scholarly journals Anti-Factor B Antibodies and Acute Postinfectious GN in Children

2020 ◽  
Vol 31 (4) ◽  
pp. 829-840 ◽  
Author(s):  
Sophie Chauvet ◽  
Romain Berthaud ◽  
Magali Devriese ◽  
Morgane Mignotet ◽  
Paula Vieira Martins ◽  
...  
Keyword(s):  
Complement Activation ◽  
Alternative Pathway ◽  
Functional Characterization ◽  
C3 Glomerulopathy ◽  
Contributing Factors ◽  
Factor B ◽  
Pathway Activation ◽  
Nephritic Syndrome ◽  
French Registry

BackgroundThe pathophysiology of the leading cause of pediatric acute nephritis, acute postinfectious GN, including mechanisms of the pathognomonic transient complement activation, remains uncertain. It shares clinicopathologic features with C3 glomerulopathy, a complement-mediated glomerulopathy that, unlike acute postinfectious GN, has a poor prognosis.MethodsThis retrospective study investigated mechanisms of complement activation in 34 children with acute postinfectious GN and low C3 level at onset. We screened a panel of anticomplement protein autoantibodies, carried out related functional characterization, and compared results with those of 60 children from the National French Registry who had C3 glomerulopathy and persistent hypocomplementemia.ResultsAll children with acute postinfectious GN had activation of the alternative pathway of the complement system. At onset, autoantibodies targeting factor B (a component of the alternative pathway C3 convertase) were found in a significantly higher proportion of children with the disorder versus children with hypocomplementemic C3 glomerulopathy (31 of 34 [91%] versus 4 of 28 [14%], respectively). In acute postinfectious GN, anti-factor B autoantibodies were transient and correlated with plasma C3 and soluble C5b-9 levels. We demonstrated that anti-factor B antibodies enhance alternative pathway convertase activity in vitro, confirming their pathogenic effect. We also identified crucial antibody binding sites on factor B, including one correlated to disease severity.ConclusionsThese findings elucidate the pathophysiologic mechanisms underlying acute postinfectious GN by identifying anti-factor B autoantibodies as contributing factors in alternative complement pathway activation. At onset of a nephritic syndrome with low C3 level, screening for anti-factor B antibodies might help guide indications for kidney biopsy to avoid misdiagnosed chronic glomerulopathy, such as C3 glomerulopathy, and to help determine therapy.

scholarly journals Time-Dependent Activation of Complement system during Storage of Platelet Product

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4287-4287
Author(s):  
Jian Chen ◽  
Shangbin Yang ◽  
Spero R Cataland ◽  
Haifeng M Wu
Keyword(s):  
Complement System ◽  
Complement Activation ◽  
Research Funding ◽  
Storage Time ◽  
Adverse Reactions ◽  
Alternative Pathway ◽  
Pathway Activation ◽  
The Complement System ◽  
Transfusion Reactions

Abstract Platelet transfusion is known for carrying a high incidence of clinically significant transfusion reactions such as febrile nonhemolytic transfusion reaction. The mechanism responsible for these transfusion-associated adverse events, however, is poorly understood. In this study, we hypothesize that prolonged in vitro storage activates the complement system in the platelet product that in turn causes a high frequency of transfusion reactions. Fresh platelet units obtained from three blood donors were stored on a temperature controlled platelet rotator between 22-24 C°. An aliquot of platelet product was obtained using sterile techniques from each unit on day 2 through day 7. The platelet product from each collection was then immediately centrifuged to obtain platelet poor plasma for the study of complement activation levels. For all study samples, C4d levels were assayed to evaluate the activation of the classical pathway, factor Bb levels were measured to determine the status of the complement alternative pathway, C3a levels were used to examine common pathway activation, and C5a and C5b-9 were assayed for determination of the terminal pathway activation of the complement system. The reference range for each complement factor was determined using citrated plasma from 40 healthy donors. As shown in table 1, both C4d and C3a demonstrated time-dependent increases relevant to storage time. On day 7, C4d and C3a levels were five-fold higher than their baseline levels measured on day 2. In contrast, factor Bb levels remained stable and within the normal range throughout the study. Over a storage span of seven days, the terminal complement factors C5a and C5b-9 were also significantly increased, although not as dramatically as C4d and C3a. Figure 1 illustrates a progressive increase of C3 activation in all three study donors over the time of storage (2-7 days). This report, for the first time, provides strong evidence that substantial complement activation occurs in the platelet products under standard storage conditions. A longer storage time of platelet product in vitro is accompanied by a remarkable elevation of complement activation biomarkers. By examining the pattern of complement profiles in the stored platelets, we further demonstrated that the activation of the classic pathway, rather than alternative pathway, appears to be the driving event that leads up to a level of over-reactivity of the complement system. Given the fact that complement hyperactivation is known to disrupt host homeostasis and cause disease, the adverse reactions seen in platelet recipients is likely related to the infusion of C3a and C5a which are known to be potent inflammatory cytokines. The observations from this study therefore provide a new perspective in understanding the pathophysiology responsible for adverse reactions from platelet transfusions. Further studies will be required to fully evaluate the clinical impact of complement activation in transfused platelet products. Figure 1 Figure 1. Disclosures Cataland: Alexion Corporation: Honoraria, Research Funding, Speakers Bureau. Wu:Alexion Corporation: Honoraria, Research Funding, Speakers Bureau.

scholarly journals Role of Complement in Protection against Cryptococcus gattii Infection

2008 ◽  
Vol 77 (3) ◽  
pp. 1061-1070 ◽  
Author(s):  
Kileen L. Mershon ◽  
Alex Vasuthasawat ◽  
Gregory W. Lawson ◽  
Sherie L. Morrison ◽  
David O. Beenhouwer
Keyword(s):  
Complement Activation ◽  
Alternative Pathway ◽  
Complement Pathway ◽  
Wild Type ◽  
Complement Components ◽  
Factor B ◽  
Alternative Pathway Of Complement ◽  
Deficient Mice

ABSTRACT Previous studies have shown that the alternative pathway of complement activation plays an important role in protection against infection with Cryptococcus neoformans. Cryptococcus gattii does not activate the alternative pathway as well as C. neoformans in vitro. The role of complement in C. gattii infection in vivo has not been reported. In this study, we used mice deficient in complement components to investigate the role of complement in protection against a C. gattii isolate from an ongoing outbreak in northwestern North America. While factor B-deficient mice showed an enhanced rate of death, complement component C3-deficient mice died even more rapidly, indicating that the alternative pathway was not the only complement pathway contributing to protection against disease. Both C3- and factor B-deficient mice had increased fungal burdens in comparison to wild-type mice. Histopathology revealed an overwhelming fungal burden in the lungs of these complement-deficient mice, which undoubtedly prevented efficient gas exchange, causing death. Following the fate of radiolabeled organisms showed that both factor B- and C3-deficient mice were less effective than wild-type mice in clearing organisms. However, opsonization of C. gattii with complement components was not sufficient to prolong life in mice deficient in complement. Killing of C. gattii by macrophages in vitro was decreased in the presence of serum from factor B- and C3-deficient versus wild-type mice. In conclusion, we have demonstrated that complement activation is crucial for survival in C. gattii infection. Additionally, we have shown that the alternative pathway of complement activation is not the only complement pathway contributing to protection.

scholarly journals The Alternative Activation Pathway and Complement Component C3 Are Critical for a Protective Immune Response against Pseudomonas aeruginosa in a Murine Model of Pneumonia

2004 ◽  
Vol 72 (5) ◽  
pp. 2899-2906 ◽  
Author(s):  
Stacey L. Mueller-Ortiz ◽  
Scott M. Drouin ◽  
Rick A. Wetsel
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Mortality Rate ◽  
Host Defense ◽  
Complement Activation ◽  
Alternative Pathway ◽  
Alternative Activation ◽  
Phagocytic Cells ◽  
Factor B ◽  
Activation Pathways

ABSTRACT Pseudomonas aeruginosa is a leading cause of hospital-acquired pneumonia, and approximately 80% of patients with cystic fibrosis are infected with this bacterium. To investigate the overall role of complement and the complement activation pathways in the host defense against P. aeruginosa pulmonary infection, we challenged C3-, C4-, and factor B-deficient mice with P. aeruginosa via intranasal inoculation. In these studies, C3−/− mice had a higher mortality rate than C3+/+ mice. Factor B−/− mice, but not C4−/− mice, infected with P. aeruginosa had a mortality rate similar to that of C3−/− mice, indicating that in this model the alternative pathway of complement activation is required for the host defense against Pseudomonas infection. C3−/− mice had 6- to 7-fold more bacteria in the lungs and 48-fold more bacteria in the blood than did C3+/+ mice at 24 h postinfection. In vitro, phagocytic cells from C3+/+ or C3−/− mice exhibited a decreased ability to bind and/or ingest P. aeruginosa in the presence of C3-deficient serum compared to phagocytic cells in the presence of serum with sufficient C3. C3−/− mice displayed a significant increase in neutrophils in the lungs and had higher levels of interleukin-1β (IL-1β), IL-6, IL-10, KC, and MIP-2 in the lungs at 24 h postinfection than did C3+/+ mice. Collectively, these results indicate that complement activation by the alternative pathway is critical for the survival of mice infected with P. aeruginosa and that the protection provided by complement is at least in part due to C3-mediated opsonization and phagocytosis of P. aeruginosa.

scholarly journals An Engineered Complement Factor H Construct for Treatment of C3 Glomerulopathy

2018 ◽  
Vol 29 (6) ◽  
pp. 1649-1661 ◽  
Author(s):  
Yi Yang ◽  
Harriet Denton ◽  
Owen R. Davies ◽  
Kate Smith-Jackson ◽  
Heather Kerr ◽  
...  
Keyword(s):  
Chinese Hamster Ovary Cells ◽  
Alternative Pathway ◽  
Treatment Options ◽  
Chinese Hamster ◽  
Factor H ◽  
Complement Factor H ◽  
Complement Factor ◽  
C3 Glomerulopathy

Background C3 glomerulopathy (C3G) is associated with dysregulation of the alternative pathway of complement activation, and treatment options for C3G remain limited. Complement factor H (FH) is a potent regulator of the alternative pathway and might offer a solution, but the mass and complexity of FH makes generation of full-length FH far from trivial. We previously generated a mini-FH construct, with FH short consensus repeats 1–5 linked to repeats 18–20 (FH1–5^18–20), that was effective in experimental C3G. However, the serum t1/2 of FH1–5^18–20 was significantly shorter than that of serum-purified FH.Methods We introduced the oligomerization domain of human FH-related protein 1 (denoted by R1–2) at the carboxy or amino terminus of human FH1–5^18–20 to generate two homodimeric mini-FH constructs (FHR1–2^1–5^18–20 and FH1–5^18–20^R1–2, respectively) in Chinese hamster ovary cells and tested these constructs using binding, fluid-phase, and erythrocyte lysis assays, followed by experiments in FH-deficient Cfh−/− mice.Results FHR1–2^1–5^18–20 and FH1–5^18–20^R1–2 homodimerized in solution and displayed avid binding profiles on clustered C3b surfaces, particularly FHR1–2^1–5^18–20. Each construct was >10-fold more effective than FH at inhibiting cell surface complement activity in vitro and restricted glomerular basement membrane C3 deposition in vivo significantly better than FH or FH1–5^18–20. FH1–5^18–20^R1–2 had a C3 breakdown fragment binding profile similar to that of FH, a >5-fold increase in serum t1/2 compared with that of FH1–5^18–20, and significantly better retention in the kidney than FH or FH1–5^18–20.Conclusions FH1–5^18–20^R1–2 may have utility as a treatment option for C3G or other complement-mediated diseases.

Schistosoma mansoni: complement activation in human and rodent sera by living parasites of various developmental stages

Parasitology ◽  
1983 ◽  
Vol 87 (1) ◽  
pp. 75-86 ◽  
Author(s):  
A. Ruppel ◽  
U. Rother ◽  
H. Vongerichten ◽  
H. J. Diesfeld
Keyword(s):  
Schistosoma Mansoni ◽  
Complement System ◽  
Developmental Stages ◽  
Alternative Pathway ◽  
Classical Pathway ◽  
Factor B ◽  
The Complement System ◽  
Dose Dependent ◽  
Living Adult

SUMMARYLiving Schistosoma mansoni of various developmental stages were studied with respect to their ability to activate the complement system in sera of humans, mice and rats. Immunofluorescence assays demonstrated that binding of human C3 occurred on fresh schistosomula as well as on schistosomula prepared from mouse lymph-nodes or lungs and on adult schistosomes. However, rodent C3 was deposited only on fresh schistosomula. Deposition of human C3 on the worms' surface required activation of the complement system. The alternative pathway was shown to be involved in deposition of human C3 on schistosomes of all ages, whereas activation of the classical pathway was demonstrable only with fresh schistosomula. Immunoelectrophoretic studies demonstrated a dose-dependent cleavage of human C3 and conversion of factor B by living adult schistosomes. The results demonstrate that the ability of living schistosomes to activate complement in vitro is dependent not only on their developmental stage but also on the species of the serum.

scholarly journals Complement alternative pathway activation by chronic lymphocytic leukemia cells: its role in their hepatosplenic localization

Blood ◽  
1984 ◽  
Vol 63 (2) ◽  
pp. 463-467 ◽  
Author(s):  
F Praz ◽  
G Karsenty ◽  
JL Binet ◽  
P Lesavre
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Alternative Pathway ◽  
Lymphocytic Leukemia ◽  
Leukemic Cells ◽  
Complement Alternative Pathway ◽  
Acetylneuraminic Acid ◽  
Pathway Activation ◽  
Do So

Abstract Using affinity-purified 125I-F(ab')2 anti-human C3, we have investigated the ability of various leukemic cells to activate complement. Lymphocytes from patients with chronic lymphocytic leukemia (CLL) activated the alternative pathway, but cells from patients with other forms of leukemia or normal lymphocytes did not do so. The amount of C3 deposited on the CLL cells was significantly higher in patients with organomegaly (i.e., splenomegaly and/or hepatomegaly). Activation of complement by CLL cells as assessed by C3 deposition on the membrane occurred both in vivo and in vitro and was not related to the N- acetylneuraminic acid content of the membrane.

scholarly journals Complement Activation via Alternative Pathway Is Critical in the Development of Laser-Induced Choroidal Neovascularization: Role of Factor B and Factor H

2006 ◽  
Vol 177 (3) ◽  
pp. 1872-1878 ◽  
Author(s):  
Nalini S. Bora ◽  
Sankaranarayanan Kaliappan ◽  
Purushottam Jha ◽  
Qin Xu ◽  
Jeong-Hyeon Sohn ◽  
...  
Keyword(s):  
Choroidal Neovascularization ◽  
Complement Activation ◽  
Alternative Pathway ◽  
Factor H ◽  
Factor B

Development Of RNAi Therapeutics Targeting The Complement Pathway

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2471-2471 ◽  
Author(s):  
Anna Borodovsky ◽  
Kristina Yucius ◽  
Andrew Sprague ◽  
James Butler ◽  
Shannon Fishman ◽  
...  
Keyword(s):  
Cell Lines ◽  
Human Cell ◽  
Hemolytic Activity ◽  
Alternative Pathway ◽  
In Vitro Screening ◽  
Human Cell Lines ◽  
Complement Pathway ◽  
Factor B ◽  
Rnai Therapeutics

Abstract The complement system is a pivotal player in multiple hematological conditions. Antibody blockade of the C5 component of complement has been approved as a treatment for both paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic-uremic syndrome (aHUS), validating C5 as an important therapeutic target. Recently, we developed a robust RNAi therapeutics platform for the delivery of siRNAs to the liver using trivalent GalNAc conjugates, enabling silencing of hepatocyte-expressed genes following subcutaneous (SC) injection. The liver is a major source of C5 and other complement pathway components. The GalNAc conjugate technology allows rapid development of siRNAs targeting multiple members of the complement cascade and evaluation of their silencing in pre-clinical models. To examine the utility of the siRNA approach for targeting complement pathway components we designed and synthesized GalNAc conjugated siRNAs targeting rodent, primate and human C5. Potent siRNA duplexes, showing greater than 95% silencing of C5 mRNA were selected using in vitro screening in human cell lines and mouse primary hepatocytes. C5 silencing and serum hemolytic activity inhibition were evaluated in rodents using single and multi-dose SC treatment regimens. A C5-targeting siRNA conjugate demonstrated a single dose ED50 of 0.625 mg/kg in the mouse with greater than 90% silencing of serum C5 achievable at higher doses. Serum C5 silencing was durable, with recovery starting two weeks after a single SC injection We went on to examine the efficacy of C5 silencing in the rat and observed robust lowering of serum C5 with 2.5 and 5 mg/kg multi-dose regimens, resulting in up to ∼90% inhibition of complement classical pathway hemolytic activity. Evaluation of the translation of this approach to higher species is in progress. Since PNH erythrocyte lysis is thought to be mediated by the activation of the alternative pathway of complement we initiated work on the development of siRNA conjugates targeting Factor B, an essential component of the alternative pathway C3 convertase. siRNAs targeting rodent, primate and human Factor B were identified by in vitro screening and demonstrate >90% silencing of Factor B mRNA in human cell lines and primary mouse hepatocytes. Evaluation of Factor B silencing in rodent models is ongoing. siRNA-mediated silencing of liver-derived complement components is a promising novel therapeutic approach for inhibiting the activity of C5 and other complement pathway targets, with the potential to enable subcutaneous treatment for patients with PNH and related disorders. Disclosures: Borodovsky: Alnylam: Employment. Yucius:Alnylam: Employment. Sprague:Alnylam: Employment. Butler:Alnylam: Employment. Fishman:Alnylam: Employment. Nguyen:Alnylam: Employment. Vaishnaw:Alnylam: Employment. Maier:Alnylam: Employment. Kallanthottathil:Alnylam: Employment. Kuchimanchi:Alnylam: Employment. Manoharan:Alnylam: Employment. Meyers:Alnylam: Employment. Fitzgerald:Alnylam: Employment.

scholarly journals A stealth adhesion factor contributes toVibrio vulnificuspathogenicity: Flp pili play roles in host invasion, survival in the blood stream and resistance to complement activation

2019 ◽  
Author(s):  
Tra–My Duong–Nu ◽  
Kwangjoon Jeong ◽  
Soo Young Kim ◽  
Wenzhi Tan ◽  
Sao Puth ◽  
...  
Keyword(s):  
Host Cell ◽  
Complement Activation ◽  
Vibrio Vulnificus ◽  
Alternative Pathway ◽  
Molecular Genetic ◽  
Wild Type ◽  
Triple Mutant ◽  
Mutant Cells

AbstractThe tad operons encode the machinery required for adhesive Flp (fimbrial low-molecular-weight protein) pili biogenesis.Vibrio vulnificus, an opportunistic pathogen, harbors three distincttadloci. Among them, onlytad1locus was highly upregulated inin vivogrowing bacteria compared toin vitroculture condition. To understand the pathogenic roles of the threetadloci during infection, we constructed single, double and triple tad loci deletion mutants. Interestingly, only theΔtad123triple mutant cells exhibited significantly decreased lethality in mice. Ultrastructural observations revealed short, thin filamentous projections disappeared on theΔtad123mutant cells. Since the pilin was paradoxically non-immunogenic, a V5 tag was fused to Flp to visualize the pilin protein by using immunogold EM and immunofluorescence microscopy. TheΔtad123mutant cells showed attenuated host cell adhesion, delayed RtxA1 exotoxin secretion and subsequently impaired translocation across the intestinal epithelium compared to wild type, which could be partially complemented with each wild type operon. TheΔtad123mutant was susceptible to complement-mediated bacteriolysis, predominantly via the alternative pathway, suggesting stealth hiding role of the Tad pili. Taken together, all threetadloci cooperate to confer successful invasion ofV. vulnificusinto deeper tissue and evasion from host defense mechanisms, ultimately resulting in septicemia.Author SummaryTo understand the roles of the three Tad operons in the pathogenesis ofV. vulnificusinfection, we constructed mutant strain with single, double and triple Tad loci deletions. Employing a variety of mouse infection models coupled with molecular genetic analyses, we demonstrate here that all three Tad operons are required forV. vulnificuspathogenicity as the cryptic pili contribute to host cell and tissue invasion, survival in the blood, and resistance to complement activation.

Sign in / Sign up

Export Citation Format

Share Document