Mannose-binding Lectin Complement Pathway Research Articles

Narsoplimab for severe transplant-associated thrombotic microangiopathy

BackgroundTransplantation-associated thrombotic microangiopathy (TA-TMA) is an endothelial injury syndrome linked to the overactivation of complement pathways. It manifests with microangiopathic hemolytic anemia, consumptive thrombocytopenia, and microvascular thrombosis leading to ischemic tissue injury. Mannose residues on fungi and viruses activate the mannose-binding lectin complement pathway, and hence activation of the lectin pathway could be one of the reasons for triggering TA-TMA. Narsoplimab, a human monoclonal antibody targeting MASP-2 is a potent inhibitor of the lectin pathway. We describe the transplant course of a pediatric patient who developed TA-TMA following Candida-triggered macrophage activation syndrome and was treated with Narsoplimab. The data collection was performed prospectively.Case presentationThe six-year-old girl underwent a human leucocyte antigen (HLA) haploidentical hematopoietic stem cell transplant using post-transplant Cyclophosphamide for severe aplastic anemia. In the second week of the transplant, the patient developed macrophage activation syndrome necessitating treatment with steroids and intravenous immunoglobulin. Subsequently, USG abdomen and blood fungal PCR revealed the diagnosis of hepatosplenic candidiasis. Candida-triggered macrophage activation syndrome responded to antifungals, steroids, intravenous immunoglobulin, and alemtuzumab. However, the subsequent clinical course was complicated by thrombotic microangiopathy. The patient developed hypertension in the 2nd week, followed by high lactate dehydrogenase (1010 U/L), schistocytes (5 per hpf), low haptoglobin (< 5 mg/dl), thrombocytopenia, and anemia in the 3rd week. Ciclosporin was stopped, and the patient was treated with 10 days of defibrotide without response. The course was further complicated by the involvement of the gastrointestinal tract and kidneys. She had per rectal bleeding with frequent but low-volume stools, severe abdominal pain, and hypoalbuminemia with a rising urine protein:creatinine ratio. Narsoplimab was started in the 5th week of the transplant. A fall in lactate dehydrogenase was observed after starting Narsoplimab. This was followed by the resolution of gastrointestinal symptoms, proteinuria, and recovery of cytopenia. The second episode of TA-TMA occurred with parvoviraemia and was also successfully treated with Narsoplimab.ConclusionLectin pathway inhibition could be useful in treating the fatal complication of transplant-associated thrombotic microangiopathy.

Abstract 11515: Mannose-Binding Lectin is Dysregulated in Cardiac Endothelial Cells of Women With Peripartum Cardiomyopathy

Introduction: Peripartum cardiomyopathy (PPCM) is a type of heart failure that presents with systolic dysfunction in the third trimester of pregnancy or early postpartum. Viral myocarditis, genetic predisposition, and hormonal changes are suggested as contributing factors to PPCM. However, the molecular basis of PPCM remained elusive. Hypothesis: Cardiac expression of genes involved in immune system response is dysregulated in PPCM. Methods: We identified women with PPCM and age/race-matched heart donors from a dataset obtained from Myocardial Applied Genomics Network (MAGNet) consortium. Left ventricular (LV) biopsies were taken at the time of heart transplantation. Bulk RNA-seq was performed on LV tissue of patients with PPCM and non-failing heart donors (NF). We used the Human Cell Atlas (HCA) reference database with accession code ERP128138 to investigate cell-specific enrichment of genes. Results: Mean age of study participants was 36.1 years and 33.3% of participants had African American ancestry. We found that LCN6 (Log2(fold_change) = -4.1, p-val = 0.0027) and FCN3 (Log2(fold_change) = -3.4, p-val = 0.0042) are downregulated in LV tissue obtained from PPCM compared to NF. LCN6 encodes lipocalin-6 and FCN3 encodes ficolin-3 which are upstream of the mannose-binding lectin complement pathway. Based on HCA dataset on adult human hearts, we observed that LCN6 and FCN3 genes are mainly expressed by endothelial cells. Conclusions: We demonstrated that expression of LCN6 and FCN3 genes, which are upstream of the mannose-binding lectin pathway, is decreased in cardiac endothelial cells of individuals with PPCM. Mannose-binding lectin is a soluble pattern recognition receptor that identifies mannose and N-acetylglucosamine residues in a wide variety of pathogens and antigen-antibody complexes and works as an opsonin that facilitates phagocytosis. Our findings suggest the possibility of impaired immune complex clearance in PPCM pathogenesis.

An Ixodes ricinus Tick Salivary Lectin Pathway Inhibitor Protects Borrelia burgdorferi sensu lato from Human Complement.

We previously identified tick salivary lectin pathway inhibitor (TSLPI) in Ixodes scapularis, a vector for Borrelia burgdorferi sensu stricto (s.s.) in North America. TSLPI is a salivary protein facilitating B. burgdorferi s.s. transmission and acquisition by inhibiting the host lectin complement pathway through interference with mannose binding lectin (MBL) activity. Since Ixodes ricinus is the predominant vector for Lyme borreliosis in Europe and transmits several complement sensitive B. burgdorferi sensu lato (s.l.) strains, we aimed to identify, describe, and characterize the I. ricinus ortholog of TSLPI. We performed (q)PCRs on I. ricinus salivary gland cDNA to identify a TSLPI ortholog. Next, we generated recombinant (r)TSLPI in a Drosophila expression system and examined inhibition of the MBL complement pathway and complement-mediated killing of B. burgdorferi s.l. in vitro. We identified a TSLPI ortholog in I. ricinus salivary glands with 93% homology at the RNA and 89% at the protein level compared to I. scapularis TSLPI, which was upregulated during tick feeding. In silico analysis revealed that TSLPI appears to be part of a larger family of Ixodes salivary proteins among which I. persulcatus basic tail salivary proteins and I. scapularis TSLPI and Salp14. I. ricinus rTSLPI inhibited the MBL complement pathway and protected B. burgdorferi s.s. and Borrelia garinii from complement-mediated killing. We have identified a TSLPI ortholog, which protects B. burgdorferi s.l. from complement-mediated killing in I. ricinus, the major vector for tick-borne diseases in Europe.

Case report of mannose-binding lectin (MBL) deficiency and postoperative sepsis and coagulopathy in a patient following total pancreatectomy for chronic pancreatitis.

Complement plays a central role against infection and coordinates the activity of coagulation and fibrinolysis. In this report we present a patient that underwent total pancreatectomy experienced sepsis, coagulopathy and bleeding that endangered the postoperative course. A sixty-five-year-old woman underwent total pancreatectomy for intractable pain without islet transplant, this patient was diagnosed as AP and MBL deficient from a blood test performed preoperatively. On the postoperative course she experienced severe haemorrhages and sepsis for 3 weeks postoperatively. An analysis of serial perioperative serum samples conducted which showed further depletion of the alternate and MBL complement pathway without restoration to baseline levels. This is the first reported case of alternative and mannose-binding lectin pathways depletion associated with major postoperative bleeding and sepsis following pancreatic surgery. Future research should examine the relationship between complement pathways activity and postoperative complications in order to possibly introduce it as a preoperative screening and possible replacement therapy prior to any major surgical intervention.

Mannose binding lectin mediated complement pathway in multiple sclerosis

Role of mannose binding lectin (MBL) complement activation pathway, an arm of innate immunity in multiple sclerosis (MS) was evaluated by analyzing the expression of MBL, MBL-associated serine protease-2 (MASP-2), and functional MBL/MASP-2 mediated C4 cleavage (fMBL) in 87 plasma and cerebrospinal fluid (CSF) samples from MS patients and non-MS controls. Median fMBL and MASP-2 plasma levels were higher in MS vs. non-MS cases. These associations remained in an analysis of subtypes of MS disease. These findings suggest a potential activation of MBL complement pathway in MS that may possibly alter the risk or progression of MS disease.

6511 POSTER Restoration of Activity in Mannose-binding Lectin Complement Pathway in Patients With Advanced Pancreatic Cancer Treated With Intravenous Omega-3 Rich Lipid Infusion and Gemcitabine is Associated With Improved Outcome

6511 POSTER Restoration of Activity in Mannose-binding Lectin Complement Pathway in Patients With Advanced Pancreatic Cancer Treated With Intravenous Omega-3 Rich Lipid Infusion and Gemcitabine is Associated With Improved Outcome

Mannose-binding lectin complement pathway plays a key role in complement activation by Paracoccidioides brasiliensis

Paracoccidioides brasiliensis (Pb) is a dimorphic fungal pathogen that causes paracoccidioidomycosis, the most severe deep mycosis from South America. Although cell mediated immunity is considered the most efficient protective mechanism against Pb infection, mechanisms of innate immunity are poorly defined. Herein, we investigated the interaction of the complement system with high and low virulence isolates of Pb. We demonstrated that Pb18, a high virulence Pb isolate, when incubated with normal human serum (NHS) induces consumption of hemolytic complement and, when immobilized, promotes binding of C4b, C3b and C5b-C9. Both, low virulence (Pb265) and high virulence (Pb18) isolates consumed C4, C3 and mannose-binding lectin (MBL) of MBL-sufficient, but not of MBL-deficient serum as revealed by deposition of residual C4, C3 and MBL on immune complexes and mannan. However, higher complement components consumption was observed with Pb265, as compared with Pb18. The suggested relationship between low virulence and significant complement activation properties of Pb isolates, was confirmed by the demonstration that virulence attenuation of Pb 18 results in acquisition of the ability to activate complement. Conversely, reactivation of attenuated Pb18, results in loss of the ability to activate complement. Our results demonstrate for the first time that Pb yeasts activate the complement system by the lectin pathway, and there is an inverse correlation between complement activating ability and Pb virulence. These differences could exert an influence on innate immunity and severity of the disease developed by infected hosts.

Functional analysis of the mannose-binding lectin complement pathway in normal pregnancy and preeclampsia

Preeclampsia is a severe complication of pregnancy characterized by hypertension and proteinuria developing after midgestation. Previous studies have shown increased complement activation in normal and preeclamptic pregnancies. We aimed to investigate the role of the mannose-binding lectin pathway in the initiation of pathological complement activation observed in patients with preeclampsia. The study included 60 preeclamptic patients, 60 healthy pregnant women and 56 healthy non-pregnant women. Functional activity of the complex of mannose-binding lectin and mannose-binding lectin-associated serine protease 2 (MBL-MASP2 complex) was determined by ELISA. Circulating levels of complement components and C-reactive protein (CRP) were also measured. MBL-MASP2 activity was significantly higher in healthy pregnant than non-pregnant women. However, increased activity of the MBL-MASP2 complex in preeclamptic patients was not observed, compared to healthy pregnant women. MBL-MASP2 activity showed no relationship with either the levels of complement parameters, or with the clinical data and level of CRP in patients with preeclampsia. In conclusion, the complement system is activated with increased terminal complex formation in the third trimester of normal human pregnancy, and is further activated in preeclampsia as shown by the elevated amounts of activation markers. The activity of MBL-MASP2 is also increased in normal pregnancy, to the same level seen in preeclampsia. In our study, no relationship between MBL-MASP2 activity and extent of complement activation was observed in preeclampsia. We tentatively conclude, albeit without an evaluation of local placental concentrations, that the mannose-binding lectin pathway may play only a minor role in pathological complement activation during preeclampsia.

Mannose-binding lectin complement pathway plays a key role in complement activation by Paracoccidioides brasiliensis

Mannose-binding lectin complement pathway plays a key role in complement activation by Paracoccidioides brasiliensis

Low levels of mannose-binding lectin confers protection against tuberculosis in Turkish children

Mannose-binding lectin (MBL) plays an important role in innate immunity mediating phagocytosis and activating the MBL complement pathway. Few studies, conducted in adult populations, have shown that genetically determined low MBL levels may confer partial protection against tuberculosis (TB). In this study we aimed to investigate the relationships between the susceptibility to TB and two low producing MBL2 gene polymorphisms (codons 54 and 57) and MBL levels in children. Forty-four TB children (27 pulmonary TB, 17 extrapulmonary TB) and 99 age-matched healthy control children were included in the study. The mean age in the study group was 7.02 +/- 4.5 years. Genotyping of the MBL2 gene for codon 54 and 57 polymorphisms was carried out, and MBL levels in serum were also detected in all subjects from both groups. None of the subjects from either group showed codon 57 polymorphisms. The frequency of the AB genotype which produces low level MBL is significantly lower in the patients (9.1%) compared to control subjects (27.3%) (p < 0.011). The difference was especially significant between the extrapulmonary group and healthy controls (p < 0.006). The BB genotype was observed in only one child from the healthy controls and no children from the patient group. The median MBL plasma concentration was also significantly lower in the control group than that found in the study group (p = 0.036). These results indicate that low levels of MBL and AB genotype may be involved in the protection against tuberculosis, especially extrapulmonary tuberculosis in children.

Fluorochrome-linked immunoassay for functional analysis of the mannose binding lectin complement pathway to the level of C3 cleavage

The humoral response to invading pathogens is mediated by a repertoire of innate immune molecules and receptors able to recognize pathogen-associated molecular patterns. Mannose binding lectin (MBL) and ficolins are initiation molecules of the lectin complement pathway (LCP) that bridge innate and adaptive immunity. Activation of the MBL-dependent lectin pathway, to the level of C3 cleavage, requires functional MASP-2, C2, C4 and C3, all of which have been identified with genetic polymorphisms that can affect protein concentration and function. Current assays for MBL and MASP-2 lack the ability to assess activation of all components to the level of C3 cleavage in a single assay platform. We developed a novel, low volume, fluorochrome linked immunoassay (FLISA) that quantitatively assesses the functional status of MBL, MASP-2 and C3 convertase in a single well. The assay can be used with plasma or serum. Multiple freeze/thaw cycles of serum do not significantly alter the assay, making it ideal for high throughput of large sample databases with minimal volume use. The FLISA can be used potentially to identify specific human disease correlations between these components and clinical outcomes in already established databases.

Mannose-binding lectin levels during pregnancy: a longitudinal study

Pregnancy is associated with changes in the immune system. Although previous studies have focussed mainly on adaptive immunity, there are indications that components of innate immunity, such as mannose-binding lectin (MBL), are associated with pregnancy outcome. Although this would suggest that pregnancy also involves adaptations in innate immunity, there are few studies in this area. Therefore, we aimed to determine whether MBL concentrations and the following steps in complement pathway activation are influenced by pregnancy. MBL and Ficolin-2 concentrations, MBL-MBL-associated serine protease (MASP) complex activity, MBL pathway activity and classical complement pathway activity were determined by enzyme-linked immunosorbent assay (ELISA) in sera from pregnant women (n=32) during each trimester and post-partum. MBL genotyping was performed by PCR. During pregnancy, MBL concentrations increased to 140% [interquartile range (IQR) 116-181%, P < 0.0001]. This increase was already present at 12 weeks of pregnancy and was most pronounced in the high-production AA-genotype. Directly Post-partum MBL concentrations dropped to 57% of baseline (IQR 44-66%, P < 0.0001). Variations in MBL levels were reflected by similar changes in the following steps of complement activation, r > 0.93 (P < 0.01). Ficolin-2 levels and classical complement pathway activity were not similarly influenced by pregnancy. Pregnancy and the post-partum period profoundly influence MBL serum concentration and MBL complement pathway activity.

Mannose-Binding Lectin Is a Regulator of Inflammation That Accompanies Myocardial Ischemia and Reperfusion Injury

The mannose-binding lectin (MBL), a circulating pattern recognition molecule, recognizes a wide range of infectious agents with resultant initiation of the complement cascade in an Ab-independent manner. MBL recognizes infectious non-self and altered self in the guise of apoptotic and necrotic cells. In this study, we demonstrate that mice lacking MBL, and hence are devoid of MBL-dependent lectin pathway activation but have fully active alternative and classical complement pathways, are protected from cardiac reperfusion injury with resultant preservation of cardiac function. Significantly, mice that lack a major component of the classical complement pathway initiation complex (C1q) but have an intact MBL complement pathway, are not protected from injury. These results suggest that the MBL-dependent pathway of complement activation is a key regulator of myocardial reperfusion ischemic injury. MBL is an example of a pattern recognition molecule that plays a dual role in modifying inflammatory responses to sterile and infectious injury.

Purpura fulminans méningococcique : rencontre malheureuse de polymorphismes génétiques ?

Despite significant progress in intensive care medicine, the mortality of septic shock has not changed in recent years. Early recognition of subtle signs in favor of meningococcal sepsis, early antibiotic treatment, and aggressive hemodynamic support remains the cornerstone of therapy of severe meningococcal shock in children. Recent work has emphasized the role of genetic polymorphisms in various systems to explain the most severe cases: anti-inflammatory cytokine profile IL-10/TNF-α, elevated levels of plasminogen activator inhibitor type-1, variants of the gene for mannose-binding lectin complement pathway. This may explain the disillusionment of pediatric intensivists, and the general failure of immunotherapy for sepsis. Reasonable hope lies upon new meningococcal vaccines.