Functional polymorphisms in the mannan-binding lectin 2 gene: Effect on MBL levels and otitis media

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.

Surfactant proteins and innate immunity of otitis media

Otitis media (OM) is the most common disease among young children and one of the most frequent reasons to visit the pediatrician. Development of OM requires nasopharyngeal colonization by a pathogen which must gain access to the tympanic cavity through the eustachian tube (ET) along with being able to overcome the defense mechanisms of the immune system and middle ear mucosa. OM can be caused by viral or bacterial infection. The three main bacterial pathogens are Streptococcus pneumoniae, nontypeable Haemophilus influenzae (NTHi), and Moraxella catarrhalis. Innate immunity is important in OM resolution as the disease occurs in very young children before the development of specific immunity. Elements of innate immunity include natural barriers and pattern recognition receptors such as Toll like receptors (TLRs), and Nod like receptors (NLRs). Surfactant proteins A (SP-A) and D (SP-D) act as pattern recognition receptors and are found in the lung and many other tissues including the ET and the middle ear where they probably function in host defense. Surfactant has a potential for use in the treatment of OM due to surface tension lowering function in the ET, and the possible immune functions of SP-D and SP-A in the middle ear and ET.

Innate Immunity in the Middle Ear Mucosa

Otitis media (OM) encompasses a spectrum of clinical presentations ranging from the readily identifiable Acute OM (AOM), which is characterised by otalgia and fever, to chronic otitis media with effusion (COME) where impaired hearing due to middle ear effusion may be the only clinical symptom. Chronic suppurative OM (CSOM) presents as a more severe form of OM, involving perforation of the tympanic membrane. The pathogenesis of OM in these varied clinical presentations is unclear but activation of the innate inflammatory responses to viral and/or bacterial infection of the upper respiratory tract performs an integral role. This localised inflammatory response can persist even after pathogens are cleared from the middle ear, eustachian tubes and, in the case of respiratory viruses, even the nasal compartment. Children prone to OM may experience an over exuberant inflammatory response that underlies the development of chronic forms of OM and their sequelae, including hearing impairment. Treatments for chronic effusive forms of OM are limited, with current therapeutic guidelines recommending a "watch and wait" strategy rather than active treatment with antibiotics, corticosteroids or other anti-inflammatory drugs. Overall, there is a clear need for more targeted and effective treatments that either prevent or reduce the hyper-inflammatory response associated with chronic forms of OM. Improved treatment options rely upon an in-depth understanding of OM pathogenesis, particularly the role of the host innate immune response during acute OM. In this paper, we review the current literature regarding the innate immune response within the middle ear to bacterial and viral otopathogens alone, and as co-infections. This is an important consideration, as the role of respiratory viruses as primary pathogens in OM is not yet fully understood. Furthermore, increased reporting from PCR-based diagnostics, indicates that viral/bacterial co-infections in the middle ear are more common than bacterial infections alone. Increasingly, the mechanisms by which viral/bacterial co-infections may drive or maintain complex innate immune responses and inflammation during OM as a chronic response require investigation. Improved understanding of the pathogenesis of chronic OM, including host innate immune response within the middle ear is vital for development of improved diagnostic and treatment options for our children.

Dysregulation of immune response in otitis media

Objective

Otitis media (OM) is a common reason for children to be prescribed antibiotics and undergo surgery but a thorough understanding of disease mechanisms is lacking. We evaluate the evidence of a dysregulated immune response in the pathogenesis of OM.

Methods

A comprehensive systematic review of the literature using search terms [otitis media OR glue ear OR AOM OR OME] OR [middle ear AND (infection OR inflammation)] which were run through Medline and Embase via Ovid, including both human and animal studies. In total, 82 955 studies underwent automated filtering followed by manual screening. One hundred studies were included in the review.

Results

Most studies were based on in vitro or animal work. Abnormalities in pathogen detection pathways, such as Toll-like receptors, have confirmed roles in OM. The aetiology of OM, its chronic subgroups (chronic OM, persistent OM with effusion) and recurrent acute OM is complex; however, inflammatory signalling mechanisms are frequently implicated. Host epithelium likely plays a crucial role, but the characterisation of human middle ear tissue lags behind that of other anatomical subsites.

Conclusions

Translational research for OM presently falls far behind its clinical importance. This has likely hindered the development of new diagnostic and treatment modalities. Further work is urgently required; particularly to disentangle the respective immune pathologies in the clinically observed phenotypes and thereby work towards more personalised treatments.

Epithelial dysfunction, respiratory infections and asthma: the importance of immunomodulation. A focus on OM-85

INTRODUCTION

Damage to the respiratory epithelium, is often a multifactorial phenomenon. The risk for developing a damage in respiratory epithelium and recurrent respiratory infections may vary among individuals. Preventive measures are based on strengthening the immune function, thus increasing the natural response to pathogens. Immunomodulatory agents are: i. synthetic molecules; ii. Probiotics, prebiotics, symbiotics; iii. Lysates, bacterial extracts immunomodulators: OM-85, RU 41740, D53; iv. Trace elements, vitamins. OM-85 is used for the prevention of recurrent respiratory tract infections and/or exacerbations both in adults and children, showing a good efficacy and safety profile. Its active principle, an extract of bacterial lysates isolated from 21 known respiratory pathogenic strains, shows protection against airway infections of bacterial and viral origin.

AREAS COVERED

This non-systematic review focuses on bacterial lysates and in particular on OM-85 and its effects on respiratory epithelium function and activity in asthma respiratory infections. Studies were selected by PubMed search of "bacterial lysate" or "OM-85" and "respiratory epithelium" or "respiratory infections", from 1993 to 2019.

EXPERT OPINION

Results highlight the ability of OM-85 to trigger immunomodulatory and protective immune responses against different pathogens in vivo, including influenza and respiratory syncytial virus as well bacterial superinfection following influenza.

Associations Between IFI44L Gene Variants and Rates of Respiratory Tract Infections During Early Childhood

Background

Genetic heterogeneity in type I interferon (IFN)–related gene IFI44L may account for variable susceptibility to respiratory tract infections (RTIs) in children.

Methods

In 2 prospective, population-based birth cohorts, the STEPS Study and the FinnBrain Birth Cohort Study, IFI44L genotypes for rs273259 and rs1333969 were determined in relation to the development of RTIs until 1 or 2 years of age, respectively. At age 3 months, whole-blood transcriptional profiles were analyzed and nasal samples were tested for respiratory viruses in a subset of children.

Results

In the STEPS Study (n = 1135), IFI44L minor/minor gene variants were associated with lower rates of acute otitis media episodes (adjusted incidence rate ratio, 0.77 [95% confidence interval, .61–.96] for rs273259 and 0.74 [.55–.99] for rs1333969) and courses of antibiotics for RTIs (0.76 [.62–.95] and 0.73 [.56–.97], respectively. In the FinnBrain cohort (n = 971), IFI44L variants were associated with lower rates of RTIs and courses of antibiotics for RTIs. In respiratory virus–positive 3-month-old children, IFI44L gene variants were associated with decreased expression levels of IFI44L and several other IFN-related genes.

Conclusions

Variant forms of IFI44L gene were protective against early-childhood RTIs or acute otitis media, and they attenuated IFN pathway activation by respiratory viruses.

Impact of mannose-binding lectin 2 gene polymorphisms on disease severity in noncystic fibrosis bronchiectasis in children

BACKGROUND

Mannose-binding lectin (MBL) is a complement protein involved in the innate immune system, and is associated with some chronic respiratory diseases including noncystic fibrosis (non-CF) bronchiectasis in adults. The aim of this study was to investigate the frequency of MBL2 gene polymorphisms in children with non-CF bronchiectasis, and the effect of MBL deficiency on disease severity.

METHODS

Fifty children with non-CF bronchiectasis (bronchiectasis group) and 50 healthy controls (control group) were included. The demographic findings, number of acute pulmonary exacerbations in the previous year, airway cultures, pulmonary function tests, and radiologic scores of the bronchiectasis group were recorded. DNA extraction was performed in both groups and MBL2 gene polymorphisms in codons 52, 54, 57 in exon 1 and H/L, Y/X in the promoter region were studied using real-time polymerase chain reaction. Haplotypes were made by genotypes, and MBL serum expression was classified according to the genotypes in the literature.

RESULTS

The bronchiectasis group consisted of 23 (46%) patients with primary ciliary dyskinesia, 5 (10%) with primary immunodeficiency diseases, and 22 (44%) with idiopathic bronchiectasis. There were no statistically significant differences between the bronchiectasis and control groups in terms of allele and genotype frequencies of polymorphisms in codons 52, 54, 57 in exon 1 and promoter H/L. However, the YX heterozygote genotype was more frequent in the control group (82%) compared with the bronchiectasis group (50%) (P = .002). The frequency of patients with intermediate serum MBL expression genotype was higher in the bronchiectasis group (20%) than in the control group (0%) (P = .001). In the bronchiectasis group, there were no significant differences in growth, annual pulmonary exacerbation rates in the last year, pulmonary function tests, radiologic scores, and microbiologic findings between low, intermediate, and high-expressing genotypes.

CONCLUSIONS

In children with non-CF bronchiectasis, MBL genotype was different from healthy controls. MBL deficiency associated only with MBL genotype was not related to disease severity in this group of patients.

Mannose-binding lectin 2 gene polymorphisms and their association with tuberculosis in a Chinese population

BACKGROUND

Immune- and inflammation-related genes (IIRGs) play an important role in the pathogenesis of tuberculosis (TB). However, the relationship between IIRG polymorphisms and TB risk remains unknown. In this study, the gene polymorphisms and their association with tuberculosis were determined in a Chinese population.

METHODS

We performed a case-control study involving 1016 patients with TB and 507 healthy controls of Han Chinese origin. Sixty-four single-nucleotide polymorphisms (SNPs) belonging to 18 IIRGs were genotyped by the PCR-MassArray assay, and the obtained data was analyzed with χ²-test, Bonferroni correction, and unconditional logistic regression analysis.

RESULTS

We observed significant differences in the allele frequency of LTA rs2229094*C (P = 0.015), MBL2 rs2099902*C (P = 0.001), MBL2 rs930507*G (P = 0.004), MBL2 rs10824793*G (P = 0.004), and IL12RB1 rs2305740*G (P = 0.040) between the TB and healthy groups. Increased TB risk was identified in the rs930507 G/G genotype (P_adjusted = 0.027) under a codominant genetic model as well as in the rs2099902 (C/T + C/C) vs T/T genotype (P_adjusted = 0.020), rs930507 (C/G + G/G) vs C/C genotype (P_adjusted = 0.027), and rs10824793 (G/A + G/G) vs A/A genotype (P_adjusted = 0.017) under a dominant genetic model after Bonferroni correction in the analysis of the overall TB group rather than the TB subgroups. Furthermore, the rs10824793_rs7916582*GT and rs10824793_rs7916582*GC haplotypes were significantly associated with increased TB risk (P = 0.001, odds ratio [OR] = 1.421, 95% confidence interval [CI]: 1.152-1.753; and P = 0.018, OR = 1.364, 95% CI: 1.055-1.765, respectively). Moreover, the rs10824793_rs7916582*AT/AT or rs10824793_rs7916582*GT/GT diplotype showed a protective (P = 0.003, OR = 0.530, 95% CI: 0.349-0.805) or harmful (P = 0.009, OR = 1.396, 95% CI: 1.087-1.793) effect against the development of TB.

CONCLUSIONS

This study indicated that MBL2 polymorphisms, haplotypes, and diplotypes were associated with TB susceptibility in the Han Chinese population. Additionally, larger sample size studies are needed to further confirm these findings in the future.

Current Understanding of Host Genetics of Otitis Media

The pathogenesis of otitis media (OM), an inflammatory disease of the middle ear (ME), involves interplay between many different factors, including the pathogenicity of infectious pathogens, host immunological status, environmental factors, and genetic predisposition, which is known to be a key determinant of OM susceptibility. Animal models and human genetics studies have identified many genes and gene variants associated with OM susceptibility: genes that encode components of multiple signaling pathways involved in host immunity and inflammatory responses of the ME mucosa; genes involved in cellular function, such as mucociliary transport, mucin production, and mucous cell metaplasia; and genes that are essential for Eustachian tube (ET) development, ME cavitation, and homeostasis. Since our last review, several new mouse models with mutations in genes such as CCL3, IL-17A, and Nisch have been reported. Moreover, genetic variants and polymorphisms in several genes, including FNDC1, FUT2, A2ML1, TGIF1, CD44, and IL1-RA variable number tandem repeat (VNTR) allele 2, have been identified as being significantly associated with OM. In this review, we focus on the current understanding of the role of host genetics in OM, including recent discoveries and future research prospects. Further studies on the genes identified thus far and the discovery of new genes using advanced technologies such as gene editing, next generation sequencing, and genome-wide association studies, will advance our understanding of the molecular mechanism underlying the pathogenesis of OM and provide new avenues for early screening and developing effective preventative and therapeutic strategies to treat OM.

Updated Guidelines for the Management of Acute Otitis Media in Children by the Italian Society of Pediatrics: Prevention

BACKGROUND

In recent years, new information has been acquired regarding the diagnosis, treatment and prevention of acute otitis media (AOM). The Italian Pediatric Society, therefore, decided to issue an update to the Italian Pediatric Society guidelines published in 2010.

METHODS

The search was conducted on Pubmed, and only those studies regarding the pediatric age alone, in English or Italian, published between January 1, 2010 and December 31, 2018, were included. Each study included in the review was assessed using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) methodology. The quality of the systematic reviews was evaluated using the A MeaSurement Tool to Assess systematic Reviews (AMSTAR) 2 appraisal tool. The guidelines were formulated using the GRADE methodology by a multidisciplinary panel of experts.

RESULTS

The importance of eliminating risk factors (passive smoking, environmental pollution, use of pacifier, obesity, limitation of day-care center attendance) and the promotion of breastfeeding and hygiene practices (nasal lavages) was confirmed. The importance of pneumococcal vaccination in the prevention of AOM was reiterated with regard to the prevention of both the first episode of AOM and recurrences. Grommets can be inserted in selected cases of recurrent AOM that did not respond to all other prevention strategies. Antibiotic prophylaxis is not recommended for the prevention of recurrent AOM, except in certain carefully selected cases. The use of complementary therapies, probiotics, xylitol and vitamin D is not recommended.

CONCLUSIONS

The prevention of episodes of AOM requires the elimination of risk factors and pneumococcal and influenza vaccination. The use of other products such as probiotics and vitamin D is not supported by adequate evidence.

The Role of Mannose-Binding Lectin Serum Level in Tubotympanic Chronic Suppurative Otitis Media

BACKGROUND

Chronic suppurative otitis media (CSOM) is a common public health problem worldwide and a major cause of hearing impairment especially in developing countries. The role of Mannose-Binding Lectin (MBL), a component of innate immunity, in CSOM has not been studied. The aim of the study was to examine whether MBL deficiency was more frequently present in cases group of tubotympanic CSOM patients rather than healthy subjects.

MATERIAL AND METHODS

This was an analytic observational study. Subjects were enrolled in the Otorhinolaryngology Clinic at Margono Soekarjo Hospital, Purwokerto, Indonesia. An independent t-test was used to compare the mean of MBL serum concentration between tubotympanic CSOM subjects and control.

RESULTS

From 36 tubotympanic CSOM patients, there were 8 (22.22%) patients with MBL deficiency (MBL level < 100 ng/ml), while no deficiency was found in the control group. The mean of MBL level in cases group was 354.88 ng/ml, with the lowest level being 0.001 ng/ml and the highest level 690.24 ng/ml, while in the control group MBL level mean was 376.27 with the lowest level being 188.71 and the highest level 794.54 ng/ml.

CONCLUSION

There was no significant difference of MBL serum level between tubotympanic CSOM and control group. However, the presence of subjects with MBL deficiency in the tubotympanic CSOM group might be considered as playing a role in the tubotympanic CSOM.

Polymorphisms of Mannose-binding Lectin and Toll-like Receptors 2, 3, 4, 7 and 8 and the Risk of Respiratory Infections and Acute Otitis Media in Children

BACKGROUND

Mannose-binding lectin (MBL) and toll-like receptors (TLRs) are important components of the innate immune system. We assessed the susceptibility of children with genetic variants in these factors to respiratory infections, rhinovirus infections and acute otitis media.

METHODS

In a prospective cohort study, blood samples from 381 Finnish children were analyzed for polymorphisms in MBL2 at codons 52, 54 and 57, TLR2 Arg753Gln, TLR3 Leu412Phe, TLR4 Asp299Gly, TLR7 Gln11Leu and TLR8 Leu651Leu. Children were followed up for respiratory infections until 24 months of age with daily diaries. Polymerase chain reaction and antigen tests were used for detection of respiratory viruses from nasal swabs.

RESULTS

Children with MBL variant genotype had a mean of 59 days with symptoms of respiratory infection per year, compared with 49 days in those with wild-type (P = 0.01). TLR8 polymorphisms were associated with an increased risk and TLR7 polymorphisms with a decreased risk of recurrent rhinovirus infections (P = 0.02 for both). TLR2 polymorphisms were associated with recurrent acute otitis media (P = 0.02). MBL polymorphisms were associated with an increased and TLR7 polymorphisms with a decreased risk of rhinovirus-associated acute otitis media (P = 0.03 and P = 0.006, respectively).

CONCLUSIONS

Genetic polymorphisms in MBL and TLRs promote susceptibility to or protection against respiratory infections. In addition to environmental factors, genetic variations may explain why some children are more prone to respiratory infections.

Genome-wide association analysis reveals variants on chromosome 19 that contribute to childhood risk of chronic otitis media with effusion

To identify genetic risk factors of childhood otitis media (OM), a genome-wide association study was performed on Finnish subjects, 829 affected children, and 2118 randomly selected controls. The most significant and validated finding was an association with an 80 kb region on chromosome 19. It includes the variants rs16974263 (P = 1.77 × 10(-7), OR = 1.59), rs268662 (P = 1.564 × 10(-6), OR = 1.54), and rs4150992 (P = 3.37 × 10(-6), OR = 1.52), and harbors the genes PLD3, SERTAD1, SERTAD3, HIPK4, PRX, and BLVRB, all in strong linkage disequilibrium. In a sub-phenotype analysis of the 512 patients with chronic otitis media with effusion, one marker reached genome-wide significance (rs16974263, P = 2.92 × 10(-8)). The association to this locus was confirmed but with an association signal in the opposite direction, in a UK family cohort of 4860 subjects (rs16974263, P = 3.21 × 10(-4), OR = 0.72; rs4150992, P = 1.62 × 10(-4), OR = 0.71). Thus we hypothesize that this region is important for COME risk in both the Finnish and UK populations, although the precise risk variants or haplotype background remain unclear. Our study suggests that the identified region on chromosome 19 includes a novel and previously uncharacterized risk locus for OM.

Second-trimester plasma mannose-binding lectin levels and risk of preterm birth

OBJECTIVE

To investigate whether mannose-binding lectin (MBL) gene polymorphisms and low levels of second-trimester plasma MBL were significant risk factors for preterm birth in Taiwanese women.

METHODS

We conducted a prospective longitudinal study to explore the associations of MBL2 gene single nucleotide polymorphisms and plasma MBL levels between preterm birth and term controls. Blood samples were collected at 16-23 weeks of gestation, and were divided into 51 mothers with preterm births and 255 term controls after delivery. Blood samples were further collected at delivery from 11 mothers with term delivery and 9 with preterm births. DNA was isolated, and polymorphisms in exon 1, the promoter untranslated regions of MBL2 were determined by polymerase chain reaction. The plasma concentrations of MBL were measured by enzyme-linked immunosorbent assay.

RESULTS

There is a positive correlation between SNP genotypes and second-trimester plasma MBL levels. Among mothers with preterm births, a higher frequency of specific genotypes with low MBL levels was not observed. The second-trimester plasma MBL levels were not significantly different between mothers with preterm births (N = 51) and term deliveries (N = 255). However, among mothers (N = 11) with term pregnancies, the MBL plasma level significantly increased from the second trimester to delivery, whereas in mothers (N = 9) who developed preterm delivery, the MBL level did not significantly change.

CONCLUSION

Genotypes associated with low levels of plasma MBL during pregnancy did not increase the risk of preterm births. A low second-trimester plasma MBL level is therefore not a predictor for the development of preterm birth.

Meta-analysis of functional MBL polymorphisms. Associations with rheumatoid arthritis and primary Sjögren's syndrome

OBJECTIVE

The aim of this study was to determine whether functional mannose-binding lectin gene (MBL) polymorphisms are associated with the susceptibility to rheumatoid arthritis (RA) or primary Sjögren's syndrome (pSS).

METHODS

A meta-analysis was conducted to investigate the potential association of RA or pSS with MBL polymorphisms, including the codon 54 (allele B), codon 57 (allele C), and codon 52 (allele D) variants of exon 1, and the - 550 (allele L) and - 221 (allele X) promoter variants.

RESULTS

A total of 12 comparative studies, including eight RA (1623 patients and 1671 controls) and four pSS (280 patients and 516 controls) studies, were included in the meta-analysis. The meta-analysis revealed no association between the MBL B allele and RA in the overall study population (odds ratio [OR] 0.991, 95 % confidence interval [CI] 0.726-1.355, p = 0.957). However, the meta-analysis showed significant associations between the MBL D, H, and X alleles and RA in the overall population (OR 1.708, 95 % CI 1.077-2.707, p = 0.023; OR 1.936, 95 % CI 1.218-3.078, p = 0.005; OR 1.582, 95 % CI 1.216-2.057, p = 0.001, respectively). An association was found between the MBL B allele and pSS in the overall study population (OR 0.691, 95 % CI 0.541-0.917, p = 0.010). Stratification by ethnicity indicated a trend toward an association between the B allele and pSS in European populations, but no association in Asian populations (OR 0.689, 95 % CI 0.465-1.021, p = 0.063; OR 0.896, 95 % CI 0.311-2.562, p = 0.838, respectively).

CONCLUSION

This meta-analysis demonstrated an association between the MBL D, L, and X alleles and the risk of RA. It also demonstrated an association between the MBL B allele and the susceptibility to pSS, suggesting a protective role of the MBL B allele against the development of pSS.

Immunity genes and susceptibility to otitis media: a comprehensive review

Otitis media (OM) is a middle ear infection associated with inflammation and pain. This disease frequently afflicts humans and is the major cause of hearing loss worldwide. OM continues to be one of the most challenging diseases in the medical field due to its diverse host targets and wide range of clinical manifestations. Substantial morbidity associated with OM is further exacerbated by high frequency of recurrent infections leading to chronic suppurative otitis media (CSOM). Children have greater susceptibility to, and thus, suffer most frequently from OM, which can cause significant deterioration in quality of life. Genetic factors have been demonstrated, in large part by twin and family studies, to be key determinants of OM susceptibility. In this review, we summarize the current knowledge on immunity genes and selected variants that have been associated with predisposition to OM. In particular, polymorphisms in innate immunity and cytokine genes have been strongly linked with the risk of developing OM. Future studies employing state-of-the-art technologies, including next-generation sequencing (NGS), will aid in the identification of novel genes associated with susceptibility to OM. This, in turn, will open up avenues for identifying high-risk individuals and designing novel therapeutic strategies based on precise targeting of these genes.

Impact of passive smoking, cooking with solid fuel exposure, and MBL/MASP-2 gene polymorphism upon susceptibility to tuberculosis

BACKGROUND

To explore the impact of passive smoking, cooking with solid fuel, mannose-binding lectin (MBL) gene, MBL-associated serine proteases 2 (MASP-2) gene, and gene-environment interactions on the susceptibility to tuberculosis (TB) in non-smokers.

METHODS

A total of 205 TB patients and 216 healthy controls were recruited to participate in this case-control study. PCR with sequence-specific primers (PCR-SSP) technology was leveraged to genotype rs7096206 of MBL genes and rs2273346 and rs6695096 of MASP-2 genes. Demographic data and information on exposures of participants were collected. Unconditioned logistic regression analysis was conducted to identify associations between the various factors and TB, and marginal structural linear odds models were used to estimate the interactions.

RESULTS

Passive smoking and cooking with solid fuel were associated with the risk of TB, with odds ratios (OR) of 1.58 and 2.93, respectively (p<0.05). Genotype CG at rs7096206 of MBL genes (OR 2.02) and genotype TC at rs6695096 of MASP-2 genes (OR 1.67) were more prevalent in the TB patients than in healthy controls (p<0.05). The relative excess risk of interaction (RERI) between rs7096206 of MBL genes and passive smoking or cooking with solid fuel exposure was 1.86 (95% confidence interval (CI) 0.59-3.16) and 2.66 (95% CI 1.85-3.47), respectively. The RERI between rs6695096 of MASP-2 genes and cooking with solid fuel exposure was 3.70 (95% CI 2.63-4.78), which was also a positive interaction. However, the RERI between rs6695096 of MASP-2 genes and passive smoking was not statistically significant.

CONCLUSIONS

Passive smoking, cooking with solid fuel, and polymorphisms of MBL (rs7096206) and MASP-2 (rs6695096) genes were associated with susceptibility to TB in non-smokers, and there were gene-environment interactions among them. Further studies are needed to explore details of the mechanisms of association.

Immunologic findings in young children with early onset of acute otitis media

CONCLUSION

No significant differences in the number of immune aberrations were seen between children with or without severe recurrent acute otitis media (rAOM); however, subnormal values of immunological markers were found more often than expected, and 4 of the 60 children had treatment-requiring immune deficiencies.

OBJECTIVE

Minor immunologic aberrations have been reported to be more frequent in children with rAOM. Immune investigation is recommended in children with severe rAOM, defined as six or more AOM episodes per year. The purpose of this study was to describe immunological findings in young children at high risk of developing rAOM, and to relate these to the number of expected aberrations and to the presence of severe rAOM.

METHODS

A total of 109 children at risk of developing rAOM were offered immune investigation including complement function, immunoglobulins with subclasses and cellular immunity.

RESULTS

Sixty patients were tested, 31 of whom had severe rAOM and 12 of whom did not develop rAOM. Low levels of IgG2 (27%), C1q (31%) and mannan-binding lectin (21%) were found up to eight times as often as expected. Although subnormal values were more frequent among children with severe rAOM, the study was too small to provide reliable evidence of any difference. Four children were diagnosed with immune deficiencies that required treatment.

Age-dependent association of mannose-binding lectin polymorphisms with the development of pulmonary tuberculosis in Viet Nam

Mannose-binding lectin (MBL) binds to pathogens and induces complement-mediated opsonophagocytosis. Although the association between MBL2 polymorphisms and tuberculosis (TB) has been studied in various populations, the results are controversial. We explored the stages of TB associated with MBL2 polymorphisms. X/Y (rs7096206) and A/B (rs1800450) were genotyped in 765 new patients with active pulmonary TB without HIV infection and 556 controls in Hanoi, Viet Nam. The MBL2 nucleotide sequences were further analyzed, and plasma MBL levels were measured in 109 apparently healthy healthcare workers and 65 patients with TB. Latent TB infection (LTBI) was detected by interferon-gamma release assay (IGRA). The YA/YA diplotype, which exhibited high plasma MBL levels, was associated with protection against active TB in younger patients (mean age = 32)≦ 45 years old (odds ratio, 0.61; 95% confidence interval, 0.46-0.80). The resistant diplotype was less frequently found in the younger patients at diagnosis (P = 0.0021). MBL2 diplotype frequencies and plasma MBL levels were not significantly different between the IGRA-positive and -negative groups. MBL2 YA/YA exhibited a protective role against the development of TB in younger patients, whereas the MBL2 genotype and MBL levels were not associated with LTBI. High MBL levels may protect against the early development of pulmonary TB after infection.

The lectin pathway of complement: advantage or disadvantage in HIV pathogenesis?

The pattern recognition molecules of the lectin complement pathway are important components of the innate immune system with known functions in host-virus interactions. This paper summarizes current knowledge of how these intriguing molecules, including mannose-binding lectin (MBL), Ficolin-1, -2 and -3, and collectin-11 (CL-11) may influence HIV-pathogenesis. It has been demonstrated that MBL is capable of binding and neutralizing HIV and may affect host susceptibility to HIV infection and disease progression. In addition, MBL may cause variations in the host immune response against HIV. Ficolin-1, -2 and -3 and CL-11 could have similar functions in HIV infection as the ficolins have been shown to play a role in other viral infections, and CL-11 resembles MBL and the ficolins in structure and binding capacity.

Polymorphisms of immunity genes and susceptibility to otitis media in children

BACKGROUND

Acute otitis media (OM) is a common disease which often develops through complex interactions between the host, the pathogen and environmental factors. We studied single nucleotide polymorphisms (SNPs) of genes involved in innate and adaptive immunity, and other host and environmental factors for their role in OM.

METHODS

Using Sequenom Massarray platform, 21 SNPs were studied in 653 children from prospective (n = 202) and retrospective (n = 451) cohorts. Data were analyzed for the relationship between SNPs and upper respiratory infection (URI) frequency, risk of acute OM during URI episodes, and proneness to recurrent OM.

RESULTS

Increased risk for OM proneness was associated with CX3CR1 (Thr280Met) SNP and with a jointly interactive group of IL-10 (-1082) SNP, IL-1β (-511) wild type genotype and white race. Family history of OM proneness independently increased the risk for frequent URIs, OM occurrence during URI, and OM proneness. Additionally, IL-1β (-31) SNP was associated with increased risk for frequent URIs, but IL-10 (-592), IL-1β (-511), IL-5 (-746) and IL-8 (-251) SNPs were associated with decreased risk of URI.

CONCLUSION

IL-1β (-31), CX3CR1 (Thr280Met), IL-10 (-1082) and IL-1β (-511) SNPs were associated with increased risk for frequent URIs or OM proneness.

Effects of Rhinovirus Infection on Nasopharyngeal Bacterial Colonization in Infants With Wild or Variant Types of Mannose-Binding Lectin and Toll-Like Receptors 3 and 4

BACKGROUND

Development of respiratory tract infections is determined by interactions between viruses, bacteria, and the host innate immune response. We investigated the impact of natural rhinovirus infection on nasopharyngeal bacterial colonization in infants with or without gene polymorphisms of mannose-binding lectin (MBL) and Toll-like receptors (TLRs) 3 and 4.

METHODS

Rhinoviruses were detected by reverse transcription-polymerase chain reaction and bacteria by culture of nasopharyngeal specimens from 2- to 3-month-old infants. Gene polymorphisms in MBL at codons 52, 54, and 57, TLR3 Leu412Phe, and TLR4 Asp299Gly were detected by pyrosequencing.

RESULTS

Of 337 infants, 61 were positive for rhinovirus and 187 were colonized by Streptococcus pneumoniae, Moraxella catarrhalis, Haemophilus influenzae, or Staphylococcus aureus. Gene polymorphisms of MBL were detected in 32%, TLR3 in 51%, and TLR4 in 18% of subjects. Presence of rhinovirus was associated with increased colonization by S pneumoniae in children with MBL polymorphisms (8 of 20 [40%] with rhinovirus, vs 9 of 87 [10%] without rhinovirus; P = .003), but not in those with wild-type MBL. In logistic regression analyses, S pneumoniae colonization associated with MBL variant (P = .035) and with the interaction between rhinovirus and MBL variant (P = .004), and M catarrhalis colonization associated with the detection of rhinovirus (P = .033).

CONCLUSIONS

The association between rhinovirus infection and nasopharyngeal pneumococcal colonization in early infancy is linked to genetic variations of MBL.

Current knowledge of the genetics of otitis media

Otitis media is one of the most common childhood infections leading to doctor's visits and a leading cause of antibiotic prescriptions in children. Twin and family studies have confirmed that the predisposition of developing a bacterial middle ear infection is genetically determined. Several case-control studies have been performed to analyze genes involved in inflammatory processes in search of potential associations. Modern genome-wide association approaches that require no prior assumptions of the involvement of a given gene locus in the risk of otitis media are currently being used to identify otitis media genes, and will hopefully give more detailed information on the pathogenesis of childhood otitis media. That information could be used in finding the high-risk patient, in the prevention of the disease, and in the design of new treatments.

Relevance of the lectin pathway of complement in rheumatic diseases

Due to its importance both in the clearance of pathogens that contribute as rheumatic etiological agents and in the disposal of apoptotic bodies and potential autoimmune initiators, deficiencies of the components of the lectin pathway of complement have been found to increase susceptibility and modulate the severity of most rheumatic disorders. This chapter introduces the general aspects of the structure, function, and genetics of lectin pathway components and summarizes current knowledge of the field regarding rheumatic diseases predisposition and modulation.

Mannan-binding lectin deficiency - Good news, bad news, doesn't matter?

Mannan-binding lectin (MBL) deficiency has been classified as a commonly occurring immune disorder, affecting approximately 30% of the human population. MBL, being part of the innate immune system, supports the recognition of infectious pathogens by binding to carbohydrate moieties expressed on microorganisms and activates the lectin pathway of the complement system. MBL2 gene polymorphisms are associated with quantitative and qualitative MBL abnormalities in the serum. The clinical impact of MBL deficiency and its association to a wide variety of diseases has been extensively studied. The picture is puzzling as the studies suggest a detrimental or beneficial or no impact of low or high MBL serum levels on disease susceptibility. In this review we attempt to extract what is relevant from the literature and address controversial issues. We finally suggest that a comprehensive understanding of the role of MBL in human diseases requires considering its context-dependency.

Evaluation of 15 functional candidate genes for association with chronic otitis media with effusion and/or recurrent otitis media (COME/ROM)

DNA sequence variants in genes involved in the innate immune response and secondary response to infection may confer susceptibility to chronic otitis media with effusion and/or recurrent otitis media (COME/ROM). We evaluated single nucleotide polymorphisms (SNPs) in 15 functional candidate genes. A total of 99 SNPs were successfully genotyped on the Sequenom platform in 142 families (618 subjects) from the Minnesota COME/ROM Family Study. Data were analyzed for association with COME/ROM using the Generalized Disequilibrium Test (GDT). Sex and age at exam were adjusted as covariates, relatedness was accounted for, and genotype differences from all phenotypically discordant relative pairs were utilized to measure the evidence of association between COME/ROM and each SNP. SNP rs2735733 in the region of the mucin 5, subtypes A/C gene (MUC5AC) exhibited nominal evidence for association with COME/ROM (P = 0.002). Two additional SNPs from this region had P values<0.05. Other variants exhibiting associations with COME/ROM at P<0.05 included the SCN1B SNP rs8100085 (P = 0.013), SFTPD SNP rs1051246 (P = 0.039) and TLR4 SNP rs2770146 (P = 0.038). However, none of these associations replicated in an independent sample of COME/ROM families. The candidate gene variants examined do not appear to make a major contribution to COME/ROM susceptibility, despite a priori evidence from functional or animal model studies for a role in COME/ROM pathology.

The role of mannose-binding lectin gene polymorphisms in susceptibility to HIV-1 infection in Southern Brazilian patients

OBJECTIVE

This study investigates the role of mannose-binding lectin (MBL) in the susceptibility to HIV-1 infection analyzing polymorphisms located at the MBL2 promoter and exon 1 regions.

MATERIALS AND METHODS

The prevalence of MBL2 variant alleles was investigated in 410 HIV-1-infected patients from the South Brazilian HIV cohort and in 345 unexposed uninfected healthy individuals. The promoter variants were genotyped using polymerase chain reaction with sequence-specific primers (PCR-SSP) and exon 1 variants were analyzed by real-time PCR using a melting temperature assay and were confirmed by PCR-restriction fragment length polymorphism (RFLP). MBL2 genotypic and allelic frequencies were compared between HIV-1-infected patients and controls using the chi-squared tests.

RESULTS

The analyses were performed subdividing the individuals according to their ethnic origin. Among Euro-derived individuals a higher frequency of the LX/LX genotype was observed in patients when compared to controls (P < 0.001). The haplotypic analysis also showed a higher frequency of the haplotypes associated with lower MBL levels among HIV-1-infected patients (P = 0.0001). Among Afro-derived individuals the frequencies of LY/LY and HY/HY genotypes were higher in patients when compared to controls (P = 0.009 and P = 0.02).

CONCLUSIONS

An increased frequency of MBL2 genotypes associated with low MBL levels was observed in Euro-derived patients, suggesting a potential role for MBL in the susceptibility to HIV-1 infection in Euro-derived individuals.

Unraveling the genetics of otitis media: from mouse to human and back again

Otitis media (OM) is among the most common illnesses of early childhood, characterised by the presence of inflammation in the middle ear cavity. Acute OM and chronic OM with effusion (COME) affect the majority of children by school age and have heritability estimates of 40-70%. However, the majority of genes underlying this susceptibility are, as yet, unidentified. One method of identifying genes and pathways that may contribute to OM susceptibility is to look at mouse mutants displaying a comparable phenotype. Single-gene mouse mutants with OM have identified a number of genes, namely, Eya4, Tlr4, p73, MyD88, Fas, E2f4, Plg, Fbxo11, and Evi1, as potential and biologically relevant candidates for human disease. Recent studies suggest that this "mouse-to-human" approach is likely to yield relevant data, with significant associations reported between polymorphisms at the FBXO11, TLR4, and PAI1 genes and disease in humans. An association between TP73 and chronic rhinosinusitis has also been reported. In addition, the biobanks of available mouse mutants provide a powerful resource for functional studies of loci identified by future genome-wide association studies of OM in humans. Mouse models of OM therefore are an important component of current approaches attempting to understand the complex genetic susceptibility to OM in humans, and which aim to facilitate the development of preventative and therapeutic interventions for this important and common disease.

Theories of otitis media pathogenesis, with a focus on Indigenous children

Otitis media is a common childhood illness associated with hearing loss, social disadvantage and medical costs. Prevalence and severity are high among Indigenous children. Respiratory bacterial and viral pathogens ascend the eustachian tube from the nasopharynx to the middle ear, causing inflammation, fluid accumulation, and bulging of the tympanic membrane, with or without pain. Among Australian Indigenous children, ear disease commences earlier in life, and involves multiple strains of bacterial pathogens at high density that persist longer. Persistent nasal discharge, overcrowded living conditions (particularly exposure to many children) and poor facilities for washing children perpetuate a vicious cycle of transmission and infection. Risk factors include environmental tobacco smoke, season, lack of breastfeeding, younger age and immature immune system, and possibly genetic factors. The innate immune system is a critical first response to infection, particularly as passive maternal antibodies decline and during the maturation of the infant adaptive immune response. The relative contributions of innate factors to protection from otitis media are currently not well understood. A diversity of antibodies that target strain-specific and conserved antigens are generated in response to natural exposure to otitis media pathogens (or to vaccines). Deficiencies in these antibodies may explain susceptibility to recurrent infections. Incremental contributions from all these elements are likely to be important in otitis media susceptibility versus protection. Effective medical and social strategies to prevent early age of onset are urgently needed.

Epidemiology, natural history, and risk factors: panel report from the Ninth International Research Conference on Otitis Media

The 2007 Recent Advances in Otitis Media Research Conference Panel Report provides an update on otitis media (OM) research published from 2003 to 2007. This report summarizes important trends in disease incidence and prevalence, describes established and newly identified risk factors for acute and chronic OM and OM with effusion, and conveys information on newly discovered genetic factors. In this report, researchers have described declining rates of OM diagnosis, antibiotic prescriptions, offices visits for OM, and middle ear surgery since the licensure and routine use of pneumococcal conjugate vaccine in infants. The panel report also recommends short and long term goals for current and future OM research.

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.

Acute-phase responsiveness of mannose-binding lectin in community-acquired pneumonia is highly dependent upon MBL2 genotypes

Mannose-binding lectin (MBL) is a pattern recognition receptor of the complement system and plays an important role in innate immunity. Whether or not MBL acts as an acute-phase response protein in infection has been an issue of extensive debate, because MBL responses have shown a high degree of heterogeneity. Single nucleotide polymorphisms (SNPs) in the promoter (wild-type Y versus X) and exon 1 (A versus 0) of the MBL2 gene can lead to MBL deficiency. This study investigated the influence of SNPs in the promoter and exon 1 of the MBL2 gene on the acute-phase responsiveness of MBL in 143 patients with community-acquired pneumonia. Acute-phase reactivity was observed only in MBL-sufficient genotypes (YA/YA, XA/YA, XA/XA and YA/0). In patients with wild-type exon 1 genotype A/A, positive acute-phase responses were associated with the presence of the YA haplotype and negative responses with its absence. Genotypes YA/0 and XA/XA produced equal levels of MBL in convalescence. In the acute phase, however, patients with genotype XA/XA displayed negative acute-phase responses more often than those with genotype YA/0. Correlation of MBL and C-reactive protein levels in the acute phase of pneumonia also depended upon the MBL2 genotype. In conclusion, acute-phase responsiveness of MBL was highly dependent upon the MBL2 genotype. These data suggest that heterogeneity in protein responses in the acute phase of disease should always be viewed in the light of possible influences of genetic differences in both structural and regulatory parts of the gene.

Mannose-binding lectin cord blood levels and respiratory symptoms during infancy: a prospective birth cohort study

Respiratory infections cause considerable morbidity during infancy. The impact of innate immunity mechanisms, such as mannose-binding lectin (MBL), on respiratory symptoms remains unclear. The aims of this study were to investigate whether cord blood MBL levels are associated with respiratory symptoms during infancy and to determine the relative contribution of MBL when compared with known risk factors. This is a prospective birth cohort study including 185 healthy term infants. MBL was measured in cord blood and categorized into tertiles. Frequency and severity of respiratory symptoms were assessed weekly until age one. Association with MBL levels was analysed using multivariable random effects Poisson regression. We observed a trend towards an increased incidence rate of severe respiratory symptoms in infants in the low MBL tertile when compared with infants in the middle MBL tertile [incidence rate ratio (IRR) = 1.59; 95% confidence interval (CI): 0.95-2.66; p = 0.076]. Surprisingly, infants in the high MBL tertile suffered significantly more from severe and total respiratory symptoms than infants in the middle MBL tertile (IRR = 1.97; 95% CI: 1.20-3.25; p = 0.008). This association was pronounced in infants of parents with asthma (IRR = 3.64; 95% CI: 1.47-9.02; p = 0.005). The relative risk associated with high MBL was similar to the risk associated with well-known risk factors such as maternal smoking or childcare. In conclusion the association between low MBL levels and increased susceptibility to common respiratory infections during infancy was weaker than that previously reported. Instead, high cord blood MBL levels may represent a so far unrecognized risk factor for respiratory morbidity in infants of asthmatic parents.

Properdin deficiency associated with recurrent otitis media and pneumonia, and identification of male carrier with Klinefelter syndrome

Properdin is an initiator and stabilizer of the alternative complement activation pathway (AP). Deficiency of properdin is a rare X-linked condition characterized by increased susceptibility to infection with Neisseria meningitidis associated with a high mortality rate. We report properdin deficiency in a large Pakistani family. The index cases were found by screening for immunodeficiency due to a history of recurrent infections. This revealed absent AP activity, but normal classical and lectin pathway activity. Sequencing of the properdin gene (PFC) revealed a novel frameshift mutation. When all available relatives (n=24) were screened for the mutation, four affected males, four female carriers and a male heterozygous carrier were identified. He was subsequently diagnosed with Klinefelter syndrome. A questionnaire revealed a striking association between properdin deficiency and recurrent otitis media (P=0.0012), as well as recurrent pneumonia (P=0.0017). This study is the first to show a significant association between properdin deficiency and recurrent infections.

Exploring the role of polymorphisms in ficolin genes in respiratory tract infections in children

Ficolins are pattern-recognition molecules that appear to be relevant for innate immune defence against infections. The ficolin genes in Caucasians are polymorphic and genetic variations may have functional consequences, both in relation to function and concentration. Low levels of Ficolin-2 have been suggested to associate with recurrent respiratory tract infections (RTI), whereas data on Ficolin-3 are still very limited. We investigated the association between variation in genes encoding Ficolin-2 (FCN2) and Ficolin-3 (FCN3) and frequency of RTI during the first 4 years of life. The study population consisted of 900 children from a large, population-based birth cohort of Dutch children, followed prospectively from birth to 4 years of age. The number of RTI was assessed by annual parental questionnaires. Nine single nucleotide polymorphisms in FCN2 and two in FCN3, all based on functionality or haplotype-tagging characteristics, were determined and haplotypes constructed. We found that single nucleotide polymorphisms in FCN2 and FCN3 were not associated with increased risk of RTI during the first 4 years of life. No difference existed between haplotype-frequencies of FCN2 and FCN3 in children grouped according to the reported number of RTI. In conclusion, at a population level, genetic variation in ficolin genes FCN2 and FCN3 do not seem to contribute to the risk of RTI in Caucasian children.

Polymorphisms in the mannan-binding lectin gene are not associated with questionnaire-reported respiratory tract infections in children

BACKGROUND

Low mannan-binding lectin (MBL) levels, caused by MBL2 polymorphisms, are suggested to contribute to susceptibility to respiratory tract infections (RTIs), particularly early in life. Large-scale replication of previous associations is needed, however. We investigated the association between MBL2 polymorphisms and the frequency of RTI in a large population-based birth cohort of white children.

METHODS

The frequency of RTI was prospectively assessed by annual parental questionnaires until children were 4 years of age. Thirteen polymorphisms in MBL2 were determined in 987 Dutch children. Haplotypes, previously shown to be associated with functional levels of MBL, were constructed, and their associations with the frequency of RTI during year 1, year 2, and the first 4 years of life were assessed. High-producing, intermediate-producing, and deficient MBL2 genotypes were defined on the basis of exon 1 and Y/X promoter polymorphisms.

RESULTS

No differences were found between investigated polymorphisms and haplotype frequencies in the population as a whole or between the groups with frequent, moderately frequent, or no RTIs reported. Deficient MBL2 genotypes were not associated with an increased risk of RTI (odds ratio, 0.71 [95% confidence interval, 0.25 to 2.05]) during years 1-4 of life. This was also true when year 1 and year 2 were studied separately.

CONCLUSION

These results suggest that, at the population level, MBL2 polymorphisms do not contribute to the risk of questionnaire-reported RTI in white children.

MBL2 single nucleotide polymorphism diversity among four ethnic groups as revealed by a bead-based liquid array profiling

In the present work we established a rapid, cost-effective and high-throughput method for genotyping using a multiplexed microsphere-based suspension array platform - Luminex xMAP which enabled us to analyze 3 SNPs in the MBL2 gene promoter and 5' UTR, and 3 coding SNPs exon 1 haplotypes, associated with different levels of MBL2 expression. Using this system MBL2 diversity in four different ethnic groups, namely, Asian (Japanese), Caucasian, Hispanic and African-American-assessed. Results showed significant variability in terms of allele, genotype, and haplotype distribution. Characteristic MBL haplotype patterns were defined for each ethnic group. A prevalence of haplotypes coding functional proteins capable of complement activation and pathogen opsonization was observed. Regardless of the significant diversity of individual haplotypes, a high, almost similar (25-28%) proportion of haplotypes associated with MBL deficiency was found in the four ethic groups. The proportion of individuals homozygous for the haplotypes resulting in complete MBL2 deficiency was also significant (2-10%). Considering the role of MBL2 in innate immunity and as a clinically relevant marker, the genotyping approach developed and the knowledge of the genetic variation in different ethnic groups will be relevant to future medical genetic studies.

Host's response in otitis media: understanding genetic susceptibility

Increasing evidence is emerging on genetic factors affecting host's response to infection in the middle ear. This review summarizes current knowledge on the field and on the contribution of nonspecific barriers, innate, and adaptive immunity. Better understanding of susceptibility to this very common disease will facilitate identification of high-risk individuals and optimization of prevention and treatment.

Mannose-binding lectin gene polymorphic variants predispose to the development of bronchopulmonary complications but have no influence on other clinical and laboratory symptoms or signs of common variable immunodeficiency

Mannose-binding lectin (MBL), activating protein of the lectin pathway of the complement system, is an important component of the non-specific immune response. MBL2 gene polymorphisms, both in the coding and promoter regions, lead to low or deficient serum MBL levels. Low serum MBL levels were shown to be associated with serious infectious complications, mainly in patients in whom other non-specific immune system barriers were disturbed (granulocytopenia, cystic fibrosis). We have analysed two promoter (-550 and -221) and three exon (codons 52, 54 and 57) MBL2 polymorphisms in a total of 94 patients with common variable immunodeficiency (CVID) from two immunodeficiency centres. Low-producing genotypes were associated with the presence of bronchiectasis (P = 0.009), lung fibrosis (P = 0.037) and also with respiratory insufficiency (P = 0.029). We could not demonstrate any association of MBL deficiency with age at onset of clinical symptoms, age at diagnosis, the number of pneumonias before diagnosis or serum immunoglobulin (Ig)G, IgA and IgM levels before initiation of Ig treatment. No association with emphysema development was observed, such as with lung function test abnormalities. No effect of MBL2 genotypes on the presence of diarrhoea, granuloma formation, lymphadenopathy, splenomegaly, frequency of respiratory tract infection or the number of antibiotic courses of the patients was observed. Our study suggests that low MBL-producing genotypes predispose to bronchiectasis formation, and also fibrosis and respiratory insufficiency development, but have no effect on other complications in CVID patients.

Cytokine polymorphisms predict the frequency of otitis media as a complication of rhinovirus and RSV infections in children

Previous studies suggested that the otitis media (OM) complication rate of viral upper respiratory infection (vURI) is conditioned by genes affecting cytokine production. Two hundred and thirty children (114 male; 187 White, 25 Black; aged 1–9.3 years, average = 3.6 ± 1.6 years) were prospectively followed over the typical cold season for cold-like illness and OM. Nasopharyngeal secretion samples collected during cold-like illness and OM were assayed for upper respiratory viruses and buccal samples were assayed for TNFα (−308), IL-10(−1082, −819, −592), IL-6 (−174) and IFN-γ (+874) polymorphisms. Logistic regression was used to identify genotypes that predict OM coincident with RSV and rhinovirus (RV) infection. Of the 157 children with RV detection (79 male; 132 White, 13 Black, 12 Other; aged 3.6 ± 1.5 years), simple logistic regression identified age (B = −0.34, Z = −2.8, P < 0.01, OR = 0.71), IL-6 (B = −0.76, Z = −3.3, P < 0.01, OR = 0.47) and IL-10 (B = 0.49, Z = 2.0, P = 0.05, OR = 1.6) as significant predictors of OM coincidence. A more complex logistic regression model for RV detection that included selected OM risk factors identified these factors as well as the TNFα genotype, OM history, breastfeeding history and daily environment as significant predictors of OM coincidence. Of the 43 children with RSV detection (21 male; 35 White, 5 Black, 3 Other, aged 3.9 ± 1.7 years), logistic regression identified IL-10 (B = 1.05, Z = 2.0, P = 0.05, OR = 2.9) as a significant predictor of OM coincidence. New OM episodes coincident with evidence of RSV and RV infection were significantly more frequent in children with high production IL-10 phenotypes. The low production IL-6 and high production TNFα phenotypes also contributed to OM risk during RV detection. Cytokine polymorphisms may be one of an expectedly large number of genetic factors contributing to the known heritability of OM.

Evidence of an association between mannose binding lectin codon 54 polymorphism and adenoidectomy and/or tonsillectomy in children

Mannose binding lectin (MBL) is a calcium-dependent lectin that plays an important role innate immunity by activating the complement pathway. There have been a number of studies describing an association between the MBL genotype and disease susceptibility. MBL deficiency has been described as one of the factors leading to a number of infections in children with recurrent upper respiratory tractus infections (URTI). We hypothesized that MBL deficiency may be associated with recurrent URTI, which requires adenoidectomy and/or adenotonsillectomy. In this study to clarify this hypothesis we investigated whether there may be an association between two low producing MBL variants and adenoidectomy and/or tonsillectomy due to recurrent URTI in children. Blood samples were collected, adenoidectomy and/or tonsillectomy due to recurrent URTI and 50 controls (mean age 80.53 +/- 32.62 months). In all patients and controls codon 54 and codon 57 polymorphisms of the MBL gene were analyzed. None of the subjects from the patient group and control group carried codon 57 polymorphism of the MBL gene. The frequency of low-level MBL genotypes (AB and BB) for codon 54 polymorphism in the patient group was found to be significantly higher compared to the control subjects (55.7% versus 14%) (p<0.001). This study shows that the presence of low-level MBL alleles is associated with adenoidectomy and/or tonsillectomy caused by recurrent URTI in children.