A survey of ficolin-3 activity in Systemic Lupus Erythematosus reveals a link to hematological disease manifestations and autoantibody profile

The complement system plays a central role in the pathogenesis of Systemic Lupus Erythematosus (SLE), but most studies have focused on the classical pathway. Ficolin-3 is the main initiator of the lectin pathway of complement in humans, but its role in systemic autoimmune disease has not been conclusively determined. Here, we combined biochemical and genetic approaches to assess the contribution of ficolin-3 to SLE risk and disease manifestations. Ficolin-3 activity was measured by a functional assay in serum or plasma samples from Swedish SLE patients (n = 786) and controls matched for age and sex (n = 566). Genetic variants in an extended 300 kb genomic region spanning the FCN3 locus were analyzed for their association with ficolin-3 activity and SLE manifestations in a Swedish multicenter cohort (n = 985). Patients with ficolin-3 activity in the highest tertile showed a strong enrichment in an SLE cluster defined by anti-Sm/DNA/nucleosome antibodies (OR 3.0, p < 0.001) and had increased rates of hematological disease (OR 1.4, p = 0.078) and lymphopenia (OR = 1.6, p = 0.039). Genetic variants associated with low ficolin-3 activity mapped to an extended haplotype in high linkage disequilibrium upstream of the FCN3 gene. Patients carrying the lead genetic variant associated with low ficolin-3 activity had a lower frequency of hematological disease (OR 0.67, p = 0.018) and lymphopenia (OR 0.63, p = 0.031) and fewer autoantibodies (p = 0.0019). Loss-of-function variants in the FCN3 gene were not associated with SLE, but four (0.5 %) SLE patients developed acquired ficolin-3 deficiency where ficolin-3 activity in serum was depleted following diagnosis of SLE. Taken together, our results provide genetic and biochemical evidence that implicate the lectin pathway in hematological SLE manifestations. We also identify lectin pathway activation through ficolin-3 as a factor that contributes to the autoantibody response in SLE.

Changes of Serum Ficolin-3 and C5b-9 in Patients with Heart Failure

Objectives:

To investigate the correlation of serum ficolin-3 and C5b-9 with cardiac function and NT-proBNP in patients with heart failure.

Methods:

Sixty patients with heart failure admitted to the Baoding First Central Hospital from May 2019 to May 2020 were selected and divided into three groups according to the classification of New York Heart Association (NYHA). Patients with NYHA grade II, III, and IV were included into group A, B, and C, respectively. Among the population undergoing physical examination at the same time, 20 cases with no significant difference in age and gender from the experimental group were selected as the control group (Group-N), and their clinical data were recorded. The serum levels of ficolin-3, C5b-9 and NT-proBNP in each group were detected and compared.

Results:

The serum concentrations of ficolin-3 and C5b-9 in Group N were significantly different from those in Group A, B and C (p<0.05), the difference between Group C and Group A and B was statistically significant (p<0.05), there was no significant difference between group A and B (p>0.05). The correlation analysis between serum ficolin-3 and NT-proBNP showed that serum ficolin-3 was negatively correlated with NT-proBNP (r=-0.606, p<0.0001), while the correlation analysis between serum C5b-9 and NT-proBNP showed that serum C5b-9 was positively correlated with NT-proBNP (r=0.499, p<0.0001). According to the etiology of heart failure, patients with heart failure were divided into coronary heart disease (25 cases), dilated cardiomyopathy (15 cases) and others (20 cases). The differences of ficolin-3 and C5b-9 among patients were compared, and there was no statistical difference (p<0.05).

Conclusion:

Ficolin-3 was inversely associated with the severity of heart failure, while C5b-9 was positively associated with the severity of cardiac impairment. Both of them have nothing to do with the etiology of heart failure.

Utilization of Whole Exome Sequencing in Non-Syndromic Premature Ovarian Failure: Ficolin-3 Gene Mutation in an Iranian Family

Background

Premature ovarian failure is a heterogeneous disorder, leading to early menopause. Several genes have been identified as the cause of non-syndromic premature ovarian failure (POF). Our aim was to explore the genetic defects in Iranian patients with POF.

Methods

We studied a family with three females exhibiting non-syndromic POF. WES was performed for one of the affected individuals after ruling out the presence of CGG repeat expansion at fragile X mental retardation 1 gene in the family. Sanger sequencing was used to confirm the candidate sequence variants in the proband, and screening of the detected mutation was performed for the other affected and unaffected members of the family.

Results

A homozygous frameshift mutation, c.349delC, was identified in ficolin-3 (FCN3) gene in the proband and two other patients. The parents and two healthy brothers were heterozygous for the mutation, and an unaffected sister was homozygous for wild type.

Conclusion

This is the first report of a mutation in FCN3 gene in a family with POF. Our findings can lead to the enhancement of genetic databases of patients with POF, specifically for families with high-risk background.

An Egyptian adolescents study

OBJECTIVE

Ficolin-3 is one of the innate immunity molecules that was thought to play a pivotal role in Streptococcus pyogenes autoimmunity and its complications; rheumatic fever (RF) and rheumatic heart disease (RHD). We aimed to disclose if there is an association between ficolin-3 (FCN3) gene polymorphisms (rs4494157 and rs10794501) and RF with or without RHD for the first time in Egyptian adolescents.

RESULTS

Serum ficolin-3 level was significantly elevated in patients suffering from RF with and without RHD in comparison with control. Regarding FCN3 gene (rs4494157) polymorphism, a significant correlation was found between the A allele and the susceptibility to RF with or without RHD (OR = 2.93, P = 0.0002 and OR = 2.23, P = 0.008 respectively). Besides, AA homozygous genotype showed a significant association with RHD risk (OR = 3.47, P = 0.026). Patients carrying the A allele (CA + AA) had significantly higher serum ficolin-3 than those carrying the CC genotype (P ˂ 0.0001). While the frequency of (rs10794501) polymorphism revealed no significant differences between the controls and RF patients with or without RHD (OR = 1.43, P = 0.261 and OR = 1.48, P = 0.208 respectively).

Ficolin-3 in rheumatic fever and rheumatic heart disease

Rheumatic fever (RF) and chronic rheumatic heart disease (RHD) are complications of oropharyngeal infection caused by Streptococcus pyogenes. Despite the importance of the complement system against infections and autoimmunity diseases, studies on the role of the lectin pathway in RF and RHD are scarce. Thus, our aim was to evaluate the association of ficolin-3 serum levels, FCN3 polymorphisms and haplotypes with the susceptibility to RF and RHD. We investigated 179 patients with a history of RF (126 RHD and 53 RF only) and 170 healthy blood donors as control group. Ficolin-3 serum concentrations were measured using enzyme-linked immunosorbent assay (ELISA). Three FCN3 single nucleotide polymorphisms (SNPs rs532781899, rs28362807 and rs4494157) were genotyped through the sequence-specific PCR method. Lower ficolin-3 serum levels were observed in RF patients when compared to controls (12.81 μg/mL vs. 18.14 μg/mL respectively, p < 0.0001, OR 1.22 [1.12-1.34]), and in RHD in comparison to RF only (RFo) (12.72 μg/mL vs. 14.29 μg/mL respectively, p = 0.016, OR 1.38 [1.06-1.80]). Low ficolin-3 levels (<10.7 μg/mL) were more common in patients (39.5 %, 30/76) than controls (20.6 %, 13/63, p = 0.018, OR = 2.51 [1.14-5.31]), and in RHD (44.4 %, 28/63) than RFo (15.4 %, 2/13, p = 0.007, OR = 3.08 [1.43-6.79]). On the other hand, FCN3 polymorphism/haplotypes were not associated with ficolin-3 serum levels or the disease. Low ficolin-3 levels might be associated with RF, being a potential marker of disease progression.

Interactions of ficolin-3 with ovarian cancer cells

BACKGROUND

Ficolin-3 is a pattern-recognition molecule with the ability to activate the lectin pathway of complement. It is found in lung, liver and blood, but its physiological role is unclear. We have investigated interaction of recombinant ficolin-3 with malignant cells and tissues.

MATERIAL AND METHODS

Cells of various lines of human origin as well as ovarian tissue sections have been studied with the use of flow cytometry and immunohistochemistry.

RESULTS

Recombinant (but not serum-derived) ficolin-3 was found to bind strongly to the ovarian cancer cell lines, SKOV-3, OVCAR-3 and ES-2, at concentrations of 2.5 μg/ml and above. Moreover, His-tagged recombinant ficolin-3 (10 μg/ml) preferentially stained ovarian tissue sections from patients with malignant tumours compared with those from patients without. Binding to cell lines was inhibited by EDTA and specific carbohydrate ligands, indicating involvement of the fibrinogen-like domain. Binding was enhanced under mildly acidic conditions and at physiological pH after pre-incubation of cells with mildly acidic buffer.

CONCLUSION

Basing on data concerning recombinant protein, it may be suggested that ficolin-3 is involved in immune response in ovarian cancer. However, unidentified serum factor(s) seem(s) to protect cancer cells from recognition by natural or rficolin-3.

Ficolin-1 and Ficolin-3 Plasma Levels Are Altered in HIV and HIV/HCV Coinfected Patients From Southern Brazil

The complement system is a key component of the innate immune system, participating in the surveillance against infectious agents. Once activated by one of the three different pathways, complement mediates cell lysis, opsonization, signalizes pathogens for phagocytosis and induces the adaptive immune response. The lectin pathway is constituted by several soluble and membrane bound proteins, called pattern recognition molecules (PRM), including mannose binding lectin (MBL), Ficolins-1, -2, and -3, and Collectin 11. These PRMs act on complement activation as recognition molecules of pathogen-associated molecular patterns (PAMPs) such as N-acetylated, found in glycoproteins of viral envelopes. In this study, Ficolin-1 and Ficolin-3 plasma levels were evaluated in 178 HIV patients (93 HIV; 85 HIV/HCV) and 85 controls from southern Brazil. Demographic and clinical-laboratory findings were obtained during medical interview and from medical records. All parameters were assessed by logistic regression, adjusted for age, ancestry, and sex. Significantly lower levels of Ficolin-1 were observed in HIV/HCV coinfected when compared to HIV patients (p = 0.005, median = 516 vs. 667 ng/ul, respectively) and to controls (p < 0.0001, 1186 ng/ul). Ficolin-1 levels were lower in males than in females among HIV patients (p = 0.03) and controls (p = 0.0003), but no association of Ficolin-1 levels with AIDS was observed. On the other hand, Ficolin-3 levels were significantly lower in controls when compared to HIV (p < 0.0001, medians 18,240 vs. 44,030 ng/ml, respectively) and HIV/HCV coinfected (p < 0.0001, 40,351 ng/ml) patients. There was no correlation between Ficolin-1 and Ficolin-3 levels and age, HIV viral load or opportunistic infections. However, Ficolin-3 showed a positive correlation with T CD4 cell counts in HIV monoinfected patients (p = 0.007). We provide here the first assessment of Ficolin-1 and-3 levels in HIV and HIV/HCV coinfected patients, which indicates a distinct role for these pattern recognition molecules in both viral infections.

Increased secreted frizzled-related protein 4 and ficolin-3 levels in gestational diabetes mellitus women

By biochemical and epidemiological similarity with type 2 diabetes mellitus (T2DM), gestational diabetes mellitus (GDM) has some overlap between prediction markers and risk factors of T2DM. The present study aimed to establish that secreted frizzled-related protein 4 (SFRP4) and ficolin-3 levels, which have been linked to insulin resistance and the development of T2DM, are elevated in GDM women. A longitudinal prospective cohort study of 86 GDM and 273 normal glucose tolerant (NGT) pregnant women was performed. The clinical parameters, lipid profiles, and serum SFRP4 and ficolin-3 levels were tested during the early and late second-trimester and third-trimester of pregnancy. Both SFRP4 and ficolin-3 levels were significantly higher in GDM women as compared to the NGT participants at three test points (p < 0.01). Spearman's correlation analysis showed that serum SFRP4 levels were significantly positively correlated with ficolin-3 during the early and late second-trimester and third-trimester of pregnancy. The elevated SFRP4 and ficolin-3 concentrations at 16-18 weeks gestation significantly associated with GDM were conformed using binary logistic regression analysis after controlling for other variables [odds ratios (OR) with 95% confidence intervals (CI) for SFRP4: 2.84 (1.78-4.53), p < 0.01; for ficolin-3: 2.45 (1.55-3.88), p < 0.01]. In Conclusions, increased SFRP4 and ficolin-3 levels are significantly associated with GDM development and might be important risk factors for this pregnancy complication.

Ficolin-3/adiponectin ratio for the prediction of gestational diabetes mellitus in pregnant women

AIMS/INTRODUCTION

To establish that the ficolin-3/adiponectin ratio is a predictor for gestational diabetes mellitus (GDM) and is eligible for screening tests for GDM.

MATERIALS AND METHODS

A prospective cohort study of 86 pregnant women who developed GDM and 273 normal glucose tolerance participants was carried out. Maternal serum ficolin-3, adiponectin levels were investigated at 16-18 weeks of gestation using enzyme-linked immunosorbent assay.

RESULTS

Compared with the normal glucose tolerance group, the GDM group showed significantly higher levels of ficolin-3 and the ratio of ficolin-3/adiponectin; and decreased levels of adiponectin between 16-18 weeks of gestation (P < 0.05 or P < 0.01). The cut-off values for the ratio of ficolin-3/adiponectin (≥1.06; sensitivity 90.9%, specificity 96.5%) to discriminate the pregnant women who developed GDM from the non-diabetic cases were identified using receiver operating characteristic analysis. Using binary logistic regression analysis, ficolin-3, retinol-binding protein-4 and adiponectin, but not C-reactive protein, triglyceride and free fatty acids were shown as predictive factors for GDM.

CONCLUSIONS

The ratio of ficolin-3/adiponectin at 16-18 weeks of gestation was changed in pregnant women who subsequently developed GDM, and might provide effective early predicting and screening for GDM.

Screening for immune-potentiating antigens from hepatocellular carcinoma patients after radiofrequency ablation by serum proteomic analysis

Background

Radiofrequency ablation (RFA) can not only effectively kill hepatocellular carcinoma (HCC) tumour cells but also release tumour antigens that can provoke an immune response. However, there is no consensus regarding which antigens could constitutively be generated after RFA and could potentiate the immune response. The aim of this study was to identify these immune-potentiating antigens.

Methods

We performed two-dimensional electrophoresis (2-DE) and MALDI-TOF-MS/MS analyses on serum obtained before and after RFA from 5 HCC patients. Further validation for selected proteins was performed utilizing ELISA analysis on another 52 HCC patients. Disease-free survival (DFS) analysis according to the differential expression of the interested protein before and after RFA was performed.

Results

Twelve decreased and 6 increased proteins after RFA were identified by MS. Three proteins, including clusterin, Ficolin-3, and serum retinol binding protein-4, were further verified by ELISA on the 52 HCC patients. Only Ficolin-3 proved to be significantly changed after RFA. The 52 patients were divided into two groups according to the expression of Ficolin-3 before and after RFA. The 1-, 2- and 3-year DFS rates were 59.1%, 31.8%, and 22.7%, respectively, for patients in the low Ficolin-3 group (22 patients) and 73.3%, 60.0%, and 50.0%, respectively, for patients in the high Ficolin-3 group (30 patients) (P = 0.038).

Conclusions

In conclusion, Ficolin-3 was overexpressed in the serum of most HCC patients after RFA. Ficolin-3 might be a biomarker for RFA treatment efficacy and a potential target for HCC immunotherapy.

Alveolar recruitment of ficolin-3 in response to acute pulmonary inflammation in humans

BACKGROUND

Ficolins serve as soluble recognition molecules in the lectin pathway of complement. They are known to participate in the systemic host-response to infection but their role in local pulmonary defence is still incompletely understood. The purpose of this study was to clarify whether acute lung and systemic inflammation induce recruitment of lectins in humans.

METHODS

Fifteen healthy volunteers received LPS intravenously (IV) or in a lung subsegment on two different occasions. Volunteers were evaluated by consecutive blood samples and by bronchoalveolar lavage 2, 4, 6, 8, or 24h after LPS (n=3 in all groups), and gene expression patterns and protein levels of mannose-binding lectin (MBL) and ficolins were determined.

RESULTS

Endobronchial LPS was associated with an increase in alveolar ficolin-3 and MBL levels (p<0.04 and p<0.001, respectively). IV LPS elicited a pronounced acute phase response with an increase in CRP (p<0.001) and plasma ficolin-1 protein levels (p<0.001), whereas no changes were observed in ficolin-1 gene expression patterns (p=0.11) or plasma protein levels of MBL, ficolin-2, or ficolin-3.

CONCLUSIONS

LPS induces a tissue-specific recruitment of ficolin-3 and ficolin-1 in the lung and systemic compartment, respectively, suggesting an important role of distinct lectin complement pathway initiators in the local pulmonary and systemic host defence.

Frequency and distribution of FCN2 and FCN3 functional variants among MBL2 genotypes

The six types of pattern recognition molecules (PRMs) that initiate complement via the lectin pathway (LP) comprise collectins and ficolins. The importance of having various PRMs to initiate the LP is currently unclear. Mannan-binding lectin (MBL) is a collectin member of the LP PRMs. MBL deficiency is common with mild clinical consequence. Thus, the lack of MBL may be compensated for by the other PRMs. We hypothesized that variants FCN2 + 6424 and FCN3 + 1637delC that cause gene-dose-dependent reduction in ficolin-2 and ficolin-3 levels, respectively, may be rare in MBL-deficient individuals due to the importance of compensation within the LP. The aim of this study was to investigate the distribution and frequency of these variants among MBL2 genotypes in healthy subjects. The allele frequency of FCN2 + 6424 and FCN3 + 1637delC was 0.099 and 0.015, respectively, in the cohort (n = 498). The frequency of FCN2 + 6424 tended to be lower among MBL-deficient subjects (n = 53) than among MBL-sufficient subjects (n = 445) (0.047 versus 0.106, P = 0.057). In addition, individuals who were homozygous for FCN2 + 6424 were sufficient MBL producers. The frequency of FCN3 + 1637delC did not differ between the groups. The frequency of FCN2 + 6424 was similar in FCN3 + 1637delC carriers (n = 15) versus wild type (n = 498). Furthermore, subjects that were heterozygote carriers of both FCN2 + 6424 and FCN3 + 1637delC were sufficient MBL producers. In conclusion, FCN2 + 6424 carriers with MBL deficiency tend to be rare among healthy individuals. MBL-deficient individuals with additional LP PRM defects may be at risk to morbidity.

Low levels of ficolin-3 are associated with diabetic peripheral neuropathy

AIMS

Ficolin-3, a soluble molecule of the innate immune system, has a primary role in the activation of the lectin pathway in the complement system. Considering that inflammatory mechanisms are involved in complement activation and take part in the pathophysiology of diabetic peripheral neuropathy (DPN), we conducted this study to explore the link between serum ficolin-3 and DPN in diabetic patients.

METHODS

A total of 466 diabetic patients were enrolled in this cross-sectional study. DPN was evaluated by neurological symptoms, neurological signs, neurothesiometer and electromyogram. The concentration of serum ficolin-3 was determined by enzyme-linked immunosorbent assay.

RESULTS

The concentration of serum ficolin-3 was lower in DPN patients compared with non-DPN patients (18.73 ± 4.75 vs. 26.69 ± 5.68 ng/mL, P < 0.001). In addition, it was found negatively correlated to the vibration perception threshold (r = -0.158; P = 0.025). The results of multiple regression analysis of DPN indicated that age, diabetes duration, serum ficolin-3 were all independent impact factors for DPN (P < 0.05). Patients were then assigned into quartiles according to the serum ficolin-3 levels, and the prevalence of DPN ascended as the concentration of ficolin-3 descended (Trend analysis, P < 0.001). Compared with ficolin-3 Quartile 1 (referent), the risk of DPN was significantly greater in Quartile 2 (OR 2.76; 95 % CI 1.56-4.88; P < 0.001), Quartile 3 (OR 3.02; 95 % CI 1.69-5.40; P < 0.001) and Quartile 4 (OR 6.84; 95 % CI 3.39-13.80; P < 0.001).

CONCLUSIONS

Lower ficolin-3 level is independently associated with DPN, and it may be a potential biomarker for DPN.

Primary Ficolin-3 deficiency--Is it associated with increased susceptibility to infections?

Ficolin-3 (also called H-ficolin or Hakata antigen) is the most potent activator of the lectin pathway of complement in vitro. Its genetically determined deficiency in Caucasians is associated with a frame-shift mutation +1637delC (rs28357092) of the FCN3 gene. When it was described for the first time, it was postulated to be strictly associated with enhanced susceptibility to infections. At present, with our knowledge extended by several other patients that issue seems to be more complicated and less clear-cut. Two new cases of primary Ficolin-3 deficiency are reported here: a 50-year old male, suffering from membranous nephropathy and an 11-month old male infant who was operated on to repair congenital heart disease. Based on those cases and a literature review, we conclude that the clinical consequences of congenital Ficolin-3 deficiency are still unclear and such questions as whether it may be life-threatening or acts as a disease modifier remain to be elucidated.

Ficolin-3 activity towards the opportunistic pathogen, Hafnia alvei

Ficolin-3 (also called H-ficolin or Hakata antigen) is a complement-activating pattern recognition molecule, possessing a fibrinogen-like domain involved in carbohydrate binding. Amongst human ficolins, Ficolin-3 has the highest concentration in serum and is the most potent lectin pathway activator in vitro. Evidence for its physiological function is sparse, although its deficiency has been suggested to increase susceptibility to infections. The specificity of Ficolin-3 is poorly characterized and currently few ligands are known. Here we report agglutination of Hafnia alvei, a Gram-negative enteric commensal bacterium and opportunist pathogen, in the presence of recombinant Ficolin-3 and calcium. Ficolin-3 also augmented phagocytosis of H. alvei by macrophages and displayed bactericidal activity. Additionally, Ficolin-3 inhibited host cells' response to TLR4/MD-2/CD14-LPS dependent NF-κB activation. This is the first demonstration of protective activity of Ficolin-3 against a human bacterial pathogen. Although human Ficolin-3 does not recognise and bind to common pathogenic bacteria, it could be an important component of innate immunity providing protection, for example, from commensal flora that can cause extraintestinal, opportunistic infections.