Abstract
BACKGROUND: Bronchial asthma is a chronic inflammatory disease of the airways, the development of which is based on genetic predictors associated with the differentiation and functioning of T-helpers. Polymorphisms in the genes of cytokines involved in the regulation of the direction of the T-helper mediated immune response are risk factors for the development of the disease and the realization of various phenotypes of bronchial asthma.
AIMS: Study of the structure and frequency of occurrence of single nucleotide polymorphisms of cytokine genes with an assessment of the risk of various phenotypes of bronchial asthma in children.
MATERIALS AND METHODS: In this case control study, 250 children were examined, including 150 children with a verified diagnosis of bronchial asthma (including 75 children with virus-induced and 75 children with allergen-induced disease phenotypes) and 100 sexually comparable healthy peers. The children underwent a comprehensive general clinical and allergological examination, genotyping, analysis of the structure, frequency of occurrence of cytokine gene polymorphisms and calculation of the odds ratio of the risk of developing different bronchial asthma phenotypes. DNA samples isolated from peripheral venous blood were used as material for molecular genetic analysis. The following mutation points were selected: IFN (T-874 A), IL-4 (C-589 T), IL-6 (C-174 G), IL-17A (G-197 A), TNF (G-308 A).
The work followed the ethical principles set forth by the Declaration of Helsinki by the World Medical Association and the Rules of Clinical Practice in the Russian Federation, the study design was approved by the Interdisciplinary Ethics Committee of the Federal State Budgetary Educational Institution of Higher Education Pacific State Medical University of the Ministry of Healthcare of the Russian Federation on April 27, 2015 (Protocol No. 8), informed voluntary consent was signed by the parents.
When processing digital data, we used the methods of descriptive, parametric and nonparametric statistics of the Statistica 10 program, comparison of unrelated groups by qualitative characteristics, assessment of the correspondence of the distributions of genotypes to the expected values at the Hardy-Weinberg equilibrium. The analysis of the frequency distributions of genotypes and alleles in two subpopulations was carried out using the Chi-square test (2).
RESULTS: A comparative analysis of the frequencies of alleles and genotypes of cytokines of various Th profiles with the definition of features in allergen-induced and virus-induced phenotypes of the disease revealed in children with bronchial asthma the predominance of homozygous genotypes IFN (A-874A), IL-4 (T-589T), IL- 6 (G-174G), IL-17A (A-197A), TNF (A-308A), and in healthy peers the prevalence is IFN (T-874T), IL-4 (C-589C), IL-6 (C -174C), IL-17A (G-197G), TNF G-308G. Heterozygous genotypes IL-4 (C -589T), IL-6 (G -174C), IL-17A (G -197A), TNF (G -308A) found in children with bronchial asthma more often than in healthy peers, with the exception of the IFN genotype (T -874A). In children with the virus-induced bronchial asthma phenotype, the presence of the IL-4 (C-589T) mutant allele was found in 30,67% of cases with an odds ratio of -19,3 CI 95%. (11,23-33,31). When carrying the mutant A genotype IFN (T-874A), the odds ratio of the risk of developing the disease reflected a high degree of probability of the virus-induced bronchial asthma phenotype (OR = 5,11 (3,18-8,23) CI 95%). Carriage of homozygous genotypes IL-6 (G-174G), IL-17A (A-197A) determined an increased risk of developing allergen-induced bronchial asthma (OR = 2,71 (1,73-4,18) CI 95% and OR = 0,51 (0,32-0,71) CI 95%, respectively). Among children with bronchial asthma, there was a statistically significant increase in the incidence of the functionally unfavorable genotype 308 A /A of the TNF 308G /A gene, and the odds ratio reflects a 2,6-fold increase in the risk of developing a virus-induced bronchial asthma phenotype (2 = 18,66; p = 0,017; OR = 2,60, CI 95% (1,67-4,01).
CONCLUSIONS: As a result of the study, significant differences were determined in the structure and frequency of occurrence of cytokine gene polymorphisms in children with allergen and virus-induced bronchial asthma, depending on the realized phenotype of the disease. Carriage of mutant alleles IFN (A-874A), IL-4 (T-589T), IL-6 (G-174G), IL-17A (A-197A), TNF (A-308A) can be characterized as genetic predictors of bronchial asthma, for the implementation of the virus-induced phenotype, the odds ratio is higher in the presence of mutant alleles IFN (A-874A), IL-4 (T-589T), TNF (A-308A), for the allergen-induced phenotype of the disease - IL-6 (G -174G), IL-17A (A-197A).
