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The aim of this systematic review and meta-analysis was to pool the data on Single Nucleotide Polymorphisms (SNPs) in immune response genes associated with dental caries. Nineteen studies were included in the review and 18 in the meta-analysis. Twenty-two SNPs were evaluated, which are linked to six different genes (MBL2, LFT, MASP2, DEFB1, FCN2 and MUC5B). Most SNPs (81.8%) are related to the possible functional impact on protein coding. The MBL2 gene was associated with caries experience in the analysis of the homozygote (OR = 2.12 CI95%[1.12-3.99]) and heterozygote (OR = 2.22 CI95%[1.44-3.44]) genotypes. The MUC5B gene was associated according to an analysis of the heterozygous genotype (OR = 1.83 CI95%[1.08-3.09]). Thus, SNPs related to immune response genes are linked to the phenotype of caries experience. Although the meta-analysis showed that the genes MBL2 and MUC5B were associated with caries, these results should be interpreted with caution due to the quality of the evidence.

The role of the lectin pathway (LP) of complement has not been explored in the thrombotic microangiopathies (TMA). We examined levels of MASP2, the effector enzyme of the LP, in three major forms of TMA and assessed the effect of the anti‐MASP2 human monoclonal antibody narsoplimab on TMA plasma‐induced activation of caspase 8 in microvascular endothelial cells. MASP2 levels were highly elevated in all TMA patients versus controls. Caspase 8 activation was suppressed by clinically relevant levels of narsoplimab. In conclusion, we found that the LP of complement is activated in TMAs of diverse etiology and LP inhibition may be of therapeutic benefit in these disorders., Summary Involvement of the alternative complement pathway (AP) in microvascular endothelial cell (MVEC) injury characteristic of a thrombotic microangiopathy (TMA) is well documented. However, the role of the lectin pathway (LP) of complement has not been explored. We examined mannose‐binding lectin associated serine protease (MASP2), the effector enzyme of the LP, in thrombotic thrombocytopenic purpura, atypical hemolytic uremic syndrome and post‐allogeneic hematopoietic stem cell transplantation (alloHSCT) TMAs. Plasma MASP2 and terminal complement component sC5b‐9 levels were assessed by enzyme‐linked immunosorbent assay (ELISA). Human MVEC were exposed to patient plasmas, and the effect of the anti‐MASP2 human monoclonal antibody narsoplimab on plasma‐induced MVEC activation was assessed by caspase 8 activity. MASP2 levels were highly elevated in all TMA patients versus controls. The relatively lower MASP2 levels in alloHSCT patients with TMAs compared to levels in alloHSCT patients who did not develop a TMA, and a significant decrease in variance of MASP2 levels in the former, may reflect MASP2 consumption at sites of disease activity. Plasmas from 14 of the 22 TMA patients tested (64%) induced significant MVEC caspase 8 activation. This was suppressed by clinically relevant levels of narsoplimab (1·2 μg/ml) for all 14 patients, with a mean 65·7% inhibition (36.8–99.4%; P

BACKGROUND This study aimed to compare the characteristics of mRNA expression of genes in complement system between acute arterial thrombotic patients and paroxysmal atrial fibrillation (PAF) patients. METHODS Twenty acute myocardial infarction (AMI) patients and 20 PAF patients were assigned into the experiment groups, and 20 stable angina pectoris (SAP) patients were enrolled in the control group. RESULTS When compared with the control group, mRNA expression of C1QA, C1QB, C1QC, C1R, CFP, C5, CR1, ITGAM, ITGAX, ITGB2, C5AR1, CD46, CD55 and CD59 genes was significantly upregulated, and CR2 gene significantly downregulated in the AMI group (P

IgA nephropathy (IgAN) is common chronic glomerulonephritis with variable prognosis, ranging from minor urinary abnormalities to end-stage renal disease. The revised Oxford classification of IgAN explains that cellular/fibrocellular crescents are associated with poor renal prognosis, proposing an extension to the MEST-C score. C3 immunofluorescent staining follows a distribution similar to IgA staining. Therefore, complement activation was reported to play a pivotal role in IgAN pathogenesis. This study included 132 IgAN patients diagnosed by renal biopsies. The clinical parameters at the time of the biopsies were obtained from patient data records. We classified the patients into C ≥ 1 and C0 groups, and compared clinical, light microscopic, and immunofluorescent features. In the C ≥ 1 group, 2 (1.5%) and 31 (23.5%) patients were assigned to C2 and C1, respectively. The remaining 99 patients (75%) were classified as C0. The C ≥ 1 group had lower average age and rate of hypertension, and higher score of urinary occult blood and E score. The C ≥ 1 group had significantly higher average immunofluorescence scores for IgA, C5b-9, mannose-associated serine protease (MASP) 1/3, MASP2, properdin, factor B, and kappa. The steroid use rate was significantly higher in the C ≥ 1 group. During the follow-up period of 2.90 years on average, the rate of renal dysfunction was not significantly different between groups. Crescent formation in IgAN was associated with activation of the lectin and alternative pathways. The C ≥ 1 group had significantly increased use of steroids, which probably caused comparable renal function during the follow-up period.

Mannan-binding lectin-associated serine protease-2 (MASP-2) has been reported to play an important role as a key enzyme in the lectin pathway of the complement system. The objectives of our study were to determine whether the single-nucleotide polymorphism (SNPs) of MASP2 and the gene-tea drinking interaction were associated with the susceptibility to TB. In total, 503 patients and 494 healthy controls were contained. Three SNPs (rs12142107, rs12711521, and rs7548659) were genotyped. The association between the SNPs and susceptibility to TB were investigated by conducting multivariate unconditional logistic regression analysis. The gene-tea drinking interactions were analyzed by the additive model of marginal structural linear odds models. Both genotype AC + AA at rs12711521 of MASP2 genes and genotype GT + GG at rs7548659 of MASP2 genes were more prevalent in the TB patient group than the healthy control group (OR: 1.423 and 1.439, respectively, P MASP2 genes was found to suggest negative interactions, which reached − 0.2311 (95% confidence interval (CI): − 0.4736, − 0.0113), − 0.7080 (95% CI − 1.3998, − 0.0163), and − 0.5140 (95% CI − 0.8988, − 0.1291), respectively (P MASP2 were associated with the susceptibility to TB. Furthermore, there were negative interactions between tea drinking and rs12142107, rs12711521, and rs75548659 of MASP2 gene, respectively. Our research provides a basis for studying the pathogenesis and prevention of tuberculosis.

Components of the complement system and atypical parameters of coagulation were reported in COVID-19 patients, as well as the exacerbation of the inflammation and coagulation activity. Mannose binding lectin (MBL)- associated serine proteases (MASPs) play an important role in viral recognition and subsequent activation of the lectin pathway of the complement system and blood coagulation, connecting both processes. Genetic variants of MASP1 and MASP2 genes are further associated with different levels and functional efficiency of their encoded proteins, modulating susceptibility and severity to diseases. Our review highlights the possible role of MASPs in SARS-COV-2 binding and activation of the lectin pathway and blood coagulation cascades, as well as their associations with comorbidities of COVID-19. MASP-1 and/or MASP-2 present an increased expression in patients with COVID-19 risk factors: diabetes, arterial hypertension and cardiovascular disease, chronic kidney disease, chronic obstructive pulmonary disease, and cerebrovascular disease. Based also on the positive results of COVID-19 patients with anti-MASP-2 antibody, we propose the use of MASPs as a possible biomarker of the progression of COVID-19 and the investigation of new treatment strategies taking into consideration the dual role of MASPs, including MASP inhibitors as promising therapeutic targets against COVID-19.

Thousands of leprosy patients not only suffer from physical deformities, but also either have or have had hepatitis B virus (HBV) coinfection. Polymorphisms of the complement system modulate susceptibility to leprosy, but genetic susceptibility to past or present HBV infection is unknown. We used sequencing and multiplex sequence-specific PCR to genotype 72 polymorphisms of seven genes (MBL2, FCN1, FCN2, FCN3, MASP1, MASP2, C3) encoding components of the lectin pathway, and two genes encoding complement receptors (CR1, VSIG4) in 190 patients, of which 74 were positive for HBsAg and/or anti-HBc (HBV+, 93.2% with a resolved infection) and 116 lepromatous patients, and 408 HBV-blood donors. In addition, we tested for levels of proteins of the lectin pathway. We found no difference between serum concentrations of mannan-binding lectin (MBL), MBL-associated serine proteins (MASP-1, MASP-2, MASP-3, MAp44), ficolin-3 (FCN-3), soluble complement receptor 1 (sCR1) and MBL mediated C4 activation, measured by ELISA or TRIFMA in up to 167 HBV+ and HBV− patients. Haplotypes lowering protein levels or encoding dysfunctional proteins increased susceptibility to HBV infection: MBL2*LYQC (OR = 3.4, p = 0.02), MASP1*AC_CC (OR = 4.0, p = 0.015) and MASP2*1C2-l (OR = 5.4, p = 0.03). Conversely, FCN1*3C2 haplotype, associated with higher gene expression, was protective (OR = 0.56, P = 0.033). Other haplotypes associated with HBV susceptibility were: MASP2*2B1-i (OR = 19.25, P = 0.003), CR1*3A (OR = 2.65, P = 0.011) and VSIG4*TGGRCG (OR = 12.55, P = 0.014). Some polymorphisms in ficolin genes associated with lower protein levels increased susceptibility to leprosy/HBV infection: FCN*1 (OR = 1.66, P = 0.029), FCN2*GGGCAC (OR = 6.73, P = 0.008), and FCN3*del_del_C (OR = 12.54, P = 0.037), and to lepromatous disease/HBV infection: FCN2*TA (OR = 2.5, P = 0.009), whereas FCN2*MAG was associated with increased FCN-2 expression and resistance against coinfection (OR = 0.29, P = 0.026). These associations were independent of demographic factors and did not increase susceptibility to leprosy per se, except MASP2*1C2-l. Associations for FCN2, FCN3, MASP1, MASP2, and VSIG4 variants were also independent of each other. In conclusion, polymorphisms compromising activation of the lectin pathway of complement increase susceptibility to HBV infection, with ficolin polymorphisms playing a major role in modulating the susceptibility among leprosy patients.

The complement system is essential for protection against infections in oncologic patients because of the chemotherapy-induced immunosuppression. One of the key elements in the activation of the complement system via the lectin pathway is the appropriate functioning of mannose-binding lectin (MBL) and mannose-binding lectin-associated serine protease 2 (MASP2) complex. The objective of our study was to find an association between polymorphisms resulting in low MBL level and activation of the MBL-MASP2 complex. Also, we aimed at finding a connection between these abnormalities and the frequency and severity of febrile neutropenic episodes in children suffering from hemato-oncologic diseases. Ninety-seven patients had been enrolled and followed from the beginning of the therapy for 8 months, and several characteristics of febrile neutropenic episodes were recorded. Genotypes of 4 MBL2 polymorphisms (-221C/G, R52C, G54D, G57E) were determined by real-time polymerase chain reaction. Activation of the MBL-MASP2 complex was evaluated by enzyme-linked immunosorbent assay at the time of diagnosis and during an infection. The number of febrile neutropenic episodes was lower, and the time until the first episode was longer in patients with normal MBL level than in patients with low MBL level coding genotypes. The MBL-MASP2 complex activation level correlated with the MBL genotype and decreased significantly during infections in patients with low MBL level. Our results suggest that infections after immunosuppression therapy in children suffering from hemato-oncologic diseases are associated with the MBL2 genotype. Our results may contribute to the estimation of risk for infections in the future, which may modify therapeutic options for individuals.

The complement system is a stakeholder of the innate and adaptive immune system and has evolved as a crucial player of defense with multifaceted biological effects. Activation of three complement pathways leads to consecutive enzyme reactions resulting in complement components (C3 and C5), activation of mast cells and neutrophils by anaphylatoxins (C3a and C5a), the formation of membrane attack complex (MAC) and end up with opsonization. However, the dysregulation of complement cascade leads to unsolicited cytokine storm, inflammation, deterioration of alveolar lining cells, culminating in acquired respiratory destructive syndrome (ARDS). Similar pathogenesis is observed with the middle east respiratory syndrome (MERS), severe acquired respiratory syndrome (SARS), and SARS-CoV-2. Activation of the lectin pathway via mannose-binding lectin associated serine protease 2 (MASP2) is witnessed under discrete viral infections including COVID-19. Consequently, the spontaneous activation and deposits of complement components were traced in animal models and autopsy of COVID-19 patients. Pre-clinical and clinical studies evidence that the inhibition of complement components results in reduced complement deposits on target and non-target tissues, and aid in recovery from the pathological conditions of ARDS. Complement inhibitors (monoclonal antibody, protein, peptide, small molecules, etc.) exhibit great promise in blocking the activity of complement components and its downstream effects under various pathological conditions including SARS-CoV. Therefore, we hypothesize that targeting the potential complement inhibitors and complement cascade to counteract lung inflammation would be a better strategy to treat COVID-19.

Depression is a common symptom of many mental disorders, especially major depressive disorder (MDD) and bipolar disorder (BD). Previous studies have reported that these diseases share common pathophysiological pathways; therefore, this study elucidated whether the plasma levels of protein markers related to common depressive symptoms differed between patients with BD and those with MDD. Plasma samples of 71 patients with mood disorders and clinical manifestations were analyzed in this study. After depleting the abundant proteins, liquid chromatography-tandem mass spectrometry and label-free quantification were performed. Five proteins, viz., cholesteryl ester transfer protein (CETP), apolipoprotein D (APOD), mannan-binding lectin serine protease 2 (MASP2), Ig lambda chain V-II region BO (IGLV2-8) and Ig kappa chain V-III region NG9 (IGKV3-20) were negatively associated with the total scores of the Hamilton depression rating scale (HAM-D), after adjusting for the covariates. CETP and APOD also showed significant negative correlations with the anhedonia/retardation and guilt/agitation scores of the HAM-D. Four proteins, namely, Ig kappa chain V-II region TEW (IGKC; IGKV2D-28), Ig lambda variable 5-45 (IGLV5-45), complement factor H (CFH) and attractin (ATRN), showed significant associations with anhedonia/retardation after adjusting for covariates. Proteins that significantly correlated with the symptoms could predict the remission state of depression (area under the curve [AUC], 0.83) and anhedonia/retardation (AUC, 0.80). Bioinformatics analysis revealed that complement activation, immune response, and lipid metabolism were significantly enriched pathways. Although our study design was cross-sectional and no controls were included, protein markers identified in this preliminary study will be further investigated in our subsequent longitudinal study.

BACKGROUND & AIMS: Acute-on-chronic liver failure (ACLF) is characterized by acute decompensation of cirrhosis (AD), organ failure(s) and high risk of short-term mortality with bacterial infection frequently as precipitating event. Innate immune pattern recognition receptors and members of the lectin pathway of complement activation are crucial to the innate immune response to pathogens. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) of innate immune components are associated with the occurrence of bacterial infections or mortality in patients with cirrhosis hospitalized for AD or ACLF. METHODS: Twenty-one innate immunity SNPs with known functional implications were genotyped in 826 AD/ACLF patients included in the CANONIC study. Associations between baseline characteristics of the patients, the occurrence of bacterial infections and survival rate at 90 days of follow-up in relation to the innate immunity genetic variants were analysed. RESULTS: The NOD2-G908R genetic variant was associated with mortality (HR 2.25, P = .004) independently of age and MELD Score. This association was also found in a predefined subgroup analysis in patients with bacterial infections (HR 2.78, P

Mannose-binding Lectin-associated Serine Proteases (MASPs) play important roles in the lectin pathway of complement system. In this study, a MASP homologous was cloned and characterized from lamprey. Homology comparison of MASP1 and MASP2 sequences from other species and phylogenetic analysis showed that the lamprey MASP gene is probably the MASP1 homologue and was named L-MASP1-like. There is no motif17 in L-MASP1-like just as MASP1. The exon composition and the synteny analysis of MASP2 gene was different from that of MASP1. Comparison of the exon numbers and the overlapping location between the exons and the structural domain indicated that L-MASP1-like had its own uniqueness. The adjacent genes of L-MASP1-like display great changes in the arrangement pattern compared with jawed vertebrates. L-MASP1-like was mainly detected in liver, intestine, and kidney. Expression of L-MASP1-like was up-regulated in liver after lamprey was challenged by S. aureus. L-MASP1-like was also up-regulated in liver, intestine, and kidney after Aeromonas, Shewanella, and LPS stimulation. Furthermore, the lamprey serum depleted of L-MASP1-like protein inhibited the apoptosis of MCF-7 cells revealed by flow cytometry analysis. In summary, this study provides a novel understanding of L-MASP1-like in the prospects of the molecular evolution, its potential role in lamprey immune response, and the involvement in promoting cell apoptosis.

The Chinese mitten crab Eriocheir sinensis is an important economic crustacean that has been exposed to various diseases. Spiroplasma eriocheiris , isolated from tremor-diseased E. sinensis , was first identified as a lethal pathogen of freshwater crustaceans. To understand the pathogenesis of S. eriocheiris to E. sinensis , the transcriptomic profiles of haemocytes in the experimental and control groups at 1 d and 7 d post-injection were obtained using Illumina HiSeq 2500. These results showed that 40,358,724, 44,462,112, 45,516,576 and 37,713,728 paired-end clean reads were obtained from the cDNA libraries of DZ1 (the control group at 1 d), DZ7 (the control group at 7 d), SY1 (the experimental group at 1 d) and SY7 (the experimental group at 7 d), respectively. In total, 106,641 unique transcript fragments (unigenes) were assembled, with an average length of 710 bp. On the first day of stimulation, 33,084 up-regulated transcripts and 19,208 down-regulated transcripts were found in the experimental group compared with those in the control group. On the seventh day of stimulation, 40,198 up-regulated transcripts and 12,032 down-regulated transcripts were found in the experimental group compared with those in the control group. Some canonical immune-related pathways were identified via KEGG pathway analysis, including complement and coagulation cascades, the VEGF signalling pathway, the Wnt signalling pathway, natural killer cell-mediated cytotoxicity, the MAPK signalling pathway, neuroactive ligand-receptor interactions, and the Lysosome pathway. We found important immune-related genes (GNPTAB, MASP2, F7, F5, NFATC, TRAF6, MAP3K5, and TRa) in the KEGG pathway, and those genes were confirmed by qRT-PCR analysis. In addition, the significantly enriched neuroactive ligand-receptor interaction pathway was associated with intense paroxysmal tremors of infected crabs. Our results provide valuable information for the further analysis of the mechanisms of E. sinensis defence against S. eriocheiris invasion.

The complement system is a front-line defense system that opsonizes and lyses invading pathogens. To survive, microbes exposed to serum must evade the complement response. To achieve this, many pathogens recruit soluble human complement regulators to their surfaces and hijack their regulatory function for protection from complement activation. C1 esterase inhibitor (C1-INH) is a soluble regulator of complement activation that negatively regulates the classical and lectin pathways of complement to protect human tissue from aberrant activation. In this article, we show that Plasmodium falciparum merozoites, the invasive form of blood stage malaria parasites, actively recruit C1-INH to their surfaces when exposed to human serum. We identified PfMSP3.1, a member of the merozoite surface protein 3 family of merozoite surface proteins, as the direct interaction partner. When bound to the merozoite surface, C1-INH retains its ability to complex with and inhibit C1s, MASP1, and MASP2, the activating proteases of the complement cascade. P. falciparum merozoites that lack PfMSP3.1 showed a marked reduction in C1-INH recruitment and increased C3b deposition on their surfaces. However, these ΔPfMSP3.1 merozoites exhibit enhanced invasion of RBCs in the presence of active complement. This study characterizes an immune-evasion strategy used by malaria parasites and highlights the complex relationship between merozoites and the complement system.

Serine protease cleaved-complement component 4 (C4) at sessile loop, which is significant for completion of lectin and classical complement pathways at the time of infections. The co-crystalized structure of C4 with Mannose-binding protein-associated serine protease 2 (MASP2) provided the structural and functional aspects of its interaction and underlined the C4 activation by MASP2. The same study also revealed the significance of complement control protein (CCP) domain through mutational study, where mutated CCP domain led to the inhibition of C4 activation. However, the interaction of trypsin serine domain with C4α sessile loop revealed another aspect of C4 activation. The human C4 cleavage by Trypsin (Tryp) in a control manner was explored but not yet revealed the identification of cleaved fragments. Hence, the present study investigated the Tryp mediated C4 activation using computational approach (protein-protein docking and molecular dynamics simulation) by comparing with the co-crystalized structure of C4-MASP2. Docking result identified the crucial interacting residues Gly219, Gln178, and Asn102 of Tryp catalytic pocket which were interacting with Arg756 and Glu759 (sessile loop) of α-Chain (C4) in a similar manner to C4-MASP2 co-crystallized complex. Moreover, MD simulation results and mutational study underlined the conformational rearrangements in the C4 due to the Tryp interaction. Comparative analysis of C4 alone, C4-Tryp, and C4-MASP2 revealed the impact of Tryp on C4 was similar as MASP2. These studies designate the role of sessile loop in the interaction with serine domain, which could be useful to understand the various interactions of C4 with other complement components.

Marsupials are born immunologically premature, relying on cells and molecules in maternal milk for immune protection. Both immunoglobulin and complement proteins have been identified in marsupial milk, but the expression of specific complement proteins remains largely unexplored. We report partial cDNA sequences for two complement-activating proteins, C3, C1r, CFP and MASP2, in liver tissues from red-tailed phascogale (Phascogale calura). Conservation of functionally relevant motifs were identified in the translated cDNA sequences from phascogale C3, CFP and MASP2 and their eutherian homologues. Gene expression of representative molecules from each of the major complement pathways was also investigated in whole body tissues from 1 to 18 day old animals and liver tissues from 31-day to 14-month old animals. Average complement expression in whole bodies and liver tissues of C1r, CFP, MASP2 and C3 increased significantly in juveniles compared to pouch young, presumably due to the maturation of the young's own complement system. Comparing expression in liver tissues only, we found that the average CFP expression were higher in pouch young compared to juveniles, while results were still statistically similar to the average expression of all tissues for C1r, MASP2 and C3. The average complement expression then significantly decreased as the animals aged into adulthood.

Mannose-binding lectin (MBL) and MBL-associated serine protease-2 (MASP-2) are important proteins in the lectin pathway of the immune system. Mannose-binding lectin and MASP-2 deficiencies have been reported to be responsible for various fungal infections. We investigated the association of MBL and MASP-2 variants with sporotrichosis in a Chinese population and revealed one rare heterozygous mutation in a disseminated cutaneous patient without immunosuppressive conditions (MASP2, p.156_159dupCHNH). We also found that sporotrichosis patients had decreased levels of MBL and MASP-2 in their serum samples compared with controls. Our findings linked, for the first time, MASP-2 deficiencies with susceptibility to Sporothrix sp.

Infections are a major cause of childhood mortality. We investigated components of the lectin pathway of complement activation in the context of sepsis at both genetic and protein levels in neonates, infants and older children. Major components of the lectin pathway and two genes for Toll-like receptors were studied in 87 neonates with confirmed sepsis and compared with 40 babies with infections who did not develop sepsis (disease controls) and 273 infection-free neonatal controls. A second cohort comprised 47 older children with sepsis and 87 controls. Low MBL-conferring genotypes (LXA/O+O/O) were more frequent in sepsis patients than in healthy controls but no significant differences in the frequency of SNPs of other lectin pathway genes (FCN1, FCN2, FCN3, MASP1/3, MASP2) or TLR receptor genes (TLR2, TLR4) were found. One case of primary MASP-2 deficiency was found among healthy pre-terms and one neonate suffering from SIRS was heterozygous for the rare FCN1 gene mutation, +6658 G>A. Generally, sepsis was associated with low serum MBL and low ficolin-2 concentrations on admission. Among neonates, ficolin-1 and MASP-2 levels were elevated in sepsis relative to healthy, but not disease, controls. Unlike neonates, ficolin-3 and MASP-2 levels were lower in older patients than in healthy controls while no difference was found for ficolin-1. With the possible exception of MBL, inherited lectin pathway insufficiencies do not seem to predispose to sepsis, rather changes in protein concentrations reflect alterations in disease course.

We report here two cases of Herpes simplex virus encephalitis (HSE) in adult patients with very rare, previously uncharacterized, non synonymous heterozygous G634R and R203W substitution in mannan-binding lectin serine protease 2 (MASP2), a gene encoding a key protease of the lectin pathway of the complement system. None of the 2 patients had variants in genes involved in the TLR3-interferon signaling pathway. Both MASP2 variants induced functional defects in vitro, including a reduced (R203W) or abolished (G634R) protein secretion, a lost capability to cleave MASP-2 precursor into its active form (G634R) and an in vivo reduced antiviral activity (G634R). In a murine model of HSE, animals deficient in mannose binding lectins (MBL, the main pattern recognition molecule associated with MASP-2) had a decreased survival rate and an increased brain burden of HSV-1 compared to WT C57BL/6J mice. Altogether, these data suggest that MASP-2 deficiency can increase susceptibility to adult HSE., Author summary Human herpes virus type 1 (HSV-1) infects a large number of individuals during their life, with manifestations usually limited to mild and self-limiting inflammation of the oral mucosa (cold sore). However, HSV-1 can cause a very severe disease of the brain called Herpes simplex encephalitis (HSE) in 1 out of 250’000–500’000 individuals per year. The reasons why HSV-1 can cause such a devastating disease in a very limited number of individuals are unknown. Increasing evidence suggests that susceptibility to HSE in children can results from genetic variations in the immune system, in particular in a viral detection pathway called the Toll-like receptor 3 (TLR3)–interferon (IFN) axis. Fewer data are available to explain HSE in adult patients. Here, we describe two adult patients with HSE who carry mutations in a gene called mannan-binding lectin serine protease 2 (MASP2), which is part of an immune pathway different from the TLR3-IFN axis, called the lectin pathway of the complement system. We demonstrate that MASP2 mutations induce functional defects in immune defense against HSV-1 that prevent viral replication. Mice deficient in the lectin pathway have higher mortality compared to wild-type mice after HSV-1 infection. Altogether, our study suggests that susceptibility to HSE in adults relies of immune deficiencies that are different from those causing HSE in children.

Leishmania donovani, the causative agent of Indian visceral leishmaniasis has to face several barriers of the immune system inside the mammalian host for its survival. The complement system is one of the first barriers and consists of a well-balanced network of proteases including S1A family serine proteases (SPs). Inhibitor of serine peptidases (ISPs) is considered as inhibitor of S1A family serine peptidases and is reported to be present in trypanosomes, including Leishmania. In our previous study, we have deciphered the role of ISPs [LdISP1 and L. donovani inhibitor of serine peptidases 2 (LdISP2)] in the survival of L. donovani inside the sandfly midgut. However, the role of theses ISPs in the survival of L. donovani inside mammalian host still remains elusive. In the present study, we have deciphered the inhibitory effect of LdISPs on the host complement S1A serine peptidases, such as C1r/C1s and MASP1/MASP2. Our study suggested that although both rLdISP1 and rLdISP2 inferred strong interaction with C1complex and MBL-associated serine proteases (MASPs) but rLdISP2 showed the stronger inhibitory effect on MASP2 than rLdISP1. Moreover, we found that rLdISP2 significantly reduces the formation of C3, C5 convertase, and membrane attacking complex (MAC) by lectin pathway (LP) resulting in significant reduction in serum mediated lysis of the parasites. The role of LdISP2 on neutrophil elastase-mediated C5aR signaling was also evaluated. Notably, our results showed that infection of macrophages with ISP2-overexpressed Leishmania parasites significantly induces the expression of C5aR both at the transcript and translational level. Simultaneously, infection with ISP2KD parasites results in downregulation of host PI3K/AKT phosphorylation and increased in IL-12 production. Taken together, our findings clearly suggest that LdISP2 promotes parasite survival inside host by inhibiting MAC formation and complement-mediated lysis via LP and by upregulation of C5aR signaling.

Mannan-binding lectin-associated serine protease 2 (MASP-2) is a member of the lectin pathway of complement and is one of two splice products from the MASP2 gene. The protein is secreted from the liver as a zymogenic protein consisting of 671 residues and circulates at a concentration of approximately 0.41 μg/mL in the serum. MASP-2 is associated with pattern-recognition molecules as a homodimer that is activated by MASP-1 when bound to an activating surface resulting in an A-chain and a B-chain linked by a disulphide bond. MASP-2 is also capable of autoactivating. Activated MASP-2 cleaves C2 and C4, which leads to formation of the C3 convertase, C4b2a, and activation of complement.

Objectives The human mannose-binding lectin (MBL) and ficolins (FCN) are involved in pathogen recognition in the first line of defence. They support activation of the complement lectin cascade in the presence of MBL-associated serine protease 2 (MASP-2), a protein that cleaves the C4 and C2 complement components. Recent studies found that distinct MBL2 and FCN2 promoter variants and their corresponding serum levels are associated with relative protection from urogenital schistosomiasis. Methods We investigated the contribution of MASP-2 levels and MASP2 polymorphisms in a Nigerian study group, of 163 individuals infected with Schistosoma haematobium and 183 healthy subjects. Results MASP-2 serum levels varied between younger children (≤12 years) and older children (>12 years) and adults (P = 0.0001). Younger children with a patent infection had significantly lower MASP-2 serum levels than uninfected children (P = 0.0074). Older children and adults (>12 years) with a current infection had higher serum MASP-2 levels than controls (P = 0.032). MBL serum levels correlated positively with MASP-2 serum levels (P = 0.01). MASP2 secretor haplotypes were associated with MASP-2 serum levels in healthy subjects. The heterozygous MASP2 p.P126L variant was associated with reduced serum MASP-2 levels (P = 0.01). Conclusions The findings indicate that higher MASP-2 serum levels are associated with relative protection from urogenital schistosomiasis in Nigerian children.

The aim of this study was to explore the role of the lectin pathway in neonatal sepsis through the study of MBL and MASP2 levels and their relationship with infection in a cohort of very-low-birth-weight infants (VLBWI). MBL and MASP2 were measured in plasma samples of n = 89 VLBWI using ELISA and correlated with clinical parameters. MBL plasma levels were aligned with genotyping data of mbl2 exon 1 polymorphisms, rs1800450, rs1800451, and rs5030737. MBL levels were clearly determined by MBL genotype, i.e., AA individuals had tenfold higher MBL levels than AO individuals. MBL and MASP2 levels did not correlate with gestational age, apart from MASP2 levels on day 7. During the first 21 days of life, we noted a gradual increase in both MBL and MASP2 levels. On day 7 of life, MASP2 levels in infants developing late-onset sepsis measured before the onset of symptoms were found to be lower, as compared to non-LOS infants. In our cohort of VLBWI, MBL levels were genetically determined, but not associated with gestational age or sepsis in the first 21 days of life. Lower MASP2 levels on day 7 may indicate increased risk for late-onset infection.

Mannan-binding lectin (MBL) and MBL-associated serine protease 2 (MASP-2) are components of the lectin pathway, which activate the complement system after binding to the HCV structural proteins E1 and E2. We haplotyped 11 MASP2 polymorphisms in 103 HCV patients and 205 controls and measured MASP-2 levels in 67 HCV patients and 77 controls to better understand the role of MASP-2 in hepatitis C susceptibility and disease severity according to viral genotype and fibrosis levels. The haplotype block MASP2*ARDP was associated with protection against HCV infection (OR = 0.49, p = .044) and lower MASP-2 levels in controls (p = .021), while haplotype block AGTDVRC was significantly increased in patients (OR = 7.58, p = .003). MASP-2 levels were lower in patients than in controls (p

In recent years the notion that malfunctioning of the immune system may result in developmental brain diseases has emerged. However, the role of immune molecules in the developing brain has not been well explored. The complement pathway converges to cleave C3. Here we show that key proteins in the lectin arm of this pathway, MASP1, MASP2 and C3, are expressed in the developing cortex and that neuronal migration is impaired in knockout and knockdown mice. Molecular mimics of C3 cleavage products rescue the migration defects that have been seen following knockdown of C3 or Masp2. Pharmacological activation of the downstream receptors rescue Masp2 and C3 knockdown as well as C3 knockout. Therefore, we propose that the complement pathway is functionally important in migrating neurons of the developing cortex., Emerging evidence suggests that immune molecules play an important role in regulating brain development. Gorelik et al. show that molecules in the lectin arm of the complement pathway are expressed in the developing mouse cortex, and regulate radial migration of excitatory neurons.

AimsThe aim of the current study was to assess the proteolytic activities of collectin-bound MASP-1 and MASP-2 in the blood of patients with ischaemic stroke, as well as the association of their six genetic polymorphisms (rs3203210, rs28945070, rs28945073 inMASP1gene and rs2273343, rs12711521, rs147270785 inMASP2gene) with this pathology.MethodsIn total, 250 patients and 300 healthy subjects were involved in this study. MBL-associated serine protease (MASP)-1 and MASP-2 activities were measured using in-house developed immunofluorescent and enzyme-linked immunosorbent assays, respectively. Sequence specific primer PCR was used to study the association ofMASP1andMASP2genetic polymorphisms with ischaemic stroke.ResultsThe results obtained demonstrate that the activities of collectin-bound MASP-1 and MASP-2 in patients with ischaemic stroke are significantly higher than those in healthy subjects (pMASP1gene and the rs147270785 polymorphism in theMASP2gene are associated with ischaemic stroke (pConclusionsIn conclusion we suggest that the complement lectin pathway serine proteases, MASP-1 and MASP-2, can be associated with ischaemic stroke development risk and may participate in pathological events leading to post-ischaemic brain damage. Moreover rs3203210 and rs147270785 single nucleotide polymorphisms in theMASP1andMASP2genes, respectively, are strongly associated with ischaemic stroke, and the minor rs3203210*C and rs147270785*A alleles of these polymorphisms may be considered as protective factors for ischameic stroke, at least in the Armenian population.

Mannose-Binding Lectin (MBL) is a serum pattern recognition molecule, able to activate complement in association with MASP proteases. Serum levels of MBL and MASP-2, activities of MBL–MASP complexes, single nucleotide polymorphisms of the MBL2 and MASP2 genes and/or their specific mRNA expression in ovarian sections were investigated in 128 patients suffering from primary ovarian cancer (OC) and compared with 197 controls (C), encompassing both patients with benign ovarian tumours (n = 123) and others with no ovarian pathology (n = 74). MBL deficiency-associated genotypes were more common among OC patients than among controls. The O/O group of genotypes was associated with ovarian cancer (OR 3.5, p = 0.02). In A/A homozygotes, MBL concentrations and activities were elevated in the OC group and correlated with C-reactive protein. Moreover, high MBL serum levels were associated with more advanced disease stage. No differences in distribution of the MASP2 +359 A>G (D120G) SNP or MASP-2 serum levels were found between cancer patients and their controls. However, the highest frequency of the A/G (MASP2) and LXA/O or O/O (MBL2) genotypes was found among OC patients with tumours of G1–2 grade (well/moderately differentiated). Furthermore, MBL deficiency-associated genotypes predicted prolonged survival. None of the parameters investigated correlated with CA125 antigen or patients’ age. The local expression of MBL2 and MASP2 genes was higher in women with ovarian cancer compared with controls. It is concluded that the expression of MBL and MASP-2 is altered in ovarian cancer, possibly indicating involvement of the lectin pathway of complement activation in the disease. Electronic supplementary material The online version of this article (doi:10.1007/s00262-014-1579-y) contains supplementary material, which is available to authorized users.

Background. Natural IgM containing anti Gal antibodies initiates classic pathway complement activation in xenotrans plantation. However in ischemia reperfusion injury IgM also induces lectin pathway activation. The present study was therefore focused on lectin pathway as well as interaction of IgM and mannose binding lectin (MBL) in pig to human xenotransplantation models. Methods. Activation of the different complement pathways was assessed by cell enzyme linked immunosorbent assay using human serum on wild type (WT) and > galactosyl transferase knockout (GalTKO)/hCD46 transgenic porcine aortic endothelial cells (PAEC). Colocalization of MBL/MASP2 with IgM C3b/c C4b/c and C6 was investigated by immunofluorescence in vitro on PAEC and ex vivo in pig leg xenoperfusion with human blood. Influence of IgM on MBL binding to PAEC was tested using IgM depleted/repleted and anti Gal immunoabsorbed serum. Results. Activation of all the three complement pathways was observed in vitro as indicated by IgM C1q MBL and factor Bb deposition on WT PAEC. MBL deposition colocalized with MASP2 (Manders’ coefficient [3D] r2=0.93) C3b/c (r2=0.84) C4b/c (r2=0.86) and C6 (r2=0.80). IgM colocalized with MBL (r2=0.87) and MASP2 (r2=0.83). Human IgM led to dose dependently increased deposition of MBL C3b/c and C6 on WT PAEC. Colocalization of MBL with IgM (Pearson’s coefficient [2D] rp2=0.88) C3b/c (rp2=0.82) C4b/c (rp2=0.63) and C6 (rp2=0.81) was also seen in ex vivo xenoperfusion. Significantly reduced MBL deposition and complement activation was observed on GalTKO/hCD46 PAEC. Conclusion. Colocalization of MBL/MASP2 with IgM and complement suggests that the lectin pathway is activated by human anti Gal IgM and may play a pathophysiologic role in pig to human xenotransplantation. Keywords: Mannose binding lectin Complement pathways Natural antibody Xenotransplantation Porcine aortic endothelial cells.

Variations in genes involved in the immune response pathways may influence the interaction between viruses (such as Human T-lymphotropic virus, HTLV-1) and the host. The mannose binding lectin (MBL) and its associated serine protease type 2 (MASP-2) promote the activation of the lectin pathway of the complement system. As the interaction of complement system with HTLV-1 is not well understood, the MBL2 promoter/exon 1 polymorphisms and a MASP2 missense polymorphism were examined in a Northeast Brazilian population, looking for a possible relationship between these variations and the susceptibility to HTLV-1 infection. The present study describes an association between a polymorphism in the MASP2 gene and susceptibility to HTLV-1 infection, and provides further evidence of an association between the MBL2 gene and HTLV-1 infection. These findings suggest an important role of the complement system activation, via the lectin pathway, in the susceptibility to HTLV-1 infection. J Med. Virol. 85:1829–1835, 2013. © 2013 Wiley Periodicals, Inc.

The effect of beta-glucans as feed additive on the profile of C-reactive protein (CRP) and complement acute phase responses was studied in common carp Cyprinus carpio after exposition to a bacterial infection with Aeromonas salmonicida. Carp were orally administered with beta-glucan (MacroGard (R)) for 14 days with a daily beta-glucan intake of 6 mg per kg body weight. Fish were then intraperitoneally injected with either PBS or 1 x 10(8) bacteria per fish and sampled at time 0, 6, 12, 24, 48, 72, 96 and 120 h post-injection (p.i.) for serum and head kidney, liver and mid-gut tissues. CRP levels and complement activity were determined in the serum samples whilst the gene expression profiles of CRP and complement related genes (crp1, crp2, c1r/s, bf/c2, c3 and masp2) were analysed in the tissues by quantitative PCR. Results obtained showed that oral administration of beta-glucan for 14 days significantly increased serum CRP levels up to 2 fold and serum alternative complement activity (ACP) up to 35 fold. The bacterial infection on its own (i.e. not combined with a beta-glucan feeding) did have significant effects on complement response whilst CRP was not detectably induced during the carp acute phase reaction. However, the combination of the infection and the beta-glucan feeding did show significant effects on both CRP and complement profiles with higher serum CRP levels and serum ACP activity in the beta-glucan fed fish than in the control fed fish. In addition, a distinct organ and time dependent expression profile pattern was detected for all the selected genes: a peak of gene expression first occurred in the head kidney tissue (6 h p.i. or 12 h p.i.), then an up-regulation in the liver several hours later (24 h p.i.) and finally up- or down-regulations in the mid-gut at 24 h p.i. and 72 h p.i. In conclusion, the results of this study suggest that MacroGard (R) stimulated CRP and complement responses to A. salmonicida infection in common carp.

Both complement activation and certain infections (including those with Yersinia sp.) may contribute to the pathogenesis of juvenile idiopathic arthritis (JIA). We investigated factors specific for the lectin pathway of complement: mannose-binding lectin (MBL), ficolins and MBL-associated serine protease-2 (MASP-2), in 144 patients and 98 controls. One hundred and six patients had oligoarticular disease and 38 had polyarticular disease. In 51 patients (out of 133 tested), Yersinia-reactive antibodies were found (JIA Ye+ group). MBL deficiency was significantly more frequent in the JIA Ye+ group than in patients without Yersinia-reactive antibodies or in controls. Median serum ficolin-2 level was significantly lower (and proportion of values deemed ficolin-2 insufficient greater) in JIA patients irrespective of their Yersinia antibody status. The minority (C) allele at -64 of the FCN2 gene was less frequent among JIA patients than among control subjects. No differences were found in the frequency of FCN3 gene +1637delC or MASP2 +359 A>G mutations nor for median values of serum ficolin-1, ficolin-3 or MASP-2. However, high levels of serum ficolin-3 were under-represented in patients, in contrast to MBL. MBL, ficolin-1, ficolin-2, ficolin-3 and MASP-2 were also readily detectable in synovial fluid samples but at a considerably lower level than in serum. Our findings suggest a possible role for the lectin pathway in the pathogenesis of JIA, perhaps secondary to a role in host defence, and indicate that investigations on the specificity of lectin pathway recognition molecules towards specific infectious agents in JIA might be fruitful.

Glaucoma is a multifactorial disease and especially mechanisms occurring independently from an elevated intraocular pressure (IOP) are still unknown. Likely, the immune system contributes to the glaucoma pathogenesis. Previously, IgG antibody depositions and retinal ganglion cell (RGC) loss were found in an IOP-independent autoimmune glaucoma model. Therefore, we investigated the possible participation of the complement system in this model. Here, rats were immunized with bovine optic nerve homogenate antigen (ONA), while controls (Co) received sodium chloride (\(\it n\) = 5–6/group). After 14 days, RGC density was quantified on flatmounts. No changes in the number of RGCs could be observed at this point in time. Longitudinal optic nerve sections were stained against the myelin basic protein (MBP). We could note few signs of degeneration processes. In order to detect distinct complement components, retinas and optic nerves were labeled with complement markers at 3, 7, 14, and 28 days and analyzed. Significantly more C3 and MAC depositions were found in retinas and optic nerves of the ONA group. These were already present at day 7, before RGC loss and demyelination occurred. Additionally, an upregulation of C3 protein was noted via Western Blot at this time. After 14 days, quantitative real-time PCR revealed significantly more \(\it C3\) mRNA in the ONA retinas. An upregulation of the lectin pathway-associated mannose-serine-protease-2 (MASP2) was observed in the retinas as well as in the optic nerves of the ONA group after 7 days. Significantly more MASP2 in retinas could also be observed via Western Blot analyses at this point in time. No effect was noted in regard to C1q. Therefore, we assume that the immunization led to an activation of the complement system via the lectin pathway in retinas and optic nerves at an early stage in this glaucoma model. This activation seems to be an early response, which then triggers degeneration. These findings can help to develop novel therapy strategies for glaucoma patients.

The aim of the present study was to investigate the changes in retinal gene expression at three time points and assess the underlying molecular mechanisms of diabetic retinopathy (DR) in a streptozotocin (STZ)-induced diabetes rat model using bioinformatics analysis. The gene expression profile of GSE28831 was extracted from the Gene Expression Omnibus database and differentially expressed genes (DEGs) were identified at three different time points (1, 4 and 12 weeks) using the limma package in R language. Gene ontology (GO) enrichment analysis of DEGs was performed followed by a principal component and pathway enrichment analysis of the selected DEGs along with protein-protein interaction network construction at the three time points. A total of 402, 105 and 213 DEGs were screened at 1, 4 and 12 weeks, respectively. In addition, the expression of 8 genes was identified to be significantly different at different time points, including cytochrome P450 2B2 (CYP2B2; downregulated gene; P=0.048; at 1 week), mannan binding lectin-associated serine protease-2 (MASP2; downregulated gene; P=0.044), lecithin retinol acyltransferase (LRAT; downregulated gene; P=0.015), retinal pigment epithelium (RPE)-specific protein 65 kDa (RPE65; downregulated gene; P=0.025), 11-cis-retinoldehydrogenase (RDH5; downregulated gene; P=0.04; at 4 weeks), mitogen-activated protein kinase 13 (MAPK13; upregulated gene; P=0.036), LRAT (downregulated gene; P=0.01) and RPE65 (downregulated gene; P=0.009; at 12 weeks). Furthermore, pathway enrichment and GO enrichment analyses revealed that DEGs at 4 weeks were primarily enriched in retinol metabolism and processes associated with visual functions, including 'visual perception' and 'retinol metabolism'. DEGs, including CYP2B2, MASP2, LRAT, RPE65, RDH5 and MAPK13 may be potential targets for the diagnosis and treatment of DR. Thus, the current study demonstrated that abnormal visual functions occur at 4 weeks in STZ-induced diabetic rats. This may provide a scientific basis for the diagnosis and treatment of DR because DEGs may be used to facilitate the development of novel therapeutic strategies to diagnose and treat DR.

Mannan-binding lectin (MBL) - associated serine protease 2 (MASP-2) co-activates the lectin pathway of complement in response to several viral infections. The quality of this response partly depends on MASP2 gene polymorphisms, which modulate MASP-2 function and serum levels. In this study we investigated a possible role of MASP2 polymorphisms, MASP-2 serum levels and MBL-mediated complement activation in the susceptibility to HIV/AIDS and HBV/HCV coinfection.A total of 178 HIV patients, 89 (50%) coinfected with HBV/HCV, 51.7% female, average age 40 (12-73) years, and 385 controls were evaluated. MASP-2 levels and MBL-driven complement activation were evaluated by enzyme-linked immunosorbent assay and 11 MASP2 polymorphisms from the promoter to the last exon were haplotyped using multiplex sequence-specific PCR.Genotype distribution was in Hardy-Weinberg equilibrium and differed between HIV+ patients and controls (P=0.030), irrespective of HBV or HCV coinfection. The p.126L variant, which was associated with MASP-2 levels 200ng/mL (OR=5.0 [95%CI=1.3-19.2] P=0.019), increased the susceptibility to HIV infection (OR=5.67 [95%CI=1.75-18.33], P=0.004) and to HIV+HBV+ status (OR=6.44 [95%CI=1.69-24.53, P=0.006). A similar association occurred with the ancient haplotype harboring this variant, AGCDV (OR=2.35 [95%CI=1.31-4.23], P=0.004). On the other hand, p.126L in addition to other variants associated with low MASP-2 levels-p.120G, p.377A and p.439H, presented a protective effect against AIDS (OR=0.25 [95%CI=0.08-0.80], P=0.020), independently of age, sex, hepatic function and viral load. MASP-2 serum levels were lower in HIV+ and HIV+HBV+ patients than in controls (P=0.0004). Among patients, MASP-2 levels were higher in patients with opportunistic diseases (P=0.001) and AIDS (P=0.004). MASP-2 levels correlated positively with MBL/MASP2-mediated C4 deposition (r=0.29, P=0.0002) and negatively with CD4+ cell counts (r=-0.21, P=0.018), being related to decreased CD4+ cell counts (OR=5.8 [95%CI=1.23-27.5, P=0.026).Genetically determined MASP-2 levels seem to have a two-edge effect in HIV and probably HCV/HBV coinfection, whereas low levels increase the susceptibility to infection, but on the other side protects against AIDS.

The pattern-recognition pathway plays an important role in infection recognition and immune responses, and previous studies have suggested an association between genetic variation in innate immunity genes and non-Hodgkin lymphoma (NHL). We evaluated NHL risk associated with genetic variation in pattern-recognition genes using data from a case–control study of NHL conducted in Connecticut women. Single nucleotide polymorphisms (SNPs) in 27 pattern-recognition genes were genotyped in 432 Caucasian incident NHL cases and 494 frequency-matched controls. Unconditional logistic regression was used to compute odds ratios (ORs) for NHL and common NHL subtypes in relation to individual SNPs and haplotypes. A gene-based analysis that adjusted for the number of tagSNPs genotyped in each gene showed a significant association with overall NHL for the MBP gene (P = 0.028), with the diffuse large B-cell lymphoma (DLBCL) subtype for the MASP2 gene (P = 0.011), and with the follicular lymphoma (FL) subtype for DEFB126 (P = 0.041). A SNP-based analysis showed that MBP rs8094402 was associated with decreased risks of overall NHL (allele risk OR = 0.72, P-trend = 0.0018), DLBCL (allele risk OR = 0.72, P-trend = 0.036), and FL (allele risk OR = 0.67, P-trend = 0.021), while MASP2 rs12711521 was associated with a decreased risk of DLBCL (allele risk OR = 0.57, P-trend = 0.0042). We also observed an increased risk of FL for DEFB126 rs6054706 (allele risk OR = 1.39, P-trend = 0.033). Our results suggest that genetic variation in pattern-recognition genes is associated with the risk of NHL or specific NHL subtypes, but these preliminary findings require replication in larger studies. Mol. Mutagen. 2013. © 2012 Wiley Periodicals, Inc.

Contains fulltext : 108497.pdf (Publisher’s version ) (Closed access) In kidney transplantation, complement activation was found to be induced by donor brain death, renal ischemia-reperfusion injury and allograft rejection. There are three known pathways of complement activation: the classical, lectin and the alternative pathway. The lectin complement pathway can be activated upon pattern recognition by mannan binding lectin (MBL) or ficolins (FCN). Single nucleotide polymorphisms (SNPs) in the genes encoding the lectin pathway proteins determine their functional activity and serum levels. The aim of this study was to investigate the role of the lectin gene profile of the donor and recipient on post-transplant outcome. A total of 12 functional SNPs in the MBL2, FCN2 and MBL-associated serine proteases 2 (MASP2) genes of 1271 donor-recipient pairs were determined. Lectin genotypic variants were analyzed for association with primary non-function (PNF), delayed graft function (DGF), biopsy proven acute rejection, death-censored graft survival and patient survival. Multivariate analyses found no association of donor and recipient MBL2 and MASP2 genotype with allograft outcome. Analysis of separate functional SNPs and haplotypes in the FCN2 gene of the donor and recipient did not reveal an association with transplant outcome. Also, the joint effect of the MBL2 and FCN2 genotype was not associated with allograft outcome.This study shows that the genetic profile of the lectin pathway of complement activation of the donor and recipient is not associated with allograft outcome after kidney transplantation. 01 februari 2012

Oral Diseases (2012) 18, 389–395 Objective: The aim of the study was to examine whether the MBL2 C(-290)G and G161A, MASP2 A359G, AMELX C287T and C522T, and ENAM C2452T polymorphisms are associated with dental caries. Subjects and methods: Genomic DNA of 95 Polish children with ‘higher caries experience’ (HC) and 84 subjects with ‘lower caries experience’ (LC) belonging to two age-groups (5 and 13 years old) was extracted from the buccal mucosa. SNPs were genotyped with PCR-RFLP methods. Results: Among 5-year-old children, we found significantly higher percentage of subjects carrying MBL2 (-290)G allele in HC group compared with LC group (43.2%vs 17.6%, P = 0.023). MBL2 C(-290)G–G161A C–G haplotype was overrepresented in LC group in 5-year-olds (P = 0.01), while the opposite association was observed in 13-year-olds, where C–G was overrepresented in HC group (P = 0.028). In 5-year-old children, the frequency of MBL2 G–G haplotype was higher in HC group compared with LC subjects (P = 0.045), while the opposite association (with borderline significance) was observed in 13-year-old children (P = 0.057). SNPs in MASP2, AMELX, and ENAM were not associated with dental caries. Conclusion: MBL2 gene polymorphism is associated with caries experience in Polish children, but the direction of this association seems to be opposite in primary and permanent dentition.

Summary Mannose-binding lectin (MBL) is a protein able to bind to carbohydrate patterns on pathogen membranes; upon MBL binding, its’ associated serine protease MBL-associated serine protease type 2 (MASP2) is autoactivated, promoting the activation of complement via the lectin pathway. For both MBL2 and MASP2 genes, the frequencies of polymorphisms are extremely variable between different ethnicities, and this aspect has to be carefully considered when performing genetic studies. While polymorphisms in the MBL-encoding gene (MBL2) have been associated, depending upon ethnicity, with several diseases in different populations, little is known about the distribution of MASP2 gene polymorphisms in human populations. The aim of our study was thus to determine the frequencies of MBL2 (exon 1 and promoter) and MASP2 (p.D371Y) polymorphisms in a Brazilian population from Rio de Janeiro. A total of 294 blood donor samples were genotyped for 27 polymorphisms in the MBL2 gene by direct sequencing of a region spanning from the promoter polymorphism H/L rs11003125 to the rs1800451 polymorphism (at codon 57 in the first exon of the gene). Genotyping for MASP2 p.D371Y was carried out using fluorogenic probes. To our knowledge, this is the first study reporting the prevalence of the MASP2 p.D371Y polymorphism in a Brazilian population. The C allele frequency 39% is something intermediate between the reported 14% in Europeans and 90% in Sub-Saharan Africans. MBL2 polymorphisms frequencies were quite comparable to those previously reported for admixed Brazilians. Both MBL2 and MASP2 polymorphisms frequencies reported in our study for the admixed Brazilian population are somehow intermediate between those reported in Europeans and Africans, reflecting the ethnic composition of the southern Brazilian population, estimated to derive from an admixture of Caucasian (31%), African (34%) and Native American (33%) populations. In conclusion, our population genetic study describes the frequencies of MBL2 and MASP2 functional SNPs in a population from Rio de Janeiro, with the aim of adding new information concerning the distribution of these SNPs in a previously unanalysed Brazilian population, thus providing a new genetic tool for the evaluation of the association of MBL2 and MASP2 functional SNPs with diseases in Brazil, with particular emphasis on the state of Rio de Janeiro.

Hepatitis C virus (HCV) has become a major public health issue and is prevalent in most countries. We examined several MASP2 functional polymorphisms in 104 Brazilian patients with moderate and severe chronic hepatitis C using the primers set to amplify the region encoding the first domain (CUB1), a critical region for the formation of functional mannan-binding lectin (MBL)/MBL-associated serine proteases (MASP)–2 complexes, and the fifth domain (CCP2), which is essential for C4 cleavage of the MASP2 gene. We identified five single nucleotide polymorphisms in patients and controls: p. R99Q, p. D120G, p.P126L, p.D371Y, and p.V377A. Our results show that the p.D371Y variant (c.1111 G > T) is associated with susceptibility to HCV infection (p = 0.003, odds ratio = 6.33, 95% confidence interval = 1.85–21.70). Considered as a dominant function for the T allele, this variant is associated with high plasma levels of the MASP-2 in hepatitis C patients (p < 0.001). However, further functional investigations are necessary to understand the degree of involvement between MASP2 and the HCV susceptibility.

Deficiency of mannan-binding lectin-associated serine protease 2 (MASP-2) has been associated with infections, whereas high levels appear to increase the risk of inflammatory disorders. Nevertheless, MASP2 haplotypes have been poorly investigated. To overcome haplotyping cost and time consumption, we developed multiplex polymerase chain reactions with sequence-specific primers (PCR-SSP) for 8 single nucleotide polymorphisms (SNPs), reducing the number of necessary reactions from 18 to 7. SNPs were distributed from the promoter to the last exon, and a single PCR-SSP was used for p.D120G. We evaluated the phylogenetic relationships and global distribution of 10 identified haplotypes in 338 Danish individuals with known MASP-2 and MAp19 levels and 309 South Brazilians. Four haplotypes were associated with reduced MASP-2 levels in plasma (lower than 200 ng/mL). Simultaneous association with the highest MASP-2 (over 600 ng/mL) and lowest MAp19 levels (lower than 200 ng/mL) was demonstrated with the intron 9 mutation (Kruskal-Wallis p

The lectin pathway of complement is a central part of innate immunity, but as a powerful inducer of inflammation it needs to be tightly controlled. The MASP2 gene encodes two proteins, MASP-2 and MAp19. MASP-2 is the serine protease responsible for lectin pathway activation. The smaller alternative splice product, MAp19, lacks a catalytic domain but retains two of three domains involved in association with the pattern-recognition molecules (PRMs): mannan-binding lectin (MBL), H-ficolin, L-ficolin and M-ficolin. MAp19 reportedly acts as a competitive inhibitor of MASP-2-mediated complement activation. In light of a ten times lower affinity of MAp19, versus MASP-2, for association with the PRMs, much higher serum concentrations of MAp19 than MASP-2 would be required for MAp19 to exert such an inhibitory activity. Just four amino acid residues distinguish MAp19 from MASP-2, and these are conserved between man, mouse and rat. Nonetheless we generated monoclonal rat anti-MAp19 antibodies and established a quantitative assay. We found the concentration of MAp19 in serum to be 217 ng/ml, i.e., 11 nM, comparable to the 7 nM of MASP-2. In serum all MASP-2, but only a minor fraction of MAp19, was associated with PRMs. In contrast to previous reports we found that MAp19 could not compete with MASP-2 for binding to MBL, nor could it inhibit MASP-2-mediated complement activation. Immunohistochemical analyses combined with qRT-PCR revealed that both MAp19 and MASP-2 were mainly expressed in hepatocytes. High levels of MAp19 were found in urine, where MASP-2 was absent., Highlights ►MAp19 and MASP-2 were both mainly expressed in hepatocytes. ►The MAp19 concentration in serum was 217 ng/ml, 11 nM, comparable to that of MASP-2. ►In serum all MASP-2, but only a minor fraction of MAp19, was associated with PRMs. ►High levels of MAp19 were found in urine, where MASP-2 was absent. ►MAp19 cannot compete with MASP-2 for binding to MBL, nor inhibit complement activation.

Gene polymorphisms, giving rise to low serum levels of mannose-binding lectin (MBL) or MBL-associated protease 2 (MASP2), have been associated with an increased risk of infections. The objective of this study was to assess the outcome of intensive care unit (ICU) patients with systemic inflammatory response syndrome (SIRS) regarding the existence of functionally relevant MBL2 and MASP2 gene polymorphisms. The study included 243 ICU patients with SIRS admitted to our hospital, as well as 104 healthy control subjects. MBL2 and MASP2 single nucleotide polymorphisms were genotyped using a sequence-based typing technique. No differences were observed regarding the frequencies of low-MBL genotypes (O/O and XA/O) and MASP2 polymorphisms between patients with SIRS and healthy controls. Interestingly, ICU patients with a noninfectious SIRS had a lower frequency for low-MBL genotypes and a higher frequency for high-MBL genotypes (A/A and A/XA) than either ICU patients with an infectious SIRS or healthy controls. The existence of low- or / high-MBL genotypes or a MASP2 polymorphism had no impact on the mortality rates of the included patients. The presence of high-MBL-producing genotypes in patients with a noninfectious insult is a risk factor for SIRS and ICU admission. Sepsis is the main cause of death in intensive care units (ICU), with mortality rates above 50% in patients with septic shock (54). Increasing evidence suggests that variations in genes encoding different components of the immune system influence an individual’s capacity to respond adequately to infections. Genetic polymorphisms of several molecules of the innate immune system, such as tumor necrosis factor alpha (TNF-) (35), interleukin-1 receptor antagonist (IL-1RA) (2), and more recently plasminogen activator inhibitor 1 (PAI-1) (12), have been associated with increased mortality in patients with severe sepsis and septic shock. The mannose-binding lectin (MBL) is an important element of the innate immune defense system. The MBL is a circulating C-type plasma lectin, mainly produced by the liver, which binds to the specific carbohydrates present on the surface of different microorganisms (21, 38). In serum, MBL is present as oligomers (mainly trimers and tetramers) bound to the MBL-associated serine proteases (MASPs, which are also produced in the liver), mainly MASP2. Once bound to the carbohydrate residues, the MBL/MASP2 complex acts as an opsonin for phagocytosis for numerous pathogens and activates comple

Mycobacterium tuberculosis is the leading cause of infectious disease in humans in the world. It evades the host immune system by being phagocytosed by macrophages and residing intracellularly. Complement-dependent opsonisation of extracellular mycobacteria may assist them to enter macrophages. This work examines in detail the mechanisms of complement activation by whole mycobacteria using Mycobacterium bovis BCG as a model organism. M. bovis BCG directly activates the classical, lectin and alternative pathways, resulting in fixation of C3b onto macromolecules of the mycobacterial surface. Investigation into the classical pathway has shown direct binding of human C1q to whole mycobacteria in the absence of antibodies. Most human sera contain IgG and IgM-anti-(M. bovis BCG), and pre-incubation with human immunoglobulin enhances C1q binding to the bacteria. Therefore classical pathway activation is both antibody-independent and dependent. The bacteria also activate the alternative pathway in an antibody-independent manner, but Factor H also binds, suggesting some regulation of amplification by this pathway. For the lectin pathway we have demonstrated direct binding of both MBL and L-ficolin from human serum to whole mycobacteria and subsequent MASP2 activation. H-ficolin binding was not observed. No M. bovis BCG cell surface or secreted protease appears likely to influence complement activation. Together, these data provide a more detailed analysis of the mechanisms by which M. bovis BCG interacts with the complement system.

Udgivelsesdato: 2009-May One collectin (mannan-binding lectin, MBL) and three ficolins (M-ficolin/ficolin-1, L-ficolin/ficolin-2 and H-ficolin/ficolin-3) share the capability to activate complement via the lectin pathway. This property depends on the ability of these lectins to form complexes with MBL-associated serine proteases (MASPs), particularly MASP-2. We report the results of an investigation of cord blood MASP-2 concentrations in a large, ethnically homogeneous cohort (n=1788) of neonates. The median value of MASP-2 in cord sera was determined to be 93 ng/ml (range

Hepatocellular carcinoma (HCC) is the fifth most frequent neoplasm with more than 500 000 new cases diagnosed yearly. Novel liver cancer biomarkers are needed. By tandem mass spectrometry, we analyzed the secretomes of 12 individual paired samples of liver cancer and adjacent normal tissues and identified 1528 proteins with >2 unique peptide hits. The false discovery rate was 3.4%. Using spectral counting, we found 87 proteins in the HCC group and 86 proteins in the normal group that showed fivefold overexpression. These proteins provided a rich source of biomarker candidates. We presented a novel paradigm in combining biomarkers that include an up-regulated cancer biomarker and a down-regulated organ-enriched marker, and identified chitinase-3-like protein 1(CHI3L1) and mannan-binding lectin serine peptidase 2 (MASP2) as the top biomarker pair for HCC diagnosis using integrative transcriptomics and proteomics analysis. Using ELISA assays, we further evaluated this biomarker pair in a separate cohort of 25 serum samples of liver cancer patients and 15 age-matched normal controls. The combined marker pair (YKL40/MASP2 ratio) performed better than either marker alone with an AUC of 0.97 for liver cancer diagnosis. Further validation of the biomarker pair in HCC patients versus disease controls and independent cohorts is warranted.

Mannan-binding lectin-associated serine protease 2 (MASP-2) is an enzyme of the innate immune system. MASP-2 forms complexes with the pattern recognition molecules mannan-binding lectin (MBL), H-ficolin, L-ficolin, or M-ficolin, and is activated when one of these proteins recognizes microorganisms and subsequently cleaves complement factors C4 and C2, thus initiating the activation of the complement system. Missense polymorphisms of MASP-2 exist in different ethnic populations. To further characterize the nature of these, we have produced and characterized rMASP-2s representing the following naturally occurring polymorphisms: R99Q, D120G, P126L, H155R, 156_159dupCHNH (CHNHdup), V377A, and R439H. Only very low levels of CHNHdup were secreted from the cells, whereas quantities similar to wild-type MASP-2 were found intracellularly, indicating that this mutation results in a misfolded protein. We found that D120G and CHNHdup could not associate with MBL, whereas R99Q, P126L, H155R, V377A, R439H, and wild-type MASP-2 bound equally well to MBL. Accordingly, when D120G and CHNHdup were mixed with MBL, no activation of complement factor C4 was observed, whereas R99Q, P126L, and V377A cleaved C4 with an activity comparable to wild-type MASP-2 and H155R slightly better. In contrast, the R439H variant was deficient in this process despite its normal binding to MBL. This variant was also not able to autoactivate in the presence of MBL and mannan. We find the R439H variant is common in Sub-Saharan Africans with a gene frequency of 10%. Our results indicate that individuals with different types of MASP-2 defects may be identified through genotyping.

N-Acetylglucosamine (GlcNAc) is the major immunoepitope of group A streptococcal cell wall carbohydrates. Antistreptococcal antibodies cross-reactive with anti-GlcNAc and laminin are present in sera of patients with rheumatic fever. The cross-reactivity of these antibodies with human heart valvular endothelium and the underlying basement membrane has been suggested to be a possible cause of immune-mediated valve lesion. Mannose-binding lectin (MBL) encoded by theMBL2gene, a soluble pathogen recognition receptor, has high affinity for GlcNAc. We postulated that mutations in exon 1 of theMBL2 gene associated with a deficient serum level of MBL may contribute to chronic severe aortic regurgitation (AR) of rheumatic etiology. We studied 90 patients with severe chronic AR of rheumatic etiology and 281 healthy controls (HC) for the variants of theMBL2gene at codons 52, 54, and 57 by using a PCR-restriction fragment length polymorphism-based method. We observed a significant difference in the prevalence of defectiveMBL2alleles between patients with chronic severe AR and HC. Sixteen percent of patients with chronic severe AR were homozygotes or compound heterozygotes for defective MBL alleles in contrast to 5% for HC (P= 0.0022; odds ratio, 3.5 [95% confidence interval, 1.6 to 7.7]). No association was detected with the variant of theMASP2gene. Our study suggests that MBL deficiency may contribute to the development of chronic severe AR of rheumatic etiology.

In this study we investigated whether partial or total MASP-2 deficiencies resulting from Asp105Gly mutation are associated with rheumatic fever (RF) and chronic rheumatic heart disease (RHD). The Asp105Gly MASP2 mutation (D105G) was detected by polymerase chain reaction-restriction fragment length polymorphism in 148 patients (43 men and 105 women; mean age 39.1 +/- 14.4 years) with a history of RF, including 106 (73%) with RHD and 42 (27%) without cardiac sequelae, and 129 control subjects (52 men and 77 women, mean age 38.4 +/- 12.2 years). The D105G mutation was detected in four patients with RHD (3.77%) and in five control subjects (3.88%), all in the heterozygous state. None of the patients without cardiac sequelae had the mutation. No significant difference was found in the frequency of the mutant allele between the groups (p0.6). These results suggest that the D105G mutation in the MASP2 gene does not play a major role in the pathogenesis of RF. Whether D105G plays a role in the development of RHD should be ascertained in future studies.

Little is known about determinants regulating expression of Mannan-binding lectin associated serine protease-2 (MASP-2), the effector component of the lectin pathway of complement activation. Comparative bioinformatic analysis of the MASP2 promoter regions in human, mouse, and rat, revealed conservation of two putative Stat binding sites, termed StatA and StatB. Site directed mutagenesis specific for these sites was performed. Transcription activity was decreased 5-fold when StatB site was mutated in the wildtype reporter gene construct. Gel retardation and competition assays demonstrated that proteins contained in the nuclear extract prepared from HepG2 specifically bound double-stranded StatB oligonucleotides. Supershift analysis revealed Stat3 to be the major specific binding protein. We conclude that Stat3 binding is important for MASP2 promoter activity.

We investigated MBL2 and MASP2 genotypes, serum MBL (mannose-binding lectin) levels and activities of its complexes with associated serine proteases (MASP-1, MASP -2), in relation to complications following cardiac surgery in 195 children. The incidence of SIRS was lower in patients carrying MBL2 A/O and O/O genotypes (p=0.024). Children with MBL levels500ng/ml had a lower risk of SIRS (p=0.014) and fever (p=0.044). Median MBL concentration was higher in patients who developed SIRS (p=0.048) but lower in those with post-operative infections (p=0.046). MBL-MASP-2 activities100mU/ml protected from SIRS (p=0.007), low cardiac output syndrome (p=0.03) and multiorgan failure (p=0.012). In contrast, MBL2 YA/YA genotypes were associated with SIRS (p=0.018), low cardiac output syndrome (p=0.018), fever (p=0.018) and high inotropic score (VIS30) (p=0.021). Thus, low MBL concentrations and associated genotypes may protect patients from systemic inflammation while high MBL serum levels and corresponding genotypes are risk factors of postoperative complications.