Serum mannose-binding lectin levels are linked with respiratory syncytial virus (RSV) disease

Mannose-binding lectin genotype is associated with respiratory disease in young children: A multicenter cohort study

BACKGROUND

Mannose-binding lectin (MBL) is an important component of the innate immune system. Polymorphisms in the MBL2 gene and promoter region are directly associated with MBL-deficiency. We sought to determine the association between MBL genotype on the frequency of common childhood respiratory infections, respiratory symptoms, and atopic outcomes in early childhood.

METHODS

MBL2 gene variants were analyzed in newborns recruited to the GO-CHILD multicenter prospective cohort study. Follow-up for respiratory infection and atopy diagnoses and symptoms, healthcare utilization, and medication prescription were conducted by postal questionnaires at 12 and 24 months.

RESULTS

Genotyping and follow-up were completed in 1004 children. Genotypes associated with MBL-deficiency were associated with an increased risk of bronchiolitis (relative risk [RR] 1.95, 95% confidence interval [CI] 1.33-2.85) and pneumonia (RR 2.46, 95% CI 1.16-5.22). MBL-deficient genotypes were associated with an increased risk of wheeze with shortness of breath episodes (RR 1.22, 95% CI 1.04-1.43), emergency department attendance (RR 1.90 95% CI 1.13-3.19), and hospital admission (RR 2.01, 95% CI 1.04-3.89) for wheeze. MBL-deficient genotypes were associated with a reduced risk of developing atopic dermatitis (RR 0.72, 95% CI 0.53-0.98).

CONCLUSION

The positive association between MBL-deficient genotypes and bronchiolitis and pneumonia, as well as a severe wheeze phenotype in some young children, supports the hypothesis that MBL is an important component of innate immunity in the vulnerable period before the maturation of the adaptive immune system. Identification of disease-modifying genotypes may help target preventative strategies in high-risk infants.

Importance of mannose-binding lectin2 polymorphism (rs1800450) in infections in children

PURPOSE

Mannose-binding lectin (MBL) is a serine protease belonging to the collectins and an important factor in the inherited immune system. We aimed to reveal the distribution of different MBL2 genotypes in patients diagnosed with acute bronchiolitis and pneumonia.

MATERIAL AND METHODS

A total of 147 patients who applied to Paediatric Emergency between 01.12.2019 and 31.12.2020 were included in the study. Patients were divided into two subgroups: Bronchiolitis and pneumonia.

RESULTS

AA genotype was found to be significantly higher in healthy controls (p = 0.039). In the pneumonia group, both AB/BB genotype was significantly higher compared to healthy controls (p = 0.001). While the AA genotype was more common in patients with acute bronchiolitis, AB/BB genotypes were more common in the pneumonia group (p = 0.001). The presence of fever, crepitation, tachypnoea, pathological x-ray finding, and high leukocyte count are significantly more common in patients with AA genotype, while more than 3 days of follow-up duration and severe clinical picture were more common in patients with AB/BB genotypes (p < 0.05, for all).

CONCLUSIONS

Genotypes with low MBL expression were significantly more common in patients with pneumonia and severe infection. All these results reveal the importance of MBL polymorphisms and their expression in infections.

The Influence of the Lectin Pathway of Complement Activation on Infections of the Respiratory System

Lung diseases are among the leading causes of morbidity and mortality. Complement activation may prevent a variety of respiratory infections, but on the other hand, could exacerbate tissue damage or contribute to adverse side effects. In this review, the associations of factors specific for complement activation via the lectin pathway (LP) with infections of the respiratory system, from birth to adulthood, are discussed. The most extensive data concern mannose-binding lectin (MBL) which together with other collectins (collectin-10, collectin-11) and the ficolins (ficolin-1, ficolin-2, ficolin-3) belong to pattern-recognition molecules (PRM) specific for the LP. Those PRM form complexes with MBL-associated serine proteases (MASP-1, MASP-2, MASP-3) and related non-enzymatic factors (MAp19, MAp44). Beside diseases affecting humanity for centuries like tuberculosis or neonatal pneumonia, some recently published data concerning COVID-19 are summarized.

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.

Factors Affecting the Immunity to Respiratory Syncytial Virus: From Epigenetics to Microbiome

Respiratory syncytial virus (RSV) is a common pathogen that infects virtually all children by 2 years of age and is the leading cause of hospitalization of infants worldwide. While most children experience mild symptoms, some children progress to severe lower respiratory tract infection. Those children with severe disease have a much higher risk of developing childhood wheezing later in life. Many risk factors are known to result in exacerbated disease, including premature birth and early age of RSV infection, when the immune system is relatively immature. The development of the immune system before and after birth may be altered by several extrinsic and intrinsic factors that could lead to severe disease predisposition in children who do not exhibit any currently known risk factors. Recently, the role of the microbiome and the resulting metabolite profile has been an area of intense study in the development of lung disease, including viral infection and asthma. This review explores both known risk factors that can lead to severe RSV-induced disease as well as emerging topics in the development of immunity to RSV and the long-term consequences of severe infection.

The Human Immune Response to Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is an important etiological agent of respiratory infections, particularly in children. Much information regarding the immune response to RSV comes from animal models and in vitro studies. Here, we provide a comprehensive description of the human immune response to RSV infection, based on a systematic literature review of research on infected humans. There is an initial strong neutrophil response to RSV infection in humans, which is positively correlated with disease severity and mediated by interleukin-8 (IL-8). Dendritic cells migrate to the lungs as the primary antigen-presenting cell. An initial systemic T-cell lymphopenia is followed by a pulmonary CD8+ T-cell response, mediating viral clearance. Humoral immunity to reinfection is incomplete, but RSV IgG and IgA are protective. B-cell-stimulating factors derived from airway epithelium play a major role in protective antibody generation. Gamma interferon (IFN-γ) has a strongly protective role, and a Th2-biased response may be deleterious. Other cytokines (particularly IL-17A), chemokines (particularly CCL-5 and CCL-3), and local innate immune factors (including cathelicidins and IFN-λ) contribute to pathogenesis. In summary, neutrophilic inflammation is incriminated as a harmful response, whereas CD8+ T cells and IFN-γ have protective roles. These may represent important therapeutic targets to modulate the immunopathogenesis of RSV infection.

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.

Post-infectious bronchiolitis obliterans and mannose-binding lectin insufficiency in Argentinean children

BACKGROUND AND OBJECTIVE

Post-infectious bronchiolitis obliterans (PIBO) is a severe disorder following acute lower pulmonary infection in young children, especially caused by adenovirus. Mannose-binding lectin (MBL) deficiency arising from polymorphisms in the coding and non-coding region on the MBL2 gene has been associated with more frequent and severe respiratory infections. Our aim was to evaluate the influence of MBL variants in the susceptibility and evolution of children with PIBO.

METHODS

One hundred eleven children with PIBO diagnosis were studied. The coding A, B, D and X promoter variants of MBL2 gene were assessed by PCR-RFLP. B and D alleles were pooled as O. The combined genotypes A/A and YA/O were grouped as sufficient MBL (sMBL), and O/O and XA/O as insufficient MBL (iMBL) groups. To evaluate the frequency of MBL2 polymorphisms in the general population, we studied DNA samples from 127 healthy donors from the blood bank of the hospital (control group).

RESULTS

iMBL variants were significantly more frequent in PIBO children compared with controls (21.6% vs 10.2%, P = 0.01). PIBO patients with iMBL required intensive care unit (P = 0.001) and mechanical assistance at the moment of viral injury (P = 0.001) more frequently than those with sMBL.

CONCLUSIONS

Insufficiency of MBL was more common in PIBO children than in healthy controls. This genetic condition was significantly associated with more severe initial disease, illustrating the relevance of innate immune defence factors prior to the maturation of the adaptative immune system.

Human genetics and respiratory syncytial virus disease: current findings and future approaches

Infection with respiratory syncytial virus (RSV) can result in a wide spectrum of pulmonary manifestations, from mild upper respiratory symptoms to severe bronchiolitis and pneumonia. Although there are several known risk factors for severe RSV disease, namely, premature birth, chronic lung disease, congenital heart disease, and T cell immunodeficiency, the majority of young children who develop severe RSV disease are otherwise healthy children. Genetic susceptibility to RSV infection is emerging as a complex trait, in which many different host genetic variants contribute to risk for distinct disease manifestations. Initially, host genetic studies focused on severe RSV disease using the candidate gene approach to interrogate common single nucleotide polymorphisms (SNPs). Many studies have reported genetic associations between severe RSV bronchiolitis and SNPs in genes within plausible biological pathways, such as in innate host defense genes (SPA, SPD, TLR4, and VDR), cytokine or chemokine response genes (CCR5, IFN, IL6, IL10, TGFB1), and altered Th1/Th2 immune responses (IL4, IL13). Due to the complexity of RSV susceptibility, genome studies done on a larger scale, such as genome-wide association studies have certainly identified more of the host factors that contribute to the development of severe RSV bronchiolitis or excessive pathology. Furthermore, whole-genome approaches can reveal robust associations between genetic markers and RSV disease susceptibility. Recent introduction of 'exome' genotyping or sequencing, which specifically analyzes the majority of coding variants, should be fruitful in sufficiently large, well-powered studies. The advent of new genomic technologies together with improved computational tools offer the promise of interrogating the host genome in search of genetic factors, rare, uncommon, or common that should give new insights into the underlying biology of susceptibility to or protection from severe RSV infection. Careful assessment of novel pathways and further identification of specific genes could identify new approaches for vaccine development and perhaps lead to effective risk modeling.

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.

Increased plasma mannose binding lectin levels are associated with bronchiolitis obliterans after lung transplantation

Background

Long-term lung allograft survival is limited by bronchiolitis obliterans syndrome (BOS). Mannose binding lectin (MBL) belongs to the innate immune system, participates in complement activation, and may predispose to graft rejection. We investigated mannose binding (MBL) during cold ischemia and in tissue samples from explanted lungs with BOS, and assessed MBL and complement proteins in plasma post-lung transplantation relative to BOS staging.

Methods

MBL was detected by immunohistochemistry lung tissue at the time of cold ischemia and in samples with BOS. MBL was assayed in the peripheral blood of 66 lung transplant patients transplanted between 1990–2007.

Results

MBL localized to vasculature and basement membrane during cold ischemia and BOS. Patients further out post-lung transplant > 5 years (n = 33), had significantly lower levels of MBL in the blood compared to lung transplant patients < 5 years with BOS Op-3 (n = 17), 1738 ± 250 ng/ml vs 3198 ± 370 ng/ml, p = 0.027, and similar levels to lung transplant patients < 5 years with BOS 0 (n = 16), 1738 ± 250 ng/ml vs 1808 ± 345 ng/ml. MBL levels in all BOS 0 (n = 30) vs. all BOS Op-3 (n = 36) were 1378 ± 275 ng/ml vs. 2578 ± 390 ng/ml, p = 0.001, respectively. C3 plasma levels in BOS 0 (n = 30) vs. BOS Op-3 (n = 36) were 101 ± 19.8 mg/ml vs. 114 ± 25.2 mg/ml, p = 0.024, respectively.

Conclusions

MBL localizes within the lung during graft ischemia and BOS, higher levels of plasma MBL are associated with BOS Op-3 and < 5 years post-transplant, and higher level of plasma complement protein C3 was associated with BOS Op-3 clinical status. MBL may serve as a biomarker for poorer outcome post-lung transplantation.

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.

Elevated levels of vitamin D and deficiency of mannose binding lectin in dengue hemorrhagic fever

Background

Altered plasma concentrations of vitamin D and mannose binding lectin (MBL), components of innate immunity, have been shown to be associated with the pathogenesis of viral infections. The objective of the present study was to find out whether plasma concentrations of MBL and vitamin D are different in patients with dengue fever (DF) and dengue hemorrhagic fever (DHF).

The results

The plasma concentrations of vitamin D and MBL were assessed in 48 DF cases, 45 DHF cases and 20 apparently healthy controls using ELISA based methods. Vitamin D concentrations were found to be higher among both DF and DHF cases as compared to healthy controls (P < 0.005 and P < 0.001). Vitamin D concentrations were not different between DF and DHF cases. When the dengue cases were classified into primary and secondary infections, secondary DHF cases had significantly higher concentrations of vitamin D as compared to secondary DF cases (P < 0.050). MBL concentrations were not significantly different between healthy controls and dengue cases. MBL concentrations were observed to be lower in DHF cases as compared to DF cases (P < 0.050). Although MBL levels were not different DF and DHF cases based on immune status, the percentage of primary DHF cases (50%) having MBL levels lower than 500 ng/ml were less compared to primary DF cases (P = 0.038).

Conclusions

The present study suggests that higher concentrations of vitamin D might be associated with secondary DHF while deficiency of MBL may be associated with primary DHF.

Association of herpes zoster infection with clinical characteristics and MBL2 gene polymorphisms in Chinese children with systemic lupus erythematosus

OBJECTIVES

In the first part of this study, we analyzed clinical factors associated with pediatric-onset systemic lupus erythematosus (SLE), and patient susceptibility to herpes zoster (HZ). In the second part of this study, we characterized MBL2 genotype polymorphisms in pediatric-onset SLE patients and their possible associations with HZ.

METHODS

This 10-year prospective cohort study compared pediatric-onset SLE patients from Taiwan with and without histories of HZ. By using 2 years as a standard interval, patients with early-onset and late-onset of HZ were compared. MBL2 gene polymorphisms in exon 1 at codon 54, and in the promoter at the position -221 and -550, were tested immediately after patient enrollment.

RESULTS

We initially enrolled 98 SLE patients, and analyzed complete clinical characteristics of 82 patients (35 patients with HZ, 47 patients without HZ). The incidence of HZ was higher in SLE patients who had methylprednisolone pulse therapy, cyclophosphamide pulse therapy, and received higher cumulative steroid dose (P < 0.05 for all 3). There were no significant associations of HZ with MBL2 genotype or serum level of mannose-binding lectin.

CONCLUSIONS

Pediatric-onset SLE patients were highly susceptible to HZ, with an incidence of 35.7%. Patients given steroid, cyclophosphamide, and high cumulative steroid dose were more likely to have had HZ. Deficiency of serum mannose-binding lectin and MBL2 gene polymorphism were not associated with HZ.

Natural killer cell responses to infections in early life

Natural killer (NK) cells are an important component of innate immune responses to infectious diseases. They mediate protection by being able to rapidly lyse infected cells and produce cytokines (primarily interferon-γ) that shape innate and adaptive immune responses. This review summarizes current knowledge on the phenotype and functional abilities of NK cells from healthy newborns/infants and on NK cell responses against viral, bacterial and protozoan infections in early life. Interestingly, NK cell blood counts are higher in newborns than in adults but they do not display striking differences in phenotype, except for an increased frequency of expression of the inhibitory CD94/NKG2A receptor. They display some inherent functional defects, mainly a lower cytolytic capacity that may contribute to the immaturity of the neonatal immune system. Changes in circulating levels of NK cells observed during pediatric infections and the ability of NK cells from newborns and children to produce interferon-γ at the encounter with pathogens indicate that NK cells participate in the immune response to infectious diseases in early life. Unfortunately, information is currently insufficient to assess whether these NK cell responses really contribute to control infections, either vertically transmitted or acquired in infancy.

Torque teno virus viremia load size in patients with selected congenital defects of innate immunity

Plasma loads of torque teno virus (TTV) among individuals differ extensively beginning early in life, suggesting a role for innate immunity. Here, congenital mannose-binding lectin deficiencies, but not deficiencies in respiratory ciliary function, correlated with increased TTV loads. Notably, however, the presence of either disorder was associated with particularly high TTV loads.

Respiratory viral infections in infants: causes, clinical symptoms, virology, and immunology

In global terms, respiratory viral infection is a major cause of morbidity and mortality. Infancy, in particular, is a time of increased disease susceptibility and severity. Early-life viral infection causes acute illness and can be associated with the development of wheezing and asthma in later life. The most commonly detected viruses are respiratory syncytial virus (RSV), rhinovirus (RV), and influenza virus. In this review we explore the complete picture from epidemiology and virology to clinical impact and immunology. Three striking aspects emerge. The first is the degree of similarity: although the infecting viruses are all different, the clinical outcome, viral evasion strategies, immune response, and long-term sequelae share many common features. The second is the interplay between the infant immune system and viral infection: the immaturity of the infant immune system alters the outcome of viral infection, but at the same time, viral infection shapes the development of the infant immune system and its future responses. Finally, both the virus and the immune response contribute to damage to the lungs and subsequent disease, and therefore, any prevention or treatment needs to address both of these factors.

Mannose-binding lectin deficiency and respiratory tract infection

Mannose-binding lectin (MBL) is an innate immune system pattern recognition protein that kills a wide range of pathogenic microbes through complement activation. A substantial proportion of all human populations studied to date have MBL deficiency due to MBL2 polymorphisms, which potentially increases susceptibility to infectious disease. MBL binds numerous respiratory pathogens but the capsule of Streptococcus pneumoniae abrogates its efficient binding. Clinical studies in humans have shown that MBL deficiency appears to predispose to severe respiratory tract infection. A recent meta-analysis shows that MBL deficiency was associated with death in patients with pneumococcal infection after adjusting for bacteraemia and comorbidities. Human clinical studies have also shown associations between MBL deficiency and various less common respiratory infections. Intracellular infections like tuberculosis may be less common with MBL deficiency because of reduced opsonophagocytosis. Lung secretions contain small amounts of MBL that are potentially sufficient to activate complement, but their measurement is confounded by dilution inherent in collection techniques. Therefore, if this protein does play a role in pulmonary immunity it is presumably through prevention of haematogenous dissemination of respiratory pathogens while adding to mucosal defences. Ficolins are collectins that are structurally and functionally related to MBL and are either present in serum or expressed in tissues including the lung. Limited variation in serum levels of L- and H-ficolin result from the presence of FCN2 and FCN3 polymorphisms. Initial studies on the impact of FCN2 polymorphisms or low L-ficolin levels do not seem to show major associations with respiratory infection. MBL is being developed as a new immunotherapeutic agent for prevention of infection in immunocompromised hosts. The available literature suggests that it may also be of benefit in MBL deficient patients with severe pneumonia. This review concentrates on clinical associations between MBL deficiency and susceptibility to respiratory tract infection.

Mannose-binding lectin MBL2 gene polymorphisms and outcome of hepatitis C virus-infected patients

INTRODUCTION

Mannose-binding lectin (MBL) is involved in host's response to several infections including hepatitis B but little is known about MBL and hepatitis C virus (HCV) infection. The present study attempts to investigate whether MBL2 genotype and serum MBL levels affect the course of HCV infection.

RESULTS AND DISCUSSIONS

We investigated the variant alleles in MBL2 gene promoter and exon-1 regions in 80 Caucasian HCV-infected patients. Mutations in MBL2 were determined by polymerase chain reaction and restriction fragment length polymorphisms analysis. Serum MBL levels were measured by ELISA. Polymorphism homozygosity in exon-1 region was significantly related to lower serum MBL levels (p < 0.001), to liver inflammation (p = 0.034, OR = 11.7) and, in a lesser degree, to fibrosis. Polymorphisms in promoter sites -221nt and -550nt were not shown to be related with serum MBL levels or progress to liver inflammation and fibrosis. Serum MBL levels were adversely associated with progression to fibrosis (p = 0.037). Response to antiviral treatment was related to hepatitis C virus genotype (p < 0.001, OR = 10.9), but not to MBL2 genotype or serum MBL levels.

CONCLUSION

These findings suggest that polymorphisms in MBL2 gene exon-1 region are related to low serum MBL levels and progression of HCV infection to liver inflammation and fibrosis.