IL-4-C-590T locus polymorphism and susceptibility to asthma in children: a meta-analysis

Impact of Interleukin-17 Receptor A Gene Variants on Asthma Susceptibility and Clinical Manifestations in Children and Adolescents

Several single nucleotide polymorphisms (SNPs) in multiple interleukin receptor genes could be associated with asthma risk and/or phenotype. Interleukin-17 (IL-17) has been implicated in tissue inflammation and autoimmune diseases. As no previous studies have uncovered the potential role of IL17 receptor A (RA) gene variants in asthma risk, we aimed to explore the association of four IL17RA SNPs (i.e., rs4819554A/G, rs879577C/T, rs41323645G/A, and rs4819555C/T) with asthma susceptibility/phenotype in our region. TaqMan allelic discrimination analysis was used to genotype 192 individuals. We found that the rs4819554 G/G genotype significantly reduced disease risk in the codominant (OR = 0.15, 95%CI = 0.05-0.45, p < 0.001), dominant (OR = 0.49, 95%CI = 0.26-0.93, p = 0.028), and recessive (OR = 0.18, 95%CI = 0.07-0.52, p < 0.001) models. Similarly, rs879577 showed reduced disease risk associated with the T allele across all genetic models. However, the A allele of rs41323645 was associated with increased disease risk in all models. The G/A and A/A genotypes have higher ORs of 2.47 (95%CI = 1.19-5.14) and 3.86 (95%CI = 1.62-9.18), respectively. Similar trends are observed in the dominant 2.89 (95%CI = 1.47-5.68, p = 0.002) and recessive 2.34 (95%CI = 1.10-4.98, p = 0.025) models. For the rs4819555 variant, although there was no significant association identified under any models, carriers of the rs4819554*A demonstrated an association with a positive family history of asthma (71.4% in carriers vs. 27% in non-carriers; p = 0.025) and the use of relievers for >2 weeks (52.2% of carriers vs. 28.8% of non-carriers; p = 0.047). Meanwhile, the rs4819555*C carriers displayed a significant divergence in the asthma phenotype, specifically atopic asthma (83.3% vs. 61.1%; p = 0.007), showed a higher prevalence of chest tightness (88.9% vs. 61.5%; p = 0.029), and were more likely to report comorbidities (57.7% vs. 16.7%, p = 0.003). The most frequent haplotype in the asthma group was ACAC, with a frequency of 22.87% vs. 1.36% in the controls (p < 0.001). In conclusion, the studied IL17RA variants could be essential in asthma susceptibility and phenotype in children and adolescents.

Interleukin-4 (C590T) Gene Polymorphism in Association with Asthma Severity

Background

A significant link between T allele of the IL-4 (C590T) gene and developing asthma in some populations was reported. However, no study discussed the link between IL-4 (C590T) gene polymorphism and asthma severity groups (mild and severe). This study investigated the link between IL-4 gene variation and asthma severity.

Methods

The study included 215 asthmatic patients, of which 102 had mild asthma, and 126 participants were healthy controls. A previously published polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to identify various IL-4 (C590T) gene polymorphism genotypes.

Results

The T allele frequency was higher in mild asthma (p=0.002) but not in severe asthma (p=0.12) compared to controls. In mild asthma, the CT genotype and (CT+TT versus CC) increased the likelihood of asthma threefold (p<0.001, 0.001). However, no significant association with severe asthma was found in either genetic model. Stratification analysis showed that the C allele and CC genotype increased the risk of severe asthma (p=0.01). The recessive genetic model indicated a decrease in the risk of severe asthma (OR=0.5, p=0.01) in the non-adjusted regression analysis. Adjusting for age, sex, and other risk factors revealed that the IL-4 gene polymorphism did not influence the risk of severe asthma (OR=0.92, p=0.80); however, being an elderly female with a history of childhood-onset disease and associated nasal polyp (NP) increased the likelihood of severe asthma, OR=1.08, 2.01, 2.36, 8.42; p<0.001, 0.05, 0.05, <0.001, respectively.

Conclusion

The T allele and CT genotype in the co-dominant genetic model and the (CT+TT) genotype in the recessive model were found to have a higher likelihood of developing mild asthma but not severe asthma; severe asthma was found to be higher in elderly females with a history of childhood-onset disease and associated nasal polyps.

Impact of cytokines genes polymorphisms and their serum levels on childhood asthma in Egyptian population

BACKGROUND

Asthma is chronic immune-mediated airway inflammation, and it is affected by a complex network of interacting cytokines. To date, the exact role of each cytokine and its genetic polymorphisms in childhood asthma development and its severity has remained poorly understood. The purpose of this study was to explore potential roles of four cytokine genes polymorphism and serum levels l [(T helper-2 (Th2) cytokine); Interleukin-4 (IL-4) 590, (Th3 cytokine); and transforming growth factor β1 (TGF-β1) 509T; (Th17) including tumor necrosis factor-alpha (TNF-α), and IL17A rs8193036] in childhood asthma risk and control in Egyptian children, for the 1st time.

MATERIALS AND METHODS

This case-control study included two children subgroups; Group1 included 216 non-asthmatic controls and (Group 2) 216 cases diagnosed with asthma (clinically and spirometry-based) were classified as controlled, partly controlled, and uncontrolled. Polymorphisms of TGF-β1-509, IL-4 590, and TNF-α-308 genes were detected using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). IL-17 was genotyped using tetra-primer amplification refractory mutation system polymerase chain reaction (ARMS-PCR). Serum cytokines levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Serum total IgE, TGF-β1, IL4, TNF-α, and IL17A levels were significantly higher in asthmatic compared to controls. Also, significant increases in serum total IgE, IL-4, TGF-β1, and TNF-α levels are combined with poor asthma control, while no significant IL17A changes. There were significant changes of IL-4-590, TNF-α-308, and IL17A genotypes and allele distributions between asthmatic and controls groups as well as different asthma control levels; while no impact of TGF-β1 SNP on asthma risk and control level. Four cytokines SNPs affected their serum levels among asthmatic patients.

CONCLUSION

There are impacts of cytokine gene polymorphisms (IL-4-590, TNF-α-308, and IL17A); but not TGF-β1 on asthma susceptibility and poor asthma control in Egyptian children.