ST2 and IL-33 polymorphisms and the development of childhood asthma: a prospective birth cohort study in Finnish children

The ST2/IL-33 signaling pathway has an important role in the host inflammatory response. Here we aimed to study the association of ST2 and IL-33 polymorphisms with serum soluble (s) ST2 and IL-33 concentrations in healthy Finnish children and, in addition, their association with childhood asthma. In total, 146 children were followed from birth to the age 7 years for the development of asthma. Single-nucleotide polymorphisms (SNPs) in ST2 and IL-33 were determined, and associations of the SNP variants with serum levels of sST2 and IL-33 at age of 13 months and with recurrent wheezing and childhood asthma at 7 years of age were analyzed. Children with ST2 rs1041973 AC/AA genotypes had significantly lower level of serum sST2 (2453 pg/mL; IQR 2265) than those with CC genotype (5437 pg/mL; IQR 2575; p = < 0.0001). Similar difference was also observed with ST2 rs13408661. No differences were observed between subjects with studied IL-33 SNPs. Children who carried genetic variants of ST2 rs1041973 or rs13408661 seemed to have a higher risk of asthma. In contrast, children who carried genetic variants of IL-33 rs12551268 were less often diagnosed with asthma. Even though these SNPs seemed to associate with asthma, the differences were not statistically significant.

Association of Toll‐like receptor 2 rs111200466 polymorphism with low serum levels of IL ‐33 in early childhood

TLR2 is one of 10 human TLRs, which plays an important role in the recognition of pathogens and activation of the innate immunity via NF-κB pathway. NF-κB activation induces the expression of various pro-inflammatory genes. This study examines the effect of TLR2 polymorphisms on the production of blood pro-inflammatory cytokines in healthy Finnish children. One hundred forty-six children who participated in a prospective observational birth cohort study in Turku, Finland, were included. DNA samples were analysed by PCR-based sequencing for two common TLR2 polymorphisms (rs5743708 Arg753Gln; rs111200466-196 to -174del). Serum concentrations of IL-33, IL-31, IL-17A and IL-17F were measured by multiplex immunoassay and sST2 by ELISA in children at the age of 13 months. Children with variant type of TLR2 rs111200466 (ins/del or del/del) had significantly lower level of serum IL-33 (median, 0.00 pg/mL; IQR 0.00-17.60) than those with ins/ins type of TLR2 (19.81 pg/mL; IQR 0.00-51.78) (p = 0.0001). Almost all study subjects had serum concentrations of IL-17A, IL-17F and IL-31 below the detection limit and therefore not included in the final analyses. No differences in levels of above four cytokines and sST2 were found between TLR2 rs5743708 genotypes (GG and GA). Our results indicated that the TLR2 rs111200466 deletion was associated with a low level of serum IL-33, suggesting that the polymorphism may impair the production of IL-33.

TLR4 Polymorphism, Nasopharyngeal Bacterial Colonization, and the Development of Childhood Asthma: A Prospective Birth-Cohort Study in Finnish Children

We aimed to explore the role of TLR4 (rs4986790) polymorphism in the nasopharyngeal (NP) bacterial colonization and its consequent impact on the development of childhood asthma. A semi-quantitative culture of NP swabs was performed on 473 children at 2 months of age and on 213 children at 13 months of age. TLR4 polymorphism was analyzed for 396 children. Children were followed from birth to the age of 7.5 years and the final outcome was physician-diagnosed asthma. The associations between TLR4 genotype, bacterial colonization, and asthma were analyzed. Children with TLR4 AG or GG genotype were more often colonized with Moraxella catarrhalis at 2 months of age (p = 0.009) and Haemophilus influenzae at 13 months of age (p = 0.018). Children who were colonized with H. influenzae at 13 months of age had a significantly higher risk of later development of asthma (p = 0.004). M. catarrhalis or H. Influenzae colonization at 2 months of age or TLR4 genotype Asp299Gly were not associated with the development of childhood asthma. TLR4 Asp299Gly polymorphism was associated with an increased risk of colonization of M. catarrhalis and H. influenzae in children. The colonization with H. influenzae at 13 months of age was associated with a higher risk of later development of childhood asthma.