Selective decrease in complement C2 hemolytic activity is a sensitive marker for cryoglobulinemia and active disease in hepatitis C patients.

BACKGROUND: Some HCV patients present low/non-detected C2 hemolytic activity (C2h) without apparent consumption of other Complement components (selective low/non-detected C2h). AIM: Characterization of the immunologic/clinical basis of this phenomenon. METHODS: C2h, HCV-viral load, cryoglobulinemia and Complement components were determined in 726 HCV patients, with sequential C2h determination in 189 patients. RESULTS: C2h was non-detected in 15.9%, low in 16.9% and normal in 67.2% subjects and showed temporal oscillation in 30.7% of patients. Samples with selective non-detected C2h presented lower C3/C4 than those with normal C2h, but still within the normal C3/C4 range. Selective non-detected C2h was associated with higher aspartate aminotransferase (AST) (p<0.001), alanine transferase (ALT) (p = 0.03) and APRI (Aspartate aminotransferase-to-Platelet Ratio Index) (p<0.001), lower serum albumin (p = 0.01) and platelet count (p = 0.012), more individuals at pre-treatment stage, with detectable HCV-RNA p<0.001), cryoglobulinemia (p<0.001) and with HCV genotype 3 (p = 0.003). Elevated ALT, HCV genotype 3, active disease and viral load were independent predictors of low/non-detected C2h. In vitro exposure of normal serum to exogenous HCV cryoglobulins caused dose-dependent decrease in C2h. CONCLUSIONS: Selective C2h decrease is a sensitive marker of Complement activation in HCV patients and is associated with cryoglobulinemia, active disease, elevated ALT, higher viral load, and HCV genotype 3.

ARGX-117, a therapeutic complement inhibiting antibody targeting C2.

BACKGROUND: Activation of the classical and lectin pathway of complement may contribute to tissue damage and organ dysfunction of antibody-mediated diseases and ischemia-reperfusion conditions. Complement factors are being considered as targets for therapeutic intervention. OBJECTIVE: We sought to characterize ARGX-117, a humanized inhibitory monoclonal antibody against complement C2. METHODS: The mode-of-action and binding characteristics of ARGX-117 were investigated in detail. Furthermore, its efficacy was analyzed in in vitro complement cytotoxicity assays. Finally, a pharmacokinetic/pharmacodynamic study was conducted in cynomolgus monkeys. RESULTS: Through binding to the Sushi-2 domain of C2, ARGX-117 prevents the formation of the C3 proconvertase and inhibits classical and lectin pathway activation upstream of C3 activation. As ARGX-117 does not inhibit the alternative pathway, it is expected not to affect the antimicrobial activity of this complement pathway. ARGX-117 prevents complement-mediated cytotoxicity in in vitro models for autoimmune hemolytic anemia and antibody-mediated rejection of organ transplants. ARGX-117 exhibits pH- and calcium-dependent target binding and is Fc-engineered to increase affinity at acidic pH to the neonatal Fc receptor, and to reduce effector functions. In cynomolgus monkeys, ARGX-117 dose-dependently reduces free C2 levels and classical pathway activity. A 2-dose regimen of 80 and 20 mg/kg separated by a week, resulted in profound reduction of classical pathway activity lasting for at least 7 weeks. CONCLUSIONS: ARGX-117 is a promising new complement inhibitor that is uniquely positioned to target both the classical and lectin pathways while leaving the alternative pathway intact.

Diagnostic and Prognostic Significance of Complement in Patients With Alcohol-Associated Hepatitis.

BACKGROUND AND AIMS: Given the lack of effective therapies and high mortality in acute alcohol-associated hepatitis (AH), it is important to develop rationally designed biomarkers for effective disease management. Complement, a critical component of the innate immune system, contributes to uncontrolled inflammatory responses leading to liver injury, but is also involved in hepatic regeneration. Here, we investigated whether a panel of complement proteins and activation products would provide useful biomarkers for severity of AH and aid in predicting 90-day mortality. APPROACH AND RESULTS: Plasma samples collected at time of diagnosis from 254 patients with moderate and severe AH recruited from four medical centers and 31 healthy persons were used to quantify complement proteins by enzyme-linked immunosorbent assay and Luminex arrays. Components of the classical and lectin pathways, including complement factors C2, C4b, and C4d, as well as complement factor I (CFI) and C5, were reduced in AH patients compared to healthy persons. In contrast, components of the alternative pathway, including complement factor Ba (CFBa) and factor D (CFD), were increased. Markers of complement activation were also differentially evident, with C5a increased and the soluble terminal complement complex (sC5b9) decreased in AH. Mannose-binding lectin, C4b, CFI, C5, and sC5b9 were negatively correlated with Model for End-Stage Liver Disease score, whereas CFBa and CFD were positively associated with disease severity. Lower CFI and sC5b9 were associated with increased 90-day mortality in AH. CONCLUSIONS: Taken together, these data indicate that AH is associated with a profound disruption of complement. Inclusion of complement, especially CFI and sC5b9, along with other laboratory indicators, could improve diagnostic and prognostic indications of disease severity and risk of mortality for AH patients.

Complement protein levels and MBL2 polymorphisms are associated with dengue and disease severity.

The complement system may be crucial during dengue virus infection and progression to severe dengue. This study investigates the role of MBL2 genetic variants and levels of MBL in serum and complement proteins in Vietnamese dengue patients. MBL2 genotypes (- 550L/H, MBL2 codon 54), MBL2 diplotypes (XA/XO, YA/XO) and MBL2 haplotypes (LXPB, HXPA, XO) were associated with dengue in the study population. The levels of complement factors C2, C5, and C5a were higher in dengue and dengue with warning signs (DWS) patients compared to those in healthy controls, while factor D levels were decreased in dengue and DWS patients compared to the levels determined in healthy controls. C2 and C5a levels were associated with the levels of AST and ALT and with WBC counts. C9 levels were negatively correlated with ALT levels and WBC counts, and factor D levels were associated with AST and ALT levels and with platelet counts. In conclusions, MBL2 polymorphisms are associated with dengue in the Vietnamese study population. The levels of the complement proteins C2, C4b, C5, C5a, C9, factor D and factor I are modulated in dengue patients during the clinical course of dengue.

Hereditary Deficiency of the Second Component of Complement: Early Diagnosis and 21-Year Follow-Up of a Family.

Complement deficiencies are rare and often underdiagnosed primary immunodeficiencies that may be associated with invasive bacterial diseases. Serious infections with encapsulated organisms (mainly Streptococcus pneumoniae, but also Neisseria meningitides and Haemophilus influenzae type B) are frequent in patients with a deficiency of the second component of complement (C2), but no data are available on long-term follow-up. This study aimed to evaluate the long-term clinical outcome and the importance of an early diagnosis and subsequent infection prophylaxis in C2 deficiency. Here, we report the 21-year follow-up of a whole family which was tested for complement parameters, genetic analysis and biochemical measurements, due to recurrent pneumococcal meningitis in the elder brother. The two sons were diagnosed with homozygous type 1 C2 deficiency, while their parents were heterozygous with normal complement parameters. For the two brothers, a recommended vaccination program and antibiotic prophylaxis were prescribed. During the long-term follow-up, no severe/invasive infections were observed in either patient. At the age of 16, the younger brother developed progressive hypogammaglobulinemia of all three classes, IgA, IgM and IgG. A next generation sequencing panel excluded the presence of gene defects related to primary antibody deficiencies. Our data show that early diagnosis, use of vaccinations and antibiotic prophylaxis may allow a normal life in hereditary C2 deficiency, which can be characterized using functional and genetic methods. Moreover, a periodical check of immunoglobulin serum levels could be useful to detect a possible hypogammaglobulinemia.

Quantification of human complement C2 protein using an automated turbidimetric immunoassay.

BACKGROUND: The measurement of complement components is clinically useful where a deficiency is suspected, or where excessive activation and consumption are present in disease. C2 deficiency carries an increased risk of developing systemic lupus erythematosus, recurrent infections and atherosclerosis. In this study, we have evaluated The Binding Site's Human Complement C2 SPAPLUS® assay. METHODS: Linearity was tested using 13 sample dilutions covering the standard measuring range. Within- and between-assay variabilities were calculated using five samples with different C2 concentrations. The correlation between C2 concentrations in EDTA-plasma and serum was assessed, as was the correlation between C2 measurements by the automated assay and radial immunodiffusion. C2 concentrations were compared with CH50 activity, and quantified in individuals with homozygous or heterozygous C2 deficiency, acquired angioedema and patients with chronic inflammatory conditions. RESULTS: The assay was linear across the measuring range (3.8-42.3 mg/L). Intra- and interassay variability were 2.3%-3.8% and 0%-3.3%, respectively. Comparison between C2 measurements in EDTA-plasma and serum provided a strong correlation (p<0.0001, R2=0.82, slope 0.92), as did the correlation between the automated and radial immunodiffusion methods (p<0.0001, R2=0.89, slope 1.07). A positive correlation between C2 concentration and CH50 activity was demonstrated (p<0.0001, R2=0.48). Significant differences were observed between the median C2 concentrations obtained in healthy controls and the patient clinical samples, with homozygous C2-deficient patients giving below detectable results. CONCLUSIONS: This C2 SPAPLUS® assay allows the automated, rapid and precice quantification of complement C2 protein and could therefore be considered as a replacement for older, more time-consuming methods.

Molecular characterization of the complement C1q, C2 and C4 genes in Brazilian patients with juvenile systemic lupus erythematosus.

OBJECTIVE: To perform a molecular characterization of the C1q, C2 and C4 genes in patients with juvenile systemic lupus erythematosus. METHODS: Patient 1 (P1) had undetectable C1q, patient 2 (P2) and patient 3 (P3) had decreased C2 and patient 4 (P4) had decreased C4 levels. All exons and non-coding regions of the C1q and C2 genes were sequenced. Mononuclear cells were cultured and stimulated with interferon gamma to evaluate C1q, C2 and C4 mRNA expression by quantitative real-time polymerase chain reaction. RESULTS: C1q sequencing revealed heterozygous silent mutations in the A (c.276 A>G Gly) and C (c.126 C>T Pro) chains, as well as a homozygous single-base change in the 3' non-coding region of the B chain (c*78 A>G). C1qA mRNA expression without interferon was decreased compared with that of healthy controls (p<0.05) and was decreased after stimulation compared with that of non-treated cells. C1qB mRNA expression was decreased compared with that of controls and did not change with stimulation. C1qC mRNA expression was increased compared with that of controls and was even higher after stimulation. P2 and P3 had Type I C2 deficiency (heterozygous 28 bp deletion at exon 6). The C2 mRNA expression in P3 was 23 times lower compared with that of controls and did not change after stimulation. The C4B mRNA expression of P4 was decreased compared with that of controls and increased after stimulation. CONCLUSIONS: Silent mutations and single-base changes in the 3' non-coding regions may modify mRNA transcription and C1q production. Type I C2 deficiency should be evaluated in JSLE patients with decreased C2 serum levels. Further studies are needed to clarify the role of decreased C4B mRNA expression in JSLE pathogenesis.

Role of complement cascade in abdominal aortic aneurysms.

OBJECTIVE: The goal of this study was to investigate the role of complement cascade genes in the pathobiology of human abdominal aortic aneurysms (AAAs). METHODS AND RESULTS: Results of a genome-wide microarray expression profiling revealed 3274 differentially expressed genes between aneurysmal and control aortic tissue. Interestingly, 13 genes in the complement cascade were significantly differentially expressed between AAA and the controls. In silico analysis of the promoters of the 13 complement cascade genes showed enrichment for transcription factor binding sites for signal transducer and activator of transcription (STAT)5A. Chromatin-immunoprecipitation experiments demonstrated binding of transcription factor STAT5A to the promoters of the majority of the complement cascade genes. Immunohistochemical analysis showed strong staining for C2 in AAA tissues. CONCLUSIONS: These results provide strong evidence that the complement cascade plays a role in human AAA. Based on our microarray studies, the pathway is activated in AAA, particularly via the lectin and classical pathways. The overrepresented binding sites of transcription factor STAT5A in the complement cascade gene promoters suggest a role for STAT5A in the coordinated regulation of complement cascade gene expression.

Genetic variation in complement component 2 of the classical complement pathway is associated with increased mortality and infection: a study of 627 patients with trauma.

BACKGROUND: Trauma is a disease of inflammation. Complement Component 2 (C2) is a protease involved in activation of complement through the classical pathway and has been implicated in a variety of chronic inflammatory diseases. We hypothesized that genetic variation in C2 (E318D) identifies a high-risk subgroup of patients with trauma reflecting increased mortality and infection (ventilator-associated pneumonia [VAP]). Consequently, genetic variation in C2 may stratify patient risk and illuminate underlying mechanisms for therapeutic intervention. METHODS: DNA samples from 702 patients with trauma were genotyped for C2 E318D and linked with covariates (age: mean 42.8 years, gender: 74% male, ethnicity: 80% white, mechanism: 84% blunt, injury severity score: mean 25.0, admission lactate: mean 3.13 mEq/L) and outcomes: mortality 9.9% and VAP: 18.5%. VAP was defined by quantitative bronchoalveolar lavage (> 10). Multivariate regression analysis determined the relationship of genotype and covariates to risk of death and VAP. However, patients with injury severity score > or = 45 were excluded from the multivariate analysis, as magnitude of injury overwhelms genetics and covariates in determining outcome. RESULTS: Fifty-two patients (8.3%) had the high-risk heterozygous genotype, associated with a significant increase in mortality and VAP. CONCLUSION: In 702 patients with trauma, 8.3% had a high-risk genetic variation in C2 associated with increased mortality (odds ratio = 2.65) and infection (odds ratio = 2.00). This variation: (1) identifies a previously unknown high-risk group for infection and mortality; (2) can be determined at admission; (3) may provide opportunity for early therapeutic intervention; and (4) requires validation in a distinct cohort of patients.

Risk factors for acute rejection in renal transplant recipients experiencing delayed graft function.

Acute rejection (AR) superimposed upon delayed graft function (DGF) following renal transplantation worsens graft outcomes. However, risk factors for AR in patients displaying DGF remain unclear. In this study, 71 patients displaying DGF >/= 5 d were investigated. All received cyclosporine, adjunctive azathioprine or mycophenolate mofetil (MMF), and corticosteroids, with 43 receiving anti-CD25 monoclonal antibody induction. AR episodes were seen in 20 of 71 (28%) patients. Higher C2 levels at days 3 and 5 and the use of MMF were associated with a reduced incidence of AR, with increased HLA-DR mismatch associated with an increased risk for AR. C2 levels at days 3 and 5 below 885 and 1096 ng/mL, respectively, showed best discriminatory values for AR. C2 levels showed no correlation with DGF duration. This study suggests that optimizing immunosuppression in patients with DGF (by ensuring adequate calcineurin inhibitor exposure and the use of potent adjunctive immunosuppression) may reduce the incidence of AR without prolonging the duration of dialysis requirement.

Acquired angioedema in non-Hodgkin's lymphoma.

This paper describes a middle-aged patient who developed repeated episodes of swelling of the orofacial tissues after dental treatment. On investigation, C1 inhibitor, C1q, C2, and C4 levels were all markedly reduced, and a diagnosis of acquired C1 inhibitor deficiency was made. The patient had been diagnosed with non-Hodgkin's lymphoma (NHL) 2 years previously and had undergone a successful course of chemotherapy. The development of her episodes of angioedema prompted thorough reinvestigation and a recurrence of NHL was identified. Therefore, acquired C1 inhibitor deficiency heralded a recurrence, although this had not been a manifestation when NHL was first diagnosed. The patient underwent a further course of chemotherapy and remains well, although C1 inhibitor, C1q, C2, and C4 levels remain reduced.

[Non-ionic iodinated dimeric versus monomeric X-ray contrast media: effects on complement factors in vivo]. / Nichtionische iodierte dimere versus monomere Röntgenkontrastmittel: Effekte auf Komplementfaktoren in vivo.

PURPOSE: To survey contrast media (CM)-induced alterations of complement factors. MATERIAL AND METHODS: In 31 adult patients, who received either an iotrolan (n = 19) or iopromide (n = 12) i. v. injection for CT examination, complement factors C1 q, C3, C4, C5 a, and C1-esterase inhibitor in serum/plasma samples were analyzed. The samples were obtained prior to and 5 min., 30 min., 1 hr., 6 hrs. and 24 hrs. after CM injection. RESULTS: 5 patients (16.1 %) developed a CM reaction. 4 of these were patients who received iotrolan. Other than minimal data, we neither found a significant influence of the CM on complement activation nor a difference between the analyzed CM. In detail, 5 min. after CM administration, we found the tendency to be for the values to decrease and then to return to the basic value. The changes induced by iotrolan were more pronounced than those induced by iopromide; nevertheless the differences were not statistically significant. A more pronounced decrease of C3 and C4 after iotrolan injection indicates the activation of the classic way, while this could not been observed after iopromide injection. One patient who experienced an unwanted reaction towards iotrolan showed shifts of C1 q, C1 INH, C3 and C4. CONCLUSION: The presented data shows different influences of CM injection on the analyzed complement factors after 5 min. that were commonly no longer present 30 min. after CM injection. The dimeric iotrolan induced a significantly increased frequency of unwanted CM reactions than the monomeric iopromide. The question of whether iotrolan is possibly able to activate the classic way of the complement cascade should be analyzed in the future in a greater patient group.

Complementing the patient: a complement component deficiency in a patient with recurrent infections and glomerulonephritis.

We present a case showing the investigation of a 7-year-old girl with empyema and glomerulonephritis whose "immunological" defect was a single complement component (C2) deficiency which prevented her from activating her classical complement pathway. A defect in complement function should be suspected in any patient with severe or recurring pyogenic infections. Investigations of "? immune deficiency" should always include tests to assess the patency of the patient's complement system.

Pharmacokinetic of cyclosporine microemulsion in pediatric kidney recipients receiving A quadruple immunosuppressive regimen: the value of C2 blood levels.

BACKGROUND: The management of cyclosporine therapy in pediatric kidney-transplant recipients is largely based on single center's experience rather than on a univocal pharmacokinetic approach based on therapeutic drug monitoring. A prospective multicenter trial was designed to address the question whether C2 blood level monitoring of cyclosporine microemulsion therapy is feasible in the pediatric setting. METHODS: Sixty-four pediatric kidney-transplant recipients receiving a triple immunosuppressive regimen based on cyclosporine microemulsion had their cyclosporine dose adjusted to the same protocol-defined C2 targets from the time of the transplant until 2 years posttransplant. The interim analyses after 1 year of enrollment is presented in this study. RESULTS: One-year patient and graft survival were 100% and 94.8%, respectively. One-year rejection rate was 15%. C2 management of cyclosporine did not affect graft function: 1-year serum creatinine and glomerular filtration rate were 1.3+/-1 mg/mL and 71.2+/-20 mL/min/1.73 m2, respectively. C2 was the best single-point predictor of the area under the concentration curve throughout the entire follow-up, with a mean coefficient of correlation of 0.97+/-0.01. CONCLUSIONS: C2 management of cyclosporine microemulsion therapy is effective and safe in pediatric kidney-transplant recipients given a combined immunosuppressive treatment.

Assays for complement proteins encoded in the class III region of human MHC.

Investigation of the complement proteins encoded in the class III region of the human MHC isclinically significant. A low level of components that make up the classical pathway is indicative of an underlying in vivo complement activation or primer complement deficiency. Hemolytic tests of C4 and C2 described are the only methods that allow quantitification of the functional complement proteins. The application of these sensitive techniques is unavoidable if inactive complement proteins are present. The complex hemolytic titration process protocol described in detail makes possible the use of this test. Assays to determine complement components belonging to the MHC III region were completed by a basic phenotyping test of the standard factor B alleles. This simple technique is a very useful first-step assay for clinical laboratories engaged in genetic studies.

Detection of apoptosis using the C2A domain of synaptotagmin I.

Binding of annexin V or the C2A domain of synaptotagmin I to phosphatidylserine expressed on the surface of apoptotic cells can, when labeled with appropriate probe molecules, be used to detect the presence of apoptosis using radionuclide, magnetic resonance, and optical imaging techniques. The preparation of a biotinylated C2A-GST fusion protein is described, and its capability, when used in conjunction with fluorescein-labeled streptavidin, of detecting apoptotic cells by flow cytometry is compared directly with the performance of a commercial preparation of fluorescein-labeled annexin V. Biotinylated C2A-GST, when used in conjunction with streptavidin-conjugated superparamagnetic iron oxide nanoparticles or Gd-chelate-avidin conjugates, was shown to be capable of detecting apoptotic cells using T(2)-weighted or T(1)-weighted magnetic resonance imaging experiments, respectively.