Activation Of Complement Pathway Research Articles

Extrarenal manifestations of atypical hemolytic uremic syndrome: a systematic review and meta-analysis.

Atypical Hemolytic Uremic Syndrome (aHUS) is categorized as a thrombotic microangiopathy (TMA), which arises due to abnormal or unregulated complement pathway activation. While the disease frequently affects renal blood vessels, it can also involve multiple other organ systems. This review examines the prevalence and clinical outcomes of aHUS patients with extrarenal involvement. A comprehensive literature search was performed using PubMed/Medline, Embase, the Web of Science Core Collection, and CINAHL. Search terms included 'aHUS', 'extrarenal', and specific organ systems such as neurological, gastrointestinal, and cardiovascular. Patient data was collected on clinical characteristics, including extrarenal symptoms, lab findings, genetic mutations, and adverse events. Meta-analysis was conducted using R software, version 3.1.0. A total of 47 studies were reviewed, comprising 890 aHUS patients, ranging in age from 3 months to 66 years. Common genetic abnormalities included factor H (CFH) mutations, seen in 12% (84/700 patients) across 19 studies, and anti-FH IgG autoantibodies, identified in 27.1% (102/376 patients) from 10 studies. The central nervous system was the most frequently involved extrarenal site [28% (240/858 patients) from 32 studies], with seizures as the predominant CNS symptom. Gastrointestinal symptoms were next most common [31% (230/741 patients) from 25 studies], followed by cardiovascular involvement [16% (97/607) from 23 studies]. Kidney failure was reported in 13.2% (61/463 patients) from 11 studies, with an overall mortality rate of 8.9% (56/632 patients) reported across 27 studies. Around 20-30% of aHUS patients experience extrarenal manifestations, with neurologic symptoms occurring most frequently. Due to the high costs and limited availability, genetic data is rarely reported, and studies are often small, underscoring the need for larger, multi-center cohort studies. 466915. Approximately 20-30% of patients with atypical Hemolytic Uremic Syndrome (aHUS) experienced extrarenal manifestations, with neurologic involvement being the most common. Current studies in aHUS patients are heterogeneous and inconsistent in reporting complement mutations with extrarenal manifestations. This systematic review highlights the significance of multi-system assessment in aHUS patients and the need for larger, multi-centered cohort studies.

The Janus-faced nature of complement in hemodialysis: interplay between complement, inflammation, and bioincompatibility unveiling a self-amplifying loop contributing to organ damage.

In hemodialysis (HD), complement activation, bioincompatibility, and inflammation are intricately intertwined. In the 1970s, as HD became a routine therapy, the observation of complement pathway activation and transient leukopenia by cellulosic dialysis membranes triggered the bioincompatibility debate and its clinical relevance. Extensive deliberations have covered definitions, assessment markers, scope, and long-term clinical consequences of membrane-dependent bioincompatibility reactions. While complement pathways' interplay with coagulation and inflammation has been delineated, HD's focus has primarily been on developing more biocompatible membranes using advanced technologies. Recent advances and understanding of the current HD delivery mode (4-hour sessions, thrice weekly) suggest that factors beyond membrane characteristics play a significant role, and a more complex, multifactorial picture of bioincompatibility is emerging. Chronic activation of the complement system and persistent low-grade "uremic inflammation" in chronic kidney disease (CKD) and HD lead to premature inflammaging of the kidney, resembling aging in the general population. Cellular senescence, modulated by complement activation and the uremic milieu, contributes to chronic inflammaging. Additionally, the formation of neutrophil extracellular traps (NETs, process of NETosis) during HD and their biological activity in the interdialytic period can lead to dialysis-induced systemic stress. Thus, complement-inflammation manifestations in HD therapies extend beyond traditional membrane-related bioincompatibility consequences. Recent scientific knowledge is reshaping strategies to mitigate detrimental consequences of bioincompatibility, both technologically and in HD therapy delivery modes, to improve dialysis patient outcomes.

Redefining Calciphylaxis as a Uniquely Bone Forming Subcutaneous C5b-9-Mediated Microvascular Injury Syndrome Associated With Localized Subcutaneous and Systemic Complement Pathway Activation.

Microvascular thrombosis is key to the pathogenesis of calciphylaxis. C5b-9-mediated microvascular injury reflective of complement pathway activation could be a key pathophysiologic event. We conducted a retrospective multicenter study of 24 patients who have had biopsy-supported calciphylaxis from the 2010-2022 data base from Emory where C5b-9 immunohistochemistry (IHC) had not been conducted and the 2019-2023 data base from Cornell where C5b-9 IHC was done as part of the routine calciphylaxis work up. IHC for C5b-9 on lesional biopsy specimens was assessed and correlated with routine light microscopic findings and clinical features. Most of the patients in our study had uremic calciphylaxis associated with obesity, diabetes, dialysis, hypertension, hyperparathyroidism and elevated serum phosphorus. Most patients did not have defined procoagulant and/or hyperviscosity states. The vascular pathology was predominantly limited to the subcutaneous fat and ranged from a calcific intimal arteriopathy to microvascular thrombosis with endothelial injury with or without endothelial calcification. In most cases (ie, in excess of 80%), there was prominent deposition of C5b-9 within the vasculature including the microvasculature and arteries of the fat at least localized to injured vessels suggesting a causal association. In about 40% of cases, there was evidence of systemic complement pathway activation revealed by concurrent dermal microvascular C5b-9 deposition. Calciphylaxis is characterized by subcuticular vascular changes that reflect an interplay between complement triggered endothelial cell injury, resultant vascular thrombosis, and subsequent abluminal calcification. Complement inhibition therapy defines a potential intervention that should be explored.

Anesthesia Management of Cold Agglutinin Disease in a Pregnant Patient: A Case Report.

Cold agglutinin disease (CAD), a rare autoimmune hemolytic anemia (AIHA), is characterized by hemolysis triggered by activation of the classical complement pathway. AIHA is estimated to affect one in 100,000 people in the general population; however, its incidence in pregnant women is unclear due to the scarcity of published studies. Here, we present the case of a 37-year-old female (G2P1102) who presented for a repeat Cesarean section. Her peripartum course was complicated by anemia (hemoglobin 7.9 g/dL, hematocrit 29.4%) attributed to cold agglutinin disease, necessitating the transfusion of 20 units of blood during this pregnancy. She had been receiving prednisone 10 mg daily for anemia. Cold temperatures can trigger the activation of cold-reactive antibodies, leading to red blood cells agglutination (clumping together). Preventing hypothermia reduces the likelihood of cold-induced hemolysis, which is the primary therapeutic strategy for cold agglutinin disease. Anesthetic management for the cesarean section was accomplished via spinal anesthesia, complemented by pain control through bilateral transversus abdominis plane (TAP) blocks. This multidisciplinary approach facilitated effective pain management while considering the patient's underlying condition.

Complement factor B, not the membrane attack complex component C9, promotes neointima formation after arterial wire injury

Background and aimsVascular restenosis due to neointima hyperplasia limits the long-term patency of stented arteries, resulting in angioplasty failure. The complement system has been implicated in restenosis. This study aimed to investigate the role of complement factor B (fB), an essential component of the alternative pathway of complement activation, in neointima formation. MethodsAngioplasty wire injury was conducted using 12-week-old mice deficient in fB or C9 (the main component of the membrane attacking complex, C5b-9) and littermate controls and neointima formation were assessed. Vascular smooth muscle cell (SMC) and endothelial cell (EC) proliferation and migration were examined in vitro. ResultsfB was mainly detected in SMCs of stenotic arteries from humans and mice. Deletion of fB substantially reduced the neointima area and intima-to-media area ratio without affecting the media area at 28 days after injury. At 7 days after injury, fB deficiency decreased SMC proliferation, unaltering neointimal macrophage infiltration and EC reendothelialization. Vascular SMC-expressed fB, not the circulation-sourced fB, played an essential role in SMC proliferation and migration in vitro. fB deficient mice exhibited lower levels of the soluble form of C5b-9, however, deletion of C9 did not alter neointima formation after wire injury, consistent with the null impact of C9 deficiency on SMC proliferation in vitro. ConclusionfB promotes neointima formation following wire-induced artery injury independent of forming the membrane-attacking complex. This is attributable to fB-dependent SMC proliferation and migration without affecting EC function. Targeting fB might protect against restenosis after percutaneous coronary intervention.

Systemic Toxicity of Recombinant Adeno-Associated Virus Gene Therapy Vectors.

Recombinant adeno-associated virus (rAAV) vectors have emerged as a promising tool for gene therapy. However, the systemic administration of rAAV vectors is not without risks, particularly for dose levels >1 × 1014 viral genome per kilogram of body weight (vg/kg). rAAV-associated toxicities can variably manifest either acutely or in a delayed manner. Acute toxicities often present shortly after administration and can include severe immune responses, hepatotoxicity, and thrombotic microangiopathy (TMA). Delayed toxicities, on the other hand, may emerge weeks to months post-treatment, potentially involving chronic liver damage or prolonged immune activation. Thrombotic microangiopathy is often associated with complement activation and endothelial damage. The activation of the complement system can additionally trigger a cascade of inflammatory responses, exacerbating systemic toxicity. While many of these toxicities are reversible with appropriate medical intervention, there have been instances where the adverse effects were severe enough to lead to fatalities. Both human and animal studies have reported these adverse effects, highlighting the critical importance of thorough preclinical testing. However, a differential toxicity profile associated with systemic AAV administration exists between humans and nonhuman primates (NHPs), in which certain toxicities reported in humans are yet to be observed in NHPs, and vice versa. This review aims to explore the recent literature on systemic rAAV toxicities, focusing on dose levels, the role of the complement activation pathway, endothelial injury, TMA, hepatotoxicity, and the bidirectional translational safety profiles from both human and animal studies.

Characteristics of glomerulonephritis with dominant C1q precipitation compared to corresponding glomerulonephritis without C1q staining on immunofluorescent examination.

The clinical significance and renal outcomes of C1q nephropathy (C1qN) are unclear; therefore, the implications of C1qN as a new pathological entity are uncertain. We compared the clinical characteristics of glomerulonephritis reclassified into cases that meet the definition of C1qN and glomerulonephritis not included in the definition of C1qN. In total, 21,697 patients who underwent native kidney biopsy at 18 hospitals throughout Korea between 1979 and 2018 were retrospectively enrolled. A total of 77 patients were selected from the group that met the definition of C1qN after reclassification; however, six patients were excluded because of secondary systemic disease. Data on outcomes, incidences of end-stage renal disease (ESRD), and mortality were collected from the hospital records, the Korean Society of Nephrology's ESRD registry, and Statistics of Korea and were then unified based on Korean ethnicity. Characteristics of pathological findings classified into C1qN, without C1q stain, and with nondominant C1q stain that did not fulfill the criteria for C1qN were compared. No differences in clinicopathological findings and incidence of ESRD were evident (matched by age and sex) between glomerulonephritis cases reclassified into the group that met the definition of C1qN and those without C1q staining. Decreased proteinuria in patients with membranous nephropathies reclassified into the group that met the definition of C1qN was the only significant finding. Immunoglobulins showed higher intensity on immunofluorescence staining of the group that met the definition of C1qN. Additionally, C3 intensity was higher in reclassified immunoglobulin A nephropathy and membranous nephropathies. Overall, reclassification into the group that met the definition of C1qN did not indicate a different clinicopathological identity. C1q activation and presumed classical complement pathway activation in kidney tissues in C1qN could not be confirmed. Hence, further studies are needed.

Complement activation by IgM autoantibodies linked to immune-mediated neuropathies depends on C2.

Complement factor C2 is a potential therapeutic target in immune-mediated neuropathies. However, literature suggests that classical complement pathway activation may proceed to C3 in the absence of C2, a so-called "C2 bypass." Here, we evaluated a C2 bypass mechanism during complement activation by pathogenic human IgM from patients with immune-mediated neuropathies. IgM autoantibodies from 51 patients with multifocal motor neuropathy (MMN) or anti-myelin-associated glycoprotein (MAG) neuropathy (AMN) were used to activate complement in exvivo disease models. C2 bypass was evaluated using C2-depleted (C2D) serum and a therapeutic anti-C2 antibody. In two different disease models of MMN, IgM anti-GM1 and IgM anti-GM2 autoantibodies from MMN patients were bound to induced pluripotent stem cell-derived motor neurons and Schwann cells, respectively, and fixed C3 upon incubation with fresh serum. C3 fixation was inhibited by anti-C2 and did not occur with C2D serum. Similarly, in an AMN model, IgM anti-MAG antibodies were incubated with fresh serum fixed C3, which in all cases was abrogated in the absence of C2 or in the presence of anti-C2. In exvivo disease models of MMN and AMN, complement activation by IgM autoantibodies from 51 patients was in all cases dependent on C2 and was inhibited by an antihuman C2 antibody. No evidence of a C2 bypass mechanism was found.

Praziquantel and factor H recruitment differentially affect the susceptibility of Schistosoma mansoni to complement-mediated damage.

Schistosomes are highly efficient evaders of human immunity, as evident by their ability to survive in human blood for years. How they protect themselves against the constant attack by a key element of innate immunity, the complement system, has remained unclear. In this study, new light is shed on the interaction between distinct life-cycle stages of Schistosoma mansoni and the human complement system. We demonstrate that schistosomula, the young stage assumed immediately after cercaria penetration of the skin, are extremely vulnerable towards complement-mediated killing as only 10-20% survive. The survival rate increases to 70% already within 30 minutes and reaches close to 100% within two hours. Pathway-specific complement inhibitors revealed the alternative pathway of complement activation as the main contributor to killing and damage of the schistosomula. Moreover, the complement regulator factor H is recruited by the schistosomula in this early stage to evade killing. Surviving parasites appear fully viable despite the ongoing complement attack, as demonstrated by the deposition of C3 fragments. However, when exposed to the widely used schistocidal drug praziquantel, the vulnerability of 24 h-old schistosomula towards complement-mediated killing is notably increased; no such effect was observed for mefloquine or oxamniquine. Similar to the younger life-cycle stages, adult worms remain under complement attack. C3 fragments were found all over the outer surface (tegument), deposited mostly on the ridges and not on the tubercles. The recruitment of factor H merits more detailed studies that pinpoint the molecules involved and elucidate the novel possibilities to intercept the uncovered immune evasion therapeutically. That praziquantel and complement work in synergy is surprising and may in the future result in enhanced understanding of the drug's mechanism of action.

IMMU-31. DAMAGE RESPONSE FROM SYSTEMIC RNA VACCINATION RESTORES HUMORAL IMMUNITY IN GLIOBLASTOMA

Abstract Therapies against glioblastoma (GBM) remain stymied by poor penetration across the blood-brain barrier (BBB) and systemic immunotolerance. These outcomes necessitate development of therapies simultaneously targeted to tumors while engineering peripheral immunity to co-localize for synergistic responses. We developed RNA loaded lipid particles (LPs) to simultaneously function as inducers of cytotoxic responses in the GBM tumor microenvironment (TME) and as systemic activators of peripheral immunity. RNA-LP mediated response was studied in mice bearing KR158b tumors and in canines and humans with spontaneous glioma and glioblastoma respectively. We found that RNA-LPs could localize to the brain TME of animals bearing murine gliomas and rapidly upregulate damage associated signaling pathways including p53-CDKN2A. This correlates with increased gene signatures for complement and proteosome processing. Simultaneously, in the periphery, RNA-LPs increase integrin expression on activated T cells and ICAM expression in brain tumors helping steer T cell translocation across the BBB. In canines with malignant gliomas, response to RNA-LPs correlated with increasing tumor size suggesting pseudoprogression. Similar to murine glioma, canine gliomas harvested within 48h of vaccine administration demonstrated rapid increases in complement and p53 pathway activation. In one human patient treated with RNA-LPs per NCT04573140 (PNOC020 trial), we demonstrate biopsy confirmed pseudoprogression with increases in p53 pathway signaling and complement activation. In post-treatment tumor biopsy samples, there was increased hyperexpanded post-infusion intratumoral IgH clones. Systemic administration of RNA-LP elicits damage response in the TME that predisposes complement activation and humoral immunity. Coupled with peripheral recruitment of T cells that can translocate across the BBB, RNA-LPs elicit potent bi-directional adaptive immunotherapy against GBM.

Aryl-hydrocarbon receptor in smooth muscle cells protect against dioxin induced adverse remodeling of atherosclerosis.

Environmental exposure to dioxin has been linked to increased myocardial infarction. Smooth muscle cells (SMC) in the coronary vasculature play a critical role in atherosclerotic plaque remodeling due to their phenotypic plasticity, however, the detailed mechanism linking dioxin exposure to adverse SMC modulation is not well understood. Single-cell RNA and ATAC sequencing and histological analyses were performed on the aorta from mouse models of atherosclerosis exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) or control. Primary human coronary artery SMC (HCASMC) treated in culture with TCDD were used to perform RNA-Seq, ATAC-Seq, and functional phenotypic assays. ChIP-Seq was performed with antibodies against Aryl-hydrocarbon receptor (AHR) and TCF21, two of known SMC modulating transcription factors. Modulated SMC were the most transcriptionally responsive cell type to dioxin in the atherosclerotic aorta. Dioxin accelerated disease phenotype by promoting a modulated SMC phenotype early, resulting in increased lesion size, migration of SMC, and macrophage recruitment to the lesion. We found C3 expressing modulated SMCs to be likely contributing to the increased macrophage recruitment and inflammation. Analysis of the RNA-Seq data from HCASMC treated with TCDD showed differential enrichment of biological pathways related to cell migration, localization, and inflammation. Furthermore, ATAC-Seq data showed a significant activation for pathways regulating vascular development, cell migration, inflammation, and apoptosis. With TCDD treatment, there was also enrichment of AHR ChIP-Seq peaks, while the TCF21 enrichment decreased significantly. The SMC-specific Ahr knockout resulted in increased oxidative stress in SMC, increased lesion size and macrophage content, and loss of SMC lineage cells in the lesion cap when exposed to TCDD, consistent with a more vulnerable plaque phenotype. Dioxin adversely remodels atherosclerotic plaque by accelerating the SMC- phenotypic modulation, and increasing inflammation and oxidative stress resulting in increased macrophage recruitment and lesion size. Dioxin may adversely affect the SMC phenotype and disease state by affecting the TCF21 occupancy in the open chromatin regions. Furthermore, we observed that SMC-specific deletion of Ahr in mice resulted in worsening of dioxin mediated SMC modulation and atherosclerosis, suggesting that Ahr in SMC confers protection against dioxin by promoting a stable plaque phenotype and reducing dioxin induced oxidative stress. Exposure to dioxin, an environmental pollutant present in tobacco smoke and air pollution, accelerates smooth muscle cell modulation, and atherosclerosis.Dioxin exposure leads to inflammatory smooth muscle cell phenotype characterized by complement pathway activation and increased macrophage recruitment to plaqueAryl-hydrocarbon receptor in SMC protects against oxidative stress, and promotes a stable plaque phenotype.

The prognostic role of activation of the complement pathways in the progression of advanced IgA nephropathy to end-stage renal disease

IntroductionThe role of complement system in late stage of IgA nephropathy (IgAN) remains unknown. We therefore investigated the effects of complement system on worsening kidney function in advanced (stage 4 CKD) IgAN.MethodsRenal specimens of 69 IgAN patients who underwent renal biopsy during stage 4 CKD between 2010 and 2021, were stained using immunofluorescence (IF) and immunohistochemistry (IHC) for glomerular complement components. The primary outcome was progression to end-stage renal disease (ESRD). Associations of complement components with baseline clinicopathological characteristics and outcomes were assessed using multivariable Cox regression and Spearman analyses.ResultsDuring a median follow-up of 18.0 months, 26 (37.7%) patients progressed to ESRD and none died. C1q and C3 deposition were detected in 12 and 66 patients, respectively. Higher eGFR [hazards ratio (HR), 0.852, 95% confidence interval (CI), 0.756–0.959; P = 0.008], higher C3 intensity (HR, 2.955, 95%CI, 1.063–8.220; P = 0.038) and T1-2 score (HR, 2.576, 95%CI, 1.205–5.576, P = 0.015) were predictive of time to ESRD in CKD 4 stage IgAN. Significant expressions of C1q (P = 0.005), C4d (P < 0.001), factor B (P < 0.001), C3 (P = 0.042) and C5b-9 (P = 0.004) were identified in ESRD group than in non-ESRD group by IHC, while MBL expression was low. Although they were not associated with baseline 24 h-UP, higher factor B and C1q expressions were both correlated with a lower baseline eGFR (P < 0.001 and = 0.04, respectively) and the deterioration of kidney function during follow-up (P = 0.046 and 0.015, respectively).ConclusionComplement deposition in IgAN patients with stage 4 CKD portends a faster deterioration of kidney function. Activation of classical and alternative complement pathways plays a major role in this stage.

High expression of PLA2G2A in fibroblasts plays a crucial role in the early progression of carotid atherosclerosis

BackgroundIn mouse models of atherosclerosis, knockout of the PLA2G2A gene has been shown to reduce the volume of atherosclerotic plaques. Clinical trials have demonstrated the potential of using the sPLA2 inhibitor Varespladib in combination with statins to reduce lipid levels. However, this approach has not yielded the expected results in reducing the risk of cardiovascular events. Therefore, it is necessary to further investigate the mechanisms of PLA2G2A.MethodsSingle-cell transcriptome data from two sets of carotid plaques, combined with clinical patient information. were used to describe the expression characteristics of PLA2G2A in carotid plaques at different stages. In order to explore the mechanisms of PLA2G2A, we conducted enrichment analysis, cell–cell communication analysis and single-cell regulatory network inference and clustering analyses. We validated the above findings at the cellular level.ResultsOur findings indicate that PLA2G2A is primarily expressed in vascular fibroblasts and shows significant cell interactions with macrophages in the early-stage, especially in complement and inflammation-related pathways. We also found that serum sPLA2 levels have stronger diagnostic value in patients with mild carotid artery stenosis. Subsequent comparisons of single-cell transcriptomic data from early and late-stage carotid artery plaques corroborated these findings and predicted transcription factors that might regulate the progression of early carotid atherosclerosis (CA) and the expression of PLA2G2A.ConclusionsOur study discovered and validated that PLA2G2A is highly expressed by vascular fibroblasts and promotes plaque progression through the activation of macrophage complement and coagulation cascade pathways in the early-stage of CA.

Revisiting Virchow’s triad: exploring the cellular and molecular alterations in cerebral venous congestion

BackgroundCerebral venous thrombosis (CVT) is a rare but serious condition that can lead to significant morbidity and mortality. Virchow’s triad elucidates the role of blood hypercoagulability, blood flow dynamics, and endothelial damage in the pathogenesis of CVT. Cerebral venous congestion (CVC) increases the risk of cerebral venous sinus thrombosis and can lead to recurrent episodes and residual symptoms. However, the precise mechanism by which blood congestion leads to thrombosis remains unclear. Our objective was to investigate the cellular and molecular alterations linked to CVC through analysis of the pathological morphology of venous sinus endothelial cells and transcriptomic profiling.ResultsThis study demonstrated a remarkable correlation between CVC and the phenotypic transformation of endothelial cells from an anticoagulant to a procoagulant state. The findings revealed that cerebral venous stasis results in tortuous dilatation of the venous sinuses, with slow blood flow and elevated pressure in the sinuses and damaged endothelial cells of the retroglenoid and internal jugular vein ligation (JVL) rat model. Mechanistically, analysis of transcriptomic results of cerebral venous sinus endothelial cells showed significant activation of platelet activation, complement and coagulation cascades pathway in the JVL rats. Furthermore, the expression of von Willebrand factor (vWF) and coagulation factor VIII (F8) in the complement and coagulation cascades and Fgg and F2 in the platelet activation was increased in the cerebral venous sinuses of JVL rats than in sham rats, suggesting that endothelial cell injury in the venous sinus induced by CVC has a prothrombotic effect. In addition, endothelial cell damage accelerates coagulation and promotes platelet activation. Significantly, the concentrations of vWF, F2 and F8 in venous sinus blood of patients with internal jugular vein stenosis were higher than in their peripheral blood.ConclusionCollectively, our data suggest that CVC can induce endothelial cell damage, which then exhibits a procoagulant phenotype and ultimately increases the risk of CVT. This research contributes to our understanding of the pathophysiology of CVC associated with procoagulant factors and reexamines the components of Virchow’s triad in the context of CVC.

Safety and Efficacy of Avacopan in Patients with C3 Glomerulopathy: Randomized, Double-Blind Clinical Trial.

Complement 3 (C3) glomerulopathy is a rare autoimmune disorder characterized by activation of the alternative complement pathway with isolated or dominant C3 deposition in glomeruli. Patients with C3 glomerulopathy may develop progressive deterioration in kidney function and kidney failure. We studied the safety and efficacy of avacopan 30 mg twice daily in patients with C3 glomerulopathy (N=57) with elevated (> 244 ng/mL) and normal (≤ 244 ng/mL) levels of C5b-9 in a randomized, double-blind, placebo-controlled, phase 2 trial, with kidney biopsies performed pre-randomization and at 26 and 52 weeks. The primary outcome was the percent change from baseline to week 26 in C3 glomerulopathy histologic index for disease activity. The study was conducted in patients with C3 glomerulopathy, including C3 glomerulonephritis and DDD. The median study duration was 60.0 weeks (interquartile range 59.9 to 61.0). There were no significant differences in the primary outcome between the avacopan and the placebo group; least square mean treatment difference (95% CI) = -0.0 (-1.9 to 1.8). The secondary measures of efficacy including C3 Glomerulopathy Histological Index for disease chronicity, urine protein:creatinine ratio (UPCR), and estimated glomerular filtration rate (eGFR) were not different between treatment groups. The overall incidence and type of adverse events for both treatment groups were comparable. No deaths were reported during the study, and no new safety signals were detected. The primary end point for the study was not met; other clinical effects of avacopan to improve certain key kidney function parameters and slow disease progression were variable and require further evaluation.

Transplacental SARS-CoV-2 protein ORF8 binds to complement C1q to trigger fetal inflammation

Prenatal SARS-CoV-2 infection is associated with higher rates of pregnancy and birth complications, despite that vertical transmission rates are thought to be low. Here, multi-omics analyses of human placental tissues, cord tissues/plasma, and amniotic fluid from 23 COVID-19 mother-infant pairs revealed robust inflammatory responses in both maternal and fetal compartments. Pronounced expression of complement proteins (C1q, C3, C3b, C4, C5) and inflammatory cytokines (TNF, IL-1α, and IL-17A/E) was detected in the fetal compartment of COVID-19-affected pregnancies. While ~26% of fetal tissues were positive for SARS-CoV-2 RNA, more than 60% of fetal tissues contained SARS-CoV-2 ORF8 proteins, suggesting transplacental transfer of this viral accessory protein. ORF8-positive fetal compartments exhibited increased inflammation and complement activation compared to ORF8-negative COVID-19 pregnancies. In human placental trophoblasts in vitro, exogenous ORF8 exposure resulted in complement activation and inflammatory responses. Co-immunoprecipitation analysis demonstrated that ORF8 binds to C1q specifically by interacting with a 15-peptide region on ORF8 (C37-A51) and the globular domain of C1q subunit A. In conclusion, an ORF8-C1q-dependent complement activation pathway was identified in COVID-19-affected pregnancies, likely contributing to fetal inflammation independently of fetal virus exposure.

Unveiling ficolins: diagnostic and prognostic biomarkers linked to the Tumor Microenvironment in Lung Cancer

BackgroundFicolins (FCNs) are a family of proteins, comprising FCN1, FCN2 and FCN3, and integral to the immune system which have been implicated in the onset and progression of tumors. Despite their recognized roles, a comprehensive analysis of FCNs in lung cancer remains elusive.MethodsWe employed a variety of bioinformatics tools, including UCSC, SangerBox, Ualcan, cBioPortal, String, Metascape, GeneMANIA, TIDE, CTD, and CAMP databases to investigate the differential expression, diagnostic and prognostic significance, genetic alterations, functional enrichment, immune infiltration, and potential immunotherapeutic implications of FCN1, FCN2, and FCN3 in lung squamous cell carcinoma (LUSC) and lung adenocarcinoma (LUAD). Additionally, RT-qPCR and immunohistochemistry were utilized to validate the expressions of FCNs at the mRNA and protein levels in LUSC and LUAD.ResultsOur comprehensive bioinformatic analysis, supported by RT-qPCR and immunohistochemistry, revealed that the expressions of FCN1, FCN2 and FCN3 were consistently downregulated in both LUSC and LUAD tumor tissues. FCNs demonstrated significant diagnostic potential for LUSC and LUAD, with the area under the receiver operating characteristic curve (AUC) for FCN1 and FCN3 exceeding 0.90. Furthermore, FCN2 and FCN3 showed a strong negative correlation with overall survival (OS) in LUSC, whereas FCN1 and FCN2 were positively correlated with OS in LUAD, suggesting their prognostic value in lung cancer. Gene enrichment analysis indicated that FCNs were predominantly associated with the complement system and complement activation pathways. Immune infiltration analysis further revealed a significant positive correlation between FCNs and the presence of neutrophils and resting mast cells. Our analysis of immunotherapy outcomes revealed a significant disparity in the immunophenoscore (IPS) among lung cancer patients treated with immune checkpoint inhibitors (ICIs), distinguishing those with high FCN expression from those with low FCN expression. Additionally, we identified small molecule compounds related to FCNs and drugs pertinent to LUSC and LUAD.ConclusionFCNs held promise as diagnostic and prognostic biomarkers for LUSC and LUAD. This study also elucidated the relationship of FCNs with the tumor microenvironment, offering novel insights into the immunotherapeutic landscape for LUSC and LUAD.

Circulating Immune Complexes and Complement Activation in Sensitized Kidney Transplant Recipients.

Chronic antibody-mediated rejection in kidney transplantation is a common cause of graft loss in the late post-transplant period. In this process, the role of the classical complement activation pathway is crucial due to the formation of immune complexes between donor-specific antibodies (DSAs) and donor antigens and the attachment of the C1q complement fragment. This study aimed to determine the levels of circulating C1q immunocomplexes (CIC-C1q) and complement activation (CH50), in sensitized kidney transplant recipients (KTRs). In this cross-sectional study we used serum samples from KTRs with de novo or preformed DSAs (n = 14), KTRs without DSAs (n = 28), and 22 subjects with no history of chronic kidney disease (controls). C1q immunocomplexes and CH50 concentration in serum were measured with the enzyme immunoassay (EIA) kit MicroVue CIC-C1q (Quidel, Athens, OH, USA) and EIA kit MicroVue CH50 (Quidel, OH, USA), respectively. Higher concentrations of CIC-C1q was observed in KTRs with DSAs in comparison with controls and with KTRs with no DSAs (6.8 ± 2.7 and 4.8 ± 1.9 vs. 5.0 ± 1.2 μg Eq/mL, respectively, p < 0.01). We found no difference in CIC-C1q between KTRs with no DSAs and controls. CIC-C1q levels were positively correlated with DSA titer. CH50 levels were decreased in KTRs with DSAs in comparison with controls and KTRs with no DSAs (39 ± 15 vs. 68 ± 40 and 71 ± 34 U Eq/mL, respectively, p < 0.01). There was no difference in CH50 between DSA-negative KTRs and controls. Kidney transplant recipients with DSAs had increased serum levels of C1q immunocomplexes and increased classical pathway complement activation.

CSF complement proteins are elevated in prodromal to moderate Alzheimer's disease patients and are not altered by the anti-tau antibody semorinemab.

Growing evidence suggests a role for neuroinflammation in Alzheimer's disease (AD). We investigated complement pathway activity in AD patient cerebrospinal fluid (CSF) and evaluated its modulation by the anti-tau antibody semorinemab. Immunoassays were applied to measure CSF complement proteins C4, factor B (FB), C3 and their cleavage fragments C4a, C3a, and factor Bb (Bb) in AD patients and a separate cognitively unimpaired (CU) cohort. All measured CSF complement proteins were increased in AD versus CU subjects, with C4a displaying the most robust increase. Finally, semorinemab did not have a significant pharmacodynamic effect on CSF complement proteins. Elevated levels of CSF C4a, C4, C3a, C3, Bb, and FB are consistent with complement activation in AD brains. Despite showing a reduction in CSF soluble tau species, semorinemab did not impact complement protein levels or activity. Further studies are needed to determine the value of complement proteins as neuroinflammation biomarkers in AD. Cerebrospinal fluid (CSF) complement proteins C4a, C3a, Bb, C4, C3, and factor B levels were increased in Alzheimer's disease (AD) patients compared to a separate cognitively unimpaired (CU) cohort. Baseline CSF complement protein levels were correlated with neuro-axonal degeneration and glial activation biomarkers in AD patients. The investigational anti-tau antibody semorinemab did not impact CSF complement protein levels or activity relative to the placebo arm.

Pharmacokinetics, pharmacodynamics, safety, and tolerability of a single-dose riliprubart, an anti-C1s humanized monoclonal antibody in East-Asian adults: results from a Phase 1, randomized, open-label trial

ABSTRACT Objectives This Phase 1 trial was planned to investigate the pharmacokinetics (PK), pharmacodynamics (PD), safety, and tolerability of a single dose of riliprubart in healthy East-Asian adult participants. Methods A single-center, parallel-group, randomized, open-label, single-dose study was performed to evaluate the PK, PD, safety, and tolerability of riliprubart (50 mg/kg intravenous [IV] or 600 mg subcutaneous [SC]) in 37 healthy East-Asian (Chinese, Japanese, and Korean) participants. Results Riliprubart was slowly absorbed after SC administration (median tmax: 7.01–10.48 days) and showed a long half-life after IV or SC administration (mean: 9.52–11.0 weeks), with a bioavailability of 74.6% after SC administration. The PD profiles, which are evaluated by classical complement pathway activity or CH50, were similar and largely overlapped across East-Asian participants after a single IV or SC dose. Riliprubart was safe and well tolerated in participants following a single IV or SC dose. Conclusions Riliprubart was safe and well tolerated and demonstrated favorable PK and PD profiles in healthy East-Asian participants following a single IV or SC dose. These results are comparable to first-in-human study results from non-East-Asian participants and support the same dosing regimen of riliprubart for global simultaneous clinical development. Clinical trial registration This trial is registered at https://cris.nih.go.kr (identifier: KCT0006571).