Mannose-binding lectin concentrations, MBL2 polymorphisms, and susceptibility to respiratory tract infections in young men

MBL2 gene variants and susceptibility to meningitis in Egyptian patients

BACKGROUND

Meningitis is inflammation of the membranes enclosing the brain and spinal cord. It is a fatal disease with severe morbidity and mortality. Mannose binding lectin (MBL) encoded by MBL2 gene activates complement system through lectin pathway in innate immunity to defense against the infections.

OBJECTIVE

the current study aimed to investigate the promoter and exon 1 variants of MBL2 gene among Egyptian patients having meningitis to explore their role in disease susceptibility.

PATIENTS AND METHODS

This case-control study, included 53 patients and 50 sex and age matched controls. MBL2 genotyping was done using Sanger sequencing.

RESULTS

The frequency of one promoter (c.-290C>G) and four in exon 1 (c.161G>A, c.170G>A, c.154C>T and c.132C>T) as well as another one located in its 5'utranslated part (c.-66C>T) variants were estimated. The incidence of the four individual exonic variants was not significantly different between cases and healthy individuals (all P> 0.05). The promoter variant, c.-290C>G was found in all examined patients (84.9% of the patients in homozygote state and 15.1% of patients in heterozygous state) with a highly significant variance in the prevalence of this variant between cases and control group (p=0.0001). Additionally, UTR variant (c.-66C>T) was also significantly higher in patients than controls (P=0.033).In comparison with clinical outcome, it was found that c.170G>A variant named C allele was associated with favorable outcome in the studied patients (P=0.025).

CONCLUSION

The results obtained showed that the Promoter (c.-290C>G) and UTR (c.-66 C>T) variants of MBL2 gene may be potential risk factors for disease susceptibility in Egyptian cases with meningitis. Our results also proposed that c.170G>A (C allele and CC genotype) could affect the severity and play a protective role in these patients. The other genetic variants of MBL2 gene, including c.132C>T, c.161G>A (A>B), and c.154C>T (A>D) that were investigated, did not show any association with susceptibility or severity of meningitis.

Mannose-binding lectin 2 gene polymorphisms and predisposition to allergic bronchial asthma in a western Romanian children population: an observational study

OBJECTIVES

To analyse: (1) the associations between different mannose-binding lectin 2 (MBL2) genotypes and susceptibility to bronchial asthma (BA) in Romanian children; and (2) the correlations between several patient sociodemographic variables and MBL2 polymorphisms.

METHODS

This prospective observational case-control study included paediatric patients with symptomatic BA and healthy controls. Participants were genotyped for two MBL2 single-nucleotide polymorphisms (SNPs): exon 1 codon 54 A/B variant rs1800450, and -550 promoter H/L variant rs11003125 (GenBank accession). Associations between MBL2 genotypes and susceptibility to BA were determined by calculated odds ratios, and Kendall Tau's correlations were used to investigate the associations between sociodemographic variables and SNPs.

RESULTS

Among 59 patients with BA and 65 healthy controls, associations between MBL2 polymorphisms and susceptibility to BA were not found to be statistically significant. Statistically significant weak positive correlations were found between age at diagnosis and A/B genotype, and between the smoking status of biologically male and female parents. A statistically significant weak inverse association was found between male parent smoking status and family history of BA.

CONCLUSION

These results may help guide future research into paediatric BA in Romania and Eastern Europe. Due to study limitations, the results require validation in future large-scale studies.

Factors associated with IgG levels in adults with IgG subclass deficiency

Background

Factors associated with IgG levels in adults with IgG subclass deficiency (IgGSD) are incompletely understood. We studied adults with IgGSD with subnormal IgG1 only, subnormal IgG1/IgG3, or subnormal IgG3 only without other subnormal IgG subclasses, IgA, or IgM. We compiled: age; sex; autoimmune condition(s) (AC); atopy; IgG, IgG subclasses, IgA, IgM; IgGsum (IgG1 + IgG2 + IgG3 + IgG4); and D (percentage difference between IgGsum and IgG). We compared attributes of patients with/without subnormal IgG (< 7.00 g/L; subnormal IgG1 subclass groups only) and analyzed IgGsum and IgG relationships. We performed backward stepwise regressions on IgG using independent variables IgG subclasses, age, and sex and on D using independent variables age and sex.

Results

There were 39 patients with subnormal IgG1 only (89.7% women), 53 with subnormal IgG1/IgG3 (88.7% women), and 115 with subnormal IgG3 only (91.3% women). Fifteen patients (38.5%) and 32 patients (60.4%) in the respective subnormal IgG1 subclass groups had subnormal IgG. Attributes of patients with/without IgG < 7.00 g/L were similar, except that AC prevalence was lower in patients with subnormal IgG1 only and IgG < 7.00 g/L than ≥ 7.00 g/L (p = 0.0484). Mean/median IgG1 and IgG2 were significantly lower in patients with IgG < 7.00 g/L in both subnormal IgG1 subclass groups (p < 0.0001, all comparisons). Regressions on IgG in three subclass groups revealed positive associations with IgG1 and IgG2 (p < 0.0001 each association). Regressions on D revealed no significant association. IgG1 percentages of IgGsum were lower and IgG2 percentages were higher in patients with subnormal IgG1 subclass levels than subnormal IgG3 only (p < 0.0001 all comparisons).

Conclusions

We conclude that both IgG1 and IgG2 are major determinants of IgG in patients with subnormal IgG1, combined subnormal IgG1/IgG3, or subnormal IgG3 and that in patients with subnormal IgG1 or combined subnormal IgG1/IgG3, median IgG2 levels are significantly lower in those with IgG < 7.00 g/L than those with IgG ≥ 7.00 g/L.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00447-3.

Mannose-binding lectin and risk of infections in type 2 diabetes: A Danish cohort study

AIMS

In individuals at increased risk of infections, e.g., patients with type 2 diabetes, low MBL may have detrimental effects. We used the Mendelian randomization principle to examine whether genetically low MBL is a risk factor for developing infections in patients with type 2 diabetes.

METHODS

Serum MBL (n = 7305) and MBL genotype (n = 3043) were determined in a nationwide cohort of patients with new type 2 diabetes and up to 8 years follow-up for hospital-treated infections and community-based antimicrobial prescriptions. The associations were examined in spline and Cox regression analyses.

RESULTS

1140 patients (16%) were hospitalized with an infection and 5077 patients (70%) redeemed an antimicrobial prescription. For low (≤100 μg/L) versus intermediate (101-1000 μg/L) serum MBL concentration, the adjusted hazard ratios (aHRs) were 1.13(95% confidence interval, 0.96-1.33) for any hospital-treated infections and 1.19(1.01-1.41) for bacterial infections. Low MBL expression genotype was not associated with risk of any hospital-treated infections except for diarrheal diseases (aHR 2.23[1.04-4.80]). Low MBL expression genotype, but not low serum MBL, was associated with increased risk for antimicrobial prescriptions (aHR 1.18[1.04-2.34] and antibacterial prescriptions 1.20[1.05-1.36]).

CONCLUSIONS

Low MBL is a weak causal risk factor for developing infections in patients with type 2 diabetes.

Genetic Polymorphism of MBL 2 in Patients with Allergic Bronchial Asthma

Mannose-binding lectin (MBL) belongs to a family of glycoproteins called lectins or collectins, which possess many of the functional features of immunoglobulins. Mannose-binding lectin is a very important component of the innate immune system, which recognizes distinct pathogens and activates the classical path of the complement-fixation method. In humans, the serum levels of collectins vary widely, and their variability is correlated with susceptibility and resistance to infection and other diseases. Recent studys show that MBL gene polymorphism is involved in the pathogenesis of many diseases, including infectious and allergic illnesses. Our study aims to determine the role of MBL polymorphism in children diagnosed with allergic bronchial asthma, especially in acute episodes. We conclude that MBL2 gene polymorphism is associated with atopy, allergic diseases and acute respiratory tract infections with MBL deficiency in early childhood. In terms of genetic polymorphism, most of the studied alleles were type A, these being the most frequently present in the studied groups, while alleles B, C or D have been explored to a lesser extent. Studies are also required for adult patients with allergic and atopic conditions, because so far, most of the research has been done on pediatric population only.

Clinical and laboratory associations of mannose-binding lectin in 219 adults with IgG subclass deficiency

Background

Mannose-binding lectin (MBL) deficiency may increase risk of respiratory tract infection in adults unselected for IgG or IgG subclass levels. In a retrospective study, we sought to determine associations of serum MBL levels with clinical and laboratory characteristics of unrelated non-Hispanic white adults at diagnosis of IgG subclass deficiency (IgGSD). We computed the correlation of first and second MBL levels expressed as natural logarithms (ln) in a patient subgroup. We compared these characteristics of all adults with and without MBL ≤50 ng/mL: age; sex; body mass index; upper/lower respiratory tract infection; diabetes; autoimmune condition(s); atopy; other allergy; corticosteroid therapy; and subnormal serum IgG subclasses, IgA, and IgM. We performed logistic regression on MBL ≤50 ng/mL (dichotomous) using the three independent variables with the lowest values of p in univariate comparisons.

Results

There were 219 patients (mean age 51 ± 13 y; 82.5% women). Thirty-six patients (16.4%) had MBL ≤50 ng/mL. Two MBL measurements were available in 14 patients. The median interval between the first and second measurements was 125 d (range 18–1031). For ln-transformed data, we observed adjusted r² = 0.9675; Pearson correlation coefficient 0.9849; and p < 0.0001. Characteristics of patients with and without MBL ≤50 ng/mL did not differ significantly in univariate comparisons. We performed a regression on MBL ≤50 ng/mL using: subnormal IgM (p = 0.0565); upper respiratory tract infection (p = 0.1094); and body mass index (p = 0.1865). This regression revealed no significant associations. Conclusions: We conclude that the proportion of the present IgGSD patients with serum MBL ≤50 ng/mL is similar to that of healthy European adults. MBL ≤50 ng/mL was not significantly associated with independent variables we studied.

Association of MBL2 gene polymorphisms with pulmonary tuberculosis susceptibility: trial sequence meta-analysis as evidence

Background

Mannose-binding lectin (MBL) or mannose-binding protein (MBP), encoded by MBL2 gene and secreted by the liver, activates complement system through lectin pathway in innate immunity against the host’s infection. Conflictingly, a number of MBL2 variants, rs1800450 (A>B), rs1800451 (A>C), rs5030737 (A>D), rs7096206 (Y>X), rs11003125 (H>L), and rs7095891 (P>Q) allele, have been found to be associated with compromised serum levels and pulmonary tuberculosis (PTB) susceptibility. The present meta-analysis study was performed to evaluate the potential association of these MBL2 gene variants with PTB susceptibility.

Materials and methods

A quantitative synthesis was performed on PubMed (Medline), EMBASE, and Google Scholar web database searches. A meta-analysis was performed to calculate the pooled odds ratios and 95% CIs for all the genetic models.

Results

A total of 14 eligible studies were included to analyze their pooled data for associations between alleles, genotypes, and minor allele carriers. The statistical analysis revealed the significant reduced PTB risk with homozygous variant genotype of rs1800451 polymorphism (CC vs AA: P=0.043; OR =0.828, 95% CI =0.689–0.994). Contrary to this, the variant allele of rs5030737 polymorphism showed association with increased PTB risk (D vs A: P=0.026; OR =1.563, 95% CI =1.054–2.317). However, the other genetic models of rs1800450 (A>B), rs7096206 (Y>X), and rs11003125 (H>L) MBL2 gene polymorphisms did not divulge any association with PTB susceptibility.

Conclusion

The current meta-analysis concludes that rs1800451 (A>C) and rs5030737 (A>D) polymorphisms of MBL2 gene play a significant role in PTB susceptibility. Further, well-designed epidemiological studies with larger sample size including consideration of environmental factors are warranted for the future.

Mannose-Binding Lectin 2 Gene Polymorphism in PANDAS Patients

Introduction

Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS), a subgroup of obsessive-compulsive disorder (OCD), has received much attention even though the specific underlying mechanisms remain unknown. Mannose-binding lectin (MBL) is a key factor in the innate immune response. The aim of this study was to investigate the role of MBL2 gene polymorphisms in pediatric OCD patients diagnosed as PANDAS, PANDAS-Variant and non-PANDAS.

Methods

The study included 102 pediatric OCD patients (59 [57.8% ] PANDAS, 20 [19.6% ] non-PANDAS, and 23 [22.5% ] PANDAS-Variant) and 60 healthy controls. Polymorphisms at codon 52, 54 and 57 of the MBL2 gene were investigated.

Results

Codon 54 polymorphism and any variant of MBL2 gene were significantly more frequent in the OCD group than in the control group (OR=2.97, 95% CI: 1.26-6.97; and OR=2.66, 95% CI: 1.32-5.38, respectively). According to regression analysis, the presence of any variant of MBL2 gene was found in 14.50-fold increased frequency in the PANDAS subgroup compared with the non-PANDAS subgroup (95% CI: 2.49-84.19).

Conclusions

Our findings support an association between MBL2 genotypes and pediatric OCD, particularly PANDAS-OCD.

Mannose-binding lectin deficiency in respiratory diseases

Mannosebinding lectin is a part of the innate immunity that, being the first barrier of the antiinfectious defense, acts in first minutes or hours after pathogen challenge. The review provides data about mechanisms of action of mannosebinding lectin and its particular pathogenic role in a wide range of respiratory diseases: bacterial pneumonia, viral respiratory tract infections, tuberculosis, cystic fibrosis, chronic obstructive pulmonary disease, and asthma in adults and children.

Association of MBL With Work-Related Respiratory Symptoms in Bakery Workers

Baker's asthma is the most prevalent occupational asthma, and IgE-mediated response is known as a major pathogenesis. However, recent studies have suggested the involvement of innate immune response because wheat flour contains bacterial endotoxins or lipopolysaccharides. To further understand a role of innate immune response in the development of work-related respiratory symptoms (WRS) in bakery workers, we investigated mannose-binding lectin (MBL), one of the initiating components of the complement cascade in a single cohort of bakery workers. A total of 373 bakery workers completed a questionnaire regarding WRS. The bakery workers were divided into 2 groups according to previous history of allergic rhinitis (AR)/bronchial asthma (BA): those with history of AR/BA (group I) and those without (group II). We measured serum MBL levels by using enzyme-linked immunosorbant assay and genotyped 4 single nucleotide polymorphisms of the MBL2 gene (226G>A in exon 1, -554G>C, -431A>C, and -225G>C in the promoter) by using TaqMan assays. Fifty-nine subjects (15.5%) were previously diagnosed with AR/BA, and 64 subjects (16.8%) complained of WRS. No significant differences were found in serum MBL levels between groups I and II. However, in group II subjects, but not in group I subjects, the serum MBL levels were significantly higher in bakery workers with WRS than in those without. In addition, the serum MBL levels were significantly different according to genetic polymorphisms of the MBL2 gene and its haplotypes. In conclusion, serum MBL, affected by genetic polymorphisms, may be associated with WRS in bakery workers with no previous history of AR/BA.

MBL2 polymorphisms and the risk of asthma: A meta-analysis

BACKGROUND

The association between MBL2 gene polymorphisms and the risk of asthma has been evaluated in multiple studies; however, the results are inconsistent.

OBJECTIVE

To perform a meta-analysis to explore whether MBL2 gene polymorphisms were associated with the risk of asthma.

METHODS

We searched PubMed, Web of Science, and Cochrane Library to find relevant articles published up to March 2016. Nine studies, including 2066 cases and 2183 controls, were included in the meta-analysis. The strength of association was evaluated by odds ratio (OR) with 95% confidence interval (CI).

RESULTS

The results reveal that MBL2 gene polymorphisms (codon 54 A/B, -550 H/L or -221 X/Y) were not associated with the risk of asthma (codon 54 A/B: BB+AB vs AA: OR, 1.02; 95% CI, 0.85-1.23; -550 H/L: LL+HL vs HH: OR, 0.81; 95% CI, 0.63-1.03; -221 X/Y: XX+YX vs YY: OR, 0.85; 95% CI, 0.69-1.04). Subgroup analysis by ethnicity implied that the MBL2 codon 54 A/B polymorphism was not significantly associated with the risk of asthma in Asians (BB+AB vs AA: OR, 0.95; 95% CI, 0.70-1.29) or whites (BB+AB vs AA: OR, 1.07; 95% CI, 0.84-1.35).

CONCLUSION

The results indicated that MBL2 gene polymorphisms (codon 54 A/B, -550 H/L or -221 X/Y) may be not associated with the risk of asthma.

Mannose-binding lectin protein and its association to clinical outcomes in COPD: a longitudinal study

BACKGROUND

Functional deficiency of mannose-binding lectin (MBL) may contribute to the pathogenesis of chronic obstructive pulmonary disease. We hypothesized that specific MBL2 gene polymorphisms and circulating MBL protein levels are associated with clinically relevant outcomes in the Predicting Outcome using systemic Markers In Severe Exacerbations of COPD PROMISE-COPD cohort.

METHODS

We followed 277 patients with stable COPD GOLD stage II-IV COPD over a median period of 733 days (IQR 641-767) taking survival as the primary outcome parameter. Patients were dichotomized as frequent (≥ 2 AECOPD/year) or infrequent exacerbators. Serum MBL levels and single nucleotide polymorphisms of the MBL2 gene were assessed at baseline.

RESULTS

The MBL2-HYPD haplotype was significantly more prevalent in frequent exacerbators (OR: 3.33; 95% CI, 1.24-7.14, p = 0.01). The median serum MBL concentration was similar in frequent (607 ng/ml, [IQR; 363.0-896.0 ng/ml]) and infrequent exacerbators (615 ng/ml, [IQR; 371.0-942.0 ng/ml]). Serum MBL was not associated with lung function characteristics or bacterial colonization in sputum. However, high serum MBL at stable state was associated with better survival compared to low MBL (p = 0.046, log rank test).

CONCLUSIONS

In COPD, the HYPD haplotype of MBL2 gene is associated with frequent exacerbations and high serum MBL is linked to increased survival. The PROMISE-COPD study was registered at www.controlled-trials.com under the identifier ISRCTN99586989.

Mannose-binding Lectin (MBL) as a susceptible host factor influencing Indian Visceral Leishmaniasis

Visceral Leishmaniasis (VL), caused by Leishmania donovani is endemic in the Indian sub-continent. Mannose-binding Lectin (MBL) is a complement lectin protein that binds to the surface of Leishmania promastigotes and results in activation of the complement lectin cascade. We utilized samples of 218 VL patients and 215 healthy controls from an Indian population. MBL2 functional variants were genotyped and the circulating MBL serum levels were measured. MBL serum levels were elevated in patients compared to the healthy controls (adjusted P=0.007). The MBL2 promoter variants -78C/T and +4P/Q were significantly associated with relative protection to VL (-78C/T, OR=0.7, 95% CI=0.5-0.96, adjusted P=0.026 and +4P/Q, OR=0.66, 95% CI=0.48-0.9, adjusted P=0.012). MBL2*LYQA haplotypes occurred frequently among controls (OR=0.69, 95% CI=0.5-0.97, adjusted P=0.034). MBL recognizes Leishmania and plays a relative role in establishing L. donovani infection and subsequent disease progression. In conclusion, MBL2 functional variants were associated with VL.

Effects of MBL2 polymorphisms in patients with diisocyanate-induced occupational asthma

Diisocyanate (DI) is the most common cause of occupational asthma (OA) in Korea. Mannose-binding lectin (MBL) initiates the lectin complement activation pathway following oxidative stress and plays an important role in the regulation of inflammatory processes. To determine whether there is a genetic association between MBL2 polymorphisms and DI-OA, 99 patients with DI-OA, 99 asymptomatic exposed controls (AECs) and 144 unexposed normal controls were enrolled in this study. Three polymorphisms (-554 G>C, -431A>C and -225 G>C) in the MBL2 promoter were genotyped, and serum MBL levels were determined by enzyme-linked immunosorbent assay. Functional variabilities in the promoter polymorphisms were analyzed by a luciferase reporter assay and electrophoretic mobility shift assay (EMSA). A significantly higher frequency of haplotype (ht) 2 [CAG] was noted in the DI-OA group compared with the AEC group (P=0.044). The patients with DI-OA carrying ht2 [CAG] had significantly lower PC20 methacholine levels (P<0.001) than the non-carriers. The serum MBL levels were significantly higher in the DI-exposed subjects (both the DI-OA patients and AECs) carrying ht1 [GAG] (P=0.028). Luciferase activity was significantly enhanced in ht1 [GAG] compared with ht2 [CAG] in human hepatocarcinoma cells (Hep3B) (P=0.002). The EMSA showed that a -554G probe produced a specific shifted band compared with the -554C probe. These findings suggest that decreased serum MBL levels due to polymorphisms of the MBL2 gene may increase susceptibility to the development of DI-OA in DI-exposed individuals.

Mannose-binding lectin 2 gene polymorphism and susceptibility to upper respiratory tract infection among endurance athletes

The aim of this study was to investigate the influence of mannose-binding lectin 2 (MBL2)-exon-1 gene polymorphisms on upper respiratory tract infection (URTI) incidence among endurance athletes. To this end, 100 healthy elite male athletes participating in the study were classified as either healthy or prone to frequent URTI. Blood samples, DNA isolation, multiplex polymerase chain reaction (PCR) and conventional PCR-RFLP were performed. Genomic DNA was extracted from peripheral leukocytes of whole blood samples using the QIAmp DNA Blood Mini Kit. For comparison of the distribution of genotypes between two groups and for estimating odds ratios (OR) for URTI susceptibility in relation to the MBL2-exon-1 polymorphism, Pearson's chi-square and logistic regression method were used, respectively. The MBL2-exon-1 genotype distribution differed between athletes with URTI and healthy athletes (χ(2) = 7.81, p = 0.02). The AO and AO + OO genotypes of MBL2 were observed at a greater frequency in the illness-prone group compared with the healthy group (34.04% vs. 11.32%). In conclusion, findings from this study have identified a potential role of genetic variation in influencing the risk for URTI in athletic populations and single-nucleotide polymorphisms (SNPs) in the MBL2-exon-1 genes were associated with an altered risk profile. These measures may have a predictive value in the identification of individuals who are more likely to experience recurrent infections when exposed to high physical stress in the areas of athletic endeavour.

Mannose-binding lectin-2 and ficolin-2 gene polymorphisms and clinical risk factors for acute rejection in kidney transplantation

INTRODUCTION

There is growing evidence that the lectin pathway is significantly associated with acute rejection. Rare studies associated both gene polymorphisms of MBL2 and FCN2 with acute rejection after kidney transplantation. The aim of the present study was to investigate the role of the lectin gene profile and clinical risk factors such as PRA level on acute rejection in kidney transplant recipients.

METHODS

We prospectively analyzed 157 kidney transplant recipients with and without acute rejection. A total of 6 well-known functional single-nucleotide polymorphisms in the MBL2 gene and 5 in the FCN2 gene of the recipients were determined by gene sequencing. MBL2 and FCN2 genotypic variants were analyzed for association with the incidence of acute rejection within the first year after kidney transplantation.

RESULTS

After adjusting for variables of P<0.2, we found the differences in the incidence of acute rejection were only according to panel-reactive antibodies (odds ratios (OR) = 6.468, 95% confidence intervals (CI)= 2.017-20.740, P = 0.002) and the HH genotypes of MBL2 promoter -550 (OR = 2.448, 95%CI = 1.026-5.839, P = 0.044).

CONCLUSION

Panel-reactive antibodies and the HH genotypes of MBL2 promoter -550 have significant impacts on the risk of developing acute rejection after kidney transplantation.

Lack of association between mannose binding lectin and antibody responses after acellular pertussis vaccinations

BACKGROUND

Mannose-binding lectin (MBL) is one of the key molecules in innate immunity and its role in human vaccine responses is poorly known. This study aimed to investigate the possible association of MBL polymorphisms with antibody production after primary and booster vaccinations with acellular pertussis vaccines in infants and adolescents.

METHODOLOGY/PRINCIPAL FINDINGS

Five hundred and sixty eight subjects were included in this study. In the adolescent cohort 355 subjects received a dose of diphtheria and tetanus toxoids and acellular pertussis (dTpa) vaccine ten years previously. Follow-up was performed at 3, 5 and 10 years. Infant cohort consisted of 213 subjects, who had received three primary doses of DTaP vaccine at 3, 5, and 12 months of age according to Finnish immunization program. Blood samples were collected before the vaccinations at 2,5 months of age and after the vaccinations at 13 months and 2 years of age. Concentrations of IgG antibodies to pertussis toxin, filamentous hemagglutinin, and pertactin and antibodies to diphtheria and tetanus toxoids were measured by standardized enzyme-linked immunosorbant assay. Single nucleotide polymorphisms of MBL2 gene exon1 (codons 52, 54, 57) were examined. MBL serum concentration was also measured from the adolescent cohort. No association was found with MBL2 exon 1 polymorphisms and antibody responses against vaccine antigens, after primary and booster dTpa vaccination.

CONCLUSIONS

This study indicates that MBL polymorphisms do not affect the production and persistence of antibodies after acellular pertussis vaccination. Our finding also suggests that MBL might not be involved in modulating antibody responses to the vaccines made of purified bacterial proteins.

Mannose-binding lectin 2 and ficolin-2 gene polymorphisms influence the susceptibility to bloodstream infections in kidney transplant recipients

INTRODUCTION

Both mannose-binding lectin (MBL) and ficolin (FCN) interact with carbohydrate structures on microbial surfaces. Polymorphisms at the promoter and exon 1 of the MBL2 gene, which are responsible for low serum levels of MBL, have been shown to play important roles to increase the risk of post-transplant infections. Three gene polymorphisms in the promoter region of FCN2 and 2 in exon 8 (+6424 G > T) are associated with serum levels of FCN2 or binding capacity toward N-acetylglucosamine on microbial surfaces.

METHODS

We prospectively analyzed 81 kidney transplant recipients for 6 well-known functional single-nucleotide polymorphisms in the MBL2 and 5 in the FCN2 gene of the recipients determined by gene sequencing. The bloodstream infections collected prospectively were associated with MBL2 and FCN2 genotypic variants over the first year after kidney transplantation.

RESULTS

Multivariate analyses only found an association of recipient QQ + PQ genotypes of MBL2 5'-UTR +4 (odds ratio [OR] = 3.677, 95% confidence intervals [CI] = 1.127-11.998, P = .031) and FCN2 exon 8 Thr 236 Met(+6359 C > T) (OR = 4.917, 95% CI = 1.229-19.667, P = .024) with the incidence of bacteremia.

CONCLUSION

Recipient QQ + PQ genotypes of MBL2 5'-UTR +4 and recipient FCN2 exon 8 Thr 236 Met(+6359 C > T) variants showed significant impacts on the risk of developing bloodstream infections after kidney transplantation.

Variant MBL2 genotypes producing low mannose-binding lectin may increase risk of Bacillus Calmette-Guerin osteitis in vaccinated newborns

AIM

The aim of this study was to evaluate whether mannose-binding lectin (MBL) plays a role in the development of osteitis after Bacillus Calmette-Guerin (BCG) vaccination as a newborn.

METHODS

Blood samples were obtained from 132 former BCG osteitis patients, now aged 21-49 years, and analysed for MBL concentration and MBL2 genotype in a controlled setting.

RESULTS

Variant genotypes in the MBL2 gene were more common in the former BCG osteitis patients (42.4%) than in the population controls (32.3%, p = 0.033). However, MBL concentrations at the age of 21-49 years were not lower in these patients than in the controls in the same age group. The variant MBL2 genotypes were associated with low serum MBL concentrations, and moreover, MBL concentration was not measurable in two of those three patients who were homozygous for the variant MBL2 genotype. Low serum MBL concentrations were not associated with any illnesses in the medical history of the BCG patients, their siblings or children.

CONCLUSION

Preliminary evidence was found that variant, low-MBL-producing genotypes may be associated with the increased risk of BCG osteitis in vaccinated newborns.

Mannose-binding lectin deficiency and acute exacerbations of chronic obstructive pulmonary disease

Background:

Mannose-binding lectin is a collectin involved in host defense against infection. Whether mannose-binding lectin deficiency is associated with acute exacerbations of chronic obstructive pulmonary disease is debated.

Methods:

Participants in a study designed to determine if azithromycin taken daily for one year decreased acute exacerbations had serum mannose-binding lectin concentrations measured at the time of enrollment.

Results:

Samples were obtained from 1037 subjects (91%) in the trial. The prevalence of mannose-binding lectin deficiency ranged from 0.5% to 52.2%, depending on how deficiency was defined. No differences in the prevalence of deficiency were observed with respect to any demographic variable assessed, and no differences were observed in time to first exacerbation, rate of exacerbations, or percentage of subjects requiring hospitalization for exacerbations in those with deficiency versus those without, regardless of how deficiency was defined.

Conclusion:

In a large sample of subjects with chronic obstructive pulmonary disease selected for having an increased risk of experiencing an acute exacerbation of chronic obstructive pulmonary disease, only 1.9% had mannose-binding lectin concentrations below the normal range and we found no association between mannose-binding lectin concentrations and time to first acute exacerbation or frequency of acute exacerbations during one year of prospective follow-up.

Association of MBL2 polymorphism with asthma after bronchiolitis in infancy

BACKGROUND

Mannose-binding lectin (MBL) is a component of innate immunity and has been linked with the pathogenesis of asthma. The aim of the present study was to evaluate the association of MBL genotypes with preschool asthma and allergy in children with bronchiolitis in early infancy.

METHODS

In all, 205 infants were hospitalized for bronchiolitis at <6 months of age. Asthma and allergy were studied from a total of 166 children at 6.4 years (mean). A total of 141 (85%) frozen whole blood samples were available for MBL genotyping and MBL2 gene mutations were determined on pyrosequencing for detection of three single-nucleotide polymorphisms.

RESULTS

Ninety-five children (67.4%) had the wild-type MBL genotype A/A and 46 had A/O or O/O genotypes. Asthma was present in 16 children (11.3%) at 5-7 years of age. Nine children (19.6%) with non-AA genotype had asthma (vs 7.4% of those with genotype AA, P= 0.03). The result remained significant after adjustment for age, gender and atopy. There were no significant associations between MBL genotypes and asthma at any age before the study. Atopic dermatitis, allergic rhinitis or paternal and/or maternal asthma had no significant associations with MBL genotypes.

CONCLUSIONS

The variant non-A/A MBL genotype is associated with asthma after bronchiolitis in infancy, but not earlier than at 5-7 years of age.

Increased risk of pertussis in adult patients with mannose-binding lectin deficiency

Mannose-binding lectin (MBL) is an important molecule of the innate immunity. The low level of MBL in the serum is associated with increased susceptibility to respiratory infections. In this study, MBL concentrations were determined from the sera of 125 Finnish pertussis patients and from 430 control subjects. Severe MBL deficiency (<50 ng/mL) was found more often in the patients than in the controls (11.2% vs 5.8%, p = 0.038). Moreover, the deficiency was detected more frequently in the adult patients than in the controls [20.4% vs 8.6%, p = 0.021; odds ratio 2.7 (95% confidence interval 1.1-6.5)]. Our findings suggest, for the first time, that MBL deficiency predisposes to pertussis infection, at least in adults.

Displasia ectodérmica anhidrótica asociada a déficit de lectina de unión a manosa

La lectina de unión a la manosa (mannose-binding lectin [MBL]) es una proteína sérica perteneciente al sistema inmunitario innato. Se une a los azúcares de las membranas de múltiples microorganismos, favoreciendo su opsonización y eliminación. El déficit de MBL resulta del polimorfismo del gen MBL2 y se asocia a una amplia variedad de infecciones recurrentes, incluidas las infecciones del tracto respiratorio. Presentamos un caso de displasia ectodérmica anhidrótica asociada a un déficit de MBL, inmunodeficiencia nunca descrita en pacientes afectados de displasia ectodérmica anhidrótica.

Mannose-binding lectin gene polymorphisms in infants with bronchiolitis and post-bronchiolitis wheezing

BACKGROUND

Mannose-binding lectin (MBL) encoded by the MBL2 gene, is an important component of the innate immunity. Low levels have been linked with respiratory infections and both high and low levels with allergy and asthma. The aims of the study were to evaluate the connection between polymorphisms of the MBL2 gene and viral findings, clinical characteristics and subsequent wheezing in young infants with bronchiolitis.

METHODS

In all, 129 full-term infants hospitalized for bronchiolitis at age less than 6 months have been followed-up until the mean age of 1.5 years. The genotyping of the MBL2 gene mutations was made by pyrosequencing for a simultaneous detection of three single nucleotide polymorphisms (SNP).

RESULTS

The MBL genotypes or allele frequencies had no significant associations with clinical characteristics of bronchiolitis. The 41 children with variant genotypes were more often infected by multiple viruses (21.9%, p = 0.047) than children with wild-type A/A genotypes (9.1%). In addition, more children with variant genotypes (31.7%, p = 0.016) had used corticosteroids because of post-bronchiolitis wheezing, compared to those with wild-type A/A genotypes (13.6%). No other significant associations with viral findings or post-bronchiolitis outcomes were found.

CONCLUSIONS

Preliminary evidence was found that the variant non-A/A genotypes may be associated with susceptibility to multiple viral infections and more severe post-bronchiolitis wheezing requiring treatment with corticosteroids.

Role of mannose-binding lectin-2 polymorphism in the development of acute cellular rejection after transplantation for hepatitis C virus-induced liver disease

The development of liver and graft disease is suspected to be affected by genetic diversity. Mannose-binding lectin-2 (MBL-2) is an important immunomodulatory factor that is involved in complement activation. The aim of our study was to elucidate the role of MBL-2 genotypes after liver transplantation (LT) for hepatitis C virus (HCV)-induced liver disease regarding the incidence of acute cellular rejection (ACR), graft inflammation, fibrosis development, and antiviral treatment response.

METHODS

A group of 149 patients who underwent LT for HCV-induced liver disease were genotyped for MBL-2 (rs7096206; G/C) by TaqMan genotyping assay. We evaluated 518 post-LT protocol biopsies and at least 98 urgent liver biopsies regarding graft fibrosis stages, inflammation grades, and evidence for rejection within MBL-2 genotype groups.

RESULT

No association of MBL-2 polymorphisms was observed regarding inflammation, fibrosis, and antiviral treatment outcome. However, the C allele of the MBL-2 gene (P = 0.001) and gender compatibility (P = 0.012) were factors significantly associated with the incidence of ACR.

CONCLUSION

MBL-2 polymorphisms and gender are involved in the development of ACR after LT. CC genotype and gender match may be regarded as risk factors for ACR in HCV-positive graft recipients. Further studies are needed to confirm and verify this observation in non-HCV groups as well.

Genetic predisposition to respiratory infection and sepsis

Genetic variations, in part, determine individual susceptibility to sepsis and pneumonia. Advances in genetic sequence analysis as well as high throughput platform analysis of gene expression has allowed for a better understanding of immunopathogenesis during sepsis. Differences in genes can also modulate immune and inflammatory response during sepsis thereby translating to differences in clinical outcomes. An increasing number of candidate genes have been implicated to play a role in sepsis susceptibility, most of which are controversial with few exceptions. This does not refute the significance of genetic polymorphisms in sepsis, but rather highlights the difficulties and pitfalls related to genetic association studies. These difficulties include differences in study design such as heterogeneous patient cohorts and differences in pathogenic organisms, linkage disequilibrium, and lack of power for detailed haplotype analysis or examination of gene-gene interactions. There is extensive diversity in the pathways of inflammation and immune response during sepsis making it even harder to prove the functional and clinical significance of one single genetic polymorphism which could be easily masqueraded or compensated by other upstream or downstream events of the pathway involved. The majority of studies have analysed candidate genes in isolation from other possible polymorphisms. It is likely that susceptibility to sepsis is the result of polymorphisms from multiple genes rather than one single mutation. Future studies should aim for multi-centered collaborative approach looking at genome wide association or gene profiling to provide a more complete appraisal of the key genetic players in determining genetic susceptibility to sepsis. This review paper will summarise the prominent candidate gene polymorphisms with known functional changes or those with haplotype data. In addition, a summary of the expanding research in the field of epigenetics and post-sepsis immunosuppression will be discussed.

Low serum mannose-binding lectin level is not associated with disease severity in non-cystic fibrosis bronchiectasis

Deficiency of mannose-binding lectin (MBL), a serum protein involved in killing and promoting phagocytosis of pathogens, is associated with respiratory infection and disease progression in a number of acute and chronic lung diseases, including cystic fibrosis (CF)- associated bronchiectasis. No such association has been studied in non-CF bronchiectasis (nCF-Br). One hundred and thirty-three adult patients with nCF-Br were studied. Serum MBL levels were measured and deficiency defined using two cut-off levels, i.e. MBL ≤100 ng/ml and ≤600 ng/ml. Parameters of severity included lung function impairment, annual exacerbation and hospital admission rates, breathlessness, and Pseudomonas aeruginosa and Haemophilus influenzae infection rates. The incidence of MBL deficiency using cut-off levels of 100 ng/ml and 600 ng/ml was 10% and 26% respectively, similar to rates seen in the general population. There was no significant difference in mean FEV1% predicted between MBL deficient and sufficient patients at both cut-off levels (≤100 ng/ml: 63.8% vs . 64.6%, P = 0.91; ≤ 600 ng/ml: 66.5% vs . 63.9%, P = 0.56). In addition, exacerbation/hospital admission rates, symptoms of breathlessness and isolation/colonisation rates with P. aeruginosa and H. influenzae were similar in both groups at both cut-off levels. In conclusion, MBL deficiency is not associated with markers of disease severity in patients with nCF-Br.

C4A deficiency in children and adolescents with recurrent respiratory infections

Increased susceptibility to recurrent viral and bacterial respiratory infections in children and young adults is not well understood. To evaluate the role of complement factor C4 in the defense against respiratory infections, we studied complement factor C4 allotypes C4A and C4B and copy numbers of C4A and C4B genes in 84 children and young adults with recurrent acute otitis media, sinusitis, or pneumonia and in 74 healthy controls. The occurrence of C4A gene deficiency was significantly higher in patients compared with controls (26% vs 14%, p = 0.048). Girls predominated in the group of patients with C4A deficiency (73% girls and 27% boys, p = 0.004). The lectin pathway of complement was more often functionally impaired in patients with C4A deficiency than in patients with no C4A deficiency (41% vs 13%, p = 0.033). Classical and alternative pathways were normal in individuals with C4 null alleles. C4A deficiency is 1 of the minor defects of the innate immunity that may predispose children and young adults to recurrent respiratory infections. C4 gene testing should be added to the list of investigations when the cause for recurrent acute otitis media, maxillary sinusitis, or pneumonia in children and young adults is sought.

Genetic susceptibility to invasive meningococcal disease: MBL2 structural polymorphisms revisited in a large case-control study and a systematic review

Invasive infection caused by Neisseria meningitidis is a worldwide public health problem. Previous reports have indicated that carriage of common 'defective' structural polymorphisms of the host mannose-binding lectin gene (MBL2) greatly increases an individual's risk of developing the disease. We report the largest case-control study so far to investigate the effect of these polymorphisms in meningococcal disease (296 PCR-positive cases and 5196 population controls, all of European ancestry) and demonstrate that no change in risk is associated with the polymorphisms overall or in any age-defined subgroup. This finding contrasts with two smaller studies that reported an increase in risk. A systematic review of all studies of MBL2 polymorphisms in people of European ancestry published since 1999, including 24,693 individuals, revealed a population frequency of the combined 'defective'MBL2 allele of 0.230 (95% confidence limits: 0.226-0.234). The past reported associations of increased risk of meningococcal disease were because of low 'defective' allele frequencies in their study control populations (0.13 and 0.04) that indicate systematic problems with the studies. The data from our study and all other available evidence indicate that MBL2 structural polymorphisms do not predispose children or adults to invasive meningococcal disease.

No association between mannose-binding lectin deficiency and H1N1 2009 infection observed during the first season of this novel pandemic influenza virus

Genetic variations in host immunity may influence susceptibility to novel infections like the recently emergent pandemic influenza virus. Prior studies demonstrated that mannose-binding lectin (MBL) inactivates influenza. Furthermore, MBL deficiency is common and appears to predispose to respiratory virus infections. Therefore, we studied whether MBL deficiency played a role in infection with the novel H1N1 2009 influenza strain in exposed health care workers. In a nested case-control study, we observed no association between phenotypic MBL deficiency, variously defined, and predisposition to H1N1 2009 influenza in 63 pairs of seropositive and seronegative participants. MBL appears to currently have little impact on innate immune responses to H1N1 2009 influenza.

Nasopharyngeal bacterial colonization and gene polymorphisms of mannose-binding lectin and toll-like receptors 2 and 4 in infants

BACKGROUND

Human nasopharynx is often colonized by potentially pathogenic bacteria. Gene polymorphisms in mannose-binding lectin (MBL), toll-like receptor (TLR) 2 and TLR4 have been reported. The present study aimed to investigate possible association between nasopharyngeal bacterial colonization and gene polymorphisms of MBL, TLR2 and TLR4 in healthy infants.

METHODOLOGY/PRINCIPAL FINDINGS

From August 2008 to June 2010, 489 nasopharyngeal swabs and 412 blood samples were taken from 3-month-old healthy Finnish infants. Semi-quantitative culture was performed and pyrosequencing was used for detection of polymorphisms in MBL structural gene at codons 52, 54, and 57, TLR2 Arg753Gln and TLR4 Asp299Gly. Fifty-nine percent of subjects were culture positive for at least one of the four species: 11% for Streptococcus pneumoniae, 23% for Moraxella catarrhalis, 1% for Haemophilus influenzae and 25% for Staphylococcus aureus. Thirty-two percent of subjects had variant types in MBL, 5% had polymorphism of TLR2, and 18% had polymorphism of TLR4. Colonization rates of S. pneumoniae and S. aureus were significantly higher in infants with variant types of MBL than those with wild type (p = .011 and p = .024). Colonization rates of S. aureus and M. catarrhalis were significantly higher in infants with polymorphisms of TLR2 and of TLR4 than those without (p = .027 and p = .002).

CONCLUSIONS

Our study suggests that there is an association between nasopharyngeal bacterial colonization and genetic variation of MBL, TLR2 and TLR4 in young infants. This finding supports a role for these genetic variations in susceptibility of children to respiratory infections.

Genotypes coding for mannose-binding lectin deficiency correlated with cryptococcal meningitis in HIV-uninfected Chinese patients

Background. There is increasing evidence that mannose-binding lectin (MBL) has a complex role in many diseases, particularly in infectious diseases. However, the relationship between MBL deficiency and cryptococcal meningitis has not been clarified. The purpose of this study was to investigate the correlation between MBL polymorphism and non-HIV cryptococcal meningitis.

Methods. A case-controlled genetic association study was conducted. Patients with cryptococcal meningitis and control subjects were genotyped for 6 alleles of MBL2 gene (H/L, Y/X, P/Q, A/D, A/B, and A/C). The distributions in allele frequency, genotypes, haplotypes, and genotype groups were compared between patients and control subjects.

Results. Study participants included 103 HIV-uninfected patients with cryptococcal meningitis and 208 healthy control subjects, all of Chinese Han ethnicity. The homozygous mutative genotypes (O/O) of the coding region were associated with cryptococcal meningitis (P = .023; odds ratio [OR], 4.29; 95% confidence interval [CI], 1.11–19.88), the correlation more overt in immunocompetent patients (P = .005; OR, 6.65; 95% CI, 1.49–33.05). MBL-deficient participant group was associated with cryptococcal meningitis (P = .039; OR, 2.09; 95% CI, .96–4.51), particularly in immunocompetent patients (P = .028; OR, 2.51; 95% CI, .96–6.22).

Conclusions. This is the first to show genotypes coding for MBL deficiency are associated with cryptococcal meningitis in nonimmunocompromised hosts.

Association of mannose-binding lectin-2 gene polymorphism with the development of hepatitis C-induced hepatocellular carcinoma

BACKGROUND

Development of end-stage liver and graft disease is suspected to be partially determined by the individual genetic background. Mannose-binding lectin (MBL) is an important immunomodulatory factor, which is supposed to be involved in complement activation and oncogenesis. Genetic polymorphisms of MBL-2 alter MBL functionality. The aim of our study was to determine the prevalence of MBL-2 polymorphism (rs7096206) in hepatitis C virus (HCV)-induced hepatocellular carcinoma (HCC) based on histological analysis of explanted livers in patients undergoing liver transplantation (LT).

METHODS

One hundred and seventy-seven patients, who underwent LT for HCV-induced liver disease, were genotyped for MBL-2 by TaqMan genotyping assay. Sixty-two patients with histologically confirmed HCC were compared with 115 patients without HCC. MBL-2 genotypes were corelated with the growth patern, tumour size and pretransplant α-fetoprotein (AFP) level of HCC patients.

RESULTS

The prevalence of GG/GC genotypes was significantly higher among HCC patients compared with tumour-free explanted livers (P = 0.004; odds ratio 2.5; 1.3-4.8). GG/GC genotype group was significantly associated with the size of HCC (P = 0.022), higher pretransplant AFP level (P = 0.010) and bilobar tumour growth (P = 0.038). Furthermore, CC genotype was found to be significantly more frequent in AFP-negative HCCs (P = 0.002).

CONCLUSION

Mannose-binding lectin-2 polymorphism seems to be involved in the development of pretransplant HCV-induced HCC and should be further investigated as potential risk factor for HCV-associated carcinogenesis.

Single nucleotide polymorphisms in collagenous lectins and other innate immune genes in pigs with common infectious diseases

Innate immune recognition of pathogens involves various surface receptors and soluble proteins that precede agglutination, complement activation, phagocytosis, and the adaptive immune response. Mannan-binding lectins (MBLs), ficolins (FCNs) and surfactant protein A (SP-A) are soluble collagenous lectins that bind surface structures of various bacteria, viruses and fungi. Some single nucleotide polymorphisms (SNPs) in collagenous lectin genes of humans and other species, including pigs, have been implicated in variation in susceptibility to infectious and inflammatory diseases. In this study we determined the frequencies of 13 SNP alleles of MBL-A, MBL-C, ficolin-α, ficolin-β, and SP-A in 1324 healthy pigs and 461 pigs diagnosed with common infectious diseases at necropsy. For comparison, we also analyzed 12 other SNP alleles in several other innate immune genes, including galectins and TLRs. Several SNPs within genes encoding porcine MBL-A, MBL-C and SP-A were more frequent in pigs diagnosed at necropsy with various diseases or pathogens. These findings suggest that several collagenous lectin SNPs are associated with disease susceptibility and therefore might be genetic markers of impaired innate immune function.

Association of IL-6 and IL-6R gene polymorphisms with susceptibility to respiratory tract infections in young Finnish men

Interleukin-1 (IL-6) is an important mediator of inflammatory response in the respiratory tract during an infection, and the action of IL-6 is mediated by an IL-6 receptor. Several polymorphisms in the IL-6 and IL-6R genes have been associated with different inflammatory disease states. We studied the association between 2 IL-6 (IL6A and IL6B) and 5 IL-6R gene polymorphisms (IL6R1 to IL6R5) and respiratory infections in 511 Finnish military recruits whose respiratory infectious episodes were followed during 6 months of service. A promoter polymorphism of the IL-6R gene, IL6R1 (-183G/A), and two intron 1 polymorphisms, IL6R2 (A/G) and IL6R3 (T/A), were associated with infections. The strongest associations were found for the IL6R1 and IL6R2 polymorphisms, which were in the same linkage disequilibrium block. Conscripts with the A/A (IL6R1), G/G (IL6R2), and A/A (IL6R3) genotypes had an increased risk for respiratory infections during service as follows: odds ratio (OR) 1.72, 95% confidence interval (CI) 1.35-2.19; OR 1.66, 95% CI 1.23-2.26; and OR 1.23, 95% CI 0.98-1.55, respectively. IL-6 gene polymorphism IL6A (-174C/G) was associated with infections only in combination with an IL-6R polymorphism. Our data suggest that polymorphisms in the 5' area of the IL-6R gene may be associated with increased susceptibility to respiratory infections.

Mannose-binding lectin gene polymorphism contributes to recurrence of infective exacerbation in patients with COPD

BACKGROUND

Mannose-binding lectin (MBL) deficiency is associated with susceptibility to respiratory infections. We investigated the impact of MBL2 gene polymorphisms and MBL deficiency on the recurrence of infective exacerbation in patients with COPD.

METHODS

A prospective study was conducted among 215 patients with COPD and 137 healthy subjects. MBL deficiency was determined by the MBL2 gene polymorphisms and serum levels of MBL.

RESULTS

The average frequency of infective exacerbations over 3 years in the 215 patients with COPD was 2.5 ± 1.3 episodes. The COPD group with three or more episodes of infective exacerbation (recurrent exacerbators) included 96 patients, and the remaining 119 patients had two or fewer episodes (less-frequent exacerbators). Among the 96 recurrent exacerbators, 12 (12.50%) had the MBL deficiency genotype compared with 5 (4.20%) among the less-frequent exacerbators (OR, 3.25; 95% CI, 1.01-11.07; P = .0253). In recurrent exacerbators, the frequency of infective exacerbation was significantly higher in patients with MBL-deficient genotypes than in those with non-MBL-deficient genotypes (4.75 ± 1.22 vs 3.52 ± 0.78, respectively; P < .0001). In addition, mortality was significantly increased in recurrent exacerbators with MBL-deficient genotypes compared with those with non-MBL-deficient genotypes (66.7% vs 31.0%, respectively; P = .0153).

CONCLUSIONS

MBL deficiency due to MBL2 polymorphisms increases the risk of recurrent infective exacerbation and worsens its outcome in patients with COPD.

Inefficient complement system clearance of Trypanosoma cruzi metacyclic trypomastigotes enables resistant strains to invade eukaryotic cells

The complement system is the main arm of the vertebrate innate immune system against pathogen infection. For the protozoan Trypanosoma cruzi, the causative agent of Chagas disease, subverting the complement system and invading the host cells is crucial to succeed in infection. However, little attention has focused on whether the complement system can effectively control T. cruzi infection. To address this question, we decided to analyse: 1) which complement pathways are activated by T. cruzi using strains isolated from different hosts, 2) the capacity of these strains to resist the complement-mediated killing at nearly physiological conditions, and 3) whether the complement system could limit or control T. cruzi invasion of eukaryotic cells. The complement activating molecules C1q, C3, mannan-binding lectin and ficolins bound to all strains analysed; however, C3b and C4b deposition assays revealed that T. cruzi activates mainly the lectin and alternative complement pathways in non-immune human serum. Strikingly, we detected that metacyclic trypomastigotes of some T. cruzi strains were highly susceptible to complement-mediated killing in non-immune serum, while other strains were resistant. Furthermore, the rate of parasite invasion in eukaryotic cells was decreased by non-immune serum. Altogether, these results establish that the complement system recognizes T. cruzi metacyclic trypomastigotes, resulting in killing of susceptible strains. The complement system, therefore, acts as a physiological barrier which resistant strains have to evade for successful host infection.

Smoking status interacts with the association between mannose-binding lectin serum levels and gene polymorphism and the carriage of oropharyngeal bacteria

Mannose-binding lectin (MBL) role in the carriage of oropharyngeal bacteria is not known. We investigated the association of smoking, MBL2 polymorphisms, and MBL concentrations with oropharyngeal carriage of respiratory bacteria in young men. Oropharyngeal specimens, MBL concentrations, and MBL2 gene polymorphisms were measured in 124 asthmatic and 394 nonasthmatic Finnish military recruits. The carriage rates of S. pneumoniae (p = 0.002), N. meningitidis (p = 0.005), and beta-hemolytic streptococci (p < 0.001) throughout the military service were significantly higher among smokers than in nonsmokers. An MBL level below the median proved to be a significant risk factor for the carriage of N. meningitidis (odds ratio [OR] = 1.9; 95% confidence interval [CI] 1.0-3.6) and beta-hemolytic streptococci (OR = 2.0; 95% CI 1.2-3.2) in the nonsmokers and a borderline significant risk factor for the carriage of S. pneumoniae (OR = 1.5; 95% CI 0.9-2.6), whereas low MBL levels producing MBL2 haplotypes (LXA/LXA, LXA/O, HYA/O, LYA/O, O/O) seemed to be associated with the carriage of N. meningitidis (OR = 1.8; 95% CI 1.0-3.4) and S. pneumoniae (OR = 1.6; 95% CI 0.9-2.7). Thus, MBL deficiency may predispose nonsmokers to oropharyngeal carriage of these bacteria. We hypothesize that the major factor contributing to elevated bacterial carriage in smokers might be increased bacterial adherence to epithelial cells, which obscures the effect of MBL.

Mannose-binding lectin genotypes: lack of association with susceptibility to thoracic empyema

Background

The role of the innate immune protein mannose-binding lectin (MBL) in host defence against severe respiratory infection remains controversial. Thoracic empyema is a suppurative lung infection that arises as a major complication of pneumonia and is associated with a significant mortality. Although the pathogenesis of thoracic empyema is poorly understood, genetic susceptibility loci for this condition have recently been identified. The possible role of MBL genotypic deficiency in susceptibility to thoracic empyema has not previously been reported.

Methods

To investigate this further we compared the frequencies of the six functional MBL polymorphisms in 170 European individuals with thoracic empyema and 225 healthy control individuals.

Results

No overall association was observed between MBL genotypic deficiency and susceptibility to thoracic empyema (2 × 2 Chi square = 0.02, P = 0.87). Furthermore, no association was seen between MBL deficiency and susceptibility to the Gram-positive or pneumococcal empyema subgroups. MBL genotypic deficiency did not associate with progression to death or requirement for surgery.

Conclusions

Our results suggest that MBL genotypic deficiency does not associate with susceptibility to thoracic empyema in humans.

Low mannose-binding lectin levels and MBL2 gene polymorphisms associate with Chlamydia pneumoniae antibodies

Objective: Mannose-binding lectin (MBL) has been shown to inhibit infection of host cells by Chlamydia pneumoniae in vitro. We studied if MBL levels and MBL2 polymorphisms associate with the presence of C. pneumoniae antibodies in vivo.

Materials and Methods: Single nucleotide polymorphisms (SNPs) of the MBL2 gene (promoter alleles H/L, X/Y and P/Q; and exon 1 variant alleles B, C and D and wild-type allele A) were genotyped and serum MBL concentrations and C. pneumoniae IgG, IgA and IgM antibodies were analysed in 889 Finnish military recruits.

Results: An MBL level below the median concentration and the MBL2 P/P genotype were significant risk factors of IgG or IgA seroconversions or the presence of IgM antibodies during military service (adjusted odds ratio (OR) 1.5; 95% confidence interval (CI) 1.1—2.1 and OR 1.5; 95% CI 1.0—2.2, respectively). In addition, the promoter Y/Y (OR 1.6; 95% CI 1.1—2.3) and exon 1 variant allele genotypes (OR 1.4; 95% CI 1.0—2.0) were possibly associated with elevated antibodies.

Conclusions: These results suggest, for the first time, that low serum MBL levels and MBL2 polymorphisms may associate with elevated C. pneumoniae antibodies and seroconversions and thus support the previous findings in vitro.

Deficient serum mannose-binding lectin levels and MBL2 polymorphisms increase the risk of single and recurrent Cryptosporidium infections in young children

Mannose-binding lectin (MBL) is an evolutionarily conserved protein that functions in human innate immunity by binding to microbial surfaces and promoting opsonophagocytosis. MBL has been shown to bind to Cryptosporidium sporozoites, and earlier work has suggested that the protective role of MBL may be most important in childhood. We evaluated the association between polymorphisms in the MBL gene (MBL2), serum MBL deficiency, and infection with Cryptosporidium, Entamoeba histolytica, and Giardia intestinalis in children. A large, prospective cohort of Bangladeshi preschool children was followed up for >3 years. Clinical outcomes, serum MBL levels, and MBL2 polymorphisms and haplotypes were determined. Statistically significant associations with E. histolytica and G. intestinalis were not found. Serum MBL deficiency, polymorphisms in the -221 promoter region, and the YO/XA MBL2 haplotype were strongly associated with Cryptosporidium infections, particularly recurrent infection. Children with multiple infections with Cryptosporidium were more likely to be MBL deficient (odds ratio [OR], 10.45), carry the -221 promoter variant (OR, 4.02), and have the YO/XA haplotype (OR, 4.91). We have identified a potentially important component of the human innate immune response to Cryptosporidum infection. Further work is needed to evaluate the mechanism of protection of MBL in Cryptosporidium infection.

Mannose-binding lectin polymorphisms and recurrent respiratory tract infection in Chinese children

In order to establish the reference value of mannose-binding lectin (MBL) serum level in children and to investigate the correlation between the polymorphisms of MBL2 gene and serum MBL level in healthy Chinese of Han ethnic group and in children of Chinese Han ethnic group with recurrent respiratory tract infections (RRTI), the concentration of oligomerized MBL was measured by enzyme-linked immunosorbent assay, and MBL2 gene polymorphisms were analyzed by restriction fragment length polymorphism of polymerase chain reaction and polymerase chain reaction-sequence specific primer. The median MBL levels in the 470 normal children were 2536 ng/ml, and the P(2.5)-P(97.5) was 161-5,070 ng/ml. Our research showed that two promoter polymorphisms at -550, -221 of start codon and coding variants at codon 54 of MBL2 gene affected the protein level significantly and the most frequent genotype in Hans is HYPA/HYPA. Our results also showed that serum MBL level was significantly lower in recurrent respiratory tract infections patients compared with healthy controls (Z, -3.04, P = 0.002). The frequency of the promoter LXP haplotype and the B allele was significantly higher in RRTI patients than in controls (chi (2) 4.05, P < 0.05; OR 1.63, 95%CI 1.01 approximately 2.62; chi (2) 4.27, P < 0.05; OR 1.94, 95%CI 1.02 approximately 3.68).

CONCLUSION

We have established that the reference value of serum MBL level in Chinese aged between 0 and 6 years (161-5,070 ng/ml), and we found that LXP and the B are risk factors for RRTI.