D2.109 - Interleukin-17A gene polymorphism contribute to the elderly asthma susceptibility: evidences from a case-control study

T helper 17 cells and interleukin-17 (IL-17) were evidently associated with the development of allergic asthma and play a crucial role in the elderly asthma, very late-onset asthma, and steroid non-responsive asthma. There has been no previously reported the association of IL-17 polymorphisms and asthma among elderly Thai individuals. This study aim to evaluate the association between IL-17A (rs2275913; G-197A, rs8193036; C-737T) and IL-17F (rs763780; A7488G) polymorphism in asthma and healthy control individuals in the elderly population and to analyze associations of genotype and allele with asthma susceptibility and clinical disease manifestation.

This case-control study enrolled 60 asthmatic patients aged between 65-85 years as the case group and 30 age-matched healthy individuals constitutes the control group. In non-asthmatic participants, baseline characteristics, pulmonary function test, FENO, CBC, skin prick test and blood sample for IL17 polymorphism. In asthmatic participants, baseline characteristics, past medical history and current medication, asthma control test score (ACT score), pulmonary function test, FENO, CBC, skin prick test and blood sample for IL17 polymorphism. The genotyping of IL-17 gene polymorphisms was carried out by using standard DNA sequencing. Logistic regression analysis was performed to assess the association between the genotypes, alleles, and most important risk factors for asthma. The effects of genetic variations of IL-17A and IL-17F genes on asthma risk were evaluated with odds ratios (OR) and 95% confidence intervals (95% CI).

The three polymorphisms were in Hardy-Weinberg equilibrium and no significant difference observed in the distribution of -737C/T and 7488A/G genotype frequencies among cases and controls. It was found that G allele of IL-17A, G-197A locus was statistically (P = 0.025) associated with an increased risk of asthma (OR 2.73, 95%CI 1.12-6.63). In addition, IL-17A, G-197A locus, GG genotype could significantly increase the asthma risk in subgroup analysis of eosinophil counts ≥ 300 cells/µL (adjusted OR 11.27, 95%CI 1.38-39.05, P = 0.024).

Our findings provided the first evidence for the significant association between genetic variations IL-17A, G-197A and susceptibility to asthma and could serve as useful marker in the clinical genetics of asthma in the elderly.