Toll-like receptor 3 L412F polymorphisms in infants with bronchiolitis and postbronchiolitis wheezing

Toll-like receptors polymorphisms and COVID-19: a systematic review

COVID-19 is a disease caused by SARS-CoV-2. It became a health problem affecting the lives of millions of people. Toll-like receptors are responsible for recognizing viral particles and activating the innate immune system. The genetic factors associated with COVID-19 remain unclear. Thus, this study aims to assess the association between the polymorphism in Toll-like receptors and susceptibility to COVID-19. We searched the electronic databases (Science Direct, PUBMED, Web of Science, and Scopus) for studies assessing the association between Toll-like receptor polymorphisms and susceptibility to COVID-19. The quality of the studies was assessed using the Q-Genie tool. Thirteen studies were included in this systematic review. The studies analyzed polymorphisms in TLR2, TLR3, TLR4, TLR7, TLR8 and TLR9. We used SNP2TFBS bioinformatic analysis to identify the variants influencing transcription factor binding sites. The Ensembl Genome Browser was used to assess the allele and genotype frequencies in different populations. The bioinformatic analysis revealed that the variant rs5743836 of TLR9 affects the transcription factor binding sites NFKB1 and RELA. The genotype frequency of the variants rs3775291, rs3853839, rs3764880 were higher in East Asian population compared to the other populations. The frequency of the rs3775290 variant was higher in East and South Asian populations. The rs179008 variant was higher in the European population, and the rs5743836 was higher in the African population. Toll-like receptors play an important role in COVID-19 susceptibility. Further studies in different populations are necessary to elucidate the role of Toll-like receptors polymorphisms in SARS-CoV-2 infection.

Impact of genetic polymorphisms related to innate immune response on respiratory syncytial virus infection in children

Respiratory syncytial virus (RSV) causes lower respiratory tract infections and bronchiolitis, mainly affecting children under 2 years of age and immunocompromised patients. Currently, there are no available vaccines or efficient pharmacological treatments against RSV. In recent years, tremendous efforts have been directed to understand the pathological mechanisms of the disease and generate a vaccine against RSV. Although RSV is highly infectious, not all the patients who get infected develop bronchiolitis and severe disease. Through various sequencing studies, single nucleotide polymorphisms (SNPs) have been discovered in diverse receptors, cytokines, and transcriptional regulators with crucial role in the activation of the innate immune response, which is implicated in the susceptibility to develop or protect from severe forms of the infection. In this review, we highlighted how variations in the key genes affect the development of innate immune response against RSV. This data would provide crucial information about the mechanisms of viral infection, and in the future, could help in generation of new strategies for vaccine development or generation of the pharmacological treatments.

Interleukin-1 receptor-associated kinase-4 gene variation may increase post-bronchiolitis asthma risk

AIM

Evidence based on studies of the encoding genes suggests that interleukin-1 receptor-associated kinase-4 (IRAK4) plays a role in childhood asthma and allergy. Our aim was to evaluate the associations of six IRAK4 gene polymorphisms with presence of asthma and allergic rhinitis and use of inhaled corticosteroids (ICSs) for asthma at 5-7 and 11-13 years of ages after hospitalisation for bronchiolitis at younger than 6 months of age.

METHODS

IRAK4 rs4251513, rs4251520, rs4251522, rs4251578, rs79154645 and rs13852554 polymorphisms were determined in 141 former bronchiolitis patients prospectively followed up until 5-7 and in 125 children until 11-13 years of age.

RESULTS

The homozygous variant IRAK4 rs4251513 genotype was associated with the presence of asthma and allergic rhinitis and use of ICSs at 5-7 and 11-13 years of ages in univariate analyses. Statistical significance remained for the presence of asthma and use of ICSs but was lost in the case of allergic rhinitis in multivariate analyses. The adjusted odds ratios were 3.48 and 4.16 for asthma and 5.22 and 14.00 for ICS use at these two ages.

CONCLUSION

The homozygous variant IRAK4 rs4251513 genotype was constantly associated with post-bronchiolitis asthma and asthma medication in school-aged children.

Immune biomarkers predicting bronchiolitis disease severity: A systematic review

Bronchiolitis is one of the leading causes of hospitalisation in infancy, with highly variable clinical presentations ranging from mild disease safely managed at home to severe disease requiring invasive respiratory support. Identifying immune biomarkers that can predict and stratify this variable disease severity has important implications for clinical prognostication/disposition. A systematic literature search of the databases Embase, PubMed, ScienceDirect, Web of Science, and Wiley Online Library was performed. English language studies that assessed the association between an immune biomarker and bronchiolitis disease severity among children aged less than 24 months were included. 252 distinct biomarkers were identified across 90 studies. A substantial degree of heterogeneity was observed in the bronchiolitis definitions, measures of disease severity, and study designs. 99 biomarkers showed some significant association with disease severity, but only 18 were significant in multiple studies. However, all of these candidate biomarkers had comparable studies that reported conflicting results. Conclusion: The heterogeneity among included studies and the lack of a consistently significant biomarker highlight the need for consensus on bronchiolitis definitions and severity measures, as well as further studies assessing their clinical utility both in isolation and in combination.

Toll-like receptor 1 and 10 variations increase asthma risk and review highlights further research directions

AIM

This paper summarises variations in the genes encoding toll-like receptors (TLRs) in relation to the aetiology and outcome of infant bronchiolitis. It compares the literature with research carried out by our group.

METHODS

A mini review was conducted to provide context for a study carried out at the Department of Paediatrics, Tampere University Hospital, Finland. In 2000-2004, 187 infants were hospitalised for bronchiolitis and then followed up: 129 at 1.5 years of age, 166 at 5-7 years of age and 138 at 11-13 years of age.

RESULTS

The review showed that the Finnish bronchiolitis study was the only prospective study on the association between TLRs and the emergence of childhood asthma or lung function reduction after bronchiolitis in infancy. It found that TLR1 and TLR10 variant genotypes were associated with more asthma at 5-7 and 11-13 years, with inconsistent results for the other eight TLR genes. Large population-based studies were also identified that stressed the importance of the TLR2 subfamily members in childhood asthma.

CONCLUSION

Our study found that variations in the TLR1 and TLR10 genes increased the asthma risk after bronchiolitis. The mini review calls for further research on the TLR2 subfamily in bronchiolitis and childhood asthma.

TLR5 rs5744174 gene polymorphism is associated with the virus etiology of infant bronchiolitis but not with post-bronchiolitis asthma

BACKGROUND AND AIM

Bronchiolitis is a leading cause of hospitalization in infants and is associated with a risk of subsequent asthma. The innate immunity genes, such as those encoding toll-like receptors (TLRs), are likely to play a role in bronchiolitis and post-bronchiolitis outcome. Thus far, only one study has considered TLR5 genes in respiratory syncytial virus (RSV) bronchiolitis. The aim of this study was to investigate the association of TLR5 gene polymorphism with virus etiology and severity of bronchiolitis, and with post-bronchiolitis asthma.

METHODS

We recruited 164 infants (age < 6 months) hospitalized for bronchiolitis in this study and determined TLR5 rs5744174 (C > T) single nucleotide polymorphism, virus etiology and severity markers of bronchiolitis, and presence of post-bronchiolitis asthma until age 11 to 13 years.

RESULTS

RSV was detected in 113 (68.9%), rhinovirus in 19 (11.6%), and some other virus in 20 (12.2%) cases. Non-RSV etiology was more common among infants with the variant CT or TT genotype in the TLR5 rs5744174 gene than in those with the CC genotype (89.7% vs 71.7%, P = 0.03). TLR5 rs5744174 polymorphism was not associated with the need of supplementary oxygen or feeding support, with the length of hospital stay, or with post-bronchiolitis asthma at any age.

CONCLUSION

The TLR5 rs5744174 variant genotype may increase the susceptibility to bronchiolitis not caused by RSV.

The role of toll-like receptor 3 in chronic contact hypersensitivity induced by repeated elicitation

BACKGROUND

Accumulating evidence suggests that Toll-like receptor (TLR)-3 signaling is involved in non-infectious immune and inflammatory reactions as well as in viral infections. The skin of patients with atopic dermatitis (AD) is often infected with virus and bacteria, leading to the aggravation of atopic symptoms. These findings suggest TLR3 signaling may be involved in the pathogenesis of AD, but the exact role of TLR3 in AD remains to be defined.

OBJECTIVE

The purpose of this study was to investigate the role of TLR3 in chronic contact hypersensitivity reactions induced by repeated elicitation, resembling the features of AD.

METHODS

Wild-type (WT) and Toll-like receptor 3 knockout (Tlr3 KO) mice were sensitized, and chronic contact hypersensitivity reactions were elicited in their ear skin via repeated application of a hapten, 2,4,6-trinitro-1-chlorobenzene (TNCB) or oxazolone.

RESULTS

The Tlr3 KO mice exhibited less ear swelling, less leukocyte infiltration into the skin, and lower serum total IgE levels than WT mice after hapten challenge. The Tlr3 KO mice also displayed lower expression levels of inflammatory cytokines (interleukin (IL)-33, IL-4, IL-10, and interferon-ɤ in their TNCB-treated ear skin than WT mice.

CONCLUSION

These results showed that TLR3 deficiency suppressed the development of chronic contact hypersensitivity reactions, suggesting that TLR3 signaling may participate in the pathogenesis of AD.

Polymorphism in the gene encoding toll-like receptor 10 may be associated with asthma after bronchiolitis

Toll-like receptors (TLRs) recognise microbes that contribute to the severity of bronchiolitis and the subsequent risk of asthma. We evaluated whether post-bronchiolitis asthma was associated with polymorphisms in the TLR3 rs3775291, TLR4 rs4986790, TLR7 rs179008, TLR8 rs2407992, TLR9 rs187084, and TLR10 rs4129009 genes. The gene polymorphisms were studied at the age of 6.4 years (mean) in 135 children hospitalised for bronchiolitis in infancy. The outcome measure was current or previous asthma. Current asthma was more common (30%) in children with the variant AG or GG genotype in the TLR10 rs4129009 gene versus those who were homozygous for the major allele A (11%) (p = 0.03). The adjusted odds ratio (aOR) was 4.30 (95% CI 1.30–14.29). Asthma ever was more common (34.6%) in girls with the TLR7 variant AT or TT genotype versus those who were homozygous for the major allele A (12.5%) (p = 0.03). The adjusted OR was 3.93 (95% CI 1.06–14.58). Corresponding associations were not seen in boys. There were no significant associations between TLR3, TLR4, TLR8, or TLR9 polymorphisms and post-bronchiolitis asthma. Polymorphism in the TLR10 gene increases and in the TLR7 gene may increase the risk of asthma in preschool-aged children after infant bronchiolitis.

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.

Rapid detection of functional gene polymorphisms of TLRs and IL-17 using high resolution melting analysis

Genetic variations in toll-like receptors (TLRs) and IL-17A have been widely connected to different diseases. Associations between susceptibility and resistance to different infections and single nucleotide polymorphisms (SNPs) in TLR1 to TLR4 and IL17A have been found. In this study, we aimed to develop a rapid and high throughput method to detect functional SNPs of above mentioned proteins. The following most studied and clinically important SNPs: TLR1 (rs5743618), TLR2 (rs5743708), TLR3 (rs3775291), TLR4 (rs4986790) and IL17 (rs2275913) were tested. High resolution melting analysis (HRMA) based on real-time PCR combined with melting analysis of a saturating double stranded-DNA binding dye was developed and used. The obtained results were compared to the "standard" sequencing method. A total of 113 DNA samples with known genotypes were included. The HRMA method correctly identified all genotypes of these five SNPs. Co-efficient values of variation of intra- and inter-run precision repeatability ranged from 0.04 to 0.23%. The determined limit of qualification for testing samples was from 0.5 to 8.0 ng/μl. The identical genotyping result was obtained from the same sample with these concentrations. Compared to "standard" sequencing methods HRMA is cost-effective, rapid and simple. All the five SNPs can be analyzed separately or in combination.

Association of TLR3 L412F Polymorphism with Cytomegalovirus Infection in Children

Intracellular Toll-like receptor 3 (TLR3) recognizes viral double-stranded RNA (dsRNA) and activates antiviral immune responses through the production of type I interferons (IFNs) and inflammatory cytokines. This receptor binds to dsRNA molecules produced during human cytomegalovirus (HCMV) replication. TLR7 senses viral single-stranded RNA (ssRNA) in endosomes, and it can interact with endogenous RNAs. We determined the genotype distribution of single-nucleotide polymorphisms (SNPs) within the TLR3 and TLR7 genes in children with HCMV infection and the relationship between TLR polymorphisms and viral infection. We genotyped 59 children with symptomatic HCMV infection and 78 healthy individuals for SNPs in the TLR3 (rs3775290, c.1377C>T, F459F; rs3775291, c.1234C>T, L412F; rs3775296, c.-7C>A) and TLR7 (rs179008, c.32A>T, Q11L; rs5741880, c.3+1716G>T) genes. SNP genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and capillary electrophoresis. The HCMV DNA load was quantified by real-time PCR. We found an increased frequency of the heterozygous genotype TLR3 L412F in children with HCMV infection compared with uninfected cases. In individuals with a mutation present in at least one allele of the L412F SNP, an increased risk of HCMV disease was found, and this result remained highly significant after Bonferroni’s correction for multiple testing (P^c < 0.001). The heterozygous genotype of this SNP was associated with the increased risk of HCMV disease in an adjusted model that included the HCMV DNA copy number in whole blood and urine (P < 0.001 and P = 0.008, respectively). Moreover, those with a heterozygous genotype of rs3775296 showed an increased relative risk of HCMV infection (P = 0.042), but this association did not reach statistical significance after correction for multiple testing. In contrast, the rs3775290 SNP of TLR3 and TLR7 SNPs were not related to viral infection. A moderate linkage disequilibrium (LD) was observed between the SNPs rs3775291 and rs3775296 (r² = 0.514). We suggest that the L412F polymorphism in the TLR3 gene could be a genetic risk factor for the development of HCMV disease.

Polymorphisms in Toll-like receptor 3 are associated with asthma-related phenotypes in the Chinese Han patients

Toll-like receptor (TLR) 3 mediates antivirus immunity and is involved in asthma exacerbation and development. However, the genetic association between TLR3 and asthma remains unclear. This study aimed to evaluate the effects of polymorphisms within TLR3 on asthma risk and asthma-related phenotypes in the Chinese Han population. A total number of 462 unrelated adult patients with asthma and 398 healthy volunteers were enrolled in this study. The genotypes of tagging single nucleotide polymorphisms (SNPs) in TLR3 gene were determined using multiplex SNaPshot SNP genotyping assays. Case-control and case-only studies were used to assess any links with asthma and asthma-related phenotypes. The results showed that the genetic variants in TLR3 were associated with asthma-related phenotypes, including eosinophil counts, serum immunoglobulin E levels and lung function. However, there was no obvious association between the TLR3 SNPs and asthma susceptibility or asthma severity. TLR3 polymorphisms may play a considerable role in the pathogenesis of asthma. It will help in better understanding the pathogenesis of asthma and development of more effective strategies for the prevention, prediction and treatment of asthma.

Post-bronchiolitis wheezing is associated with toll-like receptor 9 rs187084 gene polymorphism

Innate immunity receptors play a critical role in host defence, as well as in allergy and asthma. The aim of this exploratory study was to evaluate whether there are associations between TLR7 rs179008, TLR8 rs2407992, TLR9 rs187084 or TLR10 rs4129009 polymorphisms and viral findings, clinical characteristics or subsequent wheezing in infants with bronchiolitis. In all, 135 full-term infants were hospitalized for bronchiolitis at age less than 6 months: 129 of them were followed-up until the age of 1.5 years. The outcome measures were repeated wheezing, use of inhaled corticosteroids, atopic dermatitis during the first 1.5 years of life and total serum immunoglobulin E (IgE). There were no significant associations between the genotypes or allele frequencies of TLR7 rs179008, TLR8 rs2407992, TLR9 rs187084 or TLR10 rs4129009 polymorphisms and clinical characteristics or the severity of bronchiolitis during hospitalization. During follow-up, repeated wheezing was more common in children with TLR9 rs187084 variant genotype CC (30.5%) than in children with TLR9 wild-type genotype TT (12.2%) (p = 0.02, aOR 2.73, 95% CI 1.02–7.29). The TLR10 rs4129009 minor allele G was associated with elevated total serum IgE. TLR9 rs187084 gene polymorphism may be associated with post-bronchiolitis wheezing, and TLR10 rs4129009 gene polymorphism may be associated with atopy.

Gene Polymorphism of Toll-Like Receptors and Lung Function at Five to Seven Years of Age after Infant Bronchiolitis

Aim

Toll-like receptors (TLR) play a crucial role in innate immunity, protecting the host from pathogens such as viruses. Genetic variations in TLRs have been associated with the severity of viral bronchiolitis in infancy and with the later occurrence of post-bronchiolitis asthma. The aim of the present study was to evaluate if there are any exploratory associations between TLR gene polymorphisms and lung function at 5 to 7 years of age in former bronchiolitis patients.

Methods

We performed impulse oscillometry (IOS) at the median age of 6.3 years for 103 children who had been hospitalized for bronchiolitis at less than six months of age. The main parameters evaluated were airway resistance and reactance at 5Hz in baseline and post-exercise measurements. Data on single nucleotide polymorphisms (SNP) of TLR1 rs5743618, TLR2 rs5743708, TLR6 rs5743810 and TLR10 rs4129009 (TLR2 subfamily) and TLR3 rs3775291, TLR4 rs4986790, TLR7 rs179008, TLR8 rs2407992 and TLR 9 rs187084 were available for analyses.

Results

The TLR4 rs4986790 wild genotype A/A was associated with a greater Rrs5 response (0.72 vs. -0.42, p = 0.03) to exercise. In TLR6 rs5743810, the minor allele T was associated with greater Rrs5 response (0.80 vs. -0.03, p = 0.04) to exercise. In TLR7 rs179008, the major allele A was associated with baseline decline in dRrs/df (-1.03 vs 0.61, p = 0.01) and increased Fres (2.28 vs. 0.89, p = 0.01) in girls.

Conclusion

Among the nine studied TLRs, only TLR7 rs179008 showed some exploratory associations with post-bronchiolitis lung function deficiency, and polymorphisms of TLR4 rs4986790, and TLR6 rs5743810 in particular, with airway reactivity. These findings call for further confirmatory studies.

Impact of genetic polymorphisms on paediatric atopic dermatitis

In order to investigate whether polymorphisms of genes encoding some factors of innate and adaptive immunity play a role in the development of, or protection against atopic dermatitis (AD) and condition its severity, we genotyped 33 candidate genes and 47 single nucleotide polymorphisms (SNPs) using Custom TaqMan Array Microfluidic Cards and an ABI 7900HT analyser (Applied Biosystems, Foster City, CA, USA). The study involved 104 children with AD (29 with mild-to-moderate and 75 with severe disease; 42 girls; mean age ± SD, 5.8 ± 3.3 years) and 119 healthy controls (49 girls; mean age, 4.8 ± 3.0 years). IL10-rs1800872T, TG and MBL2-rs500737AG were all significantly more frequent among the children with AD ( P = 0.015, P = 0.004 and P = 0.030), whereas IL10-rs1800896C and TC were more frequent in those without AD ( P = 0.028 and P = 0.032). The VEGFA-rs2146326A and CTLA4-rs3087243AG SNPs were significantly more frequent in the children with mild/moderate AD than in those with severe AD ( P = 0.048 and P = 0.036). IL10-rs1800872T and TG were significantly more frequent in the children with AD and other allergic diseases than in the controls ( P = 0.014 and P = 0.007), whereas IL10-rs1800896TC and C were more frequent in the controls than in the children with AD and other allergic diseases ( P = 0.0055 and P = 0.0034). These findings show that some of the polymorphisms involved in the immune response are also involved in some aspects of the development and course of AD and, although not conclusive, support the immunological hypothesis of the origin of the inflammatory lesions.

Toll-like receptor 2 subfamily gene polymorphisms are associated with Bacillus Calmette-Guérin osteitis following newborn vaccination

AIM

Toll-like receptor (TLR) 1, 2, 6 and 10, the TLR2 subfamily, are known to be associated with immunity against tuberculosis. We evaluated whether polymorphisms in genes encoding TLR1, TLR2 and TLR6 were associated with osteitis in infants who received the Bacillus Calmette-Guérin (BCG) vaccination soon after birth.

METHODS

Blood samples from 132 adults aged 21-49 who had BCG osteitis in early childhood were analysed in a controlled study for TLR1 T1805G (rs5743618), TLR2 G2258A (rs5743708) and TLR6 C745T (rs5743810) gene single nucleotide polymorphisms.

RESULTS

The frequencies of the variant genotypes differed between the cases and controls: 11.4% versus 5.7% for TLR2 G2258A (p = 0.033) and 77.3% versus 61.6% for TLR6 C745T (p = 0.001). The TLR2 and TLR6 variant genotypes were associated with a higher risk of BCG osteitis, with adjusted odds ratios (aOR) of 2.154 (95%CI 1.026-4.521) and 1.907 (95%CI 1.183-3.075), respectively. The frequency of the TLR1 T1805G variant genotype was 19.7% in the cases and 33.6% in the controls (p = 0.003). The TLR1 variant genotype was associated with a lower risk of BCG osteitis (aOR 0.554, 95%CI 0.336-0.911).

CONCLUSION

Gene polymorphisms that regulate the function of the TLR2 subfamily play a role in the development of BCG osteitis in vaccinated infants.

Genetic polymorphisms and risk of recurrent wheezing in pediatric age

Background

Wheezing during early life is a very common disorder, but the reasons underlying the different wheezing phenotypes are still unclear. The aims of this study were to analyse the potential correlations between the risk of developing recurrent wheezing and the presence of specific polymorphisms of some genes regulating immune system function, and to study the relative importance of the associations of different viruses and genetic polymorphisms in causing recurrent episodes.

Methods

The study involved 119 otherwise healthy infants admitted to hospital for a first episode of wheezing (74 of whom subsequently experienced recurrent episodes) and 119 age- and sex-matched subjects without any history of respiratory problem randomly selected from those attending our outpatient clinic during the study period. All of the study subjects were followed up for two years, and 47 single nucleotide polymorphisms (SNPs) in 33 candidate genes were genotyped on whole blood using an ABI PRISM 7900 HT Fast Real-time instrument.

Results

IL8-rs4073AT, VEGFA-rs833058CT, MBL2-rs1800450CT and IKBKB-rs3747811AT were associated with a significantly increased risk of developing wheezing (p = 0.02, p = 0.03, p = 0.05 and p = 0.0018), whereas CTLA4-rs3087243AG and NFKBIB-rs3136641TT were associated with a significantly reduced risk (p = 0.05 and p = 0.04). IL8-rs4073AT, VEGFA-rs2146323AA and NFKBIA-rs2233419AG were associated with a significantly increased risk of developing recurrent wheezing (p = 0.04, p = 0.04 and p = 0.03), whereas TLR3-rs3775291TC was associated with a significantly reduced risk (p = 0.03). Interestingly, the study of gene-environment interactions showed that rhinovirus was significantly associated with recurrent wheezing in the presence of IL4Ra-rs1801275GG and G (odds ratio [OR] 6.03, 95% confidence interval [CI]: 1.21-30.10, p = 0.03) and MAP3K1-rs702689AA (OR 4.09, 95% CI: 1.14-14.61, p = 0.03).

Conclusions

This study shows a clear relationship between the risk of wheezing and polymorphisms of some genes involved in the immune response. Although further studies are needed to confirm the results, these findings may be useful for the early identification of children at the highest risk of developing recurrent episodes and possibly subsequent asthma.

Vitamin D-binding protein haplotype is associated with hospitalization for RSV bronchiolitis

BACKGROUND

Between 75 000 and 125 000 U.S. infants are hospitalized for respiratory syncytial virus (RSV) bronchiolitis every year. Up to half will be diagnosed with asthma in later childhood. Vitamin D deficiency has been associated with susceptibility to asthma and respiratory infections. Measured vitamin D is largely bound to vitamin D-binding protein (VDBP); VDBP levels are influenced by its gene (GC) haplotype.

OBJECTIVE

We assessed the relationship between polymorphisms rs7041 and rs4588, which define haplotypes GC1s, GC1f, and GC2, and RSV bronchiolitis susceptibility and subsequent asthma.

METHODS

We retrospectively recruited 198 otherwise healthy children (93% White) hospitalized for severe RSV bronchiolitis in Boston and 333 parents into a follow-up study to assess asthma diagnosis. Data were analysed using family-based genetic association tests. We independently validated our results in 465 White children hospitalized with RSV bronchiolitis and 930 White population controls from the Netherlands.

RESULTS

The rs7041_C allele (denoting haplotype GC1s) was overtransmitted (P = 0.02, additive model) in the entire Boston cohort, in Whites (P = 0.03), and especially in children subsequently diagnosed with asthma (P = 0.006). The GC1f haplotype was undertransmitted in the asthma subgroups (all races and White, both P < 0.05). The rs7041_C allele was also more frequent in the RSV bronchiolitis group compared with controls (OR 1.12, 95% CI 1.02, 1.4, P = 0.03) in the Netherlands, especially in mechanically ventilated patients (P = 0.009).

CONCLUSION AND CLINICAL RELEVANCE

GC1s haplotype carriage may increase the risk of RSV bronchiolitis in infancy and subsequent asthma development. The GC1s haplotype is associated with higher VDBP levels, resulting in less freely available vitamin D.

KEY MESSAGES

Vitamin D-binding protein (VDBP) haplotypes influence free vitamin D levels. We report an association between a VDBP haplotype and hospitalization for RSV bronchiolitis in infancy in two independent cohorts.

Toll-like receptor 3 increases allergic and irritant contact dermatitis

There is increasing recognition of the role of Toll-like receptor 3 (TLR3) in noninfectious inflammatory diseases, but the function of TLR3 in inflammatory skin diseases is unclear. We investigated the functions of TLR3 in allergic and irritant contact dermatitis (ICD). The contact hypersensitivity (CHS) response was lower in Toll-like receptor 3 knockout (Tlr3 KO) mice, and was greater in TLR3 transgenic (Tg) mice than in wild-type (WT) mice after challenge with 2,4,6-trinitro-1-chlorobenzene. Adoptive transfer of immunized lymph node cells from Tlr3 KO mice induced CHS in WT recipients. In contrast, adoptive transfer of those from WT mice did not fully induce CHS in Tlr3 KO recipients. The ICD reaction following croton oil application was lower in Tlr3 KO mice, and was greater in TLR3 Tg mice than in WT mice. Maturation, migration, and antigen presentation of dendritic cells and proliferation of lymphocytes between WT mice and Tlr3 KO mice were comparable. These results show that TLR3 enhances antigen-independent skin inflammation in the elicitation phase of allergic contact dermatitis and in ICD.

Toll-like receptor 2 subfamily genotypes are not associated with severity of bronchiolitis or postbronchiolitis wheezing in infants

AIM

Expression of toll-like receptor (TLR) 2 subfamily genes, including genes encoding TLR1, TLR2, TLR6 and TLR10, have been connected to allergy and asthma. This controlled study investigated the association of TLR1, TLR2 and TLR6 gene polymorphisms with clinical characteristics and subsequent wheezing in young infants with bronchiolitis.

METHODS

In all, 129 full-term infants hospitalised for bronchiolitis at the age of <6 months were clinically followed up until a mean age of 18 months. Genotyping of the TLR1 T1805G, TLR2 G2258A and TLR6 C745T polymorphisms was carried out by pyrosequencing and in 318 healthy, Finnish controls.

RESULTS

There were no significant associations between TLR1, TLR2 or TLR6 genotypes and severity of bronchiolitis or risk of postbronchiolitis wheezing. TLR6 polymorphism was associated with allergy in univariate analyses. Minor allele frequency (MAF) in the TLR1 gene (17%) in the hospitalised children was similar to our Finnish controls, but different to European controls from other studies. MAF in the TLR6 gene was 50% versus 41% in both the Finnish and European controls. MAF in the TLR2 gene was low (3%) in study subjects and in both controls.

CONCLUSION

TLR2 subfamily gene polymorphisms were not associated with severity of bronchiolitis or risk of postbronchiolitis wheezing.

The genetics of innate immunity sensors and human disease

Since their discovery, innate immunity microbial sensors have been increasingly studied and shown to play a critical role in innate responses to microbes in several experimental in vitro, ex vivo, and animal models. However, their role in the human response to infection in natural conditions has just started to be deciphered, by means of clinical studies of primary immunodeficiencies and epidemiological genetic studies. Here, we summarize the major findings concerning the genetic diversity of the various families of microbial sensors in humans, and of other molecules involved in the signaling pathways they trigger. Specifically, we review the genetic associations, revealed by both clinical and epidemiological genetics studies, of microbial sensors from five different families: Toll-like receptors, C-type lectin receptors, NOD-like receptors, RIG-I-like receptors, and cytosolic DNA sensors. In particular, we consider the relationships between variation at the genes encoding these molecules and susceptibility to and the severity of infectious diseases and other clinical conditions associated with immune dysfunction, including autoimmunity, inflammation, allergy, and cancer. Despite the fact that the genetic links between innate immunity sensors and human disorders remain still limited, human genetics studies are increasingly improving our understanding of the genuine functions of microbial sensors and downstream signaling molecules in the natural setting.

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.