Activation Of Classical Pathway Research Articles

The Biological Role of Macrophage in Lung and Its Implications in Lung Cancer Immunotherapy.

The lungs are the largest surface of the body and the most important organ in the respiratory system, which are constantly exposed to the external environment. Tissue Resident Macrophages in lung constitutes the important defense against external pathogens. Macrophages connects the innate and adaptive immune system, and also plays important roles in carcinogenesis and cancer immunotherapy. Lung cancer is the leading cause of cancer-related death worldwide, with an overall five-year survival rate of only 21%. Macrophages that infiltrate or aggregate in lung tumor microenvironment are defined as tumor-associated macrophages (TAMs). TAMs are the main components of immune cells in the lung tumor microenvironment. The differentiation and maturation process of TAMs can be roughly divided into two different types: classical activation pathway produces M1 tumor-associated macrophages, and bypass activation pathway produces M2 tumor-associated macrophages. Studies have found that TAMs are related to tumor invasion, metastasis, and treatment resistance, and show potential as a new target for tumor immunotherapy. Therefore, the biological function of macrophages in lung and the role of TAMs in the occurrence, development, and treatment of lung cancer are discussed in this paper.

Crystal structure of Trichinella spiralis calreticulin and the structural basis of its complement evasion mechanism involving C1q.

Helminths produce calreticulin (CRT) to immunomodulate the host immune system as a survival strategy. However, the structure of helminth-derived CRT and the structural basis of the immune evasion process remains unclarified. Previous study found that the tissue-dwelling helminth Trichinella spiralis produces calreticulin (TsCRT), which binds C1q to inhibit activation of the complement classical pathway. Here, we used x-ray crystallography to resolve the structure of truncated TsCRT (TsCRTΔ), the first structure of helminth-derived CRT. TsCRTΔ was observed to share the same binding region on C1q with IgG based on the structure and molecular docking, which explains the inhibitory effect of TsCRT on C1q-IgG-initiated classical complement activation. Based on the key residues in TsCRTΔ involved in the binding activity to C1q, a 24 amino acid peptide called PTsCRT was constructed that displayed strong C1q-binding activity and inhibited C1q-IgG-initiated classical complement activation. This study is the first to elucidate the structural basis of the role of TsCRT in immune evasion, providing an approach to develop helminth-derived bifunctional peptides as vaccine target to prevent parasite infections or as a therapeutic agent to treat complement-related autoimmune diseases.

The molecular determinants of classical pathway complement inhibition by OspEF-related proteins of Borrelia burgdorferi

The complement system serves as the first line of defense against invading pathogens by promoting opsonophagocytosis and bacteriolysis. Antibody-dependent activation of complement occurs through the classical pathway and relies on the activity of initiating complement proteases of the C1 complex, C1r and C1s. The causative agent of Lyme disease, Borrelia burgdorferi, expresses two paralogous outer surface lipoproteins of the OspEF-related protein family, ElpB and ElpQ, that act as specific inhibitors of classical pathway activation. We have previously shown that ElpB and ElpQ bind directly to C1r and C1s with high affinity and specifically inhibit C2 and C4 cleavage by C1s. To further understand how these novel protease inhibitors function, we carried out a series of hydrogen-deuterium exchange mass spectrometry (HDX-MS) experiments using ElpQ and full-length activated C1s as a model of Elp/protease interaction. Comparison of HDX-MS profiles between unbound ElpQ and the ElpQ/C1s complex revealed a putative C1s-binding site on ElpQ. HDX-MS-guided, site-directed ElpQ mutants were generated and tested for direct binding to C1r and C1s using surface plasmon resonance. Several residues within the C-terminal region of ElpQ were identified as important for protease binding, including a single conserved tyrosine residue that was required for ElpQ- and ElpB-mediated complement inhibition. Collectively, our study identifies key molecular determinants for classical pathway protease recognition by Elp proteins. This investigation improves our understanding of the unique complement inhibitory mechanism employed by Elp proteins which serve as part of a sophisticated complement evasion system present in Lyme disease spirochetes.

A single C1q A chain promotes leukocytes phagocytosis/chemotaxis and mediates bacterial clearance in Japanese flounder Paralichthys olivaceus

Complement component 1q (C1q) is the first component involved in the activation of complement classical pathway and acts as a linker of the innate and adaptive immune system. The C1q is a macromolecular containing three chains i.e. C1q A, C1q B, and C1q C. In teleost, the biological functions of C1q A chain is still unclear. In this study, we investigated the immunological properties of a C1q A chain from Japanese flounder (Paralichthys olivaceus) (PoC1qA). PoC1qA containing the conserved CLR and C1q domain, shares 45.4%–78.6% identities with that of other teleost and mammals. PoC1qA expression pattern was constitutive in tissues, with higher expression in spleen and liver. Besides, the PoC1qA expression was notably regulated by pathogenic invasion. In vitro the recombinant PoC1qA (rPoC1qA) could directly bind a variety of bacteria, and affect bacterial growth and survival. Moreover, PoC1qA could influence the hemolysis and bactericidal activity of fish serum. Additionally, rPoC1qA could interact with the membrane of peripheral blood leucocytes (PBLs), promoting the PBLs phagocytosis and chemotaxis, and enhancing the activation of PBLs. Consistently, in vivo rPoC1qA could restrain the bacterial replication in immune tissues. To sum up, our observations added the first evidence that an A chain of teleost C1q plays vital roles in mediating PBLs activity and antibacterial immunity.

Transient Binding Dynamics of Complement System Pattern Recognition Molecules on Pathogens.

Previous studies of pattern recognition molecules (PRMs) of the complement system have revealed difficulties in observing binding on pathogens such as Aspergillus fumigatus and Escherichia coli, despite complement deposition indicative of classical and lectin pathway activation. Thus, we investigated the binding dynamics of PRMs of the complement system, specifically C1q of the classical pathway and mannose-binding lectin (MBL) of the lectin pathway. We observed consistently increasing deposition of essential complement components such as C4b, C3b, and the terminal complement complex on A. fumigatus and E. coli. However, C1q and MBL binding to the surface rapidly declined during incubation after just 2-4 min in 10% plasma. The detachment of C1q and MBL can be linked to complement cascade activation, as the PRMs remain bound in the absence of plasma. The dissociation and the fate of C1q and MBL seem to have different mechanistic functions. Notably, C1q dynamics were associated with local C1 complex activation. When C1s was inhibited in plasma, C1q binding not only remained high but further increased over time. In contrast, MBL binding was inversely correlated with total and early complement activation due to MBL binding being partially retained by complement inhibition. Results indicate that detached MBL might be able to functionally rebind to A. fumigatus. In conclusion, these results reveal a (to our knowledge) novel "hit-and-run" complement-dependent PRM dynamic mechanism on pathogens. These dynamics may have profound implications for host defense and may help increase the functionality and longevity of complement-dependent PRMs in circulation.

Sex- and species-associated differences in complement-mediated immunity in humans and rhesus macaques.

The complement system can be viewed as a "moderator" of innate immunity, "instructor" of humoral immunity, and "regulator" of adaptive immunity. While sex is known to affect humoral and cellular immune systems, its impact on complement in humans and rhesus macaques, a commonly used non-human primate model system, has not been well studied. To address this knowledge gap, we analyzed serum samples from 90 humans and 72 rhesus macaques for the abundance and activity of the complement system components. While sequences of cascade proteins were highly conserved, dramatically different levels were observed between species. Whereas the low levels detected in rhesus samples raised questions about the suitability of the test for use with macaque samples, differences in levels of complement proteins were observed in male and female humans. Levels of total and antibody-dependent deposition of C1q and C3b on a glycosylated antigen differed between humans and rhesus, suggesting differential recognition of glycans and balance between classical and alternative activation pathways. Functional differences in complement-mediated lysis of antibody-sensitized cells were observed in multiple assays and showed that human females frequently exhibited higher lytic activity than human males or rhesus macaques, which typically did not exhibit such sex-associated differences. Other differences between species and sexes were observed in more narrow contexts-for only certain antibodies, antigens, or assays. Collectively, these results expand knowledge of sex-associated differences in the complement system in humans, identifying differences absent from rhesus macaques.IMPORTANCEThe complement system is a critical part of host defense to many bacterial, fungal, and viral infections. In parallel, rich epidemiological, clinical, and biomedical research evidence demonstrates that sex is an important biological variable in immunity, and many sex-specific differences in immune system are intimately tied with disease outcomes. This study focuses on the intersection of these two factors to define the impact of sex on complement pathway components and activities. This work expands our knowledge of sex-associated differences in the complement system in humans and also identifies the differences that appear to be absent in rhesus macaques, a popular non-human primate model. Whereas differences between species suggest potential limitations in the ability of macaque model to recapitulate human biology, knowledge of sex-based differences in humans has the potential to inform clinical research and practice.

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.

Usefulness and analytical performances of complement multiplex assay for measuring complement biomarkers in plasma

IntroductionThe complement system is involved in numerous diseases, through diverse mechanisms and degree of activation. With the emergence of complement targeting therapeutic, simple and accessible tools to evaluate the extent of complement activation are strongly needed. MethodsWe evaluated two multiplex panels, measuring complement activation fragments (C4a, C3a, C5a, Bb, Ba, sC5b9) and intact components or regulators (C1q, C2, C3, C4, C5, FD, FP, FH, FI). The specificity of each measurement was assessed by using complement proteins depleted sera and plasma collected from patients with complement deficiencies. Normal values distribution was estimated using 124 plasma samples from healthy donors and complement activation profile was assessed in plasma collected from 31 patients with various complement-mediated disorders. ResultsWe observed good inter-assay variation. All tested protein deficiencies were accurately detected. We established assay-specific reference values for each analyte. Except for C3, C4 and C4a, the majority of the measurements were in good agreement with references methods or published data. ConclusionOur study substantiates the utility of the Complement Multiplex assay as a tool for measuring complement activation and deficiencies. Quantifying complement cleavage fragments in patients exhibiting classical or alternative pathway activation allowed evaluating the activation state of the whole cascade.

Complement components regulates ferroptosis in CVB3 viral myocarditis by interatction with TFRC

BackgroundDysregulated cell death machinery and an excessive inflammatory response in Coxsackievirus B3(CVB3)-infected myocarditis are hallmarks of an abnormal host response. Complement C4 and C3 are considered the central components of the classical activation pathway and often participate in the response process in the early stages of virus infection. MethodsIn our study, we constructed a mouse model of CVB3-related viral myocarditis via intraperitoneal injection of Fer-1 and detected myocarditis and ferroptosis markers in the mouse myocardium. Then, we performed co-IP and protein mass spectrometry analyses to explore which components interact with the ferroptosis gene transferrin receptor (TFRC). Finally, functional experiments were conducted to verify the role of complement components in regulating ferroptosis in CVB3 infection. ResultsIt showed that the ferroptosis inhibitor Fer-1 could alleviate the inflammation in viral myocarditis as well as ferroptosis. Mechanistically, during CVB3 infection, the key factor TFRC was activated and inhibited by Fer-1. Fer-1 effectively prevented the consumption of complement C3 and overload of the complement product C4b. Interestingly, we found that TFRC directly interacts with complement C4, leading to an increase in the product of C4b and a decrease in the downstream complement C3. Functional experiments have also confirmed that regulating the complement C4/C3 pathway can effectively rescue cell ferroptosis caused by CVB3 infection. ConclusionsIn this study, we found that ferroptosis occurs through crosstalk with complement C4 in viral myocarditis through interaction with TFRC and that regulating the complement C4/C3 pathway may rescue ferroptosis in CVB3-infected cardiomyocytes.

Inhibition of the C1s Protease and the Classical Complement Pathway by 6-(4-Phenylpiperazin-1-yl)Pyridine-3-Carboximidamide and Chemical Analogs.

The classical pathway (CP) is a potent mechanism for initiating complement activity and is a driver of pathology in many complement-mediated diseases. The CP is initiated via activation of complement component C1, which consists of the pattern recognition molecule C1q bound to a tetrameric assembly of proteases C1r and C1s. Enzymatically active C1s provides the catalytic basis for cleavage of the downstream CP components, C4 and C2, and is therefore an attractive target for therapeutic intervention in CP-driven diseases. Although an anti-C1s mAb has been Food and Drug Administration approved, identifying small-molecule C1s inhibitors remains a priority. In this study, we describe 6-(4-phenylpiperazin-1-yl)pyridine-3-carboximidamide (A1) as a selective, competitive inhibitor of C1s. A1 was identified through a virtual screen for small molecules that interact with the C1s substrate recognition site. Subsequent functional studies revealed that A1 dose-dependently inhibits CP activation by heparin-induced immune complexes, CP-driven lysis of Ab-sensitized sheep erythrocytes, CP activation in a pathway-specific ELISA, and cleavage of C2 by C1s. Biochemical experiments demonstrated that A1 binds directly to C1s with a Kd of ∼9.8 μM and competitively inhibits its activity with an inhibition constant (Ki) of ∼5.8 μM. A 1.8-Å-resolution crystal structure revealed the physical basis for C1s inhibition by A1 and provided information on the structure-activity relationship of the A1 scaffold, which was supported by evaluating a panel of A1 analogs. Taken together, our work identifies A1 as a new class of small-molecule C1s inhibitor and lays the foundation for development of increasingly potent and selective A1 analogs for both research and therapeutic purposes.

Prevalence and Incidence of Primary Autoimmune Hemolytic Anemia and Cold Agglutinin Disease in the United States, 2016-2022: A Retrospective Study in Administrative Claims

Background Autoimmune hemolytic anemia (AIHA) is a decompensated acquired hemolysis caused by autoantibodies that act against red blood cells leading to anemia. Cold agglutinin disease (CAD) is a rare subtype of AIHA mediated by classical complement pathway activation, characterized by chronic hemolysis, severe anemia, fatigue, weakness, dizziness, and circulatory problems. The aim of this study was to update the epidemiology of AIHA and CAD in the United States using administrative claims data that includes commercially insured patients, as well as those with Medicare Advantage, Medicare Fee for Service (FFS) and Managed Medicaid plans. Methods Administrative closed claims from Optum CDM database (commercially insured single-payer and Medicare Advantage), Inovalon MORE 2 Registry (commercially insured multi-payer, Medicare Advantage, and Managed Medicaid), and 100% Medicare FFS (Part A/B services) data were used for this analysis. AIHA cases were defined as patients with at least 2 claims with ICD-9/10 diagnosis codes for AIHA (283.0, D59.1, D59.10, D59.11, D59.12, D59.13, D59.19) at least 30 days apart. CAD cases were defined as patients with at least 2 claims with ICD-10 diagnosis codes for CAD (D59.12) or at least 1 claim with diagnosis code for AIHA followed by 1 claim with diagnosis code for CAD (D59.12) at least 30 days apart. Index date was assigned to the first observed claims with the AIHA/CAD diagnosis. Analyses included patients 18 years of age and above with at least 180 days of continuous enrollment in their health plan prior to index for the assessment of the exclusion criteria. Patients with secondary causes of AIHA/CAD (e.g., lymphoma, leukemia, myeloma, cytomegalovirus, or Epstein-Barr virus) were excluded. US census data from years 2016-2021 was used to standardize the incidence and prevalence estimates by age and sex. Point prevalence was calculated as of January 1 st of each year using an all-data lookback. Period prevalence was calculated using a one calendar year assessment period. Incidence estimated new cases in a given year among patients with no prior evidence of AIHA in all data lookback. For CAD, estimates were presented for years 2022/23 due to the recency of the ICD-10 code specific to CAD (active as of 1 October 2020). Results Age and sex standardized point prevalence of AIHA per 1,000,000 persons was approximately 210 in the Medicare FFS across years 2016-2021, 160 in the Optum claims across years 2016-2022, and 50 in the MORE 2 database across years 2016-2022. One-year prevalence per 1,000,000 persons was approximately 190 in the Medicare FFS, 70 in the Optum claims, and 50 in the MORE 2 database across study years. Incidence per 1,000,000 was 50-60 in the Medicare FFS, 20-30 in the Optum claims, and 15 in the MORE 2 database. While overall standardized estimates differed across databases, incidence and prevalence estimates were similar when stratified by age group, indicating that standardization did not fully account for the underlying differences in the composition and representativeness of the overall US population in the three databases. Incidence and prevalence were higher among females than males and increased with age as expected. Incidence per 1,000,000 for year 2021 ranged from roughly 10-80 among those under the age of 45 years to 30-80 among those over the age of 65 years across the three databases. Point prevalence per 1,000,000 for year 2021 had a broader range from 30 to 220 among those under the age of 45 years and from 120 to 360 among those over the age of 65 years. The standardized point prevalence per 1,000,000 for CAD was 31 in Optum claims (year 2023), 33 in Medicare FFS (year 2021), and 14 in MORE 2 (year 2021). Prevalence of CAD was higher among females and increased with age. Conclusion This multi-database analysis provides updated epidemiology estimates for AIHA and CAD in the US. Age and sex standardized point prevalence for AIHA ranged from 60 to 210 per 1,000,000 across the 3 databases, with higher prevalence in the Medicare FFS database which primarily captures population over the age of 65 and was lower in the two databases that capture younger age groups, such as Managed Medicaid and commercially insured populations. Similarly, incidence of AIHA ranged from 15 to 60 per 1,000,000. Point prevalence of CAD ranged from 14 to 33 per 1,000,000. These estimates are in line with those previously reported for North America and Western Europe.

Classical Complement Inhibition By SAR445088 (BIVV020) in Adults with Cold Agglutinin Disease: Safety, Tolerability and Activity Results from the Open-Label, Non-Randomized, Single-Dose Phase 1b Study

Background:Cold agglutinin disease (CAD) is a rare, chronic autoimmune hemolytic anemia characterized by complement-mediated hemolysis. The classical complement inhibitor sutimlimab, is the first approved pharmacotherapy for treating patients with CAD. The second-generation complement inhibitor SAR445088 (BIVV020) is a humanized monoclonal antibody that selectively inhibits the activated form of C1s (sutimlimab inhibits total C1s). Furthermore, SAR445088 contains mutations that increase FcRn binding, preventing its degradation and allowing it to be recycled back into the system, resulting in reduced drug clearance and a prolonged half-life, which may allow a longer dosing interval than that of sutimlimab. Aims:This Phase 1b open-label study evaluated the safety, tolerability, effect on hemolysis, and pharmacodynamics (PD)/pharmacokinetics (PK) of a single intravenous (IV) dose of SAR445088. The study aimed to assess the impact of SAR445088 on complement-mediated hemolysis to support proof of concept for SAR445088 as a treatment for patients with CAD. Methods:The study design included up to three single-dose cohorts with a maximum of six patients per cohort. SAR445088 was administered on Day 1 with follow-up visits from Day 2 to Day 71; end of study (EOS) visit was on Day 106. The first cohort received a dose of 30 mg/kg IV with decisions about the selection of the dose for the next cohort being based on safety, biomarker activity, and PD. In the second cohort, patients received a lower dose of 15 mg/kg IV; a third, higher-dose cohort was not enrolled. To be enrolled in the study, participants needed to be aged ≥18 years with a confirmed diagnosis of CAD and a hemoglobin level ≤11.0 g/dL at time of screening. The primary endpoint was assessment of safety, with secondary endpoints of hematologic biomarkers and PD/PK. Results:Twelve patients received a single IV dose of SAR445088 (n=6, 30 mg/kg; n=6, 15 mg/kg). Patients enrolled in the study were mainly female (91.7%, n=11) with a median age (range) of 69 (54-80) years, and median (range) hemoglobin at baseline was 9.60 (4.8-10.9) g/dL. There were no treatment-emergent serious adverse events (AEs), discontinuations or deaths reported in the study. Fifty-eight treatment-emergent AEs (TEAEs) were reported in 11 patients (91.7%). There was one reported pre-treatment severe AE (Grade 3) of hemolytic anemia in a patient in the 15 mg/kg IV cohort which began prior to treatment and continued during the treatment period; the remainder of TEAEs were mild or moderate in severity (Grade 1 or 2). The most frequently reported AE was hematuria. No serious infections, meningococcal infections, hypersensitivity, or thromboembolic events were reported. Nine patients (n=4, 30 mg/kg IV cohort; n=5, 15 mg/kg IV cohort) reached an increase of hemoglobin ≥1.5 g/dL from baseline to Day 106 (EOS visit); eight patients (n=4 for both cohorts) reached an increase in hemoglobin &amp;gt;1.0 g/dL from baseline to Day 15 (Figure A). Total mean bilirubin decreased by Day 1 and this was sustained to Day 106 (EOS visit; Figure B).The decrease was more pronounced in the 30 mg/kg IV cohort. Improvements in clinical markers correlated with sustained reductions in CH50 in both treatment cohorts. Reductions in mean percent classical complement pathway (CP) activity were noted 1 hour after a single dose of 30 or 15 mg/kg IV, followed by gradual rebound of CP activity over the 15-week study period. Conclusion:SAR445088 was generally well tolerated; no safety concerns were identified in patients with CAD. A single IV dose of SAR445088 led to classical complement inhibition, control of hemolysis, and improvement in anemia, which was sustained for 15 weeks.

Efficacy of Sutimlimab in Improving FACIT-Fatigue Scores in Patients with Cold Agglutinin Disease: A Post-Hoc Analysis of the Phase 3 Cadenza (Part A) Study

Background Cold agglutinin disease (CAD) is a rare autoimmune hemolytic anemia characterized by chronic hemolysis mediated by classical complement pathway activation. Chronic inflammation and anemia associated with CAD can lead to profound fatigue and general weakness, impacting the patients' quality of life. Sutimlimab is a first-in-class humanized monoclonal antibody approved for the treatment of CAD. To assess the effect of sutimlimab on patients' self-reported fatigue (Functional Assessment of Chronic Illness Therapy-Fatigue [FACIT-Fatigue] scores) in CAD, a post-hoc analysis of the CADENZA Part A study was carried out. Objective To assess the effect of sutimlimab vs placebo on FACIT-Fatigue total score, and individual items of the FACIT-fatigue scale in patients with CAD. Methods CADENZA (NCT03347422) Part A was a phase 3, double-blind, 26-Week study where patients were randomized (1:1) to receive intravenous sutimlimab or placebo. The 13-item FACIT-Fatigue questionnaire comprising 11 fatigue items and 2 energy items (‘I have energy’ or 'I am able to do my usual activities') was scored on a 0 (“not at all”) to 4 (“very much”) response scale, and the total scores ranged from 0 to 52; higher scores indicated less fatigue. Least square (LS) mean difference (sutimlimab vs placebo) in change from the baseline (BL) in FACIT-Fatigue total score were estimated at all visits using mixed model for repeated measures. Treatment assessment timepoint (TAT) was the average of values from Week 23, 25, and 26 visits. Patients were considered responders if they achieved a change from BL in FACIT-Fatigue total score of ≥5, did not receive blood transfusions from Week 5 through TAT, and did not take any protocol prohibited CAD medications. Patients with missing data at a given visit were considered non-responders. Time to first response to treatment was assessed using the Kaplan-Meier product limit method. For the item level analysis of the FACIT-Fatigue scale, the proportion of patients reporting the two worst response options 'Quite a bit' or ‘Very much’ for fatigue items and ‘Not at all’ or ‘A little bit’ for energy items was calculated at BL and Week 26. Results A total of 42 patients were included in the study (sutimlimab group: n=22; placebo group: n=20). The median (range) age of patients was 66.0 (46-88) years and 78.6% (n=33) were female. The mean (SD) FACIT-Fatigue total score for the pooled population at BL was 32.30 (11.83). About 79% of patients (n=33) had a total score below the general healthy population mean of 43. The LS mean (95% CI) difference (sutimlimab vs placebo) in change from BL in the FACIT-Fatigue total score was 4.97 (0.35─9.60) at Week 1 and 8.93 (4.00─13.85) at TAT. The nominal significant difference that started at Week 1 (rapid treatment effect) was sustained throughout Part A ( Figure 1). Overall, the fatigue response rate was higher in the sutimlimab group than placebo group throughout the study. The median time (95% CI) to first FACIT-Fatigue response in the sutimlimab and placebo groups were 3.1 (1.1─3.1) and 9.1 (3.3─22.4) weeks (log-rank test p&amp;lt;0.05), respectively. At BL, ~25-30% of the patients had reported the two worst response options (‘Quite a bit’ or 'Very much') for most of the FACIT-fatigue items. Around 40.5% (17/42) of the patients responded with one of the two worst options for item 'I feel tired', and more than half of the patients (22/42; 52.4%) reported one of the two worst options (‘Not at all’ or 'A little bit') for item 'I have energy'. At Week 26, lower proportion of patients in sutimlimab group reported one of the two worst options for fatigue and energy items compared with the placebo group ( Figure 2). Conclusion Sutimlimab treatment led to rapid and sustainable improvement in FACIT-Fatigue scores and higher response rates as compared to placebo. Number needed to treat to observe a sutimlimab-related FACIT-Fatigue benefit was 4. The proportion of severe FACIT-Fatigue answers for fatigue and energy items was noticeably lower in sutimlimab-treated patients at Week 26 compared to placebo, highlighting the effect of sutimlimab in improving almost all dimensions of FACIT-Fatigue scale.

The Bioluminescent Modified Ham Test Identifies the Classical Pathway As the Major Driver of Complement Activation in Atypical Hemolytic Uremic Syndrome and Primary Antiphospholipid Syndrome

Introduction: The role of complement is increasingly recognized in disease pathogenesis, however diagnostic assays are limited by low predictive value, technical requirements, and inability to assess relative contributions of each pathway of complement (classical, alternative, or lectin). The traditional mHam was developed as a functional assay of complement-mediated eukaryotic cell death in atypical hemolytic uremic syndrome (aHUS). However, broader use of the assay has been limited by inter-operator dependence and technical requirements. We have developed a bioluminescent mHam that is robust and easily performed (no cell washes or exogenous reagent addition) and utilizes an autonomously bioluminescent HEK293 cell line to allow for real-time assessment of changes in metabolic health due to complement activation. Given both HEK293 and endothelial cells lack complement receptor 1 (CR1), a crucial regulator of the classical pathway (CP), this assay measures complement activity of greater relevance to disease pathogenesis. Methods: The bioluminescent mHam uses LiveLight (LL) HEK293 cells (490 BioTech) engineered to stably express the bacterial luciferase ( lux) and flavin reductase genes ( luxF) to create autonomous bioluminescence. A PIGA null clone (LL PIGA- HEK293) was created through proaerolysin selection (removing GPI-anchored complement regulators CD55 and CD59). To perform the assay, 40,000 cells were harvested with trypsin/EDTA and plated as triplicates in gelatin veronal buffer (GVB ++,80 µL). Serum (20 µL) was added after specified treatments (heat inactivation or inhibitor addition). Activity was monitored by serial luminescence measurements every 5 min at 37 °C. A relative luminescence of &amp;lt;25% at one hour is designated as positive based upon lowest replicate of any healthy control. Results: The bioluminescent mHam, unlike the original mHam, provides continuous measurement of complement activity (example tracing Figure 1). The complement specificity of the luminescent changes were demonstrated with heat inactivation, terminal complement blockade with eculizumab, and calcium/magnesium dependence. The relative contribution of CP to changes in luminescence was confirmed with the specific CP inhibitor sutimlimab as well as use of pathway specific buffers. Healthy control (HC) samples show a relative luminescence of 53.7% (95%CI 44.0-63.4) with no difference observed in acute thrombotic thrombocytopenic purpura (TTP) (mean 56.2%, 95%CI 41.2-71.2, p=&amp;gt;0.9999). We next utilized samples of aHUS patients known to be in remission, off complement inhibitor therapy. A large proportion of these patients have ongoing assay positivity even in the traditional mHam (9 of 13 in one unpublished cohort). The bioluminescent mHam shows that 5 of 6 aHUS patients in remission have ongoing positivity (mean 17.56%, 95%CI -10.5-45.6, p=0.0131). An acute aHUS sample showed similar results (17.8% after plasmapheresis). Unexpectedly, the relative luminescence is rescued by addition of either C1s or C5 inhibitors, but use of alternative pathway (AP) inhibitors has no significant rescuing effect ( Figure 1-2). Of aHUS patients tested while on complement inhibition, 91% (10/11) show greater than 88% blockade ( Figure 2 aHUS on therapy) . Finally, in one cohort, the traditional mHam was positive in 52% (14/27) of primary antiphospholipid syndrome (PAPS) cases and 15% (10/66) of secondary APS (SAPS) (unpublished data). Thus far, the bioluminescent mHam shows abnormal complement activity in 92% (12/13) of PAPS and 17% (2/12) of patients in SAPS ( Figure 2). Again, complement inhibition with C1s or C5 inhibitors abrogated the effect in a dose dependent manner. Conclusions: The bioluminescent mHam test is an exquisitely sensitive real-time measure of abnormal complement activity. It is easy to perform, more closely approximates the complement regulators on renal endothelium, can be utilized for therapeutic monitoring, and has already offered novel disease insights through the use of specific pathway inhibitors. Although aHUS is traditionally categorized as a disorder of the AP, these results suggest the “trigger” mediating disease pathology is the classical pathway. Also, we show that a large proportion of primary APS patients have abnormal CP activation responsive to C1s and C5 inhibition, suggesting the disease may be responsive to complement-based therapeutics.

Development and characterization of narsoplimab, a selective MASP-2 inhibitor, for the treatment of lectin-pathway-mediated disorders.

Overactivation of the lectin pathway of complement plays a pathogenic role in a broad range of immune-mediated and inflammatory disorders; mannan-binding lectin-associated serine protease-2 (MASP-2) is the key effector enzyme of the lectin pathway. We developed a fully human monoclonal antibody, narsoplimab, to bind to MASP-2 and specifically inhibit lectin pathway activation. Herein, we describe the preclinical characterization of narsoplimab that supports its evaluation in clinical trials. ELISA binding studies demonstrated that narsoplimab interacted with both zymogen and enzymatically active forms of human MASP-2 with high affinity (KD 0.062 and 0.089 nM, respectively) and a selectivity ratio of >5,000-fold relative to closely related serine proteases C1r, C1s, MASP-1, and MASP-3. Interaction studies using surface plasmon resonance and ELISA demonstrated approximately 100-fold greater binding affinity for intact narsoplimab compared to a monovalent antigen binding fragment, suggesting an important contribution of functional bivalency to high-affinity binding. In functional assays conducted in dilute serum under pathway-specific assay conditions, narsoplimab selectively inhibited lectin pathway-dependent activation of C5b-9 with high potency (IC50 ~ 1 nM) but had no observable effect on classical pathway or alternative pathway activity at concentrations up to 500 nM. In functional assays conducted in 90% serum, narsoplimab inhibited lectin pathway activation in human serum with high potency (IC50 ~ 3.4 nM) whereas its potency in cynomolgus monkey serum was approximately 10-fold lower (IC50 ~ 33 nM). Following single dose intravenous administration to cynomolgus monkeys, narsoplimab exposure increased in an approximately dose-proportional manner. Clear dose-dependent pharmacodynamic responses were observed at doses >1.5 mg/kg, as evidenced by a reduction in lectin pathway activity assessed ex vivo that increased in magnitude and duration with increasing dose. Analysis of pharmacokinetic and pharmacodynamic data revealed a well-defined concentration-effect relationship with an ex vivo EC50 value of approximately 6.1 μg/mL, which was comparable to the in vitro functional potency (IC50 33 nM; ~ 5 μg/mL). Based on these results, narsoplimab has been evaluated in clinical trials for the treatment of conditions associated with inappropriate lectin pathway activation, such as hematopoietic stem cell transplantation-associated thrombotic microangiopathy.

PSIX-9 Activation of Multiple Inflammatory Signaling Pathways May Contribute to the Pathogenesis of Idiopathic Cystitis in Felines

Abstract Feline idiopathic cystitis (FIC) is a common urinary disorder in domestic cats. Clinical signs include straining or failing to urinate, frequent urination, and discolored urine. Inflammation is a key characteristic in the pathogenesis of cystitis. We assessed circulating inflammatory markers in a retrospective study in cats housed in the Hill’s colony diagnosed with cystitis (n = 4; 15.2 to 18.6yr) and in control cats (n = 8; 5.9 to 16.5 yr). Blood samples were collected at end-of-life immediately before necropsy after they had lived their full lives. End-of-life pathology reports indicated inflammation and presence of inflammatory infiltrates in the bladder with some cats also showing renal inflammation. RNA was extracted from blood collected in PAXgene tubes, and gene expression investigated using NanoString nCounter platform. Analysis was performed using the nSolver software. There was a significant increase in IRAK4, a kinase that activates the NFκB pro-inflammatory signaling pathway, in FIC when compared with controls (1.56, P &amp;lt; 0.05). Small molecule inhibitors of IRAK4 are being developed as targets of inflammation. Signaling molecules in the NFκB pathway were also significantly increased including Rel A (p65 subunit; 1.3 fold), NFκB1 (p100 subunit; 1.3 fold), IKBKB (1.29 fold), and TANK (1.46 fold) in FIC cats (all P &amp;lt; 0.05). Another signaling pathway contributing to pro-inflammatory signaling is the JAK/STAT pathway. There was a significant increase in JAK2 (1.65) and STAT3 (1.48). Blockade of JAK2/STAT3 pathway can attenuate cytokine synthesis and reduce inflammation. STAT6 was also significantly increased in FIC cats (1.35). Activation of STAT6, by IL-4 and IL-13, can lead to systemic inflammation. Activation of the complement immune pathway was also seen in FIC. While the complement system is important for an innate immune response, its sustained activation leads to chronic pathological inflammation. There was a significant increase in complement C1s, an initiator of classical complement activation pathway, in FIC cats (1.43; P &amp;lt; 0.05). A late component, complement C7, was also upregulated in FIC (2.01 fold; P &amp;lt; 0.05). C7 binds to the C5b-6 complex which eventually becomes part of the terminal complement complex. Increased abundance of C7 and eventual terminal complement complex are associated with increased inflammation and may be important in the progression of FIC. There was also an increase in PECAM1 in FIC cats (1.87; P &amp;lt; 0.05). Signaling through PECAM1 leads to the activation of neutrophils and monocytes. DUSP1 was also elevated in FIC (2.24; P &amp;lt; 0.05). Increased abundance of DUSP1 is hypothesized to be a predictor of chronic subclinical inflammation in humans with cardiovascular disease. Our results identify activation of pro-inflammatory signaling pathways that may be potential targets for alleviating inflammation in cystitis. Pathogenesis of FIC is likely multi-factorial, and nutritional intervention to attenuate the activation of inflammatory pathways may be an important strategy in the management of cystitis.

The Relationship between Complement Components C1R and C5 Gene Polymorphism and the Values of Blood Indices in Suckling Piglets.

The main mechanism of innate immunity is the complement system. Its components include the protein products of the C1R and C5 genes, which are involved in the classical activation pathway as well as the inflammatory and cytolytic immune responses, respectively. The aim of this study was to determine the relationship between PCR-restriction fragment length polymorphism in C1R (726T > C) and C5 (1044A > C) genes, and the values of hematological and biochemical blood indices in suckling crossbred (Polish Large White × Polish Landrace × Duroc × Pietrain) piglets (n = 473), considering their age (younger, 21 ± 3 days, n = 274; older, 35 ± 3 days, n = 199) and health status. The frequencies of the C5 genotypes deviated from the Hardy-Weinberg expectations. Younger piglets, healthy piglets, piglets that deviated from physiological norms and older piglets with the C1R TT genotype all had lower white and red blood cell indices. In piglets with the C5 CC genotype, younger piglets, piglets that deviated from physiological norms and older piglets, a greater number and/or percentage of monocytes were recorded in the blood. Older piglets also showed an increase in the number of leukocytes and granulocytes, along with a tendency for a decrease in the percentage of lymphocytes in their blood. We concluded that a polymorphism in the C1R gene may exhibit a functional association or genetic linkage with other genes involved in the process of erythropoiesis. Furthermore the relationship between the C5 gene polymorphism and the number and/or percentage of monocytes in the blood may modify the body's defense abilities. Piglets with the CC genotype, having an increased number/proportion of these cells in their blood, probably display a weakened immune response to pathogens or a chronic stimulation of the immune system.

Changes in expression levels of erythrocyte and immune-related genes are associated with high altitude polycythemia

BackgroundAs a chronic mountain sickness(CMS) with the highest incidence and the greatest harm, the pathogenesis of high altitude polycythemia (HAPC) is still not fully understood.Methods37 HAPC patients and 42 healthy subjects were selected from plateau, and peripheral venous blood samples were collected for transcriptome sequencing on Illumina NovaSeq platform. The sequenced data were analyzed by bioinformatics and phenotypic association analysis.ResultsThe results showed significant differences in multiple clinical indicators including RBC and HGB et al. existed between HAPC and control. Based on the RNA-seq data, 550 genes with significant differential expression were identified in HAPC patients. GO and KEGG pathway enrichment analysis showed that the up-regulated genes were mainly enriched in processes such as erythrocyte differentiation and development and homeostasis of number of cells, while the down-regulated genes were mainly enriched in categories such as immunoglobulin production, classical pathway of complement activation and other biological processes. The coupling analysis of differential expression genes(DEGs) and pathological phenotypes revealed that 91 DEGs were in close correlation with in the phenotype of red blood cell volume distribution (width-CV and width-SD), and they were all up-regulated in HAPC and involved in the process of erythrocyte metabolism. Combined with the functional annotation of DEGs and literature survey, we found that the expression of several potential genes might be responsible for pathogenesis of HAPC. Besides, cell type deconvolution analysis result suggested that the changes in the number of some immune cell types was significantly lower in HAPC patients than control, implying the autoimmune level of HAPC patients was affected to a certain extent.ConclusionThis study provides an important data source for understanding the pathogenesis and screening pathogenic genes of HAPC. We found for the first time that there was a significant correlation between HAPC and the pathological phenotype of width-CV and width-SD, wherein the enriched genes were all up-regulated expressed and involved in the process of erythrocyte metabolism. Although the role of these genes needs to be further studied, the candidate genes can provide a starting point for functionally pinning down the underlying mechanism of HAPC.

Anti-C1q antibodies in lupus nephritis children with glomerular microthrombosis.

Glomerular microthrombosis (GMT) was a common vascular lesion in patients with lupus nephritis (LN). The objective of this study was to investigate the relationship between serum anti-beta2-glycoprotein I antibodies (a-β2GP1) and anti-complement 1q antibodies (a-C1q) antibodies and to investigate the possible mechanism of GMT in children with LN. The subjects were 191 children with LN diagnosed by renal biopsy in our hospital from January 2017 to January 2020. The patients were divided into GMT group and non-GMT group. The clinical manifestations, laboratory tests, renal pathology, prognosis of the two groups and the relationship between a-β2GP1 and a-C1q antibodies were observed. In 191 children with LN, 52 cases (27.23%) presented with GMT. The value of C3, haemoglobin (Hb), estimate glomerular filtration rate (eGFR) and anticardiolipin antibody (ACA) in GMT group were lower than that of non-GMT group (p < .05, p < .01). The value of serum creatinine (Scr), 24 h proteinuria (PRO), urine red blood cells (RBC), N-acetyl-β-d-glucosidase (NAG) and retinol-binding protein (RBP), a-C1q, a-β2GP1, Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and renal histopathological activity index (AI) score in GMT group were higher than that of non-GMT group (p < .05, p < .01). The positive proportions of serum a-C1q and a-β2GP1 in GMT group were higher than those in non-GMT group (p < .05). According to Spearman correlation analysis, a-C1q was positively correlated with AI score, SLEDAI, a-β2GP1, GMT, LN-III and LN-IV. Hb, eGFR and a-C1q Ab were associated with the formation of GMT in children with LN. The complete proteinuria remission and renal survival in GMT group were significantly lower than those in non-GMT group (p < .05, p < .01). LN children with GMT had more severe clinical manifestations and renal pathologic damages, and poor outcome. Serum a-C1q level was positively correlated with a-β2GP1, and a-β2GP1 may be involved in the formation of GMT in children with LN, which might involve in the activation of complement classical pathway.

Complement Components in Peripheral Blood from Adult Patients with IDH Wild-Type Glioblastoma

The complement system seems to influence cancer pathophysiology. The primary aim of this study was to explore complement components associated with the classical pathway (CP) of the complement system in peripheral blood from patients with IDH-wild-type (IDH-wt) glioblastoma. Patients undergoing primary surgery due to glioblastoma in the years 2019-2021 were prospectively included in the present study. Blood samples were collected prior to surgery, and analyzed with regard to CP complement components, as well as standard coagulation tests. In total, 40 patients with IDH-wt glioblastomas were included. C1q was reduced in 44% of the cases compared to the reference interval. C1r was reduced in 61% of the analyzed samples. Both C1q and C1r are parts of the initial steps of the classical complement activation pathway, which, however, was not correspondingly altered. Activated pro-thromboplastin time (APTT) was shorter in 82% of the analyzed samples compared to the reference interval. APTT was shorter in those with reduced C1q and C1r levels. C1q is an important link between the innate and acquired immunity, and C1q and C1r also interact with the coagulation system. Patients who displayed reduced levels of both C1q and C1r preoperatively had a significantly shorter overall survival compared with the rest of the cohort. Our findings demonstrate that there are alterations in C1q and C1r concentrations in peripheral blood from patients with IDH1-wt glioblastoma compared with the normal population. Patients who displayed reduced C1q and C1r levels had a significantly shorter survival.