enzyme-linked immunosorbent assay (ELISA); ADAMTS13:Ac was determined by fluorescence resonance energy transfer. Complement C3 and C3a were measured by turbidimetry and ELISA, respectively. Clinical covariates and markers of inflammation were extracted from hospital records. Results VWF:Ag and VWF:CBA were elevated in all groups of hospitalized COVID-19 patients and increased in parallel with disease severity. ADAMTS13:Ac was decreased in patients with severe COVID-19, with the lowest values in nonsurvivors. High (> 300%) VWF:Ag concentrations or decreased (< 67%) ADAMTS13:Ac were associated with higher risk of severe COVID-19 disease or in-hospital mortality. The concomitant presence of decreased ADAMTS13:Ac and increased C3a/C3 ratio—indicating complement overactivation and consumption—was a strong independent predictor of in-hospital mortality. Conclusion Our results suggest that an interaction between the VWF-ADAMTS13 axis and complement overactivation and consumption plays an important role in the pathogenesis of COVID-19.

International audience