Activated Complement Factor Research Articles

Treatment of Antineutrophil Cytoplasmic Antibody-Associated Vasculitis With Diffuse Alveolar Hemorrhage With Avacopan.

Avacopan, an activated complement factor 5 receptor antagonist, has been approved as adjunct therapy for severe active antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Current evidence supports the management of AAV presenting with diffuse alveolar hemorrhage (DAH) by administering glucocorticoids combined with either rituximab or cyclophosphamide in addition to supportive care. The role of avacopan in patients with DAH as a primary severe disease manifestation of AAV has not been well established. Furthermore, concerns remain regarding timely access to avacopan, the best glucocorticoid tapering regimen, and long-term efficacy and safety of the drug. We sought to identify clinical features and outcomes of patients presenting with DAH secondary to AAV who received avacopan in addition to glucocorticoids and rituximab or cyclophosphamide. We performed a retrospective cohort study of all consecutive patients presenting with DAH as part of active severe granulomatosis with polyangiitis or microscopic polyangiitis. Demographic and clinical characteristics were collected at presentation and follow-up. Fifteen patients met inclusion criteria and were observed for a median time of 17 weeks (interquartile range [IQR] 6-37 weeks) after initiation of avacopan. Patients were predominantly female and White, had never smoked, and were a median age of 66 years (IQR 52-72 years) at diagnosis. The majority had newly diagnosed severe AAV with renal involvement. Three patients progressed to respiratory failure. The timing of avacopan introduction and patterns of glucocorticoid tapers varied widely in this cohort. Two serious adverse events related to infection were observed, including one opportunistic infection leading to the patient's death, although neither was directly attributed to avacopan administration. We describe the clinical course of patients who presented with the severe AAV disease manifestation of DAH and received avacopan as adjunct therapy. Most patients achieved remission during follow-up, and adverse events, including infection, were observed.

Activation of Complement Factor C3/C3b Deposition on the Surface of Endothelial Cells by Histamine As one of the Causes of Endothelium Damage in COVID-19

Damage of the endothelium as a result of activation of the complement system is one of the causes of thrombotic complications in COVID-19. Factor C3 plays a key role in this process. The attachment of its proteolytic product C3b to the cells initiates the formation of the membrane attack complex C5b-9, which forms a pore in the plasma membrane and cell death. Here, we investigated how histamine, secreted in the body by leukocytes and mast cells, can affect the binding of C3b to human umbilical vein endothelial cells (HUVEC). To visualize it, FITS-conjugated antibodies against the C3c were used. These antibodies bind to intact C3 and to C3b but not to C3a. We have shown that when cultured HUVECs are incubated with human blood plasma, factor C3/C3b accumulates in the form of rounded and diffuse foci on the surface of the endothelial cell monolayer. Pre-activation of HUVEC by histamine increases the number of С3/C3b attachment sites. These data suggest that histamine may enhance endothelial damage during complement hyperactivation in COVID-19 and in endotheliopathies caused by other diseases.

Activation of Complement Factor C3/C3b Deposition on the of Endothelial Cell Surface by Histamine As one of the Causes of Endothelium Damage in COVID-19

Activation of Complement Factor C3/C3b Deposition on the of Endothelial Cell Surface by Histamine As one of the Causes of Endothelium Damage in COVID-19

Assessment of potential biomarkers for early detection and management of Glomerulonephritis patients with diabetic diseases

Abstract Introduction/Objective Glomerulonephritis is a serious kidney disease that can lead to kidney failure if not detected and treated early. Several potential biomarkers have been identified to aid in early detection of this condition. it is important to investigate and validate these novel biomarkers to improve patient outcomes in the management of glomerulonephritis. Methods/Case Report The various biomarkers such as Creatinine, urinary exosomes, Cystatin-C, interleukin-6, tumor necrosis factor-alpha (TNF-α), Fasting blood glucose, Albumin, MicroRNAs, and complement activation factors (C3, C4d) were measured and calculated in 98 infected cases with diabetic patients who had acute kidney diseases. The same biomarkers had been implemented for 87 cases with chronic renal disease on dialysis. Also, the same parameters were determined in 82 healthy persons as controls. Alternative markers' levels were determined by using Microscopic, Biochemical, ELISA, and RT-PCR techniques. The biopsy had been applied only to infected patients. Imaging diagnostic tools have been applied to all cases. Results (if a Case Study enter NA) The studied biomarkers have high sensitivity from 81.35% to 94.72% and accuracy from 88.76% to 96.83% as well as their cut off which approved the aim of this study. Thereafter, the studied markers' reports assisted in detecting glomerulonephritis diseases at early stages. Conclusion Alternative biomarkers (Cystatin-C, interleukin-6, tumor necrosis factor-alpha (TNF-α), urinary exosomes, MicroRNAs, and complement activation factors (C3, C4d)) are considered as prospective markers to differentiate healthy individuals from chronic kidney disease by their significant results. Hence, if the studied biomarker has been measured regularly for outpatients who complain of renal diseases, that can be assisted in the early detection of kidney diseases, including glomerulonephritis, and then it can be well managed.

Identification of Common Dysregulated Genes in COVID-19 and Hypersensitivity Pneumonitis: A Systems Biology and Machine Learning Approach.

A comprehensive knowledge on systems biology of severe acute respiratory syndrome coronavirus 2 is crucial for differential diagnosis of COVID-19. Interestingly, the radiological and pathological features of COVID-19 mimic that of hypersensitivity pneumonitis (HP), another pulmonary fibrotic phenotype. This motivated us to explore the overlapping pathophysiology of COVID-19 and HP, if any, and using a systems biology approach. Two datasets were obtained from the Gene Expression Omnibus database (GSE147507 and GSE150910) and common differentially expressed genes (DEGs) for both diseases identified. Fourteen common DEGs, significantly altered in both diseases, were found to be implicated in complement activation and growth factor activity. A total of five microRNAs (hsa-miR-1-3p, hsa-miR-20a-5p, hsa-miR-107, hsa-miR-16-5p, and hsa-miR-34b-5p) and five transcription factors (KLF6, ZBTB7A, ELF1, NFIL3, and ZBT33) exhibited highest interaction with these common genes. Next, C3, CFB, MMP-9, and IL1A were identified as common hub genes for both COVID-19 and HP. Finally, these top-ranked genes (hub genes) were evaluated using random forest classifier to discriminate between the disease and control group (coronavirus disease 2019 [COVID-19] vs. controls, and HP vs. controls). This supervised machine learning approach demonstrated 100% and 87.6% accuracy in differentiating COVID-19 from controls, and HP from controls, respectively. These findings provide new molecular leads that inform COVID-19 and HP diagnostics and therapeutics research and innovation.

Pharmacodynamics and Biomarker Correlates of Imvotamab (IGM-2323), the First-in-Class CD20xCD3 Bispecific IgM Antibody with Dual Mechanisms of Action, in Patients with Advanced B Cell Malignancies

Introduction: Imvotamab (IGM-2323) is a novel CD20xCD3 bispecific T cell engager utilizing an engineered IgM antibody platform, with 10 high-affinity CD20 binding domains and a single anti-CD3 scFv fused through the recombinant J-chain. Its high avidity enables irreversible target cell binding even at low CD20 levels and results in T cell dependent (TDCC) and complement dependent (CDC) mechanisms of cytotoxicity, with minimal cytokine release. Imvotamab is also designed to induce more physiologic T cell activation in order to prevent overstimulation and subsequent downregulation of immune function. The first-in-human Phase 1/2 study of imvotamab (NCT04082936) is ongoing, and preliminary results show single agent activity with durable complete responses as well as favorable safety and tolerability profile up to 1000 mg (Budde et al. ASH 2021). Here we present biomarker data highlighting pharmacodynamic effects and immune correlates that demonstrate mechanisms of action (MOA), inform optimal dose/schedule selection, and identify potential predictors of response. Methods: Data to date were obtained from patients on dose escalation cohorts that received 0.5-1000 mg under fixed or dose titration schemes (n=40). Immune profiling of peripheral blood was performed by flow cytometry. Plasma biomarker evaluation included measurement of cytokines by MSD, complement activation markers by ELISA, and ctDNA-MRD by PhasED-Seq (Foresight Dx). Tumor biomarkers were assessed in baseline and on-treatment tissue through immunohistochemistry. Results: Imvotamab biologic activity was observed starting at the 10 mg dose, as evidenced by transient elevations in plasma cytokines, which occurred over multiple sequential infusions, peaking within 2-12 hours post-infusion and returning to baseline by 24 hours. Maximal cytokine levels were observed after Cycle 1 Day 1 in the majority of patients, including those that received dose titration. In contrast to bispecific IgG T cell engagers, imvotamab induced consistently higher levels of IFNγ relative to inflammatory cytokines such as IL-6 and TNFα. However, patients with cytokine release syndrome (CRS) exhibited a poly-cytokine profile, where elevated levels of multiple cytokines in addition to IFNγ were also observed. The timing of poly-cytokine response corresponded with the onset and duration of CRS. Complement activation factors Bb, C3a, C4a, and sC5b9 transiently increased ~2-5 fold on average in plasma of nearly all patients tested, with peak values detected immediately after the first dose. Circulating B cells were depleted by the end of Cycle 1 in majority of patients with measurable B cells at baseline. In peripheral blood, imvotamab infusion resulted in rapid and transient T cell activation that coincided with T cell margination. There was a trend for higher frequency of activated CD69+ T cells and greater margination at 24 hours following intermediate 100 and 300 mg vs. higher 600 and 1000 mg plateau doses. Notably, patients with progressive disease did not show significant T cell activation. Patients with complete response had marked elevations of T cells at later cycles; these patients also had higher baseline T cell counts vs. others (median: 910 vs. 590 cells/ul). The proportion of PD1+ T cells on-treatment was ~2-fold lower in responders vs. non-responders. Paired tumor biopsies showed increase of intratumoral CD3+ T cells on-treatment regardless of response. At baseline, some complete responders had low CD20 expression, as indicated by CD20 H-scores < 30. Finally, ctDNA analysis in a subset of patients showed greater depth of decrease in responders vs. non-responders, with sustained MRD responses seen in samples > 1 year from patients with complete response. Conclusions: Acute pharmacodynamic changes confirm TDCC and CDC MOA for imvotamab in patients. The repeatable IFNγ-dominant cytokine profile is consistent with its ability to induce a more physiologic stimulation that can preserve or strengthen T cell effector function, without overstimulating undesired inflammatory cytokines related to CRS. Overall, the data support the use of dose titration as a safe and efficacious drug administration scheme and suggest a model whereby an optimal number of sufficiently activated and functional T cells may be required to elicit strong and durable clinical responses. Updated analyses will be presented at the meeting.

The complex formation of MASP-3 with pattern recognition molecules of the lectin complement pathway retains MASP-3 in the circulation.

The complement system plays an important role in host defense and is activated via three different activation pathways. We have previously reported that mannose-binding lectin-associated serine protease (MASP)-3, unlike its splicing variant MASP-1, circulates in an active form and is essential for the activation of the alternative pathway (AP) via the activation of complement factor D (FD). On the other hand, like MASP-1 and MASP-2 of the lectin pathway (LP), MASP-3 forms a complex with the pattern recognition molecules (PRMs) of the LP (LP-PRMs). Both MASP-1 and MASP-2 can be activated efficiently when the LP-PRMs complexed with them bind to their ligands. On the other hand, it remains unclear how MASP-3 is activated, or whether complex formation of MASP-3 with LP-PRMs is involved in activation of MASP-3 or its efficiency in the circulation. To address these issues, we generated wild-type (WT) and four mutant recombinant mouse MASP-3 proteins fused with PA (human podoplanin dodecapeptide)-tag (rmMASP-3-PAs), the latter of which have single amino acid substitution for alanine in the CUB1 or CUB2 domain responsible for binding to LP-PRMs. The mutant rmMASP-3-PAs showed significantly reduced in-vivo complex formation with LP-PRMs when compared with WT rmMASP-3-PA. In the in-vivo kinetic analysis of MASP-3 activation, both WT and mutant rmMASP-3-PAs were cleaved into the active forms as early as 30 minutes in the circulation of mice, and no significant difference in the efficiency of MASP-3 cleavage was observed throughout an observation period of 48 hours after intravenous administration. All sera collected 3 hours after administration of each rmMASP-3-PA showed full restoration of the active FD and AP activity in MASP-3-deficient mouse sera at the same levels as WT mouse sera. Unexpectedly, all mutant rmMASP-3-PAs showed faster clearance from the circulation than the WT rmMASP-3-PA. To our knowledge, the current study is the first to show in-vivo kinetics of MASP-3 demonstrating rapid activation and clearance in the circulation. In conclusion, our results demonstrated that the complex formation of MASP-3 with LP-PRMs is not required for in-vivo activation of MASP-3 or its efficiency, but may contribute to the long-term retention of MASP-3 in the circulation.

Magnetic Nanosorbents for Adsorption of Blood Mercury

AbstractMercury enters the human body through the food chain and various ways and exists in blood, kidney and other organs, which will cause great harm. Therefore, it is important to design a safe and effective mercury remover for the removal of blood mercury. In this work, we modified a layer of amino‐rich hyperbranched polyamide nanomaterials (HPN) on the surface of Fe3O4 nanoparticles (Fe/HPN‐NH2 NPs). Among them, tetraethylenepentamine was crosslinked with hyperbranched polyamide by methyl acrylate, which effectively increased the number of amino functional groups in the material. The morphology, structural characteristics and composition of Fe/HPN‐NH2 NPs were characterized. The results of adsorption experiments showed that Fe/HPN‐NH2 NPs had good adsorption ability for inorganic mercury and methylmercury in water. Series of in vitro biocompatibility evaluation tests such as coagulation time tests, erythrocyte morphology observation, blood routine test, complement activation and immune factor test at the molecular level showed that the synthesized Fe/HPN‐NH2 NPs had good biocompatibility. When the initial concentration of lead was 1 ppm and the concentration of adsorbent was 10 mg/mL, the removal efficiency of blood mercury can reach up to 65 % without changing the amount of other commonly existing ions. This blood mercury removal strategy provides the possibility for blood purification.

Association of mannose-binding lectin\xa02 gene\xa0polymorphisms with Guillain-Barr\xe9 syndrome

Complement activation plays a critical role in the pathogenesis of Guillain-Barré syndrome (GBS), a debilitating immune-mediated neuropathy. Mannose-binding lectin (MBL) is a complement activation factor of lectin pathway which as genetic host factor may influence the susceptibility or severity of GBS. We investigated the frequency of MBL2 promoter (− 550H/L and − 221X/Y) and functional region (exon 1 A/O) polymorphisms and their association with disease susceptibility, clinical features and serum MBL among GBS patients (n = 300) and healthy controls (n = 300) in Bangladesh. The median patient age was 30 years (IQR: 18–42; males, 68%). MBL2 polymorphisms were not significantly associated with GBS susceptibility compared to healthy controls. HL heterozygosity in GBS patients was significantly associated with mild functional disability at enrolment (P = 0.0145, OR, 95% CI 2.1, 1.17–3.82). The HY, YA, HA and HYA heterozygous haplotypes were more common among mildly affected (P = 0.0067, P = 0.0086, P = 0.0075, P = 0.0032, respectively) than severely affected patients with GBS. Reduced serum MBL was significantly associated with the LL, OO and no HYA variants and GBS disease severity. No significant association was observed between MBL2 polymorphisms and electrophysiological variants, recent Campylobacter jejuni infection or anti-ganglioside (GM1) antibody responses in GBS. In conclusion, MBL2 gene polymorphisms are related to reduced serum MBL and associated with the severity of GBS.

Predictors of Adverse Pregnancy Outcomes in Pregnant Women Living with Obesity: A Systematic Review.

Obesity is a well-recognized risk factor for pregnancy complications. Most studies to date are in large cohorts, with results presented in a way that assumes all women living with obesity are at equal risk. This study investigates which women living with obesity are at higher risk of specific pregnancy complications. A systematic search of MEDLINE and Embase identified 7894 prospective or retrospective cohort studies exploring predictors of adverse outcomes among pregnant women living with obesity. Following screening, 61 studies were deemed eligible. Studies were selected if the effects of exposure to any predictor amongst pregnant women living with obesity could be collected. Maternal characteristics assessed for association with adverse outcomes included maternal age, race/ethnicity, maternal height, mode of conception, complement activation factors, and history of various comorbidities/procedures. Gestational diabetes mellitus was the most studied outcome (n = 32), followed by preterm birth (n = 29), preeclampsia (n = 27), low birthweight infants (n = 20), small for gestational age newborns (n = 12), and stillbirth (n = 7). This review identified important characteristics that should be considered during the screening and follow-up sessions of pregnant women living with obesity, including pre-existing type 1 diabetes, maternal age < 20 years or ≥35 years, non-White ethnicity, abdominal adiposity obesity, and history of bariatric surgery.

Retention of hemostatic and immunological properties of frozen plasma and COVID-19 convalescent apheresis fresh-frozen plasma produced and freeze-dried in Canada.

Randomized clinical trial data show that early plasma transfusion may save lives among trauma patients. Supplying plasma in remote environments is logistically challenging. Freeze-dried plasma (FDP) offers a possible solution. A Terumo BCT plasma freeze-drying system was evaluated. We compared pooled frozen plasma (FP) units with derived Terumo BCT FDP (TFDP) units and pooled COVID-19 convalescent apheresis fresh-frozen plasma (CC-AFFP) with derived CC-TFDP units. Parameters measured were: coagulation factors (F) II; V; VII; VIII; IX; XI; XIII; fibrinogen; Proteins C (PC) and S (PS); antithrombin (AT); α2 -antiplasmin (α2 AP); ADAMTS13; von Willebrand Factor (vWF); thrombin-antithrombin (TAT); D-dimer; activated complement factors 3 (C3a) and 5 (C5a); pH; osmolality; prothrombin time (PT); and activated partial thromboplastin time (aPTT). Antibodies to SARS-CoV-2 in CC-AFFP and CC-TFDP units were compared by plaque reduction assays and viral protein immunoassays. Most parameters were unchanged in TFDP versus FP or differed ≤15%. Mean aPTT, PT, C3a, and pH were elevated 5.9%, 6.9%, 64%, and 0.28 units, respectively, versus FP. CC-TFDP showed no loss of SARS-CoV-2 neutralization titer versus CC-AFFP and no mean signal loss in most pools by viral protein immunoassays. Changes in protein activities or clotting times arising from freeze-drying were <15%. Although C3a levels in TFDP were elevated, they were less than literature values for transfusable plasma. SARS-CoV-2-neutralizing antibody titers and viral protein binding levels were largely unaffected by freeze-drying. In vitro characteristics of TFDP or CC-TFDP were comparable to their originating plasma, making future clinical studies appropriate.

Correlation Between Clinical and Pathological Findings of Liver Injury in 27 Patients With Lethal COVID-19 Infections in Brazil.

Liver test abnormalities are frequently observed in patients with coronavirus disease 2019 (COVID‐19) and are associated with worse prognosis. However, information is limited about pathological changes in the liver in this infection, so the mechanism of liver injury is unclear. Here we describe liver histopathology and clinical correlates of 27 patients who died of COVID‐19 in Manaus, Brazil. There was a high prevalence of liver injury (elevated alanine aminotransferase and aspartate aminotransferase in 44% and 48% of patients, respectively) in these patients. Histological analysis showed sinusoidal congestion and ischemic necrosis in more than 85% of the cases, but these appeared to be secondary to systemic rather than intrahepatic thrombotic events, as only 14% and 22% of samples were positive for CD61 (marker of platelet activation) and C4d (activated complement factor), respectively. Furthermore, the extent of these vascular findings did not correlate with the extent of transaminase elevations. Steatosis was present in 63% of patients, and portal inflammation was present in 52%. In most cases, hepatocytes expressed angiotensin‐converting enzyme 2 (ACE2), which is responsible for binding and entry of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), even though this ectoenzyme was minimally expressed on hepatocytes in normal controls. However, SARS‐CoV‐2 staining was not observed. Most hepatocytes also expressed inositol 1,4,5‐triphosphate receptor 3 (ITPR3), a calcium channel that becomes expressed in acute liver injury. Conclusion: The hepatocellular injury that commonly occurs in patients with severe COVID‐19 is not due to the vascular events that contribute to pulmonary or cardiac damage. However, new expression of ACE2 and ITPR3 with concomitant inflammation and steatosis suggests that liver injury may result from inflammation, metabolic abnormalities, and perhaps direct viral injury.

Acquired decrease of the C3b/C4b receptor (CR1, CD35) and increased C4d deposits on erythrocytes from ICU COVID-19 patients

In order to study the mechanisms of COVID-19 damage following the complement activation phase occurring during the innate immune response to SARS-CoV-2, CR1 (the regulating complement activation factor, CD35, the C3b/C4b receptor), C4d deposits on Erythrocytes (E), and the products of complement activation C3b/C3bi, were assessed in 52 COVID-19 patients undergoing O2 therapy or assisted ventilation in ICU units in Rheims France. An acquired decrease of CR1 density on E from COVID-19 patients was observed (Mean = 418, SD = 162, N = 52) versus healthy individuals (Mean = 592, SD = 287, N = 400), Student’s t-test p < 10−6, particularly among fatal cases, and in parallel with several parameters of clinical severity. Large deposits of C4d on E in patients were well above values observed in normal individuals, mostly without concomitant C3 deposits, in more than 80% of the patients. This finding is reminiscent of the increased C4d deposits on E previously observed to correlate with sub endothelial pericapillary deposits in organ transplant rejection, and with clinical SLE flares. Conversely, significant C3 deposits on E were only observed among ¼ of the patients. The decrease of CR1/E density, deposits of C4 fragments on E and previously reported detection of virus spikes or C3 on E among COVID-19 patients, suggest that the handling and clearance of immune complex or complement fragment coated cell debris may play an important role in the pathophysiology of SARS-CoV-2. Measurement of C4d deposits on E might represent a surrogate marker for assessing inflammation and complement activation occurring in organ capillaries and CR1/E decrease might represent a cumulative index of complement activation in COVID-19 patients.Taken together, these original findings highlight the participation of complement regulatory proteins and indicate that E are important in immune pathophysiology of COVID-19 patients. Besides a potential role for monitoring the course of disease, these observations suggest that novel therapies such as the use of CR1, or CR1-like molecules, in order to down regulate complement activation and inflammation, should be considered.

Human plasma protein adsorption to elastinlike polypeptide nanoparticles.

Elastin-like polypeptides (ELPs) are being developed for numerous biomedical applications. There is a limited understanding of ELP biocompatibility, with conflicting results in the literature. Protein adsorption is the fate determining event for blood-contacting biomaterials. The aim of this study is to elucidate the biocompatibility of ELP-based nanoparticles by examining the adsorbed proteome from platelet poor human plasma as a function of the physicochemical properties of these nanoparticles: diameter, amino acid hydrophobicity, and chain length. It was found that all ELP constructs had adsorbed an extremely large amount of albumin and high levels of immunoglobulin G and activated complement factor 3. Variations in the compositions of the proteomes across the eight nanoparticle systems studied were observed for plasminogen, fibronectin, activated fibrinogen, and coagulation modulating antithrombin and alpha2 macroglobulin. Plasma clotting experiments showed that ELP-based nanoparticles slightly inhibited normal blood clotting, with shorter and/or more hydrophilic constructs showing a greater difference from the control than longer or more hydrophobic constructs. These results indicate that ELP nanoparticles, regardless of chain length, particle diameter, or amino acid hydrophobicity, may have the potential to stimulate a humoral immune response via immunoglobulin G and activated complement factor 3 despite the large amounts of albumin adsorbed at the blood-material interface.

Atypical hemolytic uremic syndrome: a case report

BackgroundThrombotic microangiopathy is a pathological condition comprised of microvascular thrombosis involving any organ of the body leading to thrombocytopenia, Coombs-negative hemolytic anemia, and end-organ damage. The most common forms of thrombotic microangiopathies are Shiga toxin-producing Escherichia coli-mediated hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, and atypical hemolytic uremic syndrome. The atypical hemolytic uremic syndrome occurs due to genetic and acquired mutations in complement regulatory factors and to complement activation factors in the immune system, mainly the alternative pathway. Clinical manifestations and outcomes differ with the prevalent mutations of the patient. Currently, available treatment modalities are therapeutic plasma exchange and a monoclonal antibody against C5, eculizumab. We report a case of a Sri Lankan girl diagnosed with atypical hemolytic uremic syndrome complicated with septicemia, hemolytic anemia, acute kidney injury, pulmonary hemorrhage with respiratory failure, and hypertension who had a complete remission following long-term (30 months) therapeutic plasma exchange.Case presentationA 15-year-old Sri Lankan girl was transferred from a local hospital with the features of septicemia and acute kidney injury for specialized management. She had high blood pressure (180/100 mmHg) on admission. She underwent appendicectomy based on suspicion of acute appendicitis as the cause of sepsis. Following surgery, her condition deteriorated, and intensive care unit management was warranted because she developed pulmonary hemorrhages and respiratory failure requiring mechanical ventilation and renal replacement therapy in the form of hemodialysis. Her blood investigations showed microangiopathic hemolytic anemia, thrombocytopenia, elevated lactate dehydrogenase, and reduced human complement C3 levels, together with a normal coagulation profile. She was diagnosed with atypical hemolytic uremic syndrome and was initiated on therapeutic plasma exchange and other supportive therapy, including corticosteroids. Following a lengthy course of plasma exchange, complete recovery was achieved.ConclusionThe atypical hemolytic uremic syndrome is a rare disease entity requiring a high index of suspicion to diagnose. It is a diagnosis of exclusion. Early diagnosis with prompt treatment will render a better outcome. The atypical hemolytic uremic syndrome needs to be considered in all patients with thrombotic microangiopathy.

Links Between Complement Activation and Thrombosis

The coagulation and complement systems are central mediators of innate immune defense and aide the peri- and intravascular elimination of invading microorganisms in a process termed immuno-thrombosis. Complement and coagulation proteases are engaged in reciprocal amplifications at different levels of these enzymatic cascades. In addition, activated complement factor (C) 3 specifically stimulates platelets through C3a receptor signaling and thereby amplifies thrombus formation. A non-enzymatic function of complement activation emerged as a crucial mechanism that rapidly alters the function of the extrinsic coagulation activator tissue factor (TF) on monocytes. Activation of the classical complement pathway by therapeutic anti-thymocyte globulin preparations rapidly enhances monocyte TF procoagulant activity. On the one hand, complement activation-associated thiol-disulfide exchange supports protein disulfide isomerase-dependent conformational changes in TF. Insertion of the C5b-C7 complex supports these conformational changes in TF by exposing procoagulant phosphatidylserine (PS). Furthermore, these dual roles of complement activation play a central role in venous thrombosis. C3, but not C5-deficient mice are protected from platelet deposition. In contrast, C5 knock-out mice show diminished PS exposure on leukocytes and lack TF-dependent coagulation activation and fibrin deposition at the flow restricted venous vessel wall. Antiphospholipid antibodies (aPL) also cause TF- and complement-dependent thrombosis. Whereas C3-dependent thiol-disulfide exchange is again required for converting TF to a procoagulant form, aPL do not rely on downstream complement components for the exposure of PS and induce pathological thrombosis in C5-deficient mice. Our recent data show that aPL dissociate a cell surface-localized, inhibited complex with monocyte-expressed TF pathway inhibitor (TFPI). In addition to promoting TF procoagulant activation, complement-dependent thiol-disulfide exchange emerged as an additional central mechanism that allows for aPL internalization and endosomal signaling involving integrin- and TF cytoplasmic domain-dependent translocation of the NADPH oxidase to the endosome. A monoclonal antibody that traps TF with low procoagulant activity on the surface prevents TF endosomal trafficking, aPL signaling and aPL-induced pregnancy loss. These complement-dependent effects require assistance by thrombin-PAR1/PAR2 heterodimer signaling initiated by FXa dissociated from the inhibited TF complex. Monocyte TFPI-dysfunctional mice are protected from aPL pathogenic signaling in vitro and from aPL-induced thrombosis, but form thrombi normally in other experimental thrombosis models. These data show that formation of an inhibited TF cell surface complex specifically primes monocytes for thrombosis and pathogenic aPL signaling. Thus, the evolutionary conserved crosstalk of complement and coagulation cascades not only plays crucial roles in thrombosis, but also regulates thrombo-inflammatory signaling in autoimmune disease. Disclosures Ruf: MeruVasimmune: Equity Ownership; Iconic Therapeutics: Consultancy.

Measuring Circulating Complement Activation Products in Myeloperoxidase- and Proteinase 3-Antineutrophil Cytoplasmic Antibody-Associated Vasculitis.

There is accumulating evidence that complement activation is important in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) pathogenesis. This study was undertaken to investigate complement activation in AAV with myeloperoxidase (MPO) positivity and AAV with proteinase 3 (PR3) positivity after determining optimal methods for measuring activated complement factors in circulation. Participants included 98 patients with AAV (45 MPO-ANCA positive, 53 PR3-ANCA positive) and 35 healthy controls. Plasma was obtained from blood collected using EDTA tubes, with or without 100 μg/ml Futhan. Levels of Bb, C3a, C5a, soluble C5b-9 (sC5b-9), properdin, and C4d were measured by enzyme-linked immunosorbent assay. Group comparisons were made using Wilcoxon's 2-sample test. Paired data were analyzed using a matched pairs signed rank test. Compared to healthy controls, certain complement analyte levels were high in patients with active AAV with MPO positivity, including C3a (P < 0.0001), C5a (P = 0.0004), and sC5b-9 (P = 0.0007). During remission, levels of Bb (P = 0.001), C3a (P < 0.0001), and sC5b-9 (P = 0.003) were higher. Compared to healthy controls, C3a (P < 0.0001), C5a (P = 0.002), sC5b-9 (P = 0.0001), and C4d (P = 0.005) levels were higher in patients with active AAV with PR3 positivity; levels of C3a (P < 0.0001) and C4d (P = 0.007) were also higher duriing remission. There were no significant differences in any complement analyte for either ANCA serotype between patients with active disease and those with disease in remission. Among patients with paired samples, sC5-9 levels were significantly lower during disease remission compared to active disease. C5a was significantly lower among patients with disease in long-term remission who were not receiving therapy. For Bb, C5a, and sC5b-9, median levels and individual values were considerably higher in control and patient samples processed without Futhan compared to those processed with Futhan. Complement activation occurs in both MPO-positive AAV and PR3-positive AAV. The complement activation profile differs according to disease activity and possibly ANCA serotype. Futhan reduces in vitro complement activation and provides a more accurate measurement.

Clinical evaluation of performance, biocompatibility, and safety of vitamin E-bonded polysulfone membrane hemodialyzer compared to non-vitamin E-bonded hemodialyzer

The vitamin E-bonded polysulfone membrane hemodialyzer (ViE™-21) was evaluated in a clinical study for regulatory submission. Seventeen patients on hemodialysis were treated with conventional high-flux hemodialyzers for 2 weeks (Pre-ViE phase) and switched to the ViE-21 for 36 sessions (ViE phase) followed by an additional 2 weeks on conventional hemodialyzers (Post-ViE phase). Reduction ratios of urea, creatinine, beta-2-microglobulin, albumin, and ultrafiltration coefficients (KUF) were measured once during the Pre-ViE phase and twice during the ViE phase. Moreover, biocompatibility markers [leucocyte count, platelet count, and activated complement factor (C3a) levels] were evaluated pre-dialysis, 15 min after initiation, and post-dialysis. During the study, type and number of adverse events (AEs), and device malfunctions were recorded. ViE-21 reduction ratios and KUF were not noticeably different than those of conventional hemodialyzers. Fluctuations of leucocyte counts and C3a concentrations were similar using ViE-21 and conventional hemodialyzers; however, the platelet count fluctuation was lower in ViE-21 sessions. The frequency of episodes of hypotension occurring during the ViE phase was lower than that occurring during the Pre- and Post-ViE phases. In conclusion, this study provided performance and safety data of the ViE-21 for regulatory application. The data suggest that vitamin E-bonded hemodialyzers are beneficial in lowering platelet activation and frequency of intradialytic hypotension. Larger randomized controlled trials are needed to confirm these findings.

Polypropylene mesh implantation for hernia repair causes myeloid cell-driven persistent inflammation.

Polypropylene meshes that are commonly used for inguinal hernia repair may trigger granulomatous foreign body reactions. Here, we show that asymptomatic patients display mesh-associated inflammatory granulomas long after surgery, which are dominated by monocyte-derived macrophages expressing high levels of inflammatory activation markers. In mice, mesh implantation by the onlay technique induced rapid and strong myeloid cell accumulation, without substantial attenuation for up to 90 days. Myeloid cells segregated into distinct macrophage subsets with separate spatial distribution, activation profiles, and functional properties, showing a stable inflammatory phenotype in the tissue surrounding the biomaterial and a mixed, wound-healing phenotype in the surrounding stromal tissue. Protein mass spectrometry confirmed the inflammatory nature of the foreign body reaction, as characterized by cytokines, complement activation, and matrix-modulating factors. Moreover, immunoglobulin deposition increased over time around the implant, arguing for humoral immune responses in association with the cell-driven inflammation. Intravital multiphoton microscopy revealed a high motility and continuous recruitment of myeloid cells, which is partly dependent on the chemokine receptor CCR2. CCR2-dependent macrophages are particular drivers of fibroblast proliferation. Thus, our work functionally characterizes myeloid cell-dependent inflammation following mesh implantation, thereby providing insights into the dynamics and mechanisms of foreign body reactions to implanted biomaterials.

Complement factor and T-cell interactions during alloimmune inflammation in transplantation.

Complement factor and T-cell signaling during an effective alloimmune response plays a key role in transplant-associated injury, which leads to the progression of chronic rejection (CR). During an alloimmune response, activated complement factors (C3a and C5a) bind to their corresponding receptors (C3aR and C5aR) on a number of lymphocytes, including T-regulatory cells (Tregs), and these cell-molecular interactions have been vital to modulate an effective immune response to/from Th1-effector cell and Treg activities, which result in massive inflammation, microvascular impairments, and fibrotic remodeling. Involvement of the complement-mediated cell signaling during transplantation signifies a crucial role of complement components as a key therapeutic switch to regulate ongoing inflammatory state, and further to avoid the progression of CR of the transplanted organ. This review highlights the role of complement-T cell interactions, and how these interactions shunt the effector immune response during alloimmune inflammation in transplantation, which could be a novel therapeutic tool to protect a transplanted organ and avoid progression of CR.