Alteration of -656(G/T) and -607(C/A) polymorphisms in interleukin-18 (IL-18) gene in house dust mite-sensitive allergic rhinitis patients in Thailand

Abstract

Allergic rhinitis (AR) is an IgE-mediated inflammation of the nasal membranes, which is naturally triggered by aeroallergens. House dust mites (HDM) are the most common inhalant allergens. Interleukin-18 (IL-18) has been established as an essential cytokine that can activate the generation of IgE. This randomized controlled study aimed to identify the possible relationship of the genetic variations in the IL-18 gene with AR in mite-sensitive Thai patients. Study subjects consisted of 150 AR patients and 50 normal participants. Genomic DNA of 30 randomized AR patients and 30 randomized controls were screened by sequencing for the selection of candidate single nucleotide polymorphisms (SNPs), and further analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay for all subjects. The following five SNPs were detected in the IL-18 gene: -656 G/T, -607 C/A, and -137 G/C in promoter 1 and -920 C/T and -373 C/G in promoter 2. The results showed that -656 G/T and -607 C/A SNPs were significantly correlated with IgE levels specific to Dermatophagoides pteronyssinus (Der p) allergen (P = 0.045 and P = 0.045, respectively), and significant differences were observed in the genotype distribution of AR patients when compared with controls [P = 0.044 and P = 0.044, respectively; odds ratios (ORs): 1.941 (95%CI, 1.014-3.715) and 1.941 (95%CI, 1.014-3.715), respectively]. Our findings indicate that the IL-18 alleles, -656T (rs1946519) and -607A (rs1946518), might be associated with the higher production of Der p allergen-specific IgE in mite-sensitive AR patients.