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.

Complete factor I deficiency due to dysfunctional factor I with recurrent aseptic meningo-encephalitis.

PURPOSE: Complement regulators control the activated complement system. Defects in this homeostasis can result in tissue damage and autoimmune diseases with a heterogeneity in clinical presentation. Complement factor I (FI), a serine protease, is an important regulator of alternative pathway activation. We report a diagnostic work-up of a patient with relapsing inflammatory mediated meningo-encephalitis. Our work-up revealed a rare genetic factor I (FI) deficiency. So far, all cases of reported complete factor I deficiency have absent serum levels of FI. We present here a unique case of a complete factor I deficiency based on a functional FI defect. METHODS: Complement assays and measurement of FI activity were performed in the patient, her family, factor H-deficient patients, a patient with C3-nephritic factor and 11 healthy controls. Genetic sequencing of the FI coding regions in the patient and her parents was performed. RESULTS: The patient had absent alternative pathway activity with low levels of C3 and normal serum level of FI. The patient's plasma FI did not degrade C3b, with normalisation of C3b degradation after adding purified FI. Mutation analysis of the complement factor I gene revealed two heterozygous mutations (I322T and D506V). CONCLUSION: To our knowledge, this paper describes a complete FI deficiency caused by a defect of FI activity for the first time. Normal FI concentration does not exclude a complete FI defect, additional functional analysis of FI is required in any patient with a defect of complement activation. Recurrent aseptic meningo-encephalitis is a rare clinical presentation of complete FI deficiency.

Cryofibrinogen levels are increased in non-traumatic osteonecrosis: a new pathogenic clue to osteonecrosis?

OBJECTIVE: To determine whether levels of cryofibrinogen are increased in non-traumatic osteonecrosis (ON) and could correlate with disease staging. METHODS: We prospectively analysed cryofibrinogen levels by immunofixation electrophoresis in 50 patients with non-traumatic ON, 50 healthy volunteers and 8 patients with traumatic ON. Staging of disease involving the femoral heads and the size of necrotic lesions were assessed by the Association Research Circulation Osseous (ARCO) classification system. RESULTS: Mean cryofibrinogen levels in patients with non-traumatic ON were significantly increased relative to healthy controls and to patients with traumatic ON (222.1 ± 20.6, 59.9 ± 5.6 and 52.3 ± 14.9 mg/dl, respectively, P < 0.001). In the non-traumatic ON group, mean cryofibrinogen levels were significantly increased in patients with multifocal ON compared with patients with mono/bifocal ON (276.5 ± 56.5 and 149.3 ± 15.4 mg/dl, respectively, P = 0.03). There were no significant differences in cryofibrinogen levels observed with respect to the size of the necrotic lesions involving the femoral heads. Moreover, cryofibrinogen levels in patients with ON of the femoral heads classified according to the stage of disease were not significantly different between patients with stage 1/2 and patients with stage 3 ON (179.2 ± 31.3 vs 204.1 ± 29.0 mg/dl, respectively; P = 0.813). CONCLUSION: Cryofibrinogen levels are increased in non-traumatic ON and, more importantly, in multifocal ON. The fact that cryofibrinogen levels are not correlated with the size of lesions and the stage of disease could imply systemic rather than local involvement characterizing the pathogenesis of ON.

Characterising cytokine gene expression signatures in patients with severe sepsis.

INTRODUCTION: Severe sepsis in humans may be related to an underlying profound immune suppressive state. We investigated the link between gene expression of immune regulatory cytokines and the range of illness severity in patients with infection and severe sepsis. METHODS: A prospective observational study included 54 ICU patients with severe sepsis, 53 patients with infection without organ failure, and 20 healthy controls. Gene expression in peripheral blood mononuclear cells (PBMC) was measured using real-time polymerase chain reaction. RESULTS: Infection differed from health by decreased expression of the IL2, and IL23 and greater expression of IL10 and IL27. Severe sepsis differed from infection by having decreased IL7, IL23, IFN γ , and TNF α gene expression. An algorithm utilising mRNA copy number for TNF α , IFN γ , IL7, IL10, and IL23 accurately distinguished sepsis from severe sepsis with a receiver operator characteristic value of 0.88. Gene expression was similar with gram-positive and gram-negative infection and was similar following medical and surgical severe sepsis. Severity of organ failure was associated with serum IL6 protein levels but not with any index of cytokine gene expression in PBMCs. CONCLUSIONS: Immune regulatory cytokine gene expression in PBMC provides a robust method of modelling patients' response to infection.

Scleroderma renal crisis triggered by ibuprofen: Insights on complement-directed therapy.

Scleroderma renal crisis is a severe complication of systemic sclerosis with a poor prognosis. Therefore, identifying precipitating factors is essential. Among known risk factors, only few are reversible. On the contrary, anti-C5 therapy appears effective, at least in some cases. We describe a 59-year-old man with diffuse cutaneous systemic sclerosis who developed life-threatening scleroderma renal crisis following ibuprofen administration. Despite aggressive management, he did not improve. Renal biopsy have displayed features of thrombotic microangiopathy but no complement deposition. We then discuss the pathomechanism of scleroderma renal crisis that could drive eculizumab treatment since some renal biopsies exhibit complement deposits and others do not.

A complement atlas identifies interleukin-6-dependent alternative pathway dysregulation as a key druggable feature of COVID-19.

Improvements in COVID-19 treatments, especially for the critically ill, require deeper understanding of the mechanisms driving disease pathology. The complement system is not only a crucial component of innate host defense but can also contribute to tissue injury. Although all complement pathways have been implicated in COVID-19 pathogenesis, the upstream drivers and downstream effects on tissue injury remain poorly defined. We demonstrate that complement activation is primarily mediated by the alternative pathway, and we provide a comprehensive atlas of the complement alterations around the time of respiratory deterioration. Proteomic and single-cell sequencing mapping across cell types and tissues reveals a division of labor between lung epithelial, stromal, and myeloid cells in complement production, in addition to liver-derived factors. We identify IL-6 and STAT1/3 signaling as an upstream driver of complement responses, linking complement dysregulation to approved COVID-19 therapies. Furthermore, an exploratory proteomic study indicates that inhibition of complement C5 decreases epithelial damage and markers of disease severity. Collectively, these results support complement dysregulation as a key druggable feature of COVID-19.

TIM3+ TRBV11-2 T cells and IFNγ signature in patrolling monocytes and CD16+ NK cells delineate MIS-C.

In rare instances, pediatric SARS-CoV-2 infection results in a novel immunodysregulation syndrome termed multisystem inflammatory syndrome in children (MIS-C). We compared MIS-C immunopathology with severe COVID-19 in adults. MIS-C does not result in pneumocyte damage but is associated with vascular endotheliitis and gastrointestinal epithelial injury. In MIS-C, the cytokine release syndrome is characterized by IFNγ and not type I interferon. Persistence of patrolling monocytes differentiates MIS-C from severe COVID-19, which is dominated by HLA-DRlo classical monocytes. IFNγ levels correlate with granzyme B production in CD16+ NK cells and TIM3 expression on CD38+/HLA-DR+ T cells. Single-cell TCR profiling reveals a skewed TCRß repertoire enriched for TRBV11-2 and a superantigenic signature in TIM3+/CD38+/HLA-DR+ T cells. Using NicheNet, we confirm IFNγ as a central cytokine in the communication between TIM3+/CD38+/HLA-DR+ T cells, CD16+ NK cells, and patrolling monocytes. Normalization of IFNγ, loss of TIM3, quiescence of CD16+ NK cells, and contraction of patrolling monocytes upon clinical resolution highlight their potential role in MIS-C immunopathogenesis.

Post-operative infection and sepsis in humans is associated with deficient gene expression of γc cytokines and their apoptosis mediators.

INTRODUCTION: Lymphocyte homeostasis is dependent on the γc cytokines. We hypothesised that sepsis in humans is associated with differential gene expression of the γc cytokines and their associated apoptosis mediators. METHODS: The study population consisted of a total of 60 patients with severe sepsis, 15 with gram negative bacteraemia, 10 healthy controls and 60 patients undergoing elective lung resection surgery. Pneumonia was diagnosed by CDC NNIC criteria. Gene expression in peripheral blood leukocytes (PBLs) of interleukin (IL)-2, 7, 15 and interferon (IFN)-γ, Bax, Bim, Bcl-2 was determined by qRT-PCR and IL-2 and IL-7 serum protein levels by ELISA. Gene expression of IL-2, 7 and IFN-γ was measured in peripheral blood leukocytes (PBL), cultured in the presence of lipopolysaccharide (LPS) and CD3 binding antibody (CD3ab) RESULTS: IL-2 gene expression was lower in the bacteraemia group compared with controls, and lower still in the sepsis group (P < 0.0001). IL-7 gene expression was similar in controls and bacteraemia, but lower in sepsis (P < 0.0001). IL-15 gene expression was similar in the three groups. Bcl-2 gene expression was less (P < 0.0001) and Bim gene expression was greater (P = 0.0003) in severe sepsis compared to bacteraemic and healthy controls. Bax gene expression was similar in the three groups.In lung resection surgery patients, post-operative pneumonia was associated with a perioperative decrease in IL-2 mRNA (P < 0.0001) and IL-7 mRNA (P = 0.003). IL-2 protein levels were reduced in sepsis and bacteraemia compared to controls (P = 0.02) but similar in pneumonia and non-pneumonia groups. IL-7 protein levels were similar in all groups.In cultured PBLs, IFN-γ gene expression was decreased in response to LPS and increased in response to CD3ab with sepsis: IL-7 gene expression increased in response to LPS in controls and to CD3ab with sepsis; Bcl-2 gene expression decreased in response to combined CD3ab and IL-2 with sepsis. CONCLUSIONS: Patients with infection and sepsis have deficient IL-2 and IL-7 gene expression in PBLs. Aberrant cytokine gene expression may precede the onset of infection.

Transforming growth factor beta-1 and interleukin-17 gene transcription in peripheral blood mononuclear cells and the human response to infection.

INTRODUCTION: The occurrence of severe sepsis may be associated with deficient pro-inflammatory cytokine production. Transforming growth factor beta-1 (TGFbeta-1) predominantly inhibits inflammation and may simultaneously promote IL-17 production. Interleukin-17 (IL-17) is a recently described pro-inflammatory cytokine, which may be important in auto-immunity and infection. We investigated the hypothesis that the onset of sepsis is related to differential TGFbeta-1 and IL-17 gene expression. METHODS: A prospective observational study in a mixed intensive care unit (ICU) and hospital wards in a university hospital. Patients (59) with severe sepsis; 15 patients with gram-negative bacteraemia but without critical illness and 10 healthy controls were assayed for TGFbeta-1, IL-17a, IL-17f, IL-6 and IL-1beta mRNA in peripheral blood mononuclear cells (PBMC) by quantitative real-time PCR and serum protein levels by ELISA. RESULTS: TGFbeta-1 mRNA levels are reduced in patients with bacteraemia and sepsis compared with controls (p=0.02). IL-6 mRNA levels were reduced in bacteraemic patients compared with septic patients and controls (p=0.008). IL-1beta mRNA levels were similar in all groups, IL-17a and IL-17f mRNA levels are not detectable in peripheral blood mononuclear cells. IL-6 protein levels were greater in patients with sepsis than bacteraemic and control patients (p<0.0001). Activated TGFbeta-1 and IL-17 protein levels were similar in all groups. IL-1beta protein was not detectable in the majority of patients. CONCLUSIONS: Down regulation of TGFbeta-1 gene transcription was related to the occurrence of infection but not the onset of sepsis. Interleukin-17 production in PBMC may not be significant in the human host response to infection.

Delayed Thrombotic Complications in a Thrombotic Thrombocytopenic Purpura Patient Treated With Caplacizumab.

Thrombotic thrombocytopenic purpura (TTP) is a rare and unpredictable disease with a high mortality rate (90%) if untreated. It results from systemic microvascular thrombosis and leads to profound thrombocytopenia, hemolytic anemia and organ failure of varying severity. However, macrovascular thrombosis has been described in very rare cases. Caplacizumab has emerged as a promising new drug for the management of TTP. We report the case of a patient with idiopathic refractory TTP treated with caplacizumab who developed thrombotic complications upon discontinuation of treatment.

Case Report: Neonatal Unexplained HUS Treated With Complement Inhibitor Eculizumab.

Background: Hemolytic uremic syndrome (HUS) is rare in neonates. It is probably an under-recognized condition in the early postnatal period as it presents similarly to the most common perinatal asphyxia and to differentiate the two conditions is challenging. We describe the clinical presentation of a potential new subtype of neonatal HUS triggered by hypoxic-ischemic event. Our patient was successfully treated by a single dose of Eculizumab as early as at 9 days of life. Case Report: A 35-weeks infant was born with low hemoglobin and subsequently developed respiratory distress, hypotension, and acidosis. Blood transfusion was administered, acidosis corrected, neurological examination remained reassuring. Few hours later he developed renal failure, macroscopic hematuria, hemobilia, thrombocytopenia and coagulopathy refractory to platelet and fresh frozen plasma transfusions. No infection was found. Haptoglobin was non-measurable, and schistocytes present, complement factors C3, C4 and B were low, FBb increased. HUS was suspected. A single dose of Eculizumab™ was administered on day 9 of life. No genetic mutation of atypical HUS was found. He was discharged with improving renal function and developing cholestasis. Conclusion: In neonates with hemolytic anemia, thrombocytopenia, hematuria and renal failure, HUS should be suspected. In neonatal HUS Eculizumab should be considered as first-line therapy and discontinuation can be considered if no genetic mutation is found and clinical condition improves. In very young patients, cholestasis could appear as potential side effect of Eculizumab™.

Monitoring the immune response using real-time PCR.

Induction of an immune response to a particular antigen is the basis of vaccination. This has been done for years to prevent infectious diseases, and has the potential for the treatment of cancer. The immune response is nowadays more precisely modulated rather than simply induced, like in case of immunotherapy of allergic diseases. Likewise, autoimmune diseases are associated with an inappropriate immune response, and many efforts are made for specifically inhibiting this unwanted response. A possible line of attack is the induction of an antigen-specific immune tolerance, which also has a use in the field of transplantation, where allogeneic responses are deleterious for the graft. In all of these fields of fundamental and clinical medicine, the modulation of immune response requires the assistance of laboratory tests, among which real-time PCR appears more and more helpful. This chapter describes a protocol to quantify immune-related mRNAs using reverse transcription-real-time PCR. The transcripts can be quantified in cultured cells or in cultured whole blood, after an incubation period in the presence of the antigen to which the immune response is analyzed. This is the typical approach to evaluate the efficacy of a vaccine. The transcripts can also be quantified directly in the biological sample, giving information about the in vivo immune status of the individual. The techniques to achieve these different methods are described, and are illustrated by the analysis of the response against the toxoid tetanus antigen.

Variability of Faecal Calprotectin in Inflammatory Bowel Disease Patients: An Observational Case-control Study.

BACKGROUND AND AIMS: Several factors have been reported to affect faecal calprotectin [FC] values, and significant variation in FC concentrations has been observed in inflammatory bowel disease [IBD] patients. We aimed to evaluate FC variability in IBD patients, and to assess the robustness of a single stool punch. METHODS: This is a single-centre observational case-control study. Disease activity was assessed using endoscopic and clinical activity scores, as well as C-reactive protein levels. Stool samples were collected twice within a 1 to 6 days interval, and FC was measured on punches and homogenates by fluorometric enzyme immunocapture assay. RESULTS: In all, 260 stool samples were collected from 120 patients. Intrastool variability was low, with an intraclass correlation coefficient for single measures between three punches from a single stool sample of 0.91, and median coefficient of variation [CV] of 17%. CV of two stool samples a few days apart [intra-individual variability] were significantly higher [p <0.01] with median CV of 36%. FC standard deviations correlated with mean FC levels either for intrastool or for intra-individual variability, with a Spearman's coefficient of rank correlation of 0.85 and 0.78, respectively [p <0.01]. Disease type, location, activity, and FC levels did not influence variability. CONCLUSIONS: A single stool punch is reliable for FC measurement, considering that intrastool variability is low. Intra-individual variability a few days apart is significantly higher. Therefore, decision-making strategies based on single measurements should consider this variability, to determine the minimum optimal variation to be achieved, rather than a cut-off, especially in high FC levels.

The human response to infection is associated with distinct patterns of interleukin 23 and interleukin 27 expression.

OBJECTIVE: The development and progression of severe sepsis is related to a deficiency in pro-inflammatory cytokine production, characterised by lesser IFNgamma levels, which are not explained by variations in levels of the main putative regulator of IFNgamma, namely IL-12. As alternative regulators of IFNgamma may be of greater importance in human sepsis, we investigated the hypothesis that the development of severe sepsis is related to variations in IL-18, IL-23 and IL-27 gene expression. DESIGN AND SETTING: A prospective observational trial in a mixed intensive care unit (ICU) and hospital wards in a university teaching hospital. PATIENTS AND PARTICIPANTS: Sixty-two ICU patients with severe sepsis, 13 bacteraemic patients with no acute critical illness, and 10 healthy controls. MEASUREMENTS AND RESULTS: All subjects were assayed for IL-18, IL-23 and IL-27 mRNA levels in peripheral blood. IL-27 mRNA levels distinguished between the three groups, with levels highest in the ICU group, intermediate in the bacteraemic group and lowest in the control group. IL-23 distinguished between the groups, with levels lowest in the ICU group. In late sepsis IL-23 and TNFalpha mRNA levels were directly related. IL-18 mRNA levels did not distinguish between the patient groups. CONCLUSIONS: We conclude that the deficient pro-inflammatory response in patients with sepsis is expansive and includes deficient IL-23 and excessive IL-27 gene expression. This provides further evidence that upregulation of a cytokine-based immune response is beneficial in sepsis.

Assays for alloreactive responses by PCR.

In organ transplantation, major efforts are currently developed to minimize or even to withdraw immunosuppressive drugs. Different protocols have therefore been proposed to induce graft tolerance, that is, the survival of an allograft in the absence of continuing immunosuppression. They generally involve pre-transplant conditioning followed by hematopoietic stem cell infusion. Follow-up of immune status is mandatory in this kind of protocol, in order to investigate tolerance and consequently to reduce or withdraw immunosuppression without graft rejection. However, assessment of the alloreactive response using currently available techniques is labor-intensive and requires significant volume of patient's blood. The implementation of such tolerance protocols is thus difficult in routine practice. In this chapter, we describe a novel real-time polymerase chain reaction method based on interferon-gamma and interleukin-2 mRNAs quantification that requires only 10 ml of blood. Moreover, results can be obtained within 48 h. A modified mixed lymphocyte reaction (MLR) using whole blood T lymphocytes as responsive cells and CD3-depleted peripheral blood mononuclear cells (PBMCs) as stimulators is described. An alternative, that is, the use of PBMC as responding cells instead of whole blood, is also depicted. We successfully applied the technique in the monitoring of anti-donor reactivity in living donor liver graft recipients. We suggest that this rapid MLR assay could be valuable for the monitoring of patients undergoing solid organ or hematopoietic stem cell transplantation.

Value of non-identified ANCA (non-PR3, non-MPO) in the diagnosis of granulomatosis with polyangiitis (Wegener's granulomatosis).

OBJECTIVE: Determine the frequency of granulomatosis with polyangiitis (GPA) associated with non-identified ANCA (non-MPO, non-PR3 ANCA) and secondarily compare their clinic with GPA associated with MPO-positive or PR3-positive ANCA. METHODS: In a monocentric retrospective observational study, clinical data of 398 patients with non-identified ANCA (titer of ANCA at least 1/80 by immunofluorescence on ethanol fixed PMN) was gathered over a period of 6 years. GPA patients from this population were compared with GPA patients with identified ANCA on the basis of clinical, biological, immunological and histological features. RESULTS: The most common diseases associated with non-identified ANCA were inflammatory bowel diseases accounting for 17% of diseases. GPA accounted for only 1.8% of cases. There were no significant differences in terms of clinical and histological characteristics between GPA with non-identified ANCA and GPA with identified ANCA, but significantly higher CRP levels were observed in GPA patients with identified ANCA (p = 0.005). Localized disease (ear, nose and throat and/or lung involvement without any other systemic involvement) was more frequent in the group of GPA with nonidentified ANCA (p = 0.047) as compared to GPA with identified ANCA. This explains that the former group of patients was less frequently treated by cyclophosphamide than the latter (p = 0.016). CONCLUSION: GPA with non-MPO, non-PR3 ANCAs is relatively rare. Our study suggests that GPA with nonidentified ANCA differs from GPA with identified ANCA by the frequency of localized forms.

The occurrence of severe sepsis and septic shock are related to distinct patterns of cytokine gene expression.

Patient response to acute bacterial infection is highly variable. Differing outcomes in this setting may be related to variations in the immune response to an infectious insult. Using quantitative real-time polymerase chain reaction, we quantified gene expression of the tumor necrosis factor alpha(TNFalpha), interferon gamma (IFNgamma), and interleukin 10 (IL10), IL12p35, and IL4 genes in 3 patient groups. These groups consisted of an intensive care unit (ICU) cohort who presented with severe sepsis or septic shock, a group of noncritically ill ward patients with documented Gram-negative bacteremia, and a group of healthy controls. Greater interleukin 10 messenger RNA (mRNA) levels were detected in the ICU group in comparison with both the bacteremic and control groups (P < 0.0001). More TNF-alpha mRNA was detected in the ICU group when compared with the control group (P < 0.0001). However, TNF-alpha mRNA was most abundant in the bacteremic group (P = 0.0007). Lesser IFN-gamma mRNA levels were detected in the ICU group when compared with both the bacteremic and control groups (P < 0.0003). Cytokine mRNA levels were not associated with the occurrence of shock upon admission to ICU. On the seventh day of ICU stay, the presence of shock was associated with lesser IFN-gamma mRNA (P = 0.0004) and lesser TNF-alpha mRNA (P = 0.001). Survivors had greater TNF-alpha mRNA copy numbers on day 7 of ICU stay than nonsurvivors (P = 0.002). We conclude that a proinflammatory response is the appropriate response in the setting of infection and is associated with lesser requirements for inotropes and lesser mortality. Quantitative real-time polymerase chain reaction can be used to predict infection outcome in clinically relevant situations where enzyme-linked immunosorbent assay testing has proved disappointing.

Isolation of a thiol-dependent serine protease in peanut and investigation of its role in the complement and the allergic reaction.

A serine protease activity was detected in aqueous peanuts seeds extracts, partially purified and characterized as a thiol-dependent serine protease. The potential role of this proteolytic activity on allergic reaction to peanuts was prospected through complement activation studies in human plasma and serum, and MDCK cells to investigate a possible occludin degradation in tight junctions. The peanut protease activity induced the production of anaphylatoxins C3a and C5a, and of the terminal membrane attack complex SC5b-9 whatever the complement activation pathway. The protease activity was also involved in the partial digestion of occludin within tight junctions, with for result, an increase of the epithelial permeability to antigen absorption.