Activation Of Alternative Complement Pathway Research Articles

Improved therapeutic efficacy of a bifunctional anti-C5 mAb-FH SCR1-5 fusion protein over anti-C5 mAb in an accelerated mouse model of C3 glomerulopathy.

C3 glomerulopathy (C3G), a rare kidney disease caused by dysregulation of alternative pathway complement activation, is characterized by glomerular C3 deposition, proteinuria, crescentic glomerulonephritis, and renal failure. The anti-C5 monoclonal antibody (mAb) drug eculizumab has shown therapeutic effects in some but not all patients with C3G, and no approved therapy is currently available. Here, we developed and used a triple transgenic mouse model of fast progressing lethal C3G (FHm/mP-/-hFDKI/KI) to compare the therapeutic efficacy of a bifunctional anti-C5 mAb fused to a functional factor H (FH) fragment (short consensus repeat 1-5 [SCR1-5]) and the anti-C5 mAb itself. The new C3G mouse model is derived by humanizing factor D (hFDKI/KI) in a previously described FHm/mP-/- mouse that developed lethal C3G. We tested the effectiveness of these 2 complement inhibitors in triple transgenic mice with established C3G and glomerular disease. No FHm/mP-/-hFDKI/KI mice treated with vehicle survived the 30-d study period. All FHm/mP-/-hFDKI/KI mice treated with the C5 mAb-FH SCR1-5 fusion protein and 50% of mice treated with the anti-C5 mAb survived the 30-d treatment period. Moreover, mice treated with the C5 mAb-FH SCR1-5 fusion protein, but not those treated with the anti-C5 mAb, showed restored plasma alternative pathway complement control. The C5 mAb-FH SCR1-5 fusion protein reversed glomerular disease to a greater degree than the anti-C5 mAb. These data suggest that simultaneously inhibiting the terminal and proximal complement pathways, by anti-C5 mAb and FH SCR1-5, respectively, can reverse established C3G and is more efficacious than inhibiting the terminal pathway alone. A similar approach may be effective in treating human C3G.

Alternative Complement Pathway in Carotid Atherosclerosis: Low Plasma Properdin Levels Associate With Long-Term Cardiovascular Mortality.

Complement activation may promote atherosclerosis. Yet, data on the to which extent complement, and more specifically the alternative complement pathway, is activated in patients with carotid atherosclerosis and related to adverse outcome in these patients, are scarce. We measured, by ELISA, plasma levels of factor D, properdin, C3bBbP (C3 convertase), and factor H in patients with advanced carotid atherosclerosis in a Discovery (n=324) and in a Validation (n=206) cohort in relation to adverse outcome (mean follow-up 7.8 and 6.6 years, respectively). Our major findings were as follows. Compared with healthy controls, patients with carotid atherosclerosis had increased plasma levels of factor D, properdin, and C3bBbP (P<0.001), but not factor H, an inhibitor of the alternative complement pathway, compared with controls. Although patients with carotid atherosclerosis had elevated levels of properdin compared with controls, within these patients, low plasma levels of properdin (ie, <median levels of properdin in the patient group) were significantly associated with cardiovascular mortality. This was seen in both the Discovery (HR 2.31, P=0.019) and the Validation cohort (hazard ratio [HR], 2.81, P=0.014). In contrast to the low circulating levels, high intraplaque properdin levels (assessed by ELISA) correlated with markers of plaque vulnerability and symptomatology. We show a strong and independent association of low plasma properdin levels with cardiovascular mortality in 2 cohorts. Conversely, the plaque properdin levels linked to features of plaque vulnerability, potentially reflecting increased deposition at the site of inflammation or local production of properdin in the atherosclerotic lesion indicating local enhanced alternative complement pathway activation.

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.

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. ConclusionsfB 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.

Synergistic Benefits of Dietary Silymarin and Selenium on Growth, Immune Functions, Antioxidants, and Gut/Liver Health of Thinlip Mullet (Liza ramada) Juveniles

Abstract This study investigates the synergistic impact of silymarin (SI) levels combined with inorganic selenium (sodium selenite: Se) on growth, feed utilization, biochemical parameters, antioxidants, innate immunity, intestinal and liver histology, and gene expression of thinlip mullet (Liza ramada) juveniles. The experimental design involved thinlip mullets initially weighing 3.5±0.13 g, distributed in a completely randomized design with 30 fish per hapa (0.5 × 0.5 × 1 m), and conducted in triplicate over 60 days. Seven experimental diets were employed, including a control (without SI and Se supplementation), a negative control (with only Se supplementation), and four treatments with varying levels of silymarin (250, 450, 650, 850 mg/kg) alongside selenium (0.5 mg/kg diet). The growth performance results highlighted significant enhancements in final body weight, weight gain, and specific growth rate, particularly in the SI 850 mg/kg + Se treatment. Survival rates, feed intake, and feed conversion ratios showed positive trends across the SI-Se supplemented groups. Biochemical profiles of serum exhibited that the control diet induced elevated concentrations of glucose, cholesterol, alanine aminotransferase, aspartate aminotransferase, and urea, while Se or SI supplementation significantly mitigated these levels, with the lowest concentrations observed in the SI-Se supplemented groups. Moreover, SI supplementation increased serum protein content. Antioxidant enzyme activities, represented by superoxide dismutase (SOD), catalase (CAT), and catalase (GPx), demonstrated notable improvements in the SI-Se fortified groups, with significantly elevated GPx activity compared to the Se-supplemented and control groups. Immune system responses, including lysozyme, bactericidal, nitro-blue tetrazolium (NBT%), and serum alternative complement pathway (ACH50) activities, were highest in the SI-Se augmented groups. SI and Se in L. ramada reduce liver pro-inflammatory gene expression (IL-1 β, hepcidin) vs. control group. Histological examinations of the intestine and liver depicted structural enhancements, especially at moderate and high levels of SI with Se supplementation. The results indicate improved intestinal villi morphology and hepatic architecture, supporting the positive influence of dietary treatments on the health of thinlip mullet juveniles. In conclusion, the combined supplementation of SI at 850 mg/kg diet and Se at 0.5 mg/kg diet positively influenced the growth, biochemical profiles, antioxidant status, immune responses, gene expression, and histological integrity of thinlip mullet juveniles, providing valuable insights for optimizing aquafeed formulations.

Walter Brendel and the dawn of transplantation research in Germany.

Walter Brendel was a physiologist who headed the Institut of Experimental Surgery at the University of Munich (LMU) from 1961 until 1989. His legendary career began with the development of an anti-human lymphocyte globulin (ALG) at his Institute during the late 1960s. The initial successful treatment of a small number of patients culminated in the co-treatment of the first successfully heart-transplanted patient in Capetown, South Africa (successful reversal with ALG of an acute allograft rejection). Walter Brendel was a pioneering personality whose work has laid a wide platform for the promotion of interdisciplinarily conducted innovative research programs in various domains of translational science and medicine. Among the many innovative achievements, the most notable are: discovery of involvement of the alternative pathway of complement activation in hyperacute xenograft rejection; induction of immunological tolerance to horse IgG as a means to prevent anaphylactic reactions during ALG therapy; development and clinical implementation of the extracorporeal shock wave lithotripsy for extracorporeal destruction of renal and ureteral calculi. The legacy of Brendel continues with the foundation of the Walter-Brendel Kolleg für Transplantationsmedizin (i.e., the German Transplant School for Transplantation Medicine), which has been held annually since 1994.

Immunodeficiency: Complement disorders.

The complement system is an important component of innate and adaptive immunity that consists of three activation pathways. The classic complement pathway plays a role in humoral immunity, whereas the alternative and lectin pathways augment the innate response. Impairment, deficiency, or overactivation of any of the known 50 complement proteins may lead to increased susceptibility to infection with encapsulated organisms, autoimmunity, hereditary angioedema, or thrombosis, depending on the affected protein. Classic pathway defects result from deficiencies of complement proteins C1q, C1r, C1s, C2, and C4, and typically manifest with features of systemic lupus erythematosus and infections with encapsulated organisms. Alternative pathway defects due to deficiencies of factor B, factor D, and properdin may present with increased susceptibility to Neisseria infections. Lectin pathway defects, including Mannose-binding protein-associated serine protease 2 (MASP2) and ficolin 3, may be asymptomatic or lead to pyogenic infections and autoimmunity. Complement protein C3 is common to all pathways, deficiency of which predisposes patients to severe frequent infections and glomerulonephritis. Deficiencies in factor H and factor I, which regulate the alternative pathway, may lead to hemolytic uremic syndrome. Disseminated Neisseria infections result from terminal pathway defects (i.e., C5, C6, C7, C8, and C9). Diagnosis of complement deficiencies involves screening with functional assays (i.e., total complement activity [CH50], alternative complement pathway activity [AH50], enzyme-linked immunosorbent assay [ELISA]) followed by measurement of individual complement factors by immunoassay. Management of complement deficiencies requires a comprehensive and individualized approach with special attention to vaccination against encapsulated bacteria, consideration of prophylactic antibiotics, treatment of comorbid autoimmunity, and close surveillance.

Enhancement of Candida albicans phagocytosis and inhibitory potency of Alternative Complement Pathway by an arabinoxylan extracted from Plantago ciliata Desf. Seeds and its oligosaccharides

Leveraging bioactive compounds with immunomodulatory effects to boost immune functions represents a promising strategy for therapeutic intervention. The main objective of this work was to investigate the influence of the partial acid hydrolysis of an arabinoxylan extracted from Plantago ciliata Desf. seeds into oligosaccharides on its immunomodulatory effect. The resulting oligosaccharides and their polymer were evaluated for their potential to improve the phagocytic capacity (PC) and the phagocytic activity (PA) of polymorphonuclear neutrophils (PMNs) through the uptake of Candida albicans and to moderate alternative complement pathway (ACP) activation. As a result, the arabinoxylan derived from P. ciliata seeds (AXPCs) and its oligosaccharides (AXOPCs) significantly enhanced the PC of PMN cells, with EC50 values of 0.14 ± 0.23 and 0.12 ± 0.10 mg/mL, respectively. Zymosan used as a reference exhibited the highest PC with an EC50 0.07 ± 0.08 mg/mL. However, for PA, zymosan still demonstrated the highest activity with an EC50 of 0.22 ± 0.46 mg/mL compared to 0.33 ± 1.36 and 0.30 ± 0.74 mg/mL for AXPCs and AXOPCs, respectively. Moreover, AXPCs and AXOPCs were tested as moderator inhibitors of the complement system, showing maximum inhibition percentages of 40.11 ± 8.38% and 50.57 ± 10.45% at 1 mg/mL, with IC50 values of 1.49 ± 0.40 and 1.02 ± 0.20 mg/mL, respectively, compared to 61.52 ± 7.17% and 70.89 ± 5.78% for heparin used as a reference. These results suggest that AXPCs and AXOPCs can serve as relevant therapeutic immunomodulatory factors.

Therapeutic targeting of factor D and MASP3 in complement-mediated diseases: Lessons learned from mouse studies.

The alternative pathway (AP) plays a major role in many complement-mediated human diseases. Factor D (FD), a rate-limiting enzyme in AP complement activation, is an attractive therapeutic target. Unlike other complement proteins, FD is synthesized primarily in adipose tissue, and its levels in human blood are relatively low. However, because of FD's high turnover rate, therapeutic targeting with monoclonal antibodies and chemical inhibitors has been challenging. The recent discovery that FD activity is regulated by mannose-binding lectin-associated serine protease 3 (MASP3), through conversion of a zymogen to mature FD, has sparked interest in MASP3 inhibition as a new way to block FD function and AP complement activity. Here, we review studies of mouse models of FD and MASP3 inhibition. We additionally discuss the lessons learned from these studies and their implications for therapeutic targeting of human FD and MASP3.

Safety and efficacy of complement factor H (CFH) inhibitor GT103 in advanced non-small cell lung cancer (NSCLC): Results of a phase Ib first in human dose escalation study.

e14588 Background: CFH is a complement regulatory protein that protects cells from alternative complement pathway activation. Neutralizing antibodies against CFH on tumor cells increase deposition of C3b, facilitate antibody-dependent-cellular phagocytosis and complement dependent cytotoxicity, inhibit tumor growth, and modulate anti-tumor immunity. GT103 is a first-in class, fully human-derived IgG3 anti-CFH monoclonal antibody that recognizes a tumor specific epitope on CFH and has shown anti-tumor activity in preclinical models. Methods: We conducted a phase Ib, first-in-human, dose escalation trial evaluating safety and preliminary efficacy of GT103 in patients (pts) with advanced NSCLC refractory to standard therapies. Pts received GT103 intravenously across six dose levels/schedules following 3+3 design. Primary objectives were to determine maximum tolerated dose (MTD), recommended phase II dose (RP2D), and pharmacokinetic profile of GT103. Secondary objectives were to assess objective response rate, progression free survival (PFS), and overall survival (OS). Here we present updated safety and efficacy results of the study. Results: 31 pts were enrolled from 6/2020 to 9/2023 (median age 63yrs (range, 23-79), 61% had adenocarcinoma, 32% had previously treated brain metastasis). MTD was not reached. Treatment related AEs (TRAEs) observed in ≥10% pts included fatigue (19%), anemia (16%), diarrhea (16%), and nausea (13%). 3 pts developed ≥ grade 3 TRAE, including acute kidney injury, decreased lymphocyte count, and anemia. The best treatment response was stable disease in 9 (29%) pts. Median(m) PFS and mOS were 6 weeks (95% CI 6.0-6.1) and 25.7 weeks (95% CI 19.1-30.6), respectively. 24-week PFS and OS were 9.7% (95% CI 2.5-22.9%) and 50.6% (95% CI 31.9-66.6%), respectively. PD-L1 expression was available in 25 pts. No statistically significant difference (p=0.33) was noted in mPFS between PD-L1 positive (TPS &gt; 1%) vs negative (TPS ≤1%) pts. KRAS and EGFR mutation status was available for 22pts. mPFS and mOS were numerically longer in pts with KRAS positive vs negative disease. While there was no difference in mPFS, 24-weeks PFS was 0 vs 16.7% (95% CI 4.1-36.5%) EGFR MUT vs wild type disease. Biomarker analysis of complement regulatory proteins, FcGR expression and polymorphisms, and changes in sC5b-9 is underway. Conclusions: GT103 was well tolerated across all dose levels. The RP2D of 10mg/kg IV every 3 weeks was selected, although PK modeling will be performed to optimize the dosing schedule. Encouraging anti-tumor activity was seen in heavily pretreated pts with advanced NSCLC with a subset of patients experiencing stable disease lasting for longer than 6 months. Additional biomarker analysis is ongoing. A phase II trial combining GT103 with pembrolizumab in pts with advanced NSCLC is currently enrolling. Clinical trial information: NCT04314089 .

#1793 Association of low serum complement C3 with reduced renal survival in ANCA associated vasculitis

Abstract Background and Aims ANCA-associated vasculitis (AAV) is a condition that remains poorly understood. Recent data suggest the existence of a complement alternative pathway activation in the pathogenesis of this disease. And recent studies have correlated low complement levels to unfavourable outcomes. Our study aimed to determine whether low serum C3 levels could be used to estimate the severity of AAV and predict renal survival. Method Our study enrolled 26 patients diagnosed with AAV between January 2013 and January 2023. C3 levels were assessed at the time of diagnosis, and patients were categorized into two groups: those with low serum C3 levels and those with normal serum C3 levels (0.9–1.8 g/l). We examined the correlation between serum C3 levels and the severity of AAV at the time of diagnosis, as well as renal survival. Results The average age at diagnosis was 52.5 years, with 15 male patients (57.69%). All patients had kidney involvement, 30% of patients had respiratory symptoms (mostly due to diffuse alveolar hemorrhage) 42% had Ear Nose Throat system involvement 15% had nervous symptoms and 38% had skin signs. The mean Birmingham Vasculitis Activity Score (BVAS) at presentation was 20, and the average serum creatinine level was 360 µmol/l. The mean serum C3 and C4 levels were 108.3 and 24.5 mg/dL, respectively. Forty-two percent of the patients (eleven patients) had a low serum C3 level at presentation. Low C3 level was significantly correlated with poor renal survival (p: 0.031) and relapse after 6 months of immunosuppressive treatment (p: 0.02). Furthermore, remission at 6 months was significantly more frequent in patients with normal C3 levels. Conclusion The assessment of C3 level in AAV can be a valuable tool to predict the disease severity. Hypocomplementemia can predict worse renal outcome. This phenotype may confer a poor response to usual immunosuppressive approaches. Corresponding patients may greatly benefit from complement-targeting therapy.

Targeted complement inhibition using bispecific antibodies that bind local antigens and endogenous complement regulators.

Complement activation protects against infection but also contributes to pathological mechanisms in a range of clinical conditions such as autoimmune diseases and transplant rejection. Complement-inhibitory drugs, either approved or in development, usually act systemically, thereby increasing the risk for infections. We therefore envisioned a novel class of bispecific antibodies (bsAbs) which are capable of site-directed complement inhibition by bringing endogenous complement regulators in the vicinity of defined cell surface antigens. Here, we analyzed a comprehensive set of obligate bsAbs designed to crosslink a specific target with either complement regulator factor H (FH) or C4b-binding protein (C4BP). The bsAbs were assessed for their capacity to inhibit complement activation and cell lysis in an antigen-targeted manner. We observed that the bsAbs inhibited classical, lectin, and alternative pathway complement activation in which sufficient endogenous serum FH and C4BP could be recruited to achieve local inhibition. Importantly, the bsAbs effectively protected antigen-positive liposomes, erythrocytes, and human leukocytes from complement-mediated lysis. In conclusion, localized complement inhibition by bsAbs capable of recruiting endogenous human complement regulators (such as FH or C4BP) to cell surfaces potentially provides a novel therapeutic approach for the targeted treatment of complement-mediated diseases.

Phenotypic and Therapeutic Evaluation of Humanized C3 Transgenic Mice as a Model for C3 glomerulopathy-Like Autoimmune Disease

Abstract C3 glomerulopathy (C3G) encompasses a range of kidney disorders with autoimmune and genetic origins, where dysregulated alternative pathway (AP) complement activation stands as the underlying cause. This study develops a transgenic mouse strain that overexpresses human C3, thereby spontaneously generating a rapidly progressing and severe murine model of C3G. The C3G phenotype observed in humanized C3 transgenic mice may arise from a dysregulated interaction between human C3 protein and various mouse complement proteins, resulting in uncontrolled C3 activation via the AP. Male humanized C3 transgenic mice exhibit increased morbidity early in life. Proteinuria initiates at 4 weeks of age, accompanied by an elevation in the albumin/creatinine ratio. Significantly increased serum levels of ALT, AST, ALP, LDH, and CK in humanized C3 transgenic male mice compared to wild-type mice indicate liver and heart injuries. Moreover, serum T-CHOL and HDL levels are significantly reduced, suggesting anemia and malnutrition. Pathohistological analysis of the kidney reveals various renal lesions. Oral administration of Lnp023, a small-molecule inhibitor of complement factor B, effectively increases body weight and serum hC3 levels, improves anemia, and preserves liver, heart, and renal function. In conclusion, this novel model contributes significantly to unraveling the mechanisms underlying C3G and exploring potential therapeutic interventions.

CFH Haploinsufficiency and Complement Alterations in Early-Onset Macular Degeneration.

Complement dysregulation is a key component in the pathogenesis of age-related macular degeneration (AMD) and related diseases such as early-onset macular drusen (EOMD). Although genetic variants of complement factor H (CFH) are associated with AMD risk, the impact of CFH and factor H-like protein 1 (FHL-1) expression on local complement activity in human retinal pigment epithelium (RPE) remains unclear. We identified a novel CFH variant in a family with EOMD and generated patient induced pluripotent stem cell (iPSC)-derived RPE cells. We assessed CFH and FHL-1 co-factor activity through C3b breakdown assays and measured complement activation by immunostaining for membrane attack complex (MAC) formation. Expression of CFH, FHL-1, local alternative pathway (AP) components, and regulators of complement activation (RCA) in EOMD RPE cells was determined by quantitative PCR, western blot, and immunostaining. Isogenic EOMD (cEOMD) RPE was generated using CRISPR/Cas9 gene editing. The CFH variant (c.351-2A>G) resulted in loss of CFH and FHL-1 expression and significantly reduced CFH and FHL-1 protein expression (∼50%) in EOMD iPSC RPE cells. These cells exhibited increased MAC deposition upon exposure to normal human serum. Under inflammatory or oxidative stress conditions, CFH and FHL-1 expression in EOMD RPE cells paralleled that of controls, whereas RCA expression, including MAC formation inhibitors, was elevated. CRISPR/Cas9 correction restored CFH/FHL-1 expression and mitigated alternative pathway complement activity in cEOMD RPE cells. Identification of a novel CFH variant in patients with EOMD resulting in reduced CFH and FHL-1 and increased local complement activity in EOMD iPSC RPE supports the involvement of CFH haploinsufficiency in EOMD pathogenesis.

PolySialic Acid Nanoparticles Actuate Complement-Factor-H-Mediated Inhibition of the Alternative Complement Pathway: A Safer Potential Therapy for Age-Related Macular Degeneration.

The alternative pathway of the complement system is implicated in the etiology of age-related macular degeneration (AMD). Complement depletion with pegcetacoplan and avacincaptad pegol are FDA-approved treatments for geographic atrophy in AMD that, while effective, have clinically observed risks of choroidal neovascular (CNV) conversion, optic neuritis, and retinal vasculitis, leaving room for other equally efficacious but safer therapeutics, including Poly Sialic acid (PSA) nanoparticle (PolySia-NP)-actuated complement factor H (CFH) alternative pathway inhibition. Our previous paper demonstrated that PolySia-NP inhibits pro-inflammatory polarization and cytokine release. Here, we extend these findings by investigating the therapeutic potential of PolySia-NP to attenuate the alternative complement pathway. First, we show that PolySia-NP binds CFH and enhances affinity to C3b. Next, we demonstrate that PolySia-NP treatment of human serum suppresses alternative pathway hemolytic activity and C3b deposition. Further, we show that treating human macrophages with PolySia-NP is non-toxic and reduces markers of complement activity. Finally, we describe PolySia-NP-treatment-induced decreases in neovascularization and inflammatory response in a laser-induced CNV mouse model of neovascular AMD. In conclusion, PolySia-NP suppresses alternative pathway complement activity in human serum, human macrophage, and mouse CNV without increasing neovascularization.

High-dose systemic adeno-associated virus vector administration causes liver and sinusoidal endothelial cell injury

We analyzed retrospective data from toxicology studies involving administration of high doses of adeno-associated virus expressing different therapeutic transgenes to 21 cynomolgus and 15 rhesus macaques. We also conducted prospective studies to investigate acute toxicity following high-dose systemic administration of enhanced green fluorescent protein-expressing adeno-associated virus to 10 rhesus macaques. Toxicity was characterized by transaminitis, thrombocytopenia, and alternative complement pathway activation that peaked on post-administration day 3. Although most animals recovered, some developed ascites, generalized edema, hyperbilirubinemia, and/or coagulopathy that prompted unscheduled euthanasia. Study endpoint livers from animals that recovered and from unscheduled necropsies of those that succumbed to toxicity were analyzed via hypothesis-driven histopathological and unbiased single-nucleus RNA sequencing. All liver cell types expressed high transgene transcript levels at early unscheduled timepoints that subsequently decreased. Thrombocytopenia coincided with sinusoidal platelet microthrombi and sinusoidal endothelial injury identified via immunohistology and single-nucleus RNA sequencing. Acute toxicity, sinusoidal injury, and liver platelet sequestration were similarly observed with therapeutic transgenes and enhanced green fluorescent protein at doses ≥1×1014 GC/kg, suggesting it was the consequence of high-dose systemic adeno-associated virus administration, not green fluorescent protein toxicity. These findings highlight a potential toxic effect of high-dose intravenous adeno-associated virus on nonhuman primate liver microvasculature.

Inhibition of the Alternative Complement Pathway May Cause Secretion of Factor B, Enabling an Early Detection of Pancreatic Cancer.

This study aims to elucidate the cellular mechanisms behind the secretion of complement factor B (CFB), known for its dual roles as an early biomarker for pancreatic ductal adenocarcinoma (PDAC) and as the initial substrate for the alternative complement pathway (ACP). Using parallel reaction monitoring analysis, we confirmed a consistent ∼2-fold increase in CFB expression in PDAC patients compared with that in both healthy donors (HD) and chronic pancreatitis (CP) patients. Elevated ACP activity was observed in CP and other benign conditions compared with that in HD and PDAC patients, suggesting a functional link between ACP and PDAC. Protein-protein interaction analyses involving key complement proteins and their regulatory factors were conducted using blood samples from PDAC patients and cultured cell lines. Our findings revealed a complex control system governing the ACP and its regulatory factors, including Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation, adrenomedullin (AM), and complement factor H (CFH). Particularly, AM emerged as a crucial player in CFB secretion, activating CFH and promoting its predominant binding to C3b over CFB. Mechanistically, our data suggest that the KRAS mutation stimulates AM expression, enhancing CFH activity in the fluid phase through binding. This heightened AM-CFH interaction conferred greater affinity for C3b over CFB, potentially suppressing the ACP cascade. This sequence of events likely culminated in the preferential release of ductal CFB into plasma during the early stages of PDAC. (Data set ID PXD047043.).

Complement System Deficiencies in Elite Athletes.

Although regular physical activity improves immune competency and reduces the prevalence of inflammatory diseases, strenuous training in elite athletes is associated with an increased susceptibility to infectious complications. Therefore, the objective of our study was to assess the routinely examined parameters of the complement system in elite athletes. The study was carried out in a cohort of elite athletes (n = 134) and healthy control subjects (n = 110). In all subjects, besides a routine laboratory check-up, serum concentrations of the C3 and C4 complement components, mannose-binding lectin (MBL), as well as activation of all three complement pathways were determined. Compared to healthy controls, lower C3 and C4 complement component concentrations were observed in elite athletes (0.96 ± 0.1 vs. 1.08 ± 0.2mg/L, and 0.18 ± 0.1 vs. 0.25 ± 0.1mg/L, respectively, p < 0.05); with much higher frequency rates of C3 and C4 deficiencies in athletes (31.3 vs. 14.5%, and 6 vs. 0%, p < 0.05). Simultaneously, athletes had much higher frequency rates of deficiencies of activation of classical and alternative complement pathways; while, deficiency of activation of the lectin pathway was similar in both cohorts. We confirmed a high frequency of defects in the complement system in elite athletes. Lower concentrations of C3 and C4 complement components, with high frequencies of deficiencies of the classical and alternative complement activation pathways were the most prevalent disorder of the complement system in elite athletes. Further studies are needed to uncover the functional impacts of these observations upon the susceptibility to infectious diseases.

The spectrum of thrombotic microangiopathy related to monoclonal gammopathy.

Recent studies showed a high prevalence of monoclonal gammopathy (MG) in patients with thrombotic microangiopathy (TMA) aged over 50years and suggested that complement dysregulation is pivotal for the disease to develop. Here, we studied this premise in seven patients with TMA and coexisting MG. Patients with TMA on kidney biopsy and/or peripheral blood were recruited from the prospective COMPETE cohort (NCT04745195) and Limburg Renal Registry. Patients were screened for complement dysregulation, including genetics/factor H autoantibodies (FHAA) and functional ex vivo testing on microvascular endothelial cells. Seven (8%) out of 84 patients with TMA presented with a coexisting MG. MG clustered in patients aged over 50years (n/N=6/32, 19%). C4 and/or C3 levels were low in three patients, while four patients presented with normal complement levels. None of the patients carried rare variants in complement genes. Massive ex vivo C5b9 formation on the endothelium was noted in one patient; purified IgG from this patient caused massive ex vivo C5b9 formation via the alternative pathway of complement activation, pointing to complement dysregulation in the fluid phase. Kidney biopsies from other nephropathies linked to MG rarely exhibited concurrent TMA (n/N=1/27, 4%). MG clustered in patients with TMA aged over 50 years. TMA and coexisting MG represents a heterogeneous disease spectrum, including a small subset of patients who may present with complement dysregulation.

The dietary effects of two strain probiotics (Leuconostoc mesenteroides, Lactococcus lactis) on growth performance, immune response and gut microbiota in Nile tilapia (Oreochromis niloticus).

The aquaculture industry has been growing rapidly over the past few decades to meet future animal protein demands. However, intensive aquaculture industry faces challenges such as growth abnormalities, high mortality rates, water quality and intestinal health deterioration. Administering probiotics can serve as a nutritional strategy to enhance the immune system and growth performance of fish influxes of gut microbiota. This study aimed to evaluate the impact of two dietary probiotic strains L. mesenteroides and L. lactis on the growth performance, immunity, and gut microbiota of Nile tilapia (Oreochromis niloticus). Fish were fed with basal and experimental diet supplemented by both L. mesenteroides and L. lactis bacteria at 106 cell/g for 8 weeks. Feeding a combination of L. mesenteroides and L. lactis resulted in significant improvements in feed utilization parameters (PER and FER) (P < 0.001), alternative complement pathway activity, intestinal lactic acid bacteria count (P < 0.012), mucus secretion (P < 0.002) and peroxidase activity (P < 0.001) compared to the control groups. Serum lysozyme activity also exhibited a significant increase in the L. mesenteroides and L. lactis dietary group (P < 0.011) compared to the control and single probiotic supplemented diet groups. Furthermore, Nile tilapia fed the L. mesenteroides and L. lactis supplemented diet showed enhanced growth performance metrics (weight gain, final weight and specific growth rate) compared to those fed control and single probiotic supplemented diets (P < 0.022). Additionally, superoxide dismutase activity was significantly elevated in the L.mesenteroides and L. lactis supplemented diet groups compared to the control and single L.mesenteroides supplemented diet groups (P < 0.017). These findings strongly indicate that a dietary combination of L. mesenteroides and L. lactis probiotics could function as a beneficial immunostimulant feed supplement in Nile tilapia aquaculture.